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Chesa I eake Bay Tidal Floo'ding Study MAIN REPORT @77 f I _-@ 7 PV. oe r 41 GC 226 U54 C44 1984 0, SepteMber 194- Chesapeake Bay Tidal Flooding Study MAIN REPORT Property Of CSC L bra3w U - S . DEPARTMENT OF COMMERCE NOAA COASTAL SERVICES CENTER 2234 SOUTH HOBSON AVENUE CHARLESTON SC 29405-2413 US Army Corps of Engineers Baltimore District September 1984 FOREWORD This is one of the volumes comprising of potential social, economic, and en- the final report on the Corps of Engi- vironmental impacts. The Tidal Flood- neers' Chesapeake Bay Study. The report ing Study included development of pre- represents the culmination of many years liminary stage-damage relationships and of study of the Bay and its associated identification of Bay communities in social, economic, and environmental which structural and nonstructural processes and resources. The overall measures could be beneficial. study was done in three district devel- opmental phases. A description is pro- The final report of the Chesapeake Bay vided below of each study phase, fol- Study is composed of three major ele- lowed by a description of the organiza- ments: (1) Summary, (2) Low Fresh- tion of the report. water Inflow Study, and (3) Tidal Flooding Study. The Chesapeake Bay The initial phase of the overall program Study Summary Report includes a des- involved the inventory and assessment cription of the results, findings, and of the existing physical, economic, social, recommendations of all the above des- biological, and environmental condi- cribed phases of the Cheseapeake Bay tions of the Bay. The results of this effort Study. It is incorporated in four parts: were published in a seven volume doc- Summary Report ument titled Chesapeake Bay Existing Supplement A - Problem Conditions Report, released in 1973. Identification This was the first publication to present Supplement B - Public Involvement a comprehensive survey of the tidal Supplement C - Hydraulic Model Chesapeake and its resources as a single entity. The Low Freshwater Inflow Study con- The second phase of the program focused sists of a Main Report and six support- on projection of water resource re- ing appendices. The report includes: quirements in the Bay Region for the Main Report year 2020. Completed in 1977, the Ches- Appendix A - Problem apeake Bay Future Conditions Report Identification documents the results of that work. The Appendix B - Plan Formulation 12-volume report contains projections Appendix C - Hydrology for resource categories such as naviga- Appendix D - Hydraulic Model tion, recreation, water supply, water Test quality, and land use. Also presented are Appendix E - Biota assessments of the capacities of the Bay Appendix F - Map Folio system to meet the identified future requirements, and an identification of The Tidal Flooding Study consists sim- problems and conflicts that may occur ilarly of a Main Report and six appendi- with unrestrained growth in the future. ces. The report includes: Main Report In the third and final study phase, two Appendix A - Problem resource problems of particular concern Identification in Chesapeake Bay were addressed in Appendix B - Plan Formulation, detail: low freshwater inflow and tidal Assessment and Evaluation flooding. In the Low Freshwater Inflow Appendix C - Recreation and Study, results of testing on the Chesa- Natural Resources peake Bay Hydraulic Model were used Appendix D - Social and to assess the effects on the Bay of pro- Cultural Resources jected future depressed freshwater in- Appendix E - Engineering flows. Physical and biological changes Design and Cost Estimates were quantified and used in assessments Appendix F - Economics Table of Contents Chapter I Page Introduction ............................................... I Authority ................................................. I Study Purpose and Scope .................................... 2 Chesapeake Bay Study .................................... 2 Tidal Flooding Study ..................................... 2 Study Process and Report ................................... 2 Prior Studies and Reports ................................... 3 Study Participants and Coordination .......................... 5 Chapter 11 Problem Identification ........................................ 7 Study Area ................................................ 7 Existing Conditions ......................................... 7 Geology ................................................. 7 Climate ................................................. 7 Surface Water Hydrology .................................. 7 The Biota of Chesapeake Bay .............................. 9 Population .............................................. 9 Problems, Needs and Opportunities ........................... 10 Selection of Communities for Detailed Study ................... I I Profiles of Flood-Prone Communities ......................... 14 Cambridge, Maryland ..................................... 14 Crisfield, Maryland ....................................... 14 Pocomoke City, Maryland ................................. 14 Rock Hall, Maryland ..................................... 15 Snow Hill, Maryland ..................................... 17 St. Michaels, Maryland ................................... 17 Tilghman Island, Maryland ................................ 17 Cape Charles, Virginia .................................... 18 Hampton Roads, Virginia ................................. 18 Norfolk ............................................... 19 Portsmouth ............................................ 20 Chesapeake ............................................ 21 Hampton .............................................. 21 Poquoson, Virginia ....................................... 22 Tangier Island, Virginia ................................... 24 West Point, Virginia ...................................... 26 Statement of Planning Objectives ................................ 27 National Planning Objectives ................................. 27 Study Planning Objectives ................................... 28 Chapter III Page Formulation of Flood Protection Plans .......................... 29 Plan for Formulation Rationale .............................. 29 Technical Criteria ........................................ 29 Economic Criteria ........................................ 29 Environmental and Social Well-Being Criteria ................ 29 Management Measures ...................................... 29 Levees and Floodwalls .................................... 30 Seawalls, Bulkheads, and Revetments ....................... 30 v Table of Contents (Cont'd) Chapter III Page Other Structural Measures ................................. 30 Floodproofing ........................................... 30 Raising ................................................. 30 Utility Room Addition .................................... 30 Relocation .............................................. 30 Acquisition and Demolition ................................ 30 Flood Warning and Evacuation ............................ 30 Flood Insurance .......................................... 31 No Action ............................................... 31 Description of Plans Considered .............................. 31 Cambridge, Maryland ..................................... 31 Crisfield, Maryland ....................................... 31 Pocomoke City, Maryland ................................. 32 Rock Hall, Maryland ..................................... 32 Snow Hill, Maryland ..................................... 32 St. Michaels, Maryland ................................... 32 Tilghman Island, Maryland ................................ 35 Cape Charles, Virginia .................................... 35 Hampton Roads, Virginia ................................. 38 Poquoson, Virginia ....................................... 38 Tangier Island, Virginia ................................... 38 West Point, Virginia ...................................... 40 Chapter IV Assessment and Evaluation of Plans ............................. 43 Maryland Communities ...................................... 43 Cambridge .............................................. 43 Economic Analysis ..................................... 43 Assessment and Evaluation .............................. 43 Crisfield ................................................. 45 Economic Analysis ..................................... 45 Assessment and Evaluation .............................. 45 Pocomoke City .......................................... 46 Economic Analysis ..................................... 46 Assessment and Evaluation .............................. 46 Rock Hall ............................................... 46 Economic Analysis ..................................... 46 Assessment and Evaluation .............................. Snow Hill 46 Economic Analysis ..................................... 47 Assessment and Evaluation .............................. 47 St. Michaels ............................................. 47 Economic Analysis ..................................... 47 Assessment and Evaluation .............................. 47 Tilghman Island .......................................... 47 Economic Analysis ..................................... 47 Assessment and Evaluation .............................. 47 Virginia Communities ....................................... 47 Cape Charles ............................................ 47 Economic Analysis ..................................... 47 Assessment and Evaluation .............................. 47 Hampton Roads ........................ ................ 47 Economic Analysis ..................................... 47 Assessment and Evaluation .............................. 47 Poquoson ............................................... 62 Economic Analysis ..................................... 62 Assessment and Evaluation .............................. 63 Tangier Island ........................................... 63 Economic Analysis ..................................... 63 Assessment and Evaluation .............................. 63 vi Table of Contents (Cont'd) Page West Point .............................................. 64 Economic Analysis ..................................... 64 Assessment and Evaluation .............................. 64 Chapter V Summary and Conclusions ..................................... 71 Summary ................................................. 71 Maryland Communities ................................... 73 Virginia Communities ..................................... 73 Findings and Conclusions ................................... 76 Chapter VI Recommendations ............................................ 79 List of Abbreviations ...................................... 81 Glossary ................................................... 83 Acknowledgements and Credits ........................... 87 List of Tables Number Title Page I Chesapeake Bay Tidal Flooding Study Report Format 3 2 Recent Chesapeake Bay Storms 10 3 Tidal Flood Damages 11 4 Chesapeake Bay Area Flood-Prone Communities 11 5 Critical Communities Recommended for Detail Study 12 6 Tidal Flood-Prone Communities Examined 14 7 Cambridge Flood Plain Inventory 15 8 Crisfield Flood Plain Inventory 15 9 Pocomoke City Flood Plain Inventory 15 10 Rock Hall Flood Plain Inventory 16 11 Snow Hill Flood Plain Inventory 16 12 St. Michaels Flood Plain Inventory 16 13 Tilghman Island Flood Plain Inventory 16 14 Cape Charles Average Annual Flood Damages 18 15 Hampton-Fox Hill Area Average Annual Flood Damages 22 16 Poquoson Area I Average Annual Flood Damages 23 17 Poquoson Area 11 Average Annual Flood Damages 23 18 Poquoson Area III Average Annual Flood Damages 24 19 Poquoson Area IV Average Annual Flood Damages 24 20 Tidal Stage-Damage Data for Tanier Island 25 21 West Point Average Annual Flood Damages - Corps Frequency 26 22 West Point Average Annual Flood Damages - VIMS Frequency 27 23 Summary Economic Analysis of Alternative Plans for Cambridge 43 24 Comparative Assessment and Evaluation, Cambridge, Maryland 44 v,ii List of Tables (Cont'd) Number Title Page 25 Summary Economic Analysis of Alternative Plans for Crisfield 46 26 Comparative Assessment and Evaluation, Crisfield, 48 Maryland 27 Summary Economic Analysis of Alternative Plans for 50 Pocomoke City 28 Comparative Assessment and Evaluation, Pocomoke City, Maryland 50 29 Summary Economic Analysis of Alternative Plans for Rock Hall 51 30 Comparative Assessment and Evaluation, Rock Hall, Maryland 52 31 Summary Economic Analysis of Alternative Plans for Snow Hill 54 32 Comparative Assessment and Evaluation, Snow Hill, Maryland 54 33 Summary Economic Analysis of Alternative Plans for St. Michaels 56 34 Comparative Assessment and Evaluation, St. Michaels, Maryland 56 35 Summary Economic Analysis of Alternative Plans for Tilghman Island 59 36 Comparative Assessment and Evaluation, Tilghman Island, Maryland 59 37 Cape Charles Summary Economic Analysis 60 38 Cape Charles Comparative Assessment and Evaluation 60 39 Annual Benefits, Costs, and B/C Ratios for Hampton 62 40 Comparative Assessment and Evaluation, Fox Hill Area of Hampton, Virginia 62 41 Poquoson Annual Costs, Benefits, and B/C Ratios 63 42 Poquoson Comparative Assessment and Evaluation 64 43 Tangier Island Economic Analysis of Plans 64 44 Tangier Island Comparative Assessment and Evaluation 66 45 West Point Economic Analysis of Plans 66 46 West Point Comparative Assessment and Evaluation 68 47 Tidal Flooding Critical Problem Areas 71 48 Plans for Tidal Flood Reduction, Maryland Communities 74 49 Plans for Tidal Flood Reduction, Virginia Communities 74 List of Figures Number Title Page I Chesapeake Bay Study Area 4 2 Chesapeake Bay Study Organization 5 3 Study Area and Field Data Stations 8 4 Critical Flood-Prone Communities 13 5 Cape Charles Flood Scene, September 1960 Hurricane 18 viii List of Figures (Cont'd) Number Title Page 6 Beach, Bulkhead and Promenade at Cape Charles, March 1962 Storm 19 7 Flood Scene, March 1962 "Northeaster" at Norfolk, Virginia 20 8 Flood Scenes, March 1962 "Northeaster" at Portsmouth, Virginia 21 9 Flooding in Hampton-Fox Hill Section, March 1962 22 10 Flood Scene of March 1962 "Northeaster" at Poquoson, Virginia 23 11 Flood Scene at Tangier Island, March 1962 25 12 Cambridge Plans of Improvement 31 13 Crisfield Plans of Improvement 32 14 Pocomoke City Plans of Improvement 33 15 Rock Hall Plans of Improvement 34 16 Snow Hill Plans of Improvement 35 17 St. Michaels Plans of Improvement 35 18 Tilghman Island Plans of Improvement 36 19 Cape Charles Area Flood Map 37 20 Hampton Roads City Complex - Sites Considered 38 21 Hampton Roads-Fox Hill Study Area 39 22 Poquoson Coastal Flood Area 40 23 Map of Tangier Island 40 24 West Point Area Flood Map 41 ix CHAPTERI Introduction complete investigation and study of Chesapeake Bay is a vast natural, eco- water utilization and control of the nomic, recreation, and social resource. Chesapeake Bay Basin, including the It provides a transportation network on waters of the Baltimore Harbor and which much of the region's economic including, but not limited to the fol- development has been based, a wide va- lowing: navigation, fisheries, flood riety of water-oriented recreation oppor control, control of noxious weeds, tunities, a home for numerous fish and water pollution, water quality con- wildlife species, a source of water supply trol, beach erosion, and recreation. for both municipalities and industries, In order to carry out the purposes of and a disposal site for many waste pro- this section, the Secretary, acting ducts. Human activities interact with through the Chief of Engineers, shall the natural resources and processes of construct, operate, and maintain in the Bay to create a diverse system. the State of Maryland a hydraulic Unfortunately, problems sometimes model of the Chesapeake Bay Basin arise when people's use of the resources and associated technical center. Such conflict with the natural environment or model and center may be utilized, other intended uses. Thus, the impetus subject to such terms and conditions for the Chesapeake Bay Study came as the Secretary deems necessary, by from a need to resolve these conflicts, to any department, agency, or instru- make uses of the Bay compatible with mentality of the Federal Government the Bay ecosystem itself, and to provide or of the States of Maryland, Virgin- an efficient and effective means of man- ia, and Pennsylvania, in connection aging this diverse, dynamic resource. with any research, investigation, or study being carried on by them of any For the purposes of this report, the Ches- aspect of the Chesapeake Bay Basin. apeake Bay Study Area was defined as The study authorized by this section the shaded portion shown in Figure 1. shall be given priority. The Study Area encompassed all the counties and Standard Metropolitan (b) There is authorized to be ap- Statistical Areas (SMSA) adjacent to or propriated not to exceed $6,000,000 directly influencing Cheseapeake Bay to carry out this section, and its sub-estuaries. In all, almost 25,000 square miles in parts of three An additional appropriation for the states and the District of Columbia were Chesapeake Bay Study was provided in included. The shaded portion of Figure Section 3 of the River Basin Monetary I represents about 20,600 square miles Authorization Act of 1970, adopted on of land area and 4,400 square miles of June 19, 1970. This sections reads as water surface, and is hereafter referred follows: to as the "Study Area" or the "Bay Region." In addition to the previous authori- zation, the completion of the Chesa- AUTHORITY peake Bay Basin Comprehensive Study, Maryland, Virginia, and Penn- The authority for the Cheseapeake Bay sylvania, authorized by the River Study and the construction of the related and Harbor Act of 1965 is hereby hydraulic model was provided in Sec- authorized at an estimated cost of tion 312 of the River and Harbor Act of $9,000,000. 1965, adopted on October 27, 1965. This section reads as follows: In June 1972, Tropical Storm Agnes moved through the Mid-Atlantic states (a) The Secretary of the Army, act- causing extensive damage to the resour- ing through the Chief of Engineers, is ces of the Chesapeake Bay. Public Law authorized and directed to make a 92-607, the Supplemental Appropria- I tion Act of 1973, was signed on October In response to the first study objective, included: (1) periods of low freshwater 31, 1972, and included $275,000 for an inventory of existing conditions was inflow from the Bay's tributaries, (2) additional studies of the storm's effect completed in 1973. The findings were periods of high freshwater inflow from on Chesapeake Bay. published in a document titled Ches-- the Bay's tributaries, and (3) tidal flood- apeake Bay Existing Conditions Report. ing caused by unusual climatological/ Included in the seven-volume report was meteorological conditions. a description of the existing physical, STUDY PURPOSE AND economic, recreation, social, biological, Two of the most pressing problems SCOPE and environmental conditions of Ches- identified were tidal flooding along the apeake Bay. This report was the first Chesapeake Bay shorelines and the Chesapeake Bay Study published document that furnished a impacts of low freshwater inflow to the comprehensive survey of the entire Bay Chesapeake Bay. As recommended in Historically measures taken to control Region and treated Chesapeake Bay as a the Revised Plan of Study published in and utilize the water and related land complete entity. More importantly, the 1978 these two problems became the resources of the Bay Region were Existing Conditions Report assembled focus of the detailed study phase of the oriented toward solving individual much of the data required to project Chesapeake Bay Program. The purpose problems. No thorough examination future water resource needs in the Study of this Main Report is to discuss the had been undertaken which considered Area and to assess the ability of the Bay findings of the Tidal Flooding Study. the interrelationships among the Bay's to satisfy these needs. resources, problems, and solutions. Tidal Flooding Study In response to the second study objec- The Chesapeake Bay Study was initiated tive, an analysis of future conditions was The Tidal Flooding Study had three in 1967 to fill this gap. The study's over- completed in 1978. Results were pub- primary objectives. The first was to pro- all purpose was to conduct a compre- lished in the 12-volume Chesapeake Bay vide a better understanding of the tidal hensive investigation of the entire Bay Future Conditions Report. The primary flood stage-frequency relationship in Region so that the most beneficial uses focus of the second phase was on the the Bay Region as a whole and particu- could be made of the Bay's resources in projection of water resource needs to the larly in those communities subject to future years. Within this broad study year 2020. In addition, problems and tidal flooding. The second major objec- purpose, three major study objectives conflicts were identified which could tive was to define the environmental and were established. These study objectives result from uncontrolled growth and use socio-economic impacts of tidal flood- were identified as follows: of the Bay's resources. Taken together, ing on the affected communities. The the Existing Conditions Report and the third and final objective was to recom- � To assess the existing physical, Future Conditions Report provided the mend detailed studies of structural or chemical, biological, economic, and basic information necessary to address nonstructural measures for tidal flood- environmental conditions of Ches- the third study objective. ing protection in those communities apeake Bay. where it was determined to be economi- Based on the findings of both the Exist- cally and environmentally feasible as � To project the future water resource ing Conditions Report and the Future well as socially acceptable. needs of the Bay Region to the year Conditions Report, a myriad of either 2020. existing or emerging water resource Study Processes and Report related problems in the Chesapeake Bay � To formulate and recommend solu- Region were identified. Because the As discussed in the Foreward to the tions to priority problems using the responsibility for implementing solutions Main Report, tidal flooding was one of Chesapeake Bay Hydraulic Model. to these problems was either at the local, two major resource problems addressed state, or Federal level, and because there during the final phase of the Chesapeake As directed in the authorization, the were numerous studies and research Bay Study. The Tidal Flood Study study also included the construction and programs underway, it was necessary to Main Report provides a summary of the operation of a hydraulic model. The more specifically define the role of the investigations and analyses conducted purpose in using a physical model was to Chesapeake Bay Study. In defining this and presents the findings for the com- examine complicated hydraulic processes role, emphasis was placed on: (1) selecting munities which were examined. The six not readily amendable to analysis by problems for study that were considered tidal flooding appendices listed in Table other analytical methods. The Chesa- to be high priority and of Bay-wide sig- I contain the information supporting peake Bay Hydraulic Model was con- nificance, (2) maximizing use of the Ches- the findings which are summarized in structed between 1973 and 1976 at apeake Bay Hydraulic Model, (3) avoid- the Main Report. The identification of Matapeake, Maryland. Following model ing duplication of work conducted under tidal flooding as a problem and its gen- adjustment and verification, testing was other programs, and (4) being responsive eral impact on the Bay communities is performed between 1978 and 1982. The to the original intent of the Congress as presented in Appendix A. The formula- hydraulic model provided a means of specified in the study authorization. A tion of plans to mitigate the flood reproducing, at a manageable level, review of the potential studies indicated problem is detailed in Appendix B along many of the natural events and human that at least a portion of the Chesapeake with an evaluation of the effects these changes affecting the Bay. Data were Bay Study and model efforts should be plans may have on the communities collected from the hydraulic model tests directed toward studies of extraordi- under study. Appendix C profiles the and were then analyzed to assess the nary natural events that have Bay-wide natural and recreational resources of the consequences of these happenings. impact or significance. These events communities while Appendix D high- 2 TABLE I No recommendations for construction of any hurricane protective works CHESAPEAKE BA Y TIDAL FLOODING resulted from any of the above studies. STUDY REPORT FORMAT The following conclusions and recom- mendations are quoted frorn House APPENDIX APPENDIX TITLE Document No. 176, Eighty-Eighth Congress, first session, 25 November Main.Report 1963, Chesapeake Bay, Maryland and A Problem Identification Virginia, and are considered typical of B Plan Formulation, Assessment, and Evaluation the findings of these earlier studies. C Recreation and Natural Resources D Social and Cultural Resources On the Eastern shore of the Chesa- E Engineering Design and Cost Estimates peake Bay there were no locations at F Economics which local interests specifically re- quested construction of protective structures to prevent tidal flooding. Investigation of the shore showed that there were no locations at which construction of protective structures could bejustified although there exist in Dorchester and Somerset Coun- lights their demographic and cultural tion with the Secretary of Commerce ties large areas that would be flooded resources. The flood protection mea- and other Federal agencies concerned by hurricane-induced tides of 10 feet sures considered, and their cost, are with hurricanes is hereby authorized or greater. In these areas serious con- presented in Appendix E while Appen- and directed to cause an examination sideration should be given by local dix F presents the annualized costs and and survey to be made of the eastern authorities to developing an adequate benefits for each of the plans. and southern seaboard of the United evacuation plan. States with respect to hurricanes with particular reference to areas where On the Western shore of the Chesa- severe damages have occurred. peake Bay there were found no loca- Prior Studies and Reports tions at which extensive flooding SEC. 2. Such survey, to be made would occur from high tides since under the direction of the Chief of elevations of 20 feet or more exist at There have been several studies accom- Engineers, shall include the securing shore distances from the new high plished by the Corps that have investi of data on the behavior and fre- water shoreline. At some locations gated specific problems in the communi- quency of hurricanes, and the deter- along the shore, local interests re- ties under study. These studies are mination of methods of forecasting quested protection from beach ero- discussed in Appendix A - Problem their paths and improving warning sion. In these locations, it was found Identification. However there has been services, and of possible means of that local interests did not desire pro- only one comprehensive Bay-wide tidal preventing loss of human lives and tection from hurricane-induced tides flooding study conducted by the Corps damages to property, with due con- and since investigations to provide in the last three decades. The authoriza- sideration of the economics of pro- beach erosion protection can be ac- tion for this study was contained in Pub- posed breakwaters, seawalls, dikes, complished under existing laws, pro- lic Law 7 1, Eighty-fourth Congress, first dams and other structures, warning vision of protection was not investi- session, approved 15 June 1955, which services or other measures which gated for these areas. read: might be required. Since-there appear to be no locations Be it enacted by the Senate and The above authorization resulted in sev- on the east or west shore of the Ches- House of Representatives of the Uni- eral studies and subsequent reports apeake Bay at which protection from ted States of America in Congress which addressed various segments of the hurricane-induced tides could be jus- assemble& That in view of the severe tidal shoreline. Specific reports were tified the District Engineer recom- damage to the coastal and tidal areas prepared that considered: (1) the Balti- mends that no further planning or of the eastern and southern United more Metropolitan Area, Maryland, (2) investigation for the provision of States from the occurrence of hurri- the Washington, D.C. 'Metropolitan hurricane protective works within canes, particularly the hurricanes of Area, (3) Colonial Beach, Virginia (4) the study area be undertaken at this August 31, 1954 and September 11, Garden Creek, Mathews County, Virgin- time. The District Engineer recom- 1954, in New England, New York ia, (5) the tidewater portions of the mends, however, that this report be and New Jersey coastal and tidal Patuxent, Potomac and Rappahannock published and distributed to appro- areas, and the hurricane of October Rivers, including the adjacent Chesa- priate officials in the area who may 15, 1954 in the coastal and tidal areas peake Bay Shoreline, and (6) the entire find the information contianed there- extending south to South Carolina, tidal shoreline of the Eastern Shore of in of use in the establishment of flood and in view of the damages caused by Maryland and Virginia and the Western plain regulatory measures and evac- the other hurricanes in the past, the Shore of Maryland from the head of the uation procedures. Secretary of the Army, in coopera- Bay to the mouth of the Patuxent River. 3 *UTICA ALBANY* NOrW CK Ch ... no. 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Bull. woor -is a ;@Hl Figure I Chesapeake Bay Study Area 4 Study Participants and planning of the study was coordinated organization representing a wide range Coordination with the former National Council of of groups in the Bay Region. Two sets of Marine Resources and Engineering public meetings were held. One was held The problems of Chesapeake Bay are of Development through its Committee on at the study's outset to inform the public such complexity and magnitude and Multiple Use of the Coastal Zone. of study initiation and to solicit views as involve so many varied disciplines that to the direction the study should take, no single entity could be expected to The overall management of the Chesa- The second was held near the comple- have the requisite personnel, equipment, peake Bay Study was the responsibility tion of the future projections phase to and technical know-how to accomplish of the District Engineer of the Baltimore inform the public of progress on the the many special studies needed to com- District, Corps of Engineers. His staff overall program and to solicit views plete this comprehensive investigation. included professionals from the fields of regarding the study findings to date. Such expertise does exist, however, engineering, economics, and the social, among the many agencies which have physical, and biological sciences. In addition to the study's planning historically been responsible for certain Hydraulic modelling expertise was pro- reports, a number of other printed features of water resource development. vided by personnel from the Corps of materials and techniques were used to Engineers' Waterways Experiment Sta- inform the public about the study. These The study was conceived as a coordi- tion (WES) in Vicksburg, Mississippi. included a leaflet on the hydraulic model, nated partnership among federal, state, reprints of articles, transcripts from and local agencies and interested scien- The involvement of the general public public meetings, periodic newsletters, tific institutions. Each involved agency was also an important facet of study tours of the hydraulic model, and a film was asked to provide leadership in those coordination. The purpose in establish- titled "Planning for a Better Bay." disciplines in which it had special com- ing such coordination was to provide petence. To furnish the necessary avenues two-way communication between the More information about study coordi- for public participation, an Advisory Corps and the public-at-large. A number nation and public participation can be Group, a Steering Committee, and five of public involvement techniques were found in Chapter VI of the Summary Task Groups were established. Figure 2 employed. An informal liaison was Report and in Supplement B Public illustrates the many agencies involved in established with the Citizen's Program Involvement. the Chesapeake Bay Study. The initial for Chesapeake Bay, Inc. (CPCB), an Figure 2 Chesapeake Bay Study Organization BALTIMORE DISTRICT CORPS OF ENGINEERS ADVISORY GROUP STEERING COMMITTEE. LIAISON. A BASIC RESEARCH 1. R.K.F. ECONOMIC PROJECTION VVATER OUALITY SUPPLY. FLOOD COKTRO . 'IS" IF "LOL"' TASK GROUP WASTE FREATMENT. W.- NAVIGATION. EPOSFOKF RECREATION TASK ORO GDORII-TIO. GROUP WEEDSTASK GROUP FISHERIES TASK GROUP AW 5 CHAPTER 11 Problem Identification Study Area and in the northern portions of the East- ern Shore. The Coastal Plain reaches its As stated earlier, the Chesapeake Bay highest elevation in areas along its west- Study Area included all the counties and ern margin. Standard Metropolitan Statistical Areas (SMSA) contiguous to or directly in- The Piedmont Plateau is not, as its fluencing Chesapeake Bay and its sub- name implies, a plateau. It is character- estuaries. With regard to the detailed ized by low hills and ridges which tend problem analysis associated with tidal to rise above the general lay of the land flooding, only a portion of the Study reaching a maximum height near the Area was examined. By its very defini- Appalachian Province on the west. Many tion, the tidal flooding study was in- of the stream valleys are quite narrow volved only with those communities and steep-sided, having been cut into the that are influenced by the tidal fluctua- hard crystalline rocks which are charac- tions in the Bay Estuary. The number of teristic of the Province. communities, metropolitan areas, and towns considered in the various stages Climate of the study were reduced through con- sideration of several criteria. The com- The Chesapeake Bay Study Area is munities selected for detailed study as characterized by a generally moderate well as the process used will be discussed climate, due in a large part to its proxim- later in this chapter. The limits of the ity to the Atlantic Ocean. Variations area considered in the tidal flooding occur, however, on a local basis due to study are presented in Figure 3. the large geographical size of the Bay area. Precipitation for the Study Area Existing Conditions averaged 44 inches per year based on the period of record from 1931 to 1960. Geology Evapotranspiration amounts to about 26 inches a year with estimates as high as The Chesapeake Bay Region is divided 36 to 40 inches per year from the Bay into geologic provinces - the Coastal itself. Storm activity in the region con- Plain and the Piedmont Plateau. These sists of three types: extratropical storms provinces run roughly parallel to the or "lows", tropical storms or "hurri- Atlantic Ocean in similar fashion to the canes," and thunderstorms. Thunder- Bay itself and join at the Fall Line. This storms are responsible for the greatest natural line of demarcation generally variation in precipitation in the Bay marks both the lirnit of tide as well as the Region. A discussion of hurricanes and head of navigation. their consequences is found later in this chapter. The Coastal Plain Province includes the Eastern Shore of Maryland and Virgin- Surface Water Hydrology ia, most of Delaware, and a portion of the Western Shore. On the Eastern The source of freshwater for the Bay is Shore and in portions of the Western runoff from a drainage basin covering Shore adjacent to the Bay, the Coastal about 64,160 square miles. Approxi- Plain is largely low, featureless, and mately 88 percent of this basin is drained frequently marshy, With many islands by five major rivers, including the Sus- and shoals sometimes extending far off- quehanna, Potomac, Rappahannock, shore. It is the low elevation, character- York, and James Rivers. These river istic of the Coastal Plain, that makes the basins are subject to periodic large, cli- area particularly prone to flooding from matic extremes, resulting in large fluc- tidal events. The Province is a gently tuations in flow (i.e., droughts and rolling upland on the Western Shore floods). Of these, droughts are the more 7 geographically widespread and long- The mixing in the estuary of sea water tributary embayments. Higher salinities term in nature. The Susquehanna, and freshwater creates salinity varia- are generally found on the Eastern Shore Potomac, Rappahannock, York, and tions within the system. In Chesapeake than on a comparable area of the West- James Rivers together provide nearly 90 Bay, salinities range from about 33 parts ern Shore due to the greater river inflow percent of the Bay's mean annual inflow per thousand at the mouth of the Bay on the Western Shore and to the earth's of approximately 69,800 cubic feet per near the ocean to near zero at the north rotation. Salinity patterns also vary sea- second. end of the Bay and at the heads of its sonally according to the amount of freshwater inflow into the Bay system. Figure 3 Study Area and Field Data Station s. Due to this seasonal variation in salinity and the natural density differences between fresh and saline waters, signifi- cant non-tidal circulation often occurs within the Bay's small tributary em- bayments. In the spring, during the period of high freshwater inflow to the Bay, salinity in the embayments may be greater than in the Bay. Because of this J r salinity difference, surface water from \C B I I ---muDEL SITE the Bay flows into the tributaries on the surface, while the heavier, more saline bottom water from the tributaries flows into the Bay along the bottom. As Bay salinity becomes greater through summer and early fall, Bay waters flow into the bottom of the tributaries, while tribu- tary surface waters flow into the Bay. rob L The natural variations in salinity that occur in the Bay are part of the dynamic nature of the estuary, and the resident species of the plants and animals are /1 ordinarily able to adjust to the changes. Sudden changes in salinity, however, or 'N C. B L 4L /C changes of long duration or magnitude, may upset the equilibrium between organisms and their environment. Abnormal periods of freshwater inflow (i.e., floods and droughts) may alter salinities sufficiently to cause wide- 10- spread damage to the ecosystem. 0 AD, Dissolved oxygen is another important 0 -------- --- -- physical parameter. Dissolved oxygen I.." levels vary considerably both seasonally and according to depth. During the win- ter the Bay is high in dissolved oxygen content since oxygen is more soluble in 0 cold water than in warm. With spring V 1. M S and higher water temperatures, the dis- __.y solved oxygen content decreases. While OU warmer surface waters stay near satura- 7- tion, in deeper waters the dissolved oxy- gen content becomes significantly less despite the cooler temperatures because of increasing oxygen demands (by bot- tom dwelling organisms and decaying L SEN A r 4 A A organic material) and decreased vertical "WA WITH MIAMIR OF C SALINITY & VELOCITY STATIO04 mixing. Through the summer, the waters 0 IIAAOE 111TH ONE SAU TV OCeA *V below 30 feet become oxygen deficient. & VELOCITY STATION N By early fall, as the surface waters cool 0 TIDAL QMRVATIM 'STATIONIS and sink, vertical mixing takes place and CKSAFEAXE DAY STUDY the oxygen content at all depths begins MODEL LIMITS to steadily increase until there is an AND FIELD DATA STATIONS 8 almost uniform distribution of oxygen. generally believe that most of the nu- species of plants and animals that are While species vary in the level of dis- trients -required by estuarine organisms able to survive and reproduce in the solved oxygen they can withstand before are present in sufficient quantity in Ches- estuary. Despite the fact that relatively respiration is affected, estuarine species apeake Bay, Excesses of some nutrients few species inhabit the Bay, the Chesa- in general can function in waters with are often a more important problem peake, like most estuaries, is an extreme- dissolved oxygen levels as low as 1.0 to than deficiencies. Excesses of nitrogen ly productive ecosystem. This is so for 2.0 mg/ liter. Dissolved oxygen levels of and phosphorus, for example, may cause several reasons. Circulation patterns cre- about 5.0 mg/ liter are generally consid- an increase in the rate of eutrophication ate "nutrient traps" which act to retain ered necessary, however, to maintain a which, in turn, can eliminate desirable and recirculate nutrients. Water move- healthy environment over the long term. species, encourage the growth of obnox- ments remove wastes and transport food ious algae, and cause low dissolved oxy- enabling organisms to maintain a pro- The effects of temperature on the estu- gen conditions from the decay of dead ductive existence. The constant forma- arine system are also extremely impor organisms and other materials. Rela- tion of detrital material creates a form of tant. Since the waters of Chesapeake tively little is known about the quan- "self-enriching" system. Finally, the es- Bay are relatively shallow compared to tities of specific nutrients necessary for tuary benefits from a diversity of pro- the ocean, they are more affected by the healthy functioning of individual ducer plant types which together pro- atmosphere temperature conditions. species, or more importantly, of bio- vide year-round enegy to the system. Generally speaking, the annual temper- logical communities. Chesapeake Bay has all three types of ature range in Chesapeake Bay is between producers that power the ecosystems of 01 and 290 C. Because the mouth of the the world: macrophytes (marsh and sea estuary is close to the sea, it has a rela- While it is necessary to keep in mind the grasses), benthic microphytes (algae tively stable temperature as compared interactions of these physical and chem- which live on or near the bottom), and with the upper reaches. Some heat is ical variables when studying Chesapeake phytoplankton (minute floating plants). required by all organisms for the func- Bay, these parameters should not, in tioning of bodily processes. These pro- fact, cannot be addressed separately. Like the aquatic plant communities, the cesses are restricted, however, to a par- The Bay ecosystem is characterized by aquatic communities are not spread ticular temperature range. Temperatures the dynamic interplay between many homogeneously throughout the Bay, above or below the critical range for a complex factors. As a simple example, Although the entire estuary serves as particular species can be fatal unless the the levels of salinity and temperature nursery and primary habitat for finfish, organism is able to move out of the area. will both affect the metabolism of an spawning areas are concentrated in the Temperature also causes variations in aquatic organism. In addition, both areas of low salinity and freshwater in water density which plays a role in strat- salinity and temperature can cause a the Upper Bay and corresponding por- ification and non-tidal circulation as drop in the oxygen concentration in the tions of the major tributaries. The north- discussed earlier. water and thus an increase in the required ern part, including the Chesapeake and respiration rate of the organism. While Delaware Canal, is probably the largest Light is necessary for the survival of it is true the effects of these variables of all spawning areas in the Bay. This plants because of its role in photosyn- individually may be of a non-critical area plus the upper portions of the thesis. Turbidity, more than any other nature, the combined (or synergistic) Potomac, York, Rappahannock, James, physical factor, determines the depth effects of the three stresses may be severe and Patuxent Rivers, contains about 90 light will penetrate in an estuary. Tur- to the point of causing death. These percent of the anadromous fish (i.e., bidity is suspended material, mineral three parameters, in turn, also interact those which ascend rivers from the sea and/ or organic in origin, which is trans- with other physical and chemical varia- to reproduce) spawning grounds in the ported through the estuary by wave bles such as pH, carbon dioxide levels, Chesapeake Bay Region. Some of the action, tides, and currents. While the the availability of nutrients, and numer- fish that use the Bay as a nursery include absence of light may be beneficial to ous others. The subtle variable of time striped bass, weakfish, shad, alewife, some bottom dwelling organisms since may also become critical in many cases. blueback herring, croaker, menhaden, they can come out during day-light The important point is that the physical and kingfish. In addition to Chesapeake hours and feed in relative safety this and chemical environment provided by Bay's large resources of finfish and shell- condition limits the distribution of plant Chesapeake Bay to the indigenous biota fish, the marshes and woodlands in the life because of the restriction of photo- is extremely complex and difficult, if not area provide many thousands of acres of synthetic activity. This restriction of impossible, to completely understand. natural habitat for a variety of water- plant life (especially plankton in the fowl, other birds, reptiles, amphibians, open estuary) will reduce the benthic and mammals. (i.e., bottom dwelling) and zooplankton THE BIOTA populations which in turn will reduce OF CHESAPEAKE BAY POPULATION fish productivity. The estuary is biologically a very special The majority of the inhabitants of the place. It is a very demanding environ- Chesapeake Bay Area are concentrated ment because it is constantly changing. in relatively small areas in and around Nutrients are the minerals essential to The resident plants and animals must be the major cities. Approximately 90 per- the normal functioning of an organism. able to adjust to changes in physical and cent of the population resided in one of In Chesapeake Bay, important nutrients chemical parameters. The requirement the Region's seven Standard Metropoli- include nitrogen, phosphorus, carbon, for adjustment to the almost constant tan Statistical Areas (SMSA) in 1970. iron, manganese, and potassium. It is ecological stress limits the number of The number of urban dwellers increased 9 by almost 1.5 million during the 1960- ing in the Chesapeake Bay Region is transformed into a severe storm in as 1970 decade while the rural population caused by either hurricanes or "north- little as six hours. Most northeasters remained virtually the same. People easters." Hurricanes which reach the occur in the winter months when the have tended to move out of the inner Middle Atlantic States are usually temperature contrasts between the con- cities and rural counties and into the formed either in the Cape Verde Region tinental and maritime air masses are the suburban counties. Thirty-five of the 76 or the western Caribbean Sea and move greatest. The East Coast of the United counties and major independent cities in westerly and northwesterly. In most States has a comparatively high inci- the Study Area experienced a net out- cases these storms change to a northerly dence of this type of storm, with the area migration during the 1960-1970 period. and northeasterly direction in the vi- near Norfolk, Virginia, being one of the On the other hand, most of the subur- cinity of the East Coast of the United centers of highest frequency. ban counties experienced growth rates States. in excess of 30 percent and in-migrations In the course of recorded history, the of at least 10 percent of their 1960 popu- As a hurricane progresses over the open Chesapeake Bay Region has been sub- lation. In the Bay Region as a whole, net water of the ocean, a tidal surge is built jected to about 100 storms that have in-migration accounted for about one- up, not only by the force of the wind and caused damaging tidal flooding. The third of the 1.5 million increase in popu- the forward movement of the storm accounts of most of the storms that lation during the decade of the 1960's. wind field, but also by differences in occurred prior to 1900 are very brief and Most of this in-migration was in re- atmospheric pressures accompanying are usually found only in early news- sponse to large increases in employment the storm. The actual height reached by paper articles and private journals. The opportunities in the Bay Region. a hurricane tidal surge and the conse- elevation and the area inundated by quent damages incurred depend on these early tidal floods was seldom accu- In 1970, there were approximately 3.3 many factors including shoreline con- rately documented and it was not until million people employed in the Study figuration, bottom slope, difference in the early part of the 20th century that a Area. About 91 percent of these worked atmospheric pressures and wind speed. program to maintain continuous records in one of the Region's seven SMSA's. Generally, the tidal surge is increased as of tidal elevations was initiated. The During the 1960-1970 period, total the storm approaches land because of damages and loss of life suffered during employment increased by about three- both the decreasing depth of the ocean these early floods also is not well quarters of a million jobs or approxi- and the contours of the coastline. An documented. mately 30 percent. The National gain additional rise usually occurs when the during the same period was 19.5 percent. tidal surge invades a bay or estuary. Shown in Table 2 are the recorded tidal Tidal surges are greater and the tidal elevations at several locations for the Compared to the Nation as a whole, the flooding more severe in coastal com- most severe floods that have occurred in Bay Region has a lower proportion of munities which lie to the right of the this century. It should be noted that the workers in the blue-collar industries, storm path due to the counterclockwise relative severity of flooding varies around such as manufacturing and mining, and spiraling of the hurricane winds and the the Bay since it is a function of changes a higher proportion in the white-collar forward movement of the storm. in storm paths and variances in climato- industries, such as public administra- logical and astronomical tide conditions. tion and services. Since employment in "Northeaster" is a term given to a high the white-collar industries tends to be intensity storm which almost invariably The hurricane of 23 August 1933 was the less volatile, the Study Area has had develops near the Atlantic Coast. These most destructive ever recorded in the consistently lower unemployment rates storms form so rapidly that an appar- Bay Region. The hurricane center en- over the last several decades than the ently harmless weather situation may be tered the mainland near Cape Hatteras, Nation as a whole. Also contributing to these stable employment levels are the TABLE 2 large numbers of workers whose jobs depended on relatively consistent spend- RECENT CHESAPEAKE BA Y STORMS ing by the Federal government. This section has provided only a brief Tidal Elevations overview of the environmental and (Feet Above National Geodetic Vertical Datum) socio-economic characteristics of the Storms Norfolk Mid-Bay Washington Baltimore Chesapeake Bay Region. A more de- tailed discussion of the Bay Region is August 1933 8.0 7.3 9.6 8.2 found in Supplement A of the Summary September 1936 7.5 - 3.0 2.3 Report - Problem Identification. October 1954 "Hazel" 3.3 4.8 7.3 6.0 PROBLEMS, NEEDS, August 1955 "Connie" 4.4 4.6 5.2 6.9 AND OPPORTUNITIES August 1955 "Diane" 4.4 4.5 5.6 5.0 April 1966 "Northeaster" 6.5 2.8 4.0 3.3 Since man first settled on the shoreline March 1962 "Northeaster" 7.4 6.0 - 4.7 of the Chesapeake Bay, he has been sub- ject to the human suffering and millions of dollars of property damage resulting from tidal flooding. Serious tidal flood- 10 TABLE 3 passed slightly west of Norfolk, Virginia, and continued in a northerly direction TIDA L FL 0 OD DA MA GES passingjust east of Washington, D.C. It (Damages in S1,000's, 1979 dollars) moved at or near the critical speed for producing the maximum surge, and its Oct 1954 Aug 1955 time of arrival coincided with the astro- Location Aug 1933 "Hazel" "Connie" Mar 1962 nomical high tide as it proceeded up- stream. The results were tides ranging Baltimore Metro Area $32,700 $ 9,600 $16,000 from 8.0 feet above National Geodetic Washington Metro Area 16,700 6,700 400 Vertical Datum (NGVD) at Norfolk to Maryland 15,800 12,600 as high as 9.6 feet NGVD at Washing- Norfolk Metro Area 11,800 $ 6,700 ton, D.C. In addition to flooding dam- Virginia 34,300 age, the high winds associated with this storm generated very destructive waves *Negligible which caused extensive shoreline erosion. Shown in Table 3 is an estimate of the damages that were caused by the four TABLE 4 most damaging storms that have passed through the Bay Region. The estimates CHESAPEAKE BA Y A REA FLOOD-PRONE COMMUNITIES reflect the actual physical damages that STATEOFMARYLAND occurred, updated to reflect 1979 price levels. They do not include allowances Anne Arundel County for development that has taken place in *Arundel on the Bay Caroline County St. Mary's County the flood plain since the storm occurred. *Avalon Shores (Shady Side, Choptank Colton Curtis Pt. to Horseshoe Pt. Denton *Piney Point SELECTION OF and West Shady Side) Federalsburg St. Clement Shores Broadwater St. George Island COMMUNITIES FOR Columbia Beach Cecil County DETAILED STUDY *Deale Elkton Somerset County Eastport Northeast *Crisfield Existing flood problem areas were iden- Franklin Manor on the Bay *Smith Island tified by considering the degree of tidal and Cape Anne Charles County flooding that would be experienced by Galesville Cobb Island Talbot County those communities located along the Rose Haven Easton shoreline of the Bay and its tributaries. Dorchester County Oxford The initial step in the analysis was to Baltimore City *Cambridge *St. Michaels identify all Bay communities with a *Tilghman Island population of 1,000 or greater that are Baltimore County Harford County located either in total or in part within Back River Neck Haure de Grace Wicomico county the Standard Project Tidal Flood (SPTF) *Dundalk (Including Bivalve Plain. The Standard Project Tidal Flood Sparrows Pt.) Nanticoke is defined as the largest tidal flood that is *Middle River Neck Kent County *Salisbury likely to occur under the most severe *Patapsco River Neck *Rock Hall combination of meteorological and hy- Worcester County drological conditions that are consid- Calvert County Queen Anne's County *Pocomoke City ered reasonably characteristic of the Cove Point Dominion *Snow Hill geographic region. The Corps of Engi- North Beach on the Bay *Grasonville neers in cooperation with the U.S. Solomons Island Stevensville Weather Bureau (now the National Weather Service) determined that, for COMMONWEALTH OF VIRGINIA the Chesapeake Bay Region, the SPTF Independent Cities would average approximately 13 feet *Fredericksburg King George County Northampton County above National Geodetic Vertical Datum *Hampton *Dahlgren *Cape Charles (NGVD). The above figure is a static or Newport News standing water surface elevation which *Norfolk King William County Westmoreland County would occur in conjunction with an *Portsmouth Beach *West Point *Colonial Beach astronomical high tide and does not *Virginia Beach include the effects of waves. Wave heights *Chesapeake are dependent upon wind speed and direction, depth of water, fetch (the dis- Accomack County tance the wind blows over the water in Onancock WASHINGTON, D.C, York County generating the waves) and the length of Saxis *Poquoson time the wind blows. Assuming average *Tangier Island values for water depth and fetch and *Indicates "critically" flood-prone communities. superimposing winds characteristic of a of land that takes place during tidal TABLE 5 hurricane that would produce a tidal storms, instead of the damages that surge of 13 feet above NGVD, wave result from temporary inundation of CRITICAL COMMUNITIES heights on the Bay could be 5 feet. Based house and property. Application of non- RECOMMENDED FOR on the above combination of tidal surge structural solutions in these same areas, DETAILED STUDY and wave action the SPTF would inun- such as floodproofing and relocation, is (In the Revised Plan of Study) date all areas up to approximately 18 also inappropriate. Many of the struc- feet above NGVD. Because average tures are old and not suitable for major STATEOFMARYLAND conditions were used in determining the floodproofing modifications. Further- SPTFelevation and forease in delineat- more, these areas were established adja- Baltimore Count), Somerset CountY ing the flooded area, an elevation of 20 cent to the shoreline to take advantage Dundalk (including Crisfield feet NGVD was assumed for purposes of the resource, thus making relocation Sparrows Pt.) Smith Island of the analysis. unacceptable. Baltimore Citi, Talbot Count "i, St. Michaels The next step in the flooding analysis Based on the above considerations, the Caroline CountY Tilghman Island was to identify those communities that communities recommended for detailed Denton Wicomico Countr should be classified as "flood-prone." In study in the Revised Plan of Study were Dor(hester CountY Salisbury order for a community to be designated limited to those listed in Table 5. All of Cambridge as flood-prone, at least 50 acres of land the recommended communities were Worcester Count -t, that were developed for intensive use considered to have highly developed Kent County Pocomoke City had to be inundated by the SPTF. flood7prone areas where the potential Rock Hall Snow Hill Intensive land use was defined as resi- existed for providing some form of dential (four dwelling units/acre or flood protection. The Revised Plan of COMMONWEALTH OF VIRGINIA greater), commercial (including institu- Study further recommended that Stage tional), or industrial development. The 11 Studies be conducted and that they Independent Cities King William CountY Chesapeake West Point Bay Region communities indentified as concentrate on refinement of environ- Fredericksburg flood-prone are shown in Table 4. mental, economic, social and hydrologic Hampton Northampton Count), Approximately 82,000 acres of land in data and the formulation and evalua- Norfolk Cape Charles these communities were located in the tion of various flood damage reduction Portsmouth Westmoreland Countr Standard Project Tidal Flood Plain. measures. Accomack Couno, Colonial Beach The last step in the initial screening, pro- With the approval of the Revised Plan Tangier Island York CountY cess was to determine those communi- of Study, Stage 11 studies were initiated Poquoson ties considered to be "critically" flood- for the communities listed in Table 5. As prone. The flood problem was consid- a result of these initial studies several ered to be "critical" if 25 acres or more of additional communities were eliminated provide flood protection for the most intensively developed land were inun- from further consideration. Smith Is- flood-prone sections of these two areas dated by the 100-year flood. Those land, Maryland, and Colonial Beach would have benefit-cost ratios on the communities found to be "critical" based and Virginia Beach, Virginia, were elim- order of only 0.1. These evaluations on the above criteria are marked with an inated as detailed studies of these com- confirmed the findings of the Baltimore asterisk in Table 4. It should be noted munities were being conducted under District's Baltimore Metropolitan Flood that the elevations used for the I 00-year specific study resolutions and any fur- Study. flood were approximated based on the ther effort under the Chesapeake Bay best available historical information. Program would have been duplicative. As a result of this screening process, Denton and Salisbury, Maryland, were communities were selected for detailed During the preparation of the Revised both eliminated when preliminary stage- study and are listed by state in Table 6. Plan of Study, a further screening of damage surveys and more detailed Because of the areal expanse of the Bay those critical communities listed in mapping and flood plain delineation Region, and because of the jurisdic- Table 4 was conducted. This screening indicated that the flood problem was tional location of these communities, eliminated those communities where it limited to only scattered development at the Baltimore District, Corps of Engi- was evident that flood protection would frequencies in excess of once in 100 neers requested the Norfolk District to not be acceptable to the community. years. Likewise, Fredericksburg, Virgin- conduct the detailed tidal flooding analy- This determination was based on the fact ia, was eliminated when fluvial rather ses in the Commonwealth of Virginia that many strictly residential communi- than tidal flooding was found to be the while the Baltimore District investigated ties are located along the Bay's shoreline problem. the Maryland communities. Figure 4 for aesthetic as well as recreational rea- indicates the general location of these sons and a structural solution would Last and most significantly, Baltimore communities along the Bay Estuary. require, in most cases, a flood wall of City and the Dundalk area of Baltimore excessive height. This type of structure County were also eliminated after pre- Detailed flood damage surveys were would impact upon the use of the shore- liminary damage surveys and an evalua- conducted in 1979 in these flood-prone line for recreation and would cause vis- tion of several structural and nonstruc- communities. Following the completion ual disruption of the shoreline environ- tural measures. These preliminary eval- of preliminary alternative analyses and ment. In these communities, the ex- uations indicated that both structural other environmental and socio-economic pressed concern is related to the erosion and nonstructural measures that would studies, a report was prepared in August 12 Rtm CAD cow BALTMAORE: Akw oc POMMO pa WASHMTON D.C. t. Ichael ew lighman a Cambrid ...... ...... SALMURY n 7w Co o 'City iqrisf, Tangier Is West, Point Cape r Poqpq on Nor- a m P*t ds. Figure 4 Critical Flood-Prone Communities 13 TABLE 6 damage surveys for each of the 12 criti and wildlife including waterfowl, ro- cally flood-prone communities were dents deer, fox, and other species. The TIDAL FLOOD-PRONE done in the summer and fall of 1983. grassy' water areas in and around Cris- COMMUNITIES EXAMINED field are important nursery areas for PROFILES OF FLOOD- fingerling fish and shellfish. MARYLAND VIRGINIA PRONE COMMUNITIES In 1970, Crisfield had a population of Cambridge Cape Charles 3,075 with more than 50 percent 35 years Crisfield Hampton Roads' Cambridge, Maryland of age or older. Population has been Pocomoke City Poquoson declining in this area for several dec- Rock Hall West Point Cambridge is located in Dorchester ades. Most of the labor force in the Cris- Snow Hill Tangier Island County in the central part of Maryland's field area is employed in the Wholesale St. Michaels Eastern Shore on the Choptank River: and Retail Trade sector, the Operatives Tilghman Island the boundary between Dorchester and sector, and the Manufacturing sector. 'The Hampton Roads designation includes the Talbot Counties. Elevations in the com- Unemployment in Crisfield is typically cities of Chesapeake, Hampton, Norfolk, and munity range from zero to 30 feet NGVD. above the State average. Portsmouth, Virginia. Cambridge supports a variable oyster fishery during the fall and winter, and a The community of Crisfield is approxi- blue crab fishery during the summer and mately 2,100 acres in size and approxi- fall. The Choptank River is one of the mately 50 percent of the community is more important waterfowl areas in the subject to tidal flooding. The commu- 1980. Based on the findings it was Upper Chesapeake and supports large nity may be subjected to high velocity recommended that more detailed stud- populations of several varieties of ducks flooding as a result of the direct assault ies of several selected communities and and geese. of waves. With the presence of a major the development of Baywide stage-fre- Bay harbor in Crisfield, there is the quency relationships be continued. A Cambridge had a 1970 population of potential for high debris content in Technical Studies Work Plan detailing 11,595 which represented a 5.2 percent flood waters if boats break loose or if the stage-frequency related work was decrease from 1960 population totals. waterfront structures are battered by prepared and approved. In 1981 work The overwhelming majority of indus- waves in a major storm. was initiated on the stage-frequencY trial employment in Cambridge was in analyses and the support storm surge the Manufacturing Sector (39.7 percent) The 100-year flood hazard zone (5.1' test was conducted on the hydraulic followed by the Wholesale and Retail NGVD) covers about 938 acres of the model in 1982. This test consisted of Trade Sector (17.1 percent). U nemploy- community. Of this area 73 percent (683 obtaining surface water elevations ment in 1970 was approximately five acres) is currently developed. The 500- throughout the Bay resulting from the percent. year flood hazard zone (6.1' NGVD) ocean tide, a surge wave, a combination covers about 1,283 acres. Of this amount of the above two, and fluvial discharge. There are an estimated 3,400 acres within 71 percent (913 acres) is currently devel- The results of this test were to be used to the community of Cambridge. The 100- oped. The Crisfield flood plain is primar- adjust and calibrate a numerical storm year flood hazard zone (5.9' NGVD) ily residential in character with some surge model being developed by the covers about 70 acres of the community. non-residential development. Table 8 Waterways Experiment Station. Of this area, 76 percent (53 acres) is summarizes the type of development in currently developed. The 500-year flood various flood hazard zones. About 85 During the development of the Fiscal hazard zone (7.5'NGVD) covers about percent of the structures in the flood Year 1984 budget, the decision was 139 acres. Of this amount 88 percent plain are residential. made that the Chesapeake Bay Model (122 acres) is currently developed. should be closed and that the study should be completed by the end of Fiscal The Cambridge flood plain is mainly Pocomoke City, Maryland Year 1984. Because of this, a number of residential in character with the non- significant modifications were made to residential development located primar- Located on the Pocomoke River, Poco- the program. The storm surge numerical ily on the waterfront. Table 7 sum .ma- moke City is situated in the southwest modeling effort was deleted from the rizes the type of development in various program and all feasibility analyses were flood hazard zones. About 80 percent of portion of Worcester County about five based on existing available flood stage- the structures in the flood plain are miles from the Virginia border. Eleva- frequency information rather than the residential. tions in Pocomoke City range from refined data expected from the numeri- about zero NGVD to almost 30 feet cal modeling effort. above NGVD. Temperatures in the area Crisfield, Maryland range from a low of 38 degrees (F) in The major effort remaining on the Tidal January to a high of nearly 77 degrees Flooding Study consisted of reviewing Crisfield is the southern most city in (F) in July. Precipitation averages about and revising the 1980 report based on Maryland. it is. located in Somerset 29 inches annually. The Pocomoke River updated information when available, In County on the Little Annernessex River, and adjacent wetland areas provide an an effort to verify that the results of the just off Tangier Sound. Elevations in excellent habitat for numerous water- analyses conducted in the 1978-1980 Crisfield range from zero to about 10 fowl, wildlife and fish species. Unique to period were still valid, field checks of the feet NGVD. Crisfield abounds with fish the region are several cypress swamps 14 TABLE 7 CAMBRIDGE FLOOD PLAIN INVENTORY (April 1980 Prices) APPROXIMATE NUMBER OF STRUCTURES AVERAGE STAGE FLOOD HAZARD ANNUAL (NGVD) ZONE RESIDENTIAL COMMERCIAL INDUSTRIAL PUBLIC&OTHER TOTAL DAMAGES 4 feet 12 year (8.2%) 0 2 2 0 4 $4,000 6 feet 120 year (0,82%) 60 14 2 0 76 $12,000 8 feet 500 year (0.20%) 139 29 3 0 171 $15,000 18 feet SPTF 359 50 3 0 412 $19,000 TABLE 8 CRISFIELD FLOOD PLAIN INVENTORY (April 1980 Prices) APPROXIMATE NUMBER OF STRUCTURES AVERAGE STAGE FLOOD HAZARD ANNUAL (NGVD) ZONE RESIDENTIAL COMMERCIAL INDUSTRIAL PUBLIC&OTHER TOTAL DAMAGES 4 feet 12 year (8.2%) 57 69 0 3 129 $40,000 5 feet 80 year (1.2%) 564 162 3 13 742 $102,000 6 feet 400 year (0.25%) 1,133 193 4 18 1,348 $129,000 12 feet 500 year (0.20%) 1,679 208 4 31 1,922 $146,000 TABLE 9 POCOMOKE CITY FLOOD PLAIN INVENTORY (April 1980 Prices) APPROXIMATE NUMBER OF STRUCTURES AVERAGE STAGE FLOOD HAZARD ANNUAL (NGVD) ZONE RESIDENTIAL COMMERCIAL INDUSTRIAL PUBLIC&OTHER TOTAL DAMAGES 4 feet 8 year (12%) 2 1 0 0 3 $5,000 5 feet 25 year (4%) 16 4 1 0 21 $8,000 6 feet 70 year (1.4%) 43 8 1 0 52 $12,000 8 feet 500 year (0.20%) 125 30 2 1 178 $20,000 18 feet SPTF 597 103 3 18 721 $25,000 located along the river. Pocomoke City's flood hazard zone (6.3' NGVD) covers portion of Kent County. Elevations in 1970 population of 3,573 was a 7.3 per- about 81 acres of the community. All of Rock Hall vary from zero to 25 feet cent increase over the 1960 total of this area is currently developed. The 500- above NGVD. The average summer 3,329. Pocomoke City is one of the older year flood hazard zone (7.8' NGVD) temperature in the area is approximately communities in the State with a median covers about 171 acres of which 84 per- 75 degrees (F) and in the winter temper- age of 34.5 years compared to the State cent (144 acres) is currently developed. ature averages 36 degrees (F). Precipita- median age of 27.1 years. Approximately tion in this portion of the Eastern Shore 26 percent of the work force was in the The Pocomoke City flood plain is pri- averages about 43 inches per year. Sales and Clerical category with 27 per- marily residential in character with large Because of water quality problems in cent of the industrial employment in the amounts of non-residential development. several areas around Rock Hall, the Wholesale and Retail Trade sector. Un- Table 9 summarizes the type of devel- biota is rather restricted. Rock Hall is a employment in 1970 was relatively low opment in various flood hazard zones. nursery area for finfish with the salt- at 4.7 percent of the work force. About 80 percent of the structures in the marshes on the inside of the breakwaters flood plain are residential. serving this purpose. Geese and swans There are an estimated 1,080 acres within constitute almost 90 percent of the the community of Pocomoke City. Poco- Rock Hall, Maryland waterfowl in the Chester River while moke City is subject to tidal flooding ducks account for the remainder. from the Pocomoke River. The 100-year Rock Hall is located in the southwestern 15 TABLE 10 ROCK HALL FLOOD PLAIN INVENTORY (April 1980 Prices) APPROXIMATE NUMBER OF STRUCTURES AVERAGE STAGE FLOOD HAZARD ANNUAL (NGVD) ZONE RESIDENTIAL COMMERCIAL INDUSTRIAL PUBLIC&OTHER TOTAL DAMAGES 4 feet 8 year (12%) 29 5 1 0 35 $3,000 6 feet 25 year (4%) 143 17 6 0 166 $17,000 9 feet 140 year (0.7%) 317 22 7 0 346 $47,000 12 feet 500 year (0.2%) 423 24 7 1 455 $63,000 18 feet SPTF 613 44 8 8 673 $76,000 TABLE 11 SNOW HILL FLOOD PLAIN INVENTORY (April 1980 Prices) APPROXIMATE NUMBER OF STRUCTURES AVERAGE STAGE FLOOD HAZARD ANNUAL (NGVD) ZONE RESIDENTIAL COMMERCIAL INDUSTRIAL PUBLIC&OTHER TOTAL DAMAGES 4 feet 8 year (12%) 1 2 0 0 3 $300 5 feet 25 year (4%) 4 8 1 0 13 $3,000 6 feet 70 year (1.4%) 13 14 1 0 28 $5,000 8 feet 500 year (0.20%) 62 22 3 1 88 $9,000 18 feet SPTF 414 62 5 14 495 $11,000 TABLE 12 ST. MICHAELS FLOOD PLAIN INVENTORY (April 1980 Prices) APPROXIMATE NUMBER OF STRUCTURES AVERAGE STAGE FLOOD HAZARD ANNUAL (NGVD) ZONE RESIDENTIAL COMMERCIAL INDUSTRIAL PUBLIC&OTHER TOTAL DAMAGES 4 feet 10 year (10%) 1 2 1 9 4 $4,000 5 feet 20 year (5%) 3 2 1 9 7 $6,000 7 feet 100 year (1%) 55 5 5 2 67 $10,000 9 feet 450 year (0.22%) 255 49 6 5 315 $17,000 16 feet SPTF 713 78 10 12 813 $27,000 TABLE 13 TILGHMAN FLOOD PLAIN INVENTORY (April 1980 Prices) APPROXIMATE NUMBER OF STRUCTURES AVERAGE STAGE FLOOD HAZARD ANNUAL (NGVD) ZONE RESIDENTIAL COMMERCIAL INDUSTRIAL PUBLIC&OTHER TOTAL DAMAGES 4 feet 15 year (6%) 47 4 2 1 55 $8,000 5 feet 40 year (2.5%) 99 10 2 1 112 $15,000 6 feet 90 year (I. 1%) 167 11 3 1 182 $21,000 8 feet 500 year (0.20%) 273 13 3 2 293 $31,000 15 feet SPTF 446 22 4 8 480 $36,000 16 Population in the Rock Hall area reached cantly higher than the State median age low at only 2.9 percent of the work 1,101 in 1970 which was a 2.6 percent of 27.1 years. A large portion of those force. increase over the 1960 total of 1,073. employed in Snow Hill are in low- The median age of 34.9 years also places skilled, low income occupations such as St. Michaels is approximately 620 acres Rock Hall among the older communi- the Operatives and the Sales and Cleri- in size and is subject to tidal flooding ties when compared to the State median cal categories. A large portion of the from the Miles River. The 100-year of 27.1 years. The majority of employ- work force is employed in the Manufac- flood hazard zone (7.2' NGVD) covers ment in the area occurs in the Wholesale turing sector. about 73 acres of the community. One and Retail Trade sector, followed by the hundred percent of this area is currently Construction and Manufacturing Snow Hill is approximately 750 acres in developed. The 500-year flood hazard sectors. size and is subject to tidal flooding from zone (9.2' NGVD) covers about 292 the Pocomoke River. The 100-year flood acres. Of this amount 76 percent (222 Rock Hall is approximately 860 acres in hazard zone (6.3' NGVD) covers about acres) is currently developed. size and is subject to the tidal flooding of 92 acres of the community. Of this area the Chesapeake Bay. The community 21 percent (19 acres) is currently devel- The St. Michaels flood plain is mainly may be subject to water of high velocity oped. The 500-year flood hazard zone residential in character with the non- as a result of the direct assault of waves. (7.8'NGVD) covers about 141 acres. Of residential development located primar- With the presence of a major Bay harbor this amount 28 percent (39 acres) is cur- ily on the waterfront and a main com- in Rock Hall, there is a potential for rently developed. The Snow Hill flood mercial street. Table 12 summarizes the high debris content in flood waters if plain is primarily non-residential in type of development in various flood boats break loose in a major storm. character. Table I I summarizes the type hazard zones. About 80 percent of the of development in various flood hazard structures in the flood plain are The 100-year flood zone (8.7' NGVD) zones. About 45 percent of the struc- residential. covers about 466 acres of the commu- tures in flood plains less than the 100- nity. Of this area 57 percent (266 acres) is year flood plain are residential. Tilghman Island, Maryland currently developed. The 500-year flood hazard zone (I 1.5'NGVD) covers about St. Michaels, Maryland Tilghman Island, in Talbot County, 529 acres. Of this amount 68 percent Maryland, is about 3.5 miles long and 1 (329 acres) is currently developed. St. Michaels is located in the eastern mile wide. It is separated from the main- part of Talbot County on the Miles land by Knapps Narrows. Elevations on The Rock Hall flood plain is mainly River. Elevations in the St. Michaels Tilghman Island range from zero NGVD residential in character with the non- area range from zero to 15 feet above to approximately 10 feet above NGVD. residential development oriented pri- NGVD. Because of its location in the Important commercial finfish species marily toward the waterfront. Table 10 middle latitudes, St. Michaels'climate is include striped bass, spot, weakfish, and summarizes the types of development in moderate. Summer temperatures aver- white perch. The area also serves as an the various flood hazard zones. About age 75.2 degrees (F) while the winter important concentration areafora great 90 percent of the structures in the flood season temperatures average 36.7 degrees variety of waterfowl and supports the plain are residential. (F). Precipitation in this area averages greatest local concentration of breeding 41.7 inches annually. black ducks in the region. Snow Hill, Maryland Significant wildlife habitat is located in The 1970 census indicated that the pop- Snow Hill is located 30 miles upstream the areas adjacent to the more than 600 ulation of Tilghman Island was 1,180. from the mouth of the Pocomoke River miles of county shoreline. Principal fin- The median age of the population was in central Worchester County. Eleva- fish species found in the waters around 34.6 years reflecting a population older tions in the Snow Hill area range from St. Michaels are striped bass, spot, weak than the State median age of 27.1 years. zero to 25 feet above NGVD. The aver- fish, white and yellow perch. Oyster bars Approximately 40 percent of the work age summer temperature of the county lie just outside the entrance to St. force was employed in the Operatives is 74.8 degrees (F) while winter tempera- Michaels Harbor. Waterfowl in the area category and at least 25 percent of the tures average 38.7 degrees (F). Precipi- consist of puddle ducks, Canada geese, industrial workforce was employed in tation in this part of the Eastern Shore and whistling swans. Osprey are also the Manufacturing sector. averages about 29 inches annually. Biota known to utilize the area with mourning in the area includes largemouth bass, doves and woodcock among the migra- The community of Tilghman is approx- black crappie, striped bass, branch tory game birds. imately 1,530 acres in size. Tilghman herring, hickory shad, whiteshad, pick- Island is subjected to tidal flooding from erel, and channel catfish. Puddle ducks St. Michaels 1970 population of 1,470 the Chesapeake Bay. The community use the area for nesting and feeding was a 0.9 percent decrease from the 1960 may be subjected to high velocity flood- while wood ducks are also found in the total of 1,494. The median age of the St. ing as a result of the direct assault of area. Michaels population was 35.8 years waves on development. With the pres- which was significantly higher than the ence of a major Bay harbor and water- The 1970 population of Snow Hill was State figure of 27.1 years. The majority front development in Tilghman, there is 2,201. This represented a 4.8 percent of industrial employment in St. Michaels the potential for high debris content in decrease over the 1960 total of 2,311. is the Manufacturing and Wholesale flood waters if the boats break loose in a The median age of the Snow Hill popu- and Retail Trade sectors. Unemploy- major storm or if waterfront property is lation was 33.3 years which was signifi- ment in St. Michaels in 1970 was very demolished. The 100-year flood hazard 17 TABLE 14 CAPE CHARLES A VERA GE ANNUAL DAMA GES (January 1983 Price Levels) Noe- Annual Total Flood Loss Damage Stage Probability A verage to Stage ............. $1,000 Elevation in Years Interval Interval Noted 4,i I' cy 11,753.00 12.00 0.00 $37,423 5,247.00 10.00 1,000.00 0.100 $8,500 28.923 2,748.00 9.00 300.00 0.233 9,328 19,595 610.00 8.00 100.00 0.667 11,193 8,402 238.00 7.40 50.00 1.000 4,240 4,162 A 131.00 7.00 35.00 0.857 1,581 2,581 40.00 6.50 20.00 2.143 1,832 748 4.00 6.00 12.00 3.333 733 15 FIG URE 5 CA PE CHA RLESFLOOD SCENE SEPTEMBER 0,00 5.90 11.00 0,758 15 $0 1960 HURRICANE zone (6.1' NGVD) covers about 1,108 were commercial; and eight were public other large employment sectors. acres of the communitv. Of this area 21 structures. Average annual damage percent (236 acres) is currently devel- estimates are presented in Table 14. The The 100-year tidal flood stage is esti- oped. The 500-year flood hazard zone area has a temperate climate, with a 30- would be inundated by the 100-year (7.9' NGVD) covers about 1,397 acres. year average annual temperature of 57.8 stage still water level. Wave action would Of this amount 25 percent (355 acres) is degrees (F). Precipitation averages 42 raise the stage by four feet. Storm tides currently developed. inches annually with the heaviest rain- have penetrated several blocks into the fall occurring between June and developed sections of the town on a The Tilghman Island flood plain is September. number of occasions. The water level of primarily residential in character with the 1933 storm reached a maximum ele- the non-residential development oriented vation of 7.0 feet in Cape Charles. The toward the waterfront. Table 13 sum- Several salt marsh habitats are located tidal surge created by the northeaster of marizes the type of development in var- in the vicinity of Cape Charles. The May 1962 reached an elevation of 7.2 ious flood hazard zones. About 90 per- waters in the area are highly productive feet. Figure 5 shows flooding in Cape cent of the structures in the flood plain and contain a variety of living natural Charles resulting from the September are residential. resources of commercial and recreational 1960 hurricane while Figure 6 presents importance. The surrounding land in- views of the bulkhead and beach areas Cape Charles, Virginia cludes agricultural fields, natural wood- immediately after the March 1962 storm lands, a golf course, and a limited amount and after emergency restoration. Cape Charles is an incorporated town of residential, municipal, and industrial located in Northampton County on the development beyond the immediate Cape Hampton Roads, Virginia western shore of the Delmarva Penin- Charles vicinity. sula approximately I I miles from the The Hampton Roads region of Virginia entrance of Chesapeake Bay. The area is represents a multiple city complex in relatively flat with elevations ranging southeastern Virginia centered about from zero to 12 feet NGVD with most Cape Charles' 1980 population of 1,512 Hampton Roads Harbor. This harbor is below eight feet. Cape Charles is the represents about 10 percent of the surrounded by the largest urban popula- largest town in the county in both land County population. The town's econ- tion concentration in Virginia. As one of area and population. Most of the devel- omy is based on farming, fishing, some the finest harbor complexes in the Unit- opment in Cape Charles has taken place tourism, and light industry. The greatest ed States, the area contains two major on the low ground near the water's edge. amount of manufacturing or industrial railroad terminals, shipbuilding and Almost the entire town is below the level employment is in fish and shellfish harv- drydock installations, military bases, of the standard project tidal flood which esting. According to the National Marine industrial companies, several deep water is at elevation 12 feet NGVD. A field Fisheries Service (NMFS), over 50 per- terminals for shipping and unloading survey performed for this community cent of Virginia's total surf clam land- cargo, and various other supportive included an inventory of 538 structures. ings were from Northampton County. enterprises for a major harbor. Termi- Of this total, 445 were residential, 85 Retail Trade and Services are the two nals are serviced by an extensive rail- 18 jot ,4 Cape Charles Beach and Promenade Cape Charles Beach and Promenade following March 1962 Storm after Emergency Retoration AW 4qQW FIGURE6 BEACH, BULKHEAD AND PROMENADE A T CAPE CHARLES - MARCH 1962 STORM road and trucking system for inland Existing marshes within the Hampton Chesapeake and Virginia Beach are transport. Roads complex are predominantly expected to grow 81.3 percent and 122.7 composed of salt marsh cordgrass percent, respectively, during the same The shorelands of Chesapeake, Nor- (Spartina alterniflora), salt grass (Dis- period. folk, and Portsmouth have elevations tichlis spicata) and other wetlands flora less than 20 feet, of which 75 percent is to a lesser degree. A variety of small Historical unemployment rates in the classified as low shore (20 ft. or less of mammals may be found associated with study area have remained below U.S. relief) and 25 percent being artificial fill the wetland sites. These areas will also levels. In 1982, the rate was 6.6 percent (Owen, et al., 1976). The artificial fill is have significant populations of resident for the Norfolk-Virginia Beach- associated with the various large dock- and migratory waterfowl and other birds. Portsmouth SMSA and 7.2 percent for ing facilities and the Craney Island Dis- population densities vary and become the Newport News-Hampton SMSA. posal Area which is located at the more diversified where marshes are Employment within the area is related entrance of the Elizabeth River. Owen, bordered by undisturbed woodland sec- to the major economic activities of the et al. (1966) characterizes the shoreline tions. The marshes and adjacent sand two SMSA's. These will continue to be as being 39 percent artificially stabil- (and mud) flat areas also contain a vari- port, military/ Federal government, and ized, but includes in his figures a stabil- ety of invertebrate types, including shell- manufacturing operations. Also the ser- ized portion of the Norfolk beach area fish. A variety of fish are alsopresent. vices industry is expected to experience outside the harbor entrance along the the most growth in the period 1980 to low Chesapeake Bay. However, a high The ports of Hampton Roads and the 2030. percentage of stabilized and/or bulk- services and activities associated with headed shoreline frontage is found within them have a profound influence on the NOrfolk Hampton Roads Harbor, especially in area's economy. Hampton Roads is the the industrialized and downtown areas leader in export tonnage and second Norfolk is located on the south shore of of Norfolk and Portsmouth. only to the port of New York in export- Hampton Roads and Chesapeake Bay. import tonnage in the United States. It is bound by water on three sides and is Along the north shore of Hampton The value of these exports increased penetrated by smaller estuaries making Roads is the city of Hampton with a from $1.8 billion in 1970 to $8.85 billion interior areas vulnerable to tidal land area of 55 square miles and an in 198 1. flooding. inland water area of 17.3 square miles. Hampton is boardered along its western The greatest increases in population are Approximately 75 percent of the land in side by the city of Newport News and to anticipated for Chesapeake and Vir,ain- Norfolk is below elevation 13.0 (the the east by the Chesapeake Bay. Several ia Beach. Based on census data for standard project flood) and 20 percent is small creeks and the Hampton River 1970 and 1980, Chesapeake grew by 27.8 below elevation 9.0. Minor flooding up enter Hampton Roads from the city's percent and Virginia Beach grew by 52.3 to elevations of four to five feet is asso- shoreline. Thirty-five percent of Hamp- percent. By comparison, Hampton grew ciated with periods of moderately high ton's entire shoreline has bulkheads or by only 1.5 percent while Norfolk and sustained winds from the northeast, % I-- seawalls. Combinations of shore protec- Portsmouth both lost residents. The north, and northwest and may be expe- tive structures including riprap, groins, Virginia Department of Planning and rienced several times within any one year. and bulkheaded property are common Budget expects the study area to grow Flooding of this magnitude is not serious along the shoreline. by 44.7 percent from 1980-2030 while and goes unnoticed except for the tem- 19 porary difficulties which may be expe- rienced by the boating interests due to wr rough seas. The main source of concern 7 -,1 is the large and infrequent floods which are associated with major storm events such as hurricanes or severe northeaster-type storms. Storm surges which, together with the normal astro- Fr nomical tide, produce elevations of six feet or higher cause widespread flooding in the city. Wave action has been responsible for most of the structural damage along the shore front. The disastrous hurricane of 23 August 1933 inundated about 600 acres in the downtown Norfolk area. The greatest concentration of damage occurred in the Central Business District where 52 acres, containing streets, stores, and FIGURE 7 FLOOD SCENE, MARCH 1962 "NORTHEASTER" business offices were flooded from I to ATNORFOLK, VIRGINIA 4.5 feet by salt water, polluted by indus- trial and sanitary wastes. High water blocked practically all movement to and featureless with land elevations seldom from the school at 5th and Jefferson from the central business district. Other exceeding 15 feet above NGVD. While Streets. Also, many persons including sections of the downtown area flooded some developments on the flood plain entire families, were evacuated from included 1 50 acres in the Hague area, are more susceptible to flood damage their homes on First and Second Streets. 140 acres in th Tidewater Drive area, than others, experiences gained particu- A number of roads were rendered im- and 72 acres in the waterfront area. The larly in the March 1962 northeaster storm passable for 2 days. Telephone and exposed beach resorts of Willoughby and the August 1933 hurricane, have electric power services were disrupted. and Ocean View felt the full fury of the shown that the flood problem is serious Along the Western Branch of Elizabeth storm. and that damage can be widespread River, much of the damage was sus- throughout the city. The August 1933 tained by boats and facilities. Several hurricane produced flooding to eleva- homes and businesses were flooded and During the March 1962 northeaster, tion eight throughout most of the city. one industry suffered additional loss more than 1,000 persons were evacuated from having to suspend operations for from the area along Chesapeake Bay. A Damage during smaller floods under the duration of the storm. Flood scenes few were also evacuated from other elevation five is confined to streets. typical of the March 1962 northeaster in areas. The flow of automobile traffic Resulting traffic problems are created. Portsmouth are shown in Figure 8, The was impeded by the flooding of streets, Also' there would be some minor flood- August 1933 storm caused extensive including access roads to tunnels. A ing of other low-lying property. How damage, inundating hundreds of acres photograph of one of the many areas ever, between elevations 5 and 10, there of the city including downtown com- flooded during the March 1962 storm is are large concentrations of commercial, mercial and industrial areas as well as shown in Figure 7. In Norfolk there are residential, and industrial buildings. It is residential areas. numerous other areas that experience within this zone that serious flood dam- occasional flooding. These areas lie along age has been suffered during past tidal Since then, the City of Portsmouth has rivers and creeks and are scattered floods and where the potential exists for closed streets, raised roads, and con- throughout the city. There is no plan to even greater loss in future floods. structed a floodwall that extends for a eliminate this situation that would be distance of 3,500 feet along the water- economically feasible. The city sustained a great deal of dam- front. The floodwall does provide some age during the 1962 northeaster, primar- protection to the downtown area. Sur- ily from flooding in several low areas face drainage behind the protective Portsmouth bordering on the Elizabeth River and works includes a number of openings Southern Branch. Three hundred and through the wall which have been pro- Portsmouth is located near the conflu- twenty houses and 20 commercial and vided with flap gates. However, there ence of the Western and Southern industrial businesses received damage in are questions as to whether the flap Branches of the Elizabeth River tidal various degrees from flooding to a depth gates in the floodwall would perform as estuary. Forming a part of the greater of water as much as 4-V2 feet. One thou- designed during a major tidal storm. Hampton Roads Harbor, Portsmouth sand automobiles were inundated. Fed- is a major port of call for oceangoing eral, state, and local agencies were active During discussions with the superin- vessels. during the emergency and in removing tendent of surveys in Portsmouth, one debris after the water subsided. Emer- problem area was discovered. It is land- Typical of Virginia's coastal plain, the gency operations consisted mainly in ward of Crawford Bay where many topography of Portsmouth is flat and evacuating children and other personnel homes have been restored. The concrete 20 year, elevation 8.5), and standard pro- ject tidal flood (elevation 13). High tides during the March 1962 storm entered into the Eastern and Southern Branches of Elizabeth River in Chesa- peake. No mass evacuation of people was required. However, many were MOEN forced to abandon their homes and businesses to avoid the high water. Hampton Hampton is located on the shores of Hampton Roads and Chesapeake Bay. Much of the land is below elevation 10 ---------- and there are developments in areas as low as elevation five. Generally, the ter Now-:- rain slopes fairly uniformly from the higher elevations to sea level. There are Waveriv Boulevard Between Court and Dinwiddie Streets no protective barriers such as sand of elevation five or higher, cause wide- spread flooding in the city, Many times in surrounding water areas. Consequently, an increase in the level of Chesapeake Bay and other bodies of water (which practically encompass the city) cause flooding of land masses to the same .:0 level. "72- N More than two-thirds of the land area of the city would be inundated by the standard project tidal flood (elevation the land area would be inundated by the 13) and approximately one quarter of 100-year tidal flood (elevation 8.5). It is estimated that about 20,000 people are located within the area affected by the latter flood. The Federal Emergency Management Agency has conducted a wave height study for Hampton. Wave Corner of Washington Street and Crawford Parkway heights that can be expected with the FIGURE8 FLOOD SCENES, MARCH 1962 "NORTHEASTER" 100-year flood on both the Chesapeake AT PORTSMOUTH, VIRGINIA Bay and the Hampton Roads sides would reach elevation 13. The main source of concern is the large and infrequent floods which are asso- bulkhead here is below elevation six. Flooding of that portion of the citv ciated with major storm events such as The city also has a problem with sand affected by the level of water in Chesa- hurricanes and severe northeast storms. depositing in Crawford Bay which blocks peake Bay occurs as a result of high Storm surges which, together with the the drainage outlets and mustbedredged water in the Elizabeth River and its normal lunar tide, produce water levels periodically. Southern and Western Branches. Storm of elevation five or higher, cause wides- surges, which together with the normal pread flooding in the city. Many times in Chesapeake lunar tide produce a water level of eleva- the past, the city has been essentially tion five or higher in the northern sec- paralized with practically all normal The topography of Chesapeake is typi- tion of the city, cause widespread flood- functions within the area brought to a cal of the flat Tidewater coastal plain in ing and produce damage. Floods this standstill because of such flooding. An which the city is located. Development high and higher have occurred many important factor to shorefront areas is Cal; consists generally of residences along times in the past. Also most major roads that high water is generally associated the northern boundary and'is* a contifi- and bridges would have areas wherein with high waves which have inflicted uation of the urban growth of the cities flooding will occur during both the structural damage to shorefront struc- of Norfolk and Portsmouth. intermediate regional tidal flood (100- tures and eroded sand and other mate- 21 _4 --- - --- rial from the beaches. Figure 9 shows 7 flooding that occurred in theHampton- Fox Hill area as a result of the March 1962 northeaster. A One area typical of Fox Hill was selected -4 4, for analysis. The data for the 61 struc- tures located in this area were evaluated through the use of a computer program 05 t and stage-damages were determined for existing conditions. These figures were 7' updated to January 1983 price levels. The damage-frequency relationship was based on the stage-damage curve com- piled for the area and the stage-frequency curve presented in Appendix E - Engi- a neering Design and Cost Estimates. The 14 W, resultant average annual damages up to any tidal flood stage are presented in 1W-7'- Table 15. Poquoson, Virginia 4 The City of Poquoson is located on the w estern shore of Chesapeake Bay in the area known as the Lower Peninsula of Virginia. The city is bounded on the 77- north by the Poquoson River, a tidal , 4 - . - . inlet of Chesapeake Bay. There are FIGURE9 FLOODING INHAMPTON-FOX HILL numerous creeks along the northern SECTION, MARCH 1962 shoreline, with Bennett Creek being the largest and most significant harbor. The eastern shore is bounded by a tidal marsh bordering the Chesapeake Bay. TABLE 15 This marsh, referred to as Plum Tree Island is about 1.1 miles wide and has HAMPTON-FOX HILL AREA ground elevations of less than five feet. AVERAGE ANNUAL DAMAGES On the south, the city is bounded by (January 1983 Prke Levels) Back River and its Northwest Branch. The mean range of tide is 2.4 feet. Annual Total Flood Loss The city is typical of most coastal com- Damage Stage Probability A verage To Stage munities in that practically all of the $1,000 Elevation In Years Interval Interval Noted existing development has taken place on 1,805.10 11.00 0 $100,098 the low ground near the edge of the water. Three-fifths of Poquoson is below 1,702.80 10.50 1,000.00 0.100 $1,754 98,344 elevation 5.0 including many developed 1,583.80 10.00 600.00 0.067 1,096 97,249 areas. Eighty-five percent of the city is below elevation 7.0 which is the level of 1,532.50 9.80 500.00 0.033 519 96,729 the 25-year flood, exclusive of wave 1,271.70 9.00 180.00 0.356 4,985 91,744 action. There are no tidal flood protec- tion measures in the city nor are there 1,093.00 8.50 100.00 0.444 5,255 86,489 any dunes along the Poquoson shoreline. 903.50 8.00 60.00 0.667 6,655 79,834 Poquoson has been one of the fastest 544.10 7.00 26.00 2.179 15,775 64,059 growing cities in the State, its popula- tion increasing from 4,278 in 1960 to 514.80 6.90 25.00 0.154 815 63,245 5,441 in 1970. The most recent census showed a 1980 population of 8,726. The 256.90 6.00 12.00 4,333 16,720 46,524 city is primarily residential in character. 75.60 5.00 4.60 13.406 22,287 24,237 Poquoson mainly serves as a residential base for citizens who commute tojobs in 3.10 4.00 1.20 61,594 $24.237 $0 the nearby larger cities, military bases, and Government installations. 22 4W Z iousl% stated. Poquoson is bor- _4r As pre% dered b-, the Poquoson River to the he Plum Tree Island Wildlife north. t Refuge to the east. and the North%16est Branch of the Back Ri%er to the south. This area contains numerous creeks. A& coves, and an extensive salt marsh. Beginning at Poquoson Shores at Hunts Neck, there is an extensi%Le tidal flat %% ith fringing marsh areas scattered along the shoreline. Scattered sandy beaches and FIGL*REIO FLOOD SCENE OF MARCH 1962 occasional piers may be seen. This patt- ".\'ORTHEASTER"ATPOQUOSON, VIRGINIA ern extends into Roberts Creek \%here the prominent wetlands vegetation is saltmarsh cordgrass (Spartina alierni- TABLE 16 flora), saltmeadow hay (Spariina pat- ens), and salt grass (Distichlis spicaia). POQUOSON AREA I Poquoson is bordered on the west by an A VERA GE A NNUAL FLOOD DAMA GES extensive acreage of natural woodland. (January 198.3 Price Levels) The city is scattered over a large area with no central core or city complex. Total Annual Loss This condition results in acreage of Damage Flood Probability A verage TO Stage woodland and land in various types of $1,000 Stage In Years Interval interval Noted agricultural use between parts of the 588.10 11.00 0 $3.258 city. However, the city is in a phase of 278.80 10.00 1,000.00 0.100 $433 2.824 burgeoning growth with numerous resi- dential homes under construction 257.40 9.80 500.00 0.100 268 2.556 throughout the city which infringe into the wooded sections. Of major signifi- 167.10 9.00 175.00 0.371 798 1. 7W cance is the Plum Tree Island Wildlife 79.20 8.50 100.00 0.429 529 I.M Refuge. Vast in size. this area is mainly salt marsh with stretches of well estab- 27.30 8.00 60.00 0.667 355 in lished pine growth on the higher ridges within the refuge. 17.00 7.00 25.00 2.333 517 368 0 6.00 12.00 4.333 $368 so Large sections of Poquoson have been subjected to tidal flooding in varying degrees of intensity many times in the TABLE 17 past. Past flooding indicated by high water marks has been as high as eleva- POQUOSON AREA H tion 9.0. Many developed areas are at A VERAGE ANNUAL FLOOD DAMAGES elevation 5.0 or below. During periods (January 1983 Price Levels) of high tidal flooding, the shoreline is subject to wave action across the low marsh areas and shallow inlets and Total Annual LOSS creeks. Damage Flood Probability A verage To Stage $1,000 Stage In Years Interval interval Noted The greatest known flood in the Poquo- 1,112.80 11.00 0 S15,021 son area occurred in August 1933. It was the result of a hurricane which swept 867.60 10.00 1,000.00 0.100 $990 14,030 northward past Poquoson on a path 782.10 9.80 500.00 0.100 825 13,206 along the axis of Chesapeake Bay. Max- imum tide heights during this flood 563.10 9.00 175.00 0.371 2A" 10,707 reached elevation 9.0, based on high water marks, with an average height of 415.80 8.50 100.00 0.429 2,ON 8,610 about 8.3. 280.80 8.00 60.00 0.667 2,322 6,288 Another great flood in March 1962, the 80.00 7,00 25.00 2.333 4,209- 2,078 result of a northeaster, was the second largest ever recorded at Poquoson. This 11.50 6.00 12.00 4.333 1,983 % flood, although the second largest in 0 5.80 10.00 1.667 $96 so height of stage reached, was the most severe of record in terms of monetary damage along the Virginia coast. 23 TABLE 18 The danger of becoming trapped in one's home in this type of flood is very POQUOSON AREA III real. A VERA GE ANNUAL FLOOD DAMAGES In 1980, a field survey was made of this (January 1983 Price Levels) community. This included a field inves- Total Annual Loss tigation, a study of the available maps, Damage Flood ProbabilitV A verage To Stage and an inspection of the city. A damage- $1,000 Stage in Years Interval Interval Noted frequency relationship was developed based on the stage-damage curves com- 2,437.80 11.00 0 $66,477 piled for the area, and the Corps stage- 2,142.80 10.00 1,000,00 0.100 $2,290 64,187 frequency curve. The total average an- nual damages for any tidal flood stage 2,079.00 9.80 500.00 0.100 2,111 62,076 for the four areas of Poquoson that were 1,666.80 9M 175.00 0.371 6,956 55,119 investigated are shown in Tables 16-19. 1,366.20 8.50 100.00 0.429 6,499 48,620 Tangier Island, Virginia 1,080.70 8.00 WOO 0.667 8,156 40,464 Tangier is an island, 3.5 miles long and 1 556.40 7.00 25.00 2.333 19,100 21,364 mile wide, located in the lower half of Chesapeake Bay. The town is part of 145.30 6.00 12.00 4.333 15,204 6,161 Accomack County. The 771 inhabitants live on three ridges on the island known 118.80 5.80 10.00 1.667 2,201 3,960 as West Ridge, Main Ridge, and Canton 0 5.00 6.00 6.667 $3,960 so Ridge. Their homes are wood frame construction or trailers. The residents usually earn their living from the sea. This includes sportfishing and shell fish- TABLE 19 ing was well as an extensive crab industry. POQUOSON AREA Il A VERA GE A NNUA L FL OOD DA MA GES Tangier Island is triangularly shaped (January 1983 Price Levels) and is composed of three distinct bodies of land. The two larger components lie Total Annual Loss along a north-south axis, approximately Damage Flood Probability A verage To stage 2.8 miles long, divided about mid-point $1,000 Stage In Years Interval Interval Noted by the Tangier North Channel, with the entire island 1.6 miles in width. To the 11,287.60 11.00 0 $416,631 east and adjacent to Mailboat Harbor is the third portion, identified as East 9,814.50 10.00 1,000.00 10.100 $10,551 406,080 Point Marsh. 9,306,00 9.80 500.00 0.100 9,560 396,519 East Point Marsh is a small marsh 7,732.70 9.00 175.00 0.371 31,643 364,876 island of about 110 acres. It contains a few buildings, a large dredge-material 6,633.00 8.50 100.00 0.429 30,784 334,092 disposal area, and approximately 67 to 80 acres of saltmarsh interspaced with 5,380.80 8.00 60.00 0.667 40,046 294,046 numerous standing ponds and small 3,107A0 7.00 25.00 2.333 99,029 195,017 creeks. Along the northeastern side of this island, severe shore erosion has 1,403.40 6,00 12.00 4333 97,734 97,283 been taking place. Waters that are of shallow and intermediate depth along 425.30 5.00 6.00 8.333 76,196 21,087 the island's eastern margin became deeper within a mile, with depths in- 20.20 4.00 4M 8.333 18,562 2,525 creasing into Tangier Sound. 0 3,00 2.00 25.000 $2,525 $0 The most developed and populated por- tion of the Tangier Island group is that area located south of the Tangier North Hundreds of homes were flooded, some A flood that may be expected once in Channel (Tangier South). Consisting of approximately 385 acres, Tangier South by as much as two to four feet. By the 100 years (although it could occur more is characterized by three parallel ridges nature of its development, damages were often and in any year) would inundate that are bordered and separated by low widely dispersed in the area, and the almost the entire city. In some residen- land saltmarsh. The roads, various flood losses amounted to $500,000. One tial areas of the city, there would be four buildings, and all the houses have been scene of flooding in this area is shown in feet of water or more that would be constructed on these higher elevated Figure 10. standing in the yards and on the roads. ridges. Between the three ridges are two 24 pA16 - r 1VW OW AJ N, _44 FIGUREII FLOOD SCENE AT TANGIER ISLAND, MARCH1962 this storm. In 1980, a diligent search was TABLE20 made by the staff of the Norfolk District Office for high water data on past tidal TIDAL STA GE-DAMA GE DA TA FOR TANGIER ISLAND floods. As can best be ascertained, the (Corps of Engineers Frequencies) 1933 tidal flood reached an elevation of January 1983 Price Levels about 7.0 feet above mean sea level. According to the U.S. Geological Sur- Total Annual Loss vey, the three ridges that are inhibated Damage Flood Probabilio, A verage To Stage now are below elevation 5.0 as are the S1,000 Stage In Years Interval Interval Noted salt marshes that surround the island. Thus, a major storm that would inundate 7,643.00 11.00 0.00 $481,734 the entire island (south) would threaten the safety and lives of the entire popula- 6,978.00 10.00 1,000.00 0.100 $7,310 474@423 tion. Escape by boat, helicopter, or plane to the mainland would not be 6,811.00 9.80 500.00 0.100 6,894 467.529 practical. 6,023.00 9.00 175.00 0.371 23,835 443,694 Tangier Island is subject to tidal flood- 5,445.00 8.50 100.00 0.429 24,574 419,120 ing - the extent of which is dependent on the still water stage. Stage-frequency 4,708.00 8.00 60.00 0.667 33,843 385,277 relationships for the Island have been developed by both the Corps and the 3,315.00 7.00 25.00 2.333 93,602 291,675 Virginia Institute of Marine Science (VIMS). Based on the Corps data, the 1,940.00 6.00 12.00 4.333 113,858 177,817 100-year tidal flood elevation of 8.5 1,683.00 5.80 10.00 1.667 30,192 147,625 would inundate the entire island and all structures would be damaged. Damage 847.00 5.00 6.00 6.667 84,333 63,292 to residential and commercial property would exceed $1.3 million. Based on the 246.00 4.00 4.00 8.333 45,542 17,750 VIMS frequency relationship which was developed using a two dimensional depth 28.00 3.00 3.00 8.333 11,417 6,333 integrated numerical model, the 100- year tidal flood would have a stage of 4.1 12.00 2.00 2.00 16.667 3,333 3,000 and cause only $68,000 in damage. Using 0.00 1.00 1.00 50.000 $3,000 $0 the Corps frequency data, events ex- ceeding the 100-year tidal flood would create a serious problem. The lives of some islanders would be threatened and 298 residential, 25 commercial and seven creeks that extend across the length of The people of Tangier indicated that public buildings would receive major the island. These creeks further divide they do not mind the high tide that damage. into various waterways into the marsh. comes up to the roads. The last time that The southern end of this island is basi- they had an unusually high water level Based on field surveys, the stage-damage cally all saltmarsh and tidal flats with a was during the March 1962 storm, a relationship was established for all sand spit extending from the western scene of which is shown in Figure 11. structures on Tangier Island. The margin to form Code Harbor. Very few houses were flooded during damage-frequency relationship was de- 25 veloped based on the stage-damage rela- Considerable marsh development is also northeaster on 7 March 1962 or 6.46 feet tionship and the Corps stage-frequency present along the Pamunkey and upper above mean low water or 5.5 feet above curves. The average annual flood dam- York Rivers.. At these sites, alternate mean sea level. According to the Coast ages for Tangier Island are presented in sections of fringe marsh with broad and Geodetic Survey, the height of Table 20. patches of salt marsh vegetation are flooding at West Point is somehwat West Point, Virginia common. A few pound net stakes may higher than at Gloucester Point. In a be seen in both the lower Mattaponi and storm tide of the 1962 magnitude, it is West Point, an incorporated town with Pamunkey Rivers, but no extensive difficult to determine the exact height at a 1980 population of 2,725, is located in fishery was noted. Accretion at a rate of West Point. The range for this storm is King William County on the west side of approximately 1.3 feet per year, is esti- estimated to vary from 5.7 to 6.4 feet Chesapeake Bay. It lies at the conflu- mated along the eastern shoreline of with an average of about 6 feet above ence of the Mattaponi and Pamunkey West Point. However, along the western mean sea level. Rivers and the upper end of York River, shoreline, there is slight erosion of 0.8 33 miles upstream from Chesapeake foot per year between Eltharn Bridge The plant engineer for The Chesapeake Bay. The mean range of tide is 2.8 feet. and the southern end of the City (Hobbs, Corporation resided in West Point dur- et a]., 1975). ing the August 1933 hurricane. He stated West Point is a wholesale and retail that the water reached a stage from I I trading center. It is also the nucleus of to 12 feet at The Chesapeake Corpora- an industrial complex which includes a Data on the heights of past major storms tion plant. This is based on a depth of 5 large paper manufacturing plant - The at West Point are lacking. The Virginia to 6 feet of water over the basement Chesapeake Corporation of Virginia. State Water Control Broad installed a floor of the power plant which is at ele- This plant occupies the left bank of the gage in September 1968, but it was vation 6.41 feet. Undoubtedly, this un- Pamunkey River from 14th Street north removed recently. usual height was due to the 1 -to 2-mile for about 0.8 mile. width and 22-foot depth of the York The U.S. Coast and Geodetic tide gage River with wind driving the waters up- West Point connects with Interstate 64 at Gloucester Point has been in exist- stream in the 33-mile fetch of river to by Virginia Highway 33, a four-lane ence since 1952. The highest tide West Point. concrete road eight miles long that observed was about 7.9 feet during the crosses both the Mattaponi and Pamunkey Rivers. Water to the town and to the Chesapeake Corporation is supplied by wells. The sewerage system includes secondary treatment for both the Town of West Point and Chesa- peake Corporation. Power is supplied TABLE 21 by the Virginia Electric and Power Company. WESTPOINTA VERAGEANNUAL FLOOD DAMAGES (CORPS FREQUENCY) A large portion of the city is surrounded January 1983 Price Levels - on three sides by water. To the north and landward, there exists a 2eneral Total Annual Loss rural setting with woodlands, agricultur- Damage Flood Probabilii v A verage To Stage al lands,, a few roads, and limited resi $1,000 Stage In Years Interval Interval Noted dential development. Common field 3,505.80 11.00 0 $62,477 crops include corn, soybeans, wheat, and other grains. Local timerland owners 2,072.30 10.00 1,000.00 0.100 $2,789 59,688 develop large amounts of Loblolly and Virginia pine, which are sold as saw- 1,821.60 9.80 500.00 0J00 1,947 57,741 timber, piling, and pulpwood. The low 1,149.60 9.00 175.00 0.371 5,518 52,223 land bordering the river systems con- tains large areas of wetlands. The shore- 910.80 8.50 100.00 0.429 4,415 47,808 line around the city also contains patches of wetlands marsh, plus stretches of 699.70 8.00 60.00 0.667 5,368 42,440 bulkheaded property. Piers and docking 363.10 7.00 25.00 2,333 12,399 30,040 facilities are also scattered around the shoreline, 205,10 6.00 12.00 4.333 12,311 17,729 Fringe and more extensive marsh acre- 84.00 5.00 6.00 8.333 12,046 5,683 age is present to West Point Creek and 13.10 4.00 4.00 8.333 4,046 1,638 beyond to Lord Delaware Bridge on Virginia Highway 33. Moving farther 0 3.00 3.00 25.000 $1,638 $0 up the Mattaponi River, large stands of salt marsh vegetation and fringe sec- tions occur on both sides of the river. 26 0 The value of output resulting from external economies associated with TABLE 22 a plan. WEST POINT A VERA GE ANNUAL FLOOD DAMA GES The components of the EQ objective (VIMS FREQUENCY) included: - January 1983 Price Levels - 0 Management, protection, enhance- Total Annual Loss ment, or creation of areas of natu- Damage Flood Probabilitv A verage To Stage ral beauty or human enjoyment. $/,000 Stage In Years Interval Interval Noted 0 Management, preservation, and/ or 1,148.40 9.00 0 $25,591 enhancement of especialiv valuable 542.50 7.60 1,000.00 0.100 $845 24,745 or outstanding archaelogical, his torical, biological, or geological re- 364.30 7.00 500.00 0.100 453 24,292 sources and ecological systems. 205.90 6.00 120.00 0.633 1,806 22,486 0 Enhancement of quality aspects of 198.00 5.90 100.00 0.167 337 22,150 water, land, and air by control of pollution or prevention of erosion 130.70 5.40 50.00 1.000 1,644 20,506 and restoration of eroded areas. 83.20 5.00 21.00 2.762 2,954 17,552 0 Avoiding irreversible commitments 11.90 4.00 3.00 28.571 13,586 3,967 of resources to future needs. 0 3.00 1.00 66.667 $3,967 $0 The NED objective sought to achieve the maximum net benefits from a Na- tional viewpoint, while the EQ objective sought to maximize environmental bene- fits (and the least amount of adverse impacts) measured primarily in non- monetary units. In formulating alterna- Elevations were established by the Corps the objectives provided the yardstick tive plans to maximize these National at street intersections at and below 15th against which the alternative plans were objectives, trade-offs occurred. These Street. The Chesapeake Corporation measured. Two levels of objectives were trade-offs were considered with refer- ence to the without condition. When plant, practically all of the area (240 considered important for the Chesapeake I acres) at and below elevation 10.0 feet is Bay Tidal Flooding Study: National plans were to be finalized, the impacts located downstream from 15th Street. planning objectives and study planning and trade-offs of each were tabulated to About 70 acres and 25 buildings are on objectives. aid decision-makers in selecting a pro- ground which is at or below the 5-foot gram for further consideration. contour. Approximately 100 buildings National Planning Objectives The Principles and Standards promul- are located on the 40 acres between the I gated by the Water Resources Council 5-and 10-foot contours. The remaining Guidelines for the formulation and eva - provided the basis for the water resourc- land located in this urbanized area below uation of plans of improvement for all es planning procedures followed during 15th Street is not more than a foot above Federal water and related land resource the Tidal Flooding Study. The Tidal elevation 10.0 feet. activities were contained in the Water Flooding Study was initiated and con- Resources Council's "Principles and ucted under these guidelines and the The probable future damage from tidal Standards for Planning Water and Re- findings and conclusions presented re- flooding was estimated exclusive of the lated Land Resources," established pur- flect the Principals and Standards. It damage to be sustained by The Chesa- suant to Section 103 of the Water Re- should be noted, however, that on 9 peake Corporation. A damage-frequency sources Planning Act (P.L. 89-80). These September 1992, the WRC repealed the relationship was developed based on the Principles and Standards required that Principles and Standards and, in their state-damage by the Corps and/ or VIMS. Federal and Federally-assisted water place, established new "Principles and The total average annual damages for and land activities be planned toward Guidelines." any tidal flood stage for West Point are achievement of National Economic presented in Tables 21 and 22. Development (NED) and Environmen- The major change resulting from the tal Quality (EQ) as co-equal national implementation of the Principles and Statement of Planned objectives. The components of the NED Guidelines is that the co-equal national Objectives objective included: objectives of NED and EQ have been ut of combined into one Federal objective. Planning objectives were established to 9 The value of increased outp The Federal objective of water and guide the formulation and evaluation of goods and services resulting from a related land resources planning is to flood protection plans. Simply stated, plan. contribute to national economic devel- 27 opment consistent with protecting the water-based recreational opportu- provides the basic constraints as to the Nation's environment, pursuant to na- nities. scope and geographic area of study. tional environmental statutes, applica- Based on the findings presented in the ble executive orders, and other Federal * Maintain, enhance, and / or increase Existing and Future Conditions Reports, planning requirements. the commercial and sportfishing the scope of the final phase of the study opportunities and resources. was further limited to studies of tidal Study Planning Objectives flooding and low freshwater inflow as * Maintain or improve water naviga- recommended in the Revised Plan of Within the framework of National ob- tion facilities which provide trans- Stud 'v and as discussed in previous jectives, a second level of planning ob- portation advantageous to the Na- paragraphs. jectives was developed which related to tion's transportation system. the problems, needs, concerns, and op- portunities of the specific study area. 9 Reduce tidal flooding damages. Study planning objectives are expres- sions of public and professional con- 9 Reduce damages due to shoreline cerns about the future use of water and erosion. related land resources. They were de- rived through an analysis of the existing * Develop power facilities where its resource base and the expected future provision can contribute to a needed conditions within the study area. The increase in power supply. purpose in defining study planning ob- jectives was to establish "targets" to * Control the occurrence of certain guide the formulation of alternative aquatic plants where they interfere plans and to enable evaluations of the with man's use of the Bay. plan effectiveness. Planning objectives sometimes conflicted with each other, * Maintain or improve adequate out- reflecting different perceptions of how lets for approved on-farm drainage the water resources should be managed systems for surface water manage- in the future. ment. During the early phase of the planning As they related more directly to the tidal process, the planning objectives were flooding problem, which is the subject general in scope and often many in of this report, the following are the spe- number. Based on the existing and fu- cific planning objectives that were iden- ture problems, needs, and opportunities tified for the communities under study. identified during the initial iterations of the planning process, including the * Protect life and property. preparation of the Chesapeake Bay Existing Conditions and Future Condi- 0 Reduce flood damages and health tions reports, the following were recom- hazards due to flooding. mended as planning objectives for the Chesapeake Bay Study program: 9 Minimize adverse impacts on cul- tural resources and the natural � Preserve, restore, and enhance the environment. integrity of the Chesapeake Bay ecosystem. 9 Minimize adverse impacts on aes- thetic values and community co- � Manage, preserve, and enhance hesion. areas of significant natural, histori- cal, cultural, and scientific interest * Avoid inducing any additional flood for the inspiration, enjoyment, and plain damages. education of man. Planning constraints are those physical, � Assure sufficient quantities of water environmental, social, economic, and to meet the needs of domestic, institutional boundaries which define municipal, industrial (including the limits of study. The broad institu power plants), and agricultural tional constraints on the planning proc- users. ess are embodied in a large volume of law, regulation and policy. These con- � Assure water of suitable qualities straints form the framework in which for all intended or potential water water resources projects are conceived, resource uses. developed and evaluated. As it related to the Chesapeake Bay Study, the study � Maintain, enhance, and/or increase authority which was quoted in Chapter I 28 CHAPTER III Formulation of Flood Protection Plans Plan Formulation Rationale the appropriate Federal interest rate of 71/8 percent(FY 1980) or77/8 The analysis of plans considered in pre- percent (FY 1983). liminary planning was based prim.arily 3. Interest during construction was on technical and economic criteria to not included in the economic anal- facilitate early identification of those ysis because it was either not ap- plans which were not justified. Subse- plicable or it would not effect the quent plan formulation was based on technical, economic, and intangible cri- economic feasibility of a plan. teria, including beneficial and detrimen- Environmental and Social tal effects on the environment. These criteria permitted the development of Well-Being Criteria plans of improvement which represented the best response to the stated planning Environmental and social well-being objectives. criteria considered in the plan formula- tion process included the following: Technical Criteria I . Loss of life and property and The following technical criteria were hazards to health and safety should adopted for use in formulating the plans be eliminated. considered in those communities under study: 2. Archaeological, historical, aesthetic, geological and ecological resour- I .Flood protection should be de- ces should be preserved, main- signed to provide protection against tained or enhanced. the 100-year tidal flood (approxi- mately equal to the flood of record) 3. Community cohesion and desir- and up to the 500-year tidal flood, able community growth should be if practicable. preserved, maintained or enhanced. 2. Flood protection design criteria, The following sections of this chapter such as freeboard requirements provide a general presentation of the and design features, should be management measures considered in compatible with the existing site plan formulation and an analysis of all conditions, available materials and plans considered. Included is a general the type of structure selected. overview of the criteria used in develop- ing the plans as well as descriptions of 3. The plans developed should be the plans. For additional information engineeringly feasible. on the development of these plans, refer to Appendix B - Plan Formulation, Economic Criteria Assessment, and Evaluation; Appendix E - Engineering Design and Cost Es- The economic criteria which were a timates; and Appendix F - Economics. plied in the plan formulation studies included the following: Management Measures I .Tangible and intangible bene- As required by the Principles and fits should exceed costs. Standards, co-equal consideration was given to both structural and nonstruc- 2. Benefits and costs should be ex- tural protection measures as a means of pressed in comparable quantita- solving flood-related problems. In an tive economic terms based on either effort to identify potential measures a 50- or 100-vear project life and which could address one or more of the 29 specific planning objectives, a broad Other Structural Measures pending on the type of structure, foun- range of measures was identified during dation composition, and height of rais- development of the Plan of Study and Other types of structural measures that ing, various measures may have to be early in Stage 11. Most of the measures can be employed along coastal areas to employed. These measures may include were carried forward in the Stage 11 provide protection from tidal flooding such items as physically raising the planning. include sand dunes and breakwaters. superstructure, provision of a new Dunes along the coast can prevent the foundation and basement walls, utility The following sections discuss those movement of storm tides and waves into additions, and landscaping. management measures which were in- the area behind the beach. Breakwaters vestigated in detail. Several of the mea- can serve to provide protection from Utility Room Addition sures presented were quickly eliminated waves thus creating harbors of refuge This alternative consists of relocating all based on engineering and/or economic criteria and are so noted. Fu'rther dis- and protection for harbor facilities. basement utilities to a wood-frame util- Given both the nature of the tidal flood- u cussion of these structural and non- ity room constructed adjacent to the structural measures can be found in ing and the communities under study, home at the first floor level. This addi- Appendix E - Engineering Design and further consideration was not given to tion reduces part of the damages in the Cost Estimates. these two measures. basement by moving those utilities sub- ject to damage to a less frequently flooded location. Levees and Floodwalls Floodproofing Relocation Levees and floodwalls, while differing in Floodproofing is a combination of design, appearance and cost, serve essen structural changes and adjustments to Relocation of a structure to a site out of tially the same purpose. Both are con- structures and building contents which the flood plain involves physically mov- structed near the shoreline to protect are designed to reduce flood damages. ing the structure a reasonable distance landside development from inundation Although it is more simply and econom- to a prepared flood-free site of compara- by tidal floodwaters. A substantial re- ble value. The costs of house relocation ically incorporated into new construc- duction in both nuisance and major tion, floodproofing is also applicable to have been developed on the premise that tidal flooding problems can be realized existin structures that are structurally the Corps will administer all the neces- with these structural measures. The levees sound. 9A preliminary inventory of the sary contracts to include moving the examined consisted of earth embank- communities under study revealed that superstructure, razing the abandoned ments having a top width of approxi- most residential and some older com- site, preparation of a new site, and mod- mately 10 feet and side slopes of I on 3. mercial buildings that may require flood- ifying the house as necessary to accom- The waterside face of the levee is armored proofing were of metal or wood frame modate the move. with stone where appropriate to prevent construction and therefore not able to wave damage. Levees are generally less withstand the hydrostatic forces. Con- Acquisition and Demolition expensive than floodwalls and are par- versely, several of the new commercial ticularly applicable where construction buildings constructed of concrete block Acquisition and demolition includes re- materials are available and there is suffi- were capable of incorporating flood- location of the homeowner, the pur- cient area between the shoreline and the proofing measures rather easily. There- chase of a particular structure at a fair area to be protected. Floodwalls are fore, consideration was given to only and reasonable price, demolition of the generally concrete with vertical faces basement floodproofing of residential structure and restoration of the site by and, because of their cost, are used in structures and commercial floodproof- filling, grading and seeding where re- areas where close proximity of the de- ing of structurally sound structures. quired. It should be noted that the esti- velopment precludes the construction of Basement floodproofing consists of rais- mates developed for this alternative in- levees. ing the superstructure of residential clude an allowance for costs associated structures, removal of the existing foun- with the Uniform Relocation Assistance Seawalls, Bulkheads, dation including basement walls, con- and Real Property Acquisition Policies and Revetments struction of a new reinforced concrete Act of 1970. substructure with waterstops, provision Seawalls, bulkheads, and revetments Of check valves in the storm and sanitary Flood Warning and Evacuation are structures placed parallel to the lines, and landscaping. Commercial Early in the study, a flood warning and shoreline to separate a land area from a floodproofing includes the floodproof- evacuation plan was identified as a water area. These struc .tures serve to ing of the first floor and/ or basement by potential tidal flood control alternative. both retain the land behind them and provision of a floodwall, flood shields, Hurricane tidal-flood damages can be provide protection from wave damage. waterproofing compounds, back flow reduced by the provision of improved Generally, these structures are used valves and sump pumps. forecasting and warning services, and where it is necessary to maintain the the establishment of evacuation plans. shore in an advanced position relative to Raising A hurricane warning system, combined that of adjacent shores, where there is with emergency mobilization, would aid little or no protective beach or where it is This alternative consists of raising the in the prevention of loss of life and of desired to maintain a certain depth Of elevation of the basement and/or first damage to items which are readily mov- water along the shoreline. floor of a damage-prone structure. De- able, but would not prevent the actual 30 flooding of properties. Further study tection against the 40- and 120-year junction (Point A) to the vicinity of the revealed that the National Weather Ser- flood events in the same area as the junction of Route 358 and Crisfield vice has a "self-help" program for coor- structural plans. The nonstructural mea- Park Road (Point Q. A shorter plan dinating and developing flood warning sures which comprised these plans in- (Point A to Point B) was also consid- systems in conjunction with local gov- clude floodproofing, provision of utility ered. These structural plans were de- ernments. In addition, it was found that additions and acquisition and demoli- signed to provide protection with free- the National Ocean Survey has received tion of some structures. Approximately board against either the 80-year (5.0 ft. the authority to study, in detail, flood 16 and 30 structures are impacted for the NGVD) or the 400-year flood (6.0 ft. warning and evacuation along the coast- 40- and 120-year plans, respectively. NGVD). al regions of the United States under the NOAA Coastal Hazards Program. Ac- Crisfield, Maryland The two nonstructural plans consist of COTdingly, detailed investigation of flood utility additions, relocation, acquisition warning and evacuation plans was not Four structural and two nonstructural and demolition, and floodproofing. deemed appropriate. plans of protection were considered for Nearly 200 structures would be involved. Crisfield. The structural plans were These nonstructural plans would be Flood Insurance combinations of earth levee and flood- undertaken in the same area as the struc- wall totaling approximately four miles tural plans. Protection to both elevation Although flood insurance does not re- in length. As shown in Figure 13, one 4.0 feet NGVD (12-year flood) and ele- duce flood damages, it does provide line of protection would reach from the vation 5.0 feet NGVD (80-year flood) some compensation for flood damages Route 380 - Johnson Creek Road was considered. which have been suffered. All the com- munities under study in the Bay area Figure 12 Cambridge Plans of Improvement became eligible for flood insurance in 1974 under either the regular or the emergency programs authorized by the Flood Disaster Protection Act of 1973 and administered by FEMA. Residents of the communities may purchase flood insurance under this program and ac- 4,X cordingly, there was no need to investi- JS, so gate this measure. No Action One nonstructural option that must Q obviously be considered is that of "NO ACTION." There will be numerous flood-prone structures that, because of their structural condition, level and fre- CHOPTAtIK quency of expected flooding or other R I V E R HICH ST. factors, will not be recommended for YACHT CLUB any type of structural or nonstructural BOA flood protection. BASIN Description of Plans Considered Cambridge, Maryland A total of eight plans of protection were CAMBRID6F considered for Cambridge. Six of the plans were structural and the remaining two were nonstructural. The structural GUY plans consisted of combinations of earth MARSH levees and concrete floodwalls which provide two degrees of flood protection to the urban area between Pinks Pond (Point A) and the eastern shore of Cam- A bridge Creek (Point D) as shown in Fig- LEGEND ure 12. These structural plans were Pins POND SCALE 1"@ 1160' designed to provide protection with three Levee & Floodwall Protection feet of freeboard against either the 120- NOTE: Letters (A,B,etc.) Denote Beginning year flood or the event approximating & Ending Of Various Alternatives the 500-year flood. The two nonstructur al plans were designed to provide pro- 31 4, HE . 7 Rock Hall. The structural plans were combinations of earth levees and flood- -:ZO -667, walls designed to provide protection with freeboard against either a stage of DRT AIRP, 9.0 feet NGVD (140-year flood) or 12.0 ANES #&A_ - feet NGVD (approximate 500-year ISLAND 11 flood). As shown in Figure 15, several different alignments were investigated. DAUGHERTY TOWN It Consideration was given to protecting W 11 lb A' the Gratitude area as well as Rock Hall. It should be noted that for the higher S E degree of protection, levee segment F-G HOPEWELL C, is required in order to prevent flooding PARK from Grays Inn Creek. 358 The four nonstructural plans examined @N' CD 3JACK NVILLE@ 413 consisted of utility additions, reloca- ions, acquisition and demolition and 0 6t floodproofing. The total number of structures affected would range between 60 X CASH1 30 and 170 all of which are located in 417 both Rock Hall and Gratitude. Four S levels of protection were considered including protection against the 15, 25, 'CRISFIIE D 50 and 80-year floods. Snow Hill, Maryland C CRISFIELOU- OUNTRYL @380 A total of seven plans of protection were considered for Snow Hill. Four of the X, 1> plans were structural and three were '@5_ C"F, nons tructural. The four structural plans V WN consist of approximately 7,000 feet of levee and floodwall which would pro- I 'N z vide protection with freeboard against either a 70-year (elevation 6.0 feet NGVD) or an approximate 500-year 1@@ j@ILAWSOV:-' (elevation 8.0 feet NGVD) flood. As LEGEND- shown in Figure 16 nearly the entire community of Snow Hill would be pro- SCALE Mile tected by the plans considered. Levee & Floodwall Protection The three nonstructural plans would NOTE: Letters (A,B,etc.) Denote Beginning & Ending Of Various Alteraatives provide protection for the same general area as the structural plans and are Figure 13 Cri@field Plans qf Improvement designed against the 25-year (5.0 feet NGVD), 70-year (6.0 feet NGVD) and the 220-year (7.0 feet NGVD) floods. The measures employed would include relocation, acquisition and demolition, Pocomoke City, Maryland The three nonstructural plans were and floodproofing. designed to provide protection for the A total of five plans of protection were same general area as the structural plans St. Michaels, Maryland considered for Pocomoke City. Two of against the 25-year (5.0 feet NGVD), the plans examined were structural and 70-year (6.0 feet NGVD) and 220-year A total of four plans of protection (two three were nonstructural in nature. The (7.0 feet NGVD) floods. The measures structural and two nonstructural) were two structural plans consisted of ap- conside'red included providing utility considered for St. Michaels. The struc- proximately 10,000 feet of levee and additions, relocation, acquisition and tural plans consist of combinations of floodwall which provide protection with demolition, raising and flo-odproofing. earth levees and floodwalls which would freeboard against either a 70-year (eleva provide varying degrees of protection tion 6.0 NGVD) or 500-year (elevation Rock Hall, Maryland for the entire community of St. Michaels. 8.0 NGVD) flood. As shown in Figure The alignment of the plans considered is 14 nearly all of the low lying portions of Six structural and four nonstructural shown in Figure 17. Plan SM-1 would Pocomoke City would be protected. plans of protection were considered for be constructed in two parts (Point A to 32 j0_- V;.@7 @@7; z 5, U s, 7 4V 4o 0 If P C 0 M 0 K E CI T Y LEGEND SCALE1 880' Levee & Floodwall Protection NOTE: Letters (A,B,etc.) Denote Beginning & Ending OF Various Alternatives FIGURE14 POCOMOKE CITY PLANS OF IMPROVEMENT 33 ROCKHALL F=== GRATITUDE SECTION . ......... . D ... ............ ROCK HALL SECTION At I 73! ilk LEGEND SCALE 1 1140' Levee & Floodwall Protection NOTE: Letters (A,B,etc.) Denote Beginning & Ending Of Various Alternatives FIGURE15 ROCKHALL PLANS OF IMPROVEMENT 34 Point B and Point C to Point D) and would provide protection against a flood with a recurrence interval of once in 100 years (elevation 7.0 feet NGVD). Plan Q SM-2 would be one continuous line of protection between Points A and D and would protect against the 450-year flood I (elevation 9.0 feet NGVD). The two nonstructural plans were ap- piled in the entire St. Michaels commu- /y nity and were designed to protect against the 45-and 100-year floods (elevations 6.0 and 7.0 NGVD, respectively). The measures considered included . utility LJ additions, raising, acquisition and "/V demolition, and floodproofing. Tilghman Island, Maryland Four structural and three nonstructural g@ plans of protection were considered for Tilghman. As shown in Figure 18, Knapps Narrows separates Tilghman Island from the mainland. Considera- T SNOW H I LL tion was given to providing protection @K '@T LEGEND to the residential and commercial devel- SCALE 1" 1145' opment north of the Narrows (northern 41@ Levee Floodwall Protection section) and also the communities of Tilghman and Avalon which are located NOTE: Letters (A,B,etc.) Denote Beginning & Ending Of Various Alternatives on the Island itself (southern section). FIGURE16 SNOWHILL PLANS OF IMPROVEMENT Two levels of protection (90 and 500- A year event) were investigated for both the northern and southern sections (six feet and eight feet NGVD, respectively). Nonstructural plans were considered for both the northern section and the entire island. Measures considered included relocation, acquisition and demolition, raising and floodproofing. Three design IL levels to include protection against the 15,40 and 90-year floods wereevaluated (four feet, five feet, and six feet eleva- tions, respectively). Cape Charles, Virginia In Cape Charles, the analysis of structur- al measures were limited to investigating several modifications that could be made to the existing bulkhead that is located adjacent to Bay Avenue (Figure 19). Providing nap gates and ty;ng into high ground at each end of the existing bulk- head would in effect provide protection S T. M ICHAELS to the stillwater 100-year flood level. The measures could be considered for implementation by the Town of Cape LUE END Charles. S 'W CkLE I' z750" Levee & Floo4wall protection Consideration was given to four non- NOTE: Letters (A,B,etc.) Denote Beginning structural plans that provide protection & Ending Of Various Alternatives against the 35-year (elevation 7.0 feet FIGURE17 ST. MICHAELS PLANS OF IMPROVEMENT 35 IrI Tilghma 'r . - @. t,- 33' NORTHERN SECTION BM SOUTHERN "SECTION AValo Tilghman Island L.,nd,log 4 73@ 9M 6 TI L, G H M A 6 I S LA N D Upper Bar Neck oint 10% Fairbank BM- x TILGHMAN 6 o-er ISLAND Blackwalnu d@ Lower Bar Neck Point Cove LEGEND SME l-r 2000' Levee & Floodwall Protection NOTE: Letters (A,B,etc.) Denote Beginning & Ending of Various Alternatives Blackwalnut Point FIGURE18 TILGHAfANISLAND PLANS OF IMPROVEMENT 36 N ---------- __j a asks: a, is v : 0 0 a EXISTINO 000afteft Owasso BULKHEAD a 0 Is, .090 .:*am as AND GROINS 0 goal a Fas ou .64000.0 a town @@iso 40 *aaa's a do 1. @ 0. as: 0 -om a a" -0006 assooso :018. . (-. I 4 a i : a 4:.Oo. sees loss so a.* 0. 1 6. .46 -**so mar go- at, see Cape Charles Harbor 0 L 0 1AW Harbor a a it q Z it it LEGEND INTERMEDIATE REGIONAL TIDAL FLOOD (100 YEAR) STANDARD PROJECT TIDAL FLOOD 1000 0 1000 20" SCALE(APPROX.) FEET FIGURE19 CAPE CHARLES AREA FLOOD MAP 37 NGVD) and the I 00-year (elevation 8.0 sures and four specific areas were inves- and 100 years. The plans under study feet NGVD) floods. Measures consid- tigated in detail (Figure 22). affected as few as nine structures (Plan ered included raising houses and build POQ-3, 25-year event) and as many as ings, utility additions, and flood proof- (1), POQ-1 - primarily a commercial 383 structures (Plan POQ-4, 100-year). ing. The area considered for these plans area. included the flood plain (35-or 100-year) Tangier Island, Virginia for the entire community. (2) POQ-2 - a trailer court area. Both structural and nonstructural plans Hampton Roads, Virginia (3) POQ-3 - a typical area with homes were investigated for Tangier Island. of above average value. One structural plan consisted of provid- For the purposes of this study, a com- ing a floodwall around each of the three plete investigation was not conducted (4) POQ-4 -an area of moderate value ridges (West Ridge, Main Ridge and on the feasibility of structural measures homes in the central Poquoson Canton Ridge - see Figure 23) of high in the entire Hampton Roads area. area. ground where all the development is Rather, several small typical areas within located. Each of these walls would be Norfolk and Hampton were investigated The types of nonstructural measures built to the 100-year flood level plus relative to the applicability of structural considered included relocation, raising, three feet of freeboard. A second struc- measures. and acquisition and demolition. The plans tural plans was to surround the com- were designed against floods having munity center or school with a flood wall Four areas along the Lafayette River a recurrence interval of once in 10, 25, designed to provide protection against and Wayne Creek in Norfolk (Figure 20) were investigated to determine the feasibility of constructing tidal flood barriers at the four points where existing bridges crossed these small tidal streams. Based on field investigations, the above 7L, _4 plans were not found to be practicable and no further analyses are included in this report. A fifth location investigated was the Fox Hill area of Hampton (Fig- ure 2 1). The structural'protectibn consid- ered was a 6,200-foot floodwall that protected approximately 50 structures to the 100-year flood level. r As with the structural measures, no investigations were made of the entire Hampton Roads area relative to the feasibility of nonstructural plans. How- WEI ever, the Fox Hill area was chosen as a sample area for nonstructural plans. Wmdw PO.,t P orr Based on a field survey of the 379 struc- tures in Fox Hill, a sample area which includes 61 homes was selected for study. Two nonstructural plans which provided 25-and 100-year levels of protection for these 61 homes were developed. The nonstructural measures considered con- sisted solely of raising the existing LEI structures. Poquoson, Virginia A 00 Based on field investigations and a Ad review of the nature of the topography and the flood problem, it is concluded at this time that structural measures for the protection of Poquoson are not practi- cable. An exception would be the flood proofing of the Middle School or con- struction of a wall to enclose the struc- ture, if necessary, to a level approaching the elevation of a rare flood. Considera- FIG URE 20 HAMPTON ROADS CITY COMPLEX STRUCTURAL SITES tion was given to nonstructural mea- IN NORFOLK CONSIDERED-NOT RECOMMENDED 38 4 'Ro 4 ... ....... @j, itl C6 dop Roo4 01 Hole I % RES IL /f oLighthoun (Abond) to Vi [email protected] S It\ Z S vv awAri po ol H' 3 Gmnd View LEGEND I Ase. 1,'Zh t, Area of detailed study Ir K Cemr Vt 'K cs: r $000 000 1000 SCALE FEET S, WIPTON ROADS CITY COMPLEX STRUCTURAL AND % W 'm NONSTRUCTURAL STUDY AREA IN HAMPTON FIG URE 21 HAMPTONR ADS-FOXHILL STUDYARE 39 the standard project flood. The area protected would then serve a sanctuary during rare flood events. Two nonstructural plans were investigated. Each plan involved only the raising of structures. The two levels of protection considered were the 25-and 100-year flood levels. It should be noted that for purposed of the analyses, both a stage-frequency curve developed by the Corps and the stage-frequency relationship developed by the Virginia Institute of Marine Science (VIMS) for FEMA were considered. West Point, Virginia Structural protection in the form of a floodwall along First and Kirby Streets (see Figure 24) was given some initial consideration that structural measures were not practicable based on the elevation and density of the development. In the study area, which includes 15th street and below, the nonstructural measures considered were limited to the raising of structures to prevent damages from the 25-and 100-year flood levels. The nonstructural plans were evaluated using both Corps and VIMS stage-frequency relationships. The plans considered involved the raising of as few as three structures (25-year plan) to as many as 43 structures (100-year plan). FIGURE 23 MAP OF TANGIER ISLAND 40 0 a 0 a one Ldl 000 a-o. ON, It us. a a IL Ong0 @-Iwo D33 ELTHAM BR. !was: At h A*. I ii: %j 80 a No V" .4-s"I @I A 5 3 -A I - I a to LEGEND 5' Contour Interv I 10 Contour Interval to 0 Soo 1000 1500 SCALE FEET FIGURE24 WESTPOINT AREAFLOODMAP 41 CHAPTERIV Assessment and Evaluation of Plans Maryland Communities Cambridge costs and benefits of each of the eight plans considered. Economic Analysis Assessment and Evaluation A total of eight plans of protection were considered for the Cambridge area. The The floodwall/levee plans would meet structural plans were the most costly the study objective of providing flood with first costs ranging from $5.1 to $9.1 protection for the low lying urban areas million as shown in Table 23. The struc- within the City of Cambridge. The two tural plans were also the least cost effec- levels of protection considered would tive with all plans having benefit-cost prevent flooding from the 120-year (ap- ratios of approximately 0.1. The non- proximate FOR) and the flood ap- structural plans were considerably less proximating the 500-year event. expensive (S357,000 and $749,000) than the structural plans; however, there is no As noted in the preceding paragraph, economic justification for their imple- there is no economic j ustificatio n for the mentation either. Table 23 also presents structural plans of protection. In addi- a detailed breakdown of the annual tion, if the structural plans were imple- TABLE 23 SUMMA R Y ECONOMIC A NA L YSIS OF A L TERNA TI VE PLA NS FOR CAMBRIDGE (April 1980 Prices) (SI,000's) PLAN heni CA-1 CA -2 CA-3 CA -4 CA-5 CA-6 CA-7 CA -8 Costs First $7,588 $5,869 $5,156 $9,121 $7,028 $6,061 $357 $749 Annual I&A 541 419 368 651 501 432 26 55 O&M 47 36 32 56 44 38 0 0 Total $ 588 $ 455 $ 400 $ 707 $ 545 $ 470 $ 26 $ 55 Benefits Intensification $ 0 $ 0 S 0 $ 0 $ 0 $ 0 $ 0 $ 0 Location 0 0 0 0 0 0 0 0 Employment 79 61 54 94 72 62 4 8 Inundation Reduction Existing 6 5 3 10 7 5 to 12 Future' 0 0 0 0 0 0 0 0 -rotai $ 85 $ 66 $ 57 $ 104 $ 79 $ 67 $ 14 $ 20 Net Benefits -$503 -$389 -$343 -$603 -$466 4403 -$12 -$35 Benefit-Cost Ratio 0.1 0.1 0.1 0.1 0.1 0.1 0.5 0.4 'Consists of affluence factor for residential contents only. 43 TA BLE 24 COMPA RA TI VE A SSESSMEN T A ND E VA L UA TION CAMBRIDGE, MARYLAND Slu.tv Objective Plan Description of Plan Beneficial Effects Reduce flood Plan CA-1 15,500 feet of Levee/wall which runs Will reduce flood hazard and provide damages in Map Ref A-D along a portion of the southern bank of degree of protection indicated for the Cambridge. the Choptank River from the city's portion of Cambridge within the city western Limits (Pink's Pond) eastward; limits. including Cambridge Creek and ending near the Port Commission Terminal (6' NG VD design elev.). Reduce flood Plan CA-2 11,400 feet of Levee/wall which begins Will reduce flood hazard and provide damages in Cam- Map Ref B-D near Mill St. and includes the municipal degree of protection indicated for the bridge. boat basin and Cambrdige Creek ending area of Cambridge Creek and the muni- near the Port Commission Terminal (6' cipal boat basin only. NG VD design elev.) Reduce flood Plan CA-3 9,700 feet of Levee/wall which begins Will reduce flood hazard and provide damages in Map Ref C-D near High St., includes Cambridge Creek degree of protection indicated for the Cambridge. and ends near the Port Commission area of Cambridge Creek ontv. Terminal (6'NG VD design elev.). Reduce flood Plan CA-4 15,625 feet of Levee/wall which runs Will reduce flood hazard and provide damages in Map Ref A-D along a portion of the southern bank of degree of protection indicated for the Cambridge. the Choptank River from the citv's portion of Cambridge within the city western limits (Pink's Pond) eastward; limits. including the municipal boat basin and Cambridge Creek areas and ending near the Port Commission Terminal (8' NG VD design elev.). Reduce flood Plan CA-5 11,550 feet of Levee/wall which begins Will reduce flood hazard and provide damages in Map Ref B-D near Mill St. and includes the municipal degree of protection indicated for the Cambridge boat basin and Cambridge Creek ending area of Cambridge Creek and the ending near the Port Commission municipal boat basin only. Terminal (8'NGVD design elev.). Reduce flood Plan CA-6 9,850 feet of Levee/wall which begins Will reduce flood hazard and provide damages in Map Ref C-D near High St., includes Cambridge Creek degree of protection indicated for the Cambridge. and ends near the Port Commission area of Cambridge Creek only. Terminal (8' NG VD design elev.). Reduce flood Plan CA-7 Nonstructural protection to the 5' NG VD Will reduce flood hazard and provide damages in (40-year) flood level; includes utility degree of protection iondicated for the Cambridge. addition, standard floodproofing and entire community. floodproofing by floodwall. Reduce flood Plan CA-8 Nonstructural protection to the 6'NG VD Will reduce flood hazard and provide damages in Cambridge. (120-year) flood levee; includes utility degree of protection indicated for the addition, acquisition and demolition, entire community. standard floodproofing and floodproofing by floodwall. D.O. P. =Degree of Protection F.C. = First Cost A.A.C.= Average Annual Costs A.A.B. = Average Annual Benefits B.C.R. = Benefit-Cost Ratio .44', mented the use of the shoreline would be severely restricted and access would have to be provided to existing wharves and piers. Construction impacts asso- ciated with the structural plans would include noise pollution, destruction of Adverse Effects Economics benthic organisms due to turbidity and siltation, loss of some wetland areas and Destruction of fringe marsh areas scattered around D.O.P.= 120-year the creation of dust. Last, there would the shores of Cambridge Creek (< 10 acres). F.C. = $7,588,000 be adverse aesthetic impacts associated Approximately six acres of wetland type #17 [email protected]. = $597,000 (irregularly flooded salt marsh) will be cut off by A.A.B. = $85,500 with constructing a floodwall/levee construction of flood wall/ Levee resulting in B.C,R. = 0.14 between the existing development and eventual destruction. Less than five acres of marsh the scenic vista of the Choptank River. will be affected due to construction near Gray Marsh. Temporary destruction of benthic The two nonstructural plans considered organisms due to construction. Recolonization may occur after completion of construction. Some would provide protection against either permanent loss of habitat may also occur. Increased a 40-year flood (elevation five feet siltation and turbidity which may effect submerged NGVD) or a 120-year flood (elevation aquatic vegetation and fish. Use of shoreline will be six feet NGVD). Both plans were found restricted and access to existing piers and wharves lacking from the standpoint of economic difficult. Adverse effects to the aesthetic conditions of the area. feasibility. The nonstructural plans would not be expected to have a signifi- Same as above. D.O.P.= 120-year cant environmental impact. There would F.C. = $5,869,200 be only minor temporary impacts dur- A. A.C.= $454,000 A.A. B. = $65,900 ing the relocation or demolition of the B.C. R. = O@ 14 structures affected. There would also be some adverse social impacts associated Same as above. D.O.P.= 120-year with those individuals required to relo- F.C@ = S5,156,400 A.A.C. = $399,600 cate. A full array of the beneficial and A.A. B. = $57,300 adverse effects of each of the plans is B.C. R. = 0. 14 included in Table 24. Same as above. D.O.P. = stand. project flood Crisfield F.C. = $9,120,600 A.A.C. = $706,700 Economic Analysis A.A.B. = $103,800 B.C. R. = 0. 15 A total of six plans of protection were considered for Crisfield. As shown in Table 25, the total first cost of the plans ranged from $7.3 to $0.7 million with Same as above. D.O.P. = stand, project flood the least costly plan being the nonstruc- F.C. = $7,028,400 tural plan that would provide protection A.A.C. = $545,000 to elevation 4.0. This plan was also A.A. B. = $79,200 B.C.R. = 0.14 found to be the most cost effective with a benefit-cost ratio of 0.6. The benefits Same as above. D.O.P. = stand. project flood accruing to the plans are categorized as F.C. = $6,061,200 employment and inundation reduction A.A.C. = $469,900 (existing and future). Table 26 presents A.A.B. = $67,200 B,C. R. = 0. 14 a detailed breakdown of the annual Construction of small floodwalls may result in benefits and costs for all the plans D.O.P. = 40-year considered. adverse environmental effects such as destruction of F.C. = $356,300 adjacent wetland areas, increased siltation and A.A.C. = $26,200 turbidity and destruction of benthic organisms. Use A.A.B. = $13,500 Assessment and Evaluation of shoreline will be restricted and access to existing B.C.R. = 0.52 piers and wharves difficult. The floodwall/ levee plans investigated Same as above. D. 0. P. = 120-year would nearly encircle the Town of Cris- F.C. = $749,150 field and protect -against floods with A.A.C. = $55,150 return intervals of approximately 80 to A.A.B. = $20,200 400 years. As noted in the preceding B.C.R. = 0.37 paragraph, there is no economic justifi- cation for any of the plans considered. The construction impacts associated with building levees and floodwalls in Cris- 45 TABLE25 SUMMARY ECONOMIC ANALYSIS OF ALTERNATIVE PLANS FOR CRISFIELD (April 1980 Prices) ($1,000's) PLAN ITEM CR-I CR-2 CR-3 CR-4 CR-5 CR-6 Costs First $ 7,019 $ 7,333 S 5,807 $ 7,215 $ 676 $ 6,294 Annual ]&A 501 523 414 515 50 463 O&M 42 44 35 43 0 0 Total S 543 $ 567 $ 449 $ 558 50 $ 463 Benefits Intensification $ 0 $ 0 $ 0 0 0 $ 0 Location 0 0 0 0 0 0 Einployment 72 76 60 75 7 65 inundation Reduction Existing 71 92 66 85 24 89 Future' 2 3 2 3 1 3 Total $ 145 $ 171 $ 128 $ 163 $ 32 157 Net Benefits -$398 -$396 -$321 -$395 _$18 -$306 Benefit-Cost Ratio 0.3 0.3 0.3 0.3 0.6 0.3 'Consists of affluence factor for residential contents only. field would be essentially the same as costs of $3.5 and $4.3 million for plans impacts of a structural plan in the those previously discussed for PC-I and PC-2, respectively. From an Cypress Park area. The beneficial and Cambridge; however, a more substan- economic standpoint, both structural adverse impacts of all the plans consid- tial acreage of wetlands and fringe plans were very ineffective as they had ered are shown in Table 29. marshes would be destroyed. Also, benefit-cost ratios of 0, 1 or less. The adverse social impacts would be expected nonstructural plans while less costly Rock Hall to be major due to the extensive nature ($1.3 to $0.3 million) were also not eco- of the plan and the limiting of access to nomically justified. Table 27 presents a Economic Analyst's the water of a predominately water- detailed breakdown of all annual costs oriented community. and benefits for each of the plans A total of 10 plans of protection were considered. considered for Rock Hall. Included in The nonstructural plans would not be Table 29 is a summary of the findings of expected to have significant long-term Assessment and Evaluation the economic analysis conducted for environmental or social impacts of an each plan. The table includes first costs, adverse nature. Plan CR-5 has the most The plans of protection investigated annual costs, annual benefits and favorable economic evaluation (B-C would have satisfied to varying degrees benefit-cost ratios for each plan. Ratio + 0.6); however, it is unlikely that the study objective of providing flood a more rigorous examination of the protection for the flood-prone area in The benefits accruing to the plans con- costs and benefits associated with this Pocomoke City. As noted previously sidered are categorized as employment plan would result in a favorable project. none of the plans investigated were and inundation reduction (existing and A full array of the beneficial and adverse found to be economically feasible. The future). With benefit-cost ratios of either effects of each of the plans is included in best plan from an economic standpoint 0.2 or 0.3, it is obvious there is no eco- Table 26. was PC-3 which was a nonstructural nomic justification for any of the plans plan having a benefit-cost ratio of 0.5. of improvement. Pocomoke City The environmental and social impacts Assessment and Evaluation Economic Analysis associated with the alternatives consid- ered would be similar to those pre- The floodwall/levee plans investigated Five plans of protection were consid- viousky discussed for Cambridge and would protect Rock Hall and Gratitude ered for Pocomoke City. The structural Crisfield. An area of concern would be against floods with return inverbals of plans were the most costly with first the adverse environmental/ aesthetic approximately 140 and 500 years. While 46 meeting the study objective of providing costs ranging from nearly $12.0 to $0.7 bulkhead to at least the level of the 100- flood protection for the community, the million. As shown in Table 33, a com- year storm plus wave action and free- structural plans would have some parison of annual benefits and costs board, construction of dikes on the adverse environmental and social im- yields B-C ratios of 0.2 and lower for the north and south sides of the town to the pacts as noted in Table 30. The non- alternatives considered. same level, reconstruction of some of structural plans R H-7 thru R H- 10, while the storm outlets and the installation not providing the degree of protection Assessment and Evaluation therein of tide gates, and the construc- offered by the structural plans, would tion of a pumping station. Such a pro- not be expected to have significant en- Based on review of the findings of the ject would not bejustified on the basis of vironmental or social impacts. The one economic analyses it may be concluded the benefits to be derived. Included as exception would be Plan RH-10 which that further investigation of St. Michaels Table 37 is a summary of the benefits requires such a large number of reloca- is not warranted. Consideration of some and costs associated with the four non- tions and acquisitions and demolitions of the adverse social and environmental structural plans. It should be noted that that adverse social impacts would likely impacts associated with the structural all plans considered had benefit-cost be severe. As noted in the preceding plans would also strongly support the ratios of 0. 13 or less. paragraph, all plans considered lacked above conclusion. Of particular concern economic justification and it is unlikely would be the adverse social/ aesthetic Assessment and Evaluation that a more detailed examination would impacts associated with levee and materially effect the results of the stu- floodwall construction in the harbor As shown in Table 38 the plans studied dies to date. area in the vicinity of the Chesapeake would have little impact on the com- Maritime Museum. A full listing of all munity except during construction Snow Hill impacts associated with the plans is operations. The addition of earth levees included in Table 34. on the north and south sides of the town Economic Analysis to the same level as the top of the exist- Tilghman Island ing bulkhead could be so sloped as to A total of seven plans of protection were create no adverse effect. A closure may considered for Snow Hill. The structu- Economic Analysis be required on the south side where the ral plans were the most costly with the commercial area is located. first costs ranging from $2.8 to $3.7 mil- Seven plans of protection were consid- lion. From an economic standpoint none ered for Tilghman Island. As shown in Raising the few residential buildings of the structural plans, while less costly Table 35 the total first costs of the alter- and stores, constructing small adjoining $1.2 to $0.3 million), were also not eco- natives had a wide range ($8.9 to $0.1 buildings to house existing utilities that nomically justified. Table 31 presents a million). As further indicated in the are now located in the basements of detailed breakdown of the annual costs Table all plans were found to lack eco- these structures and providing tempo- and benefits for each of the plans nomic justification by a wide margin. rary closures for windows in basements considered. The structural plans all had benefit-cost would have practically no effect on ratios less than 0.1 while the most cost adjacent property or on the community. Assessment and Evaluation effective nonstructural plan (TI-5) had a No significant environmental and/ or benefit-cost ratio of only 0.3. biological impacts appear to be asso- The plans of protection investigated ciated with the above plans. would have satisfied to varying degrees Assessment and Evaluation the study objective of providing flood . Hampton Roads protection for the flood-prone area in Based on the results of the economic Snow Hill. As noted previously, none of analyses it appears that further consid- Economic Analysis the plans investigated were found to be eration of flood protection measures for economically feasible. Tilghman Island is not warranted. The The first cost of the three plans consid- adverse environmental and social im- ered in Fox Hill ranged from almost The environmental and social impacts pacts associated with the structural plans $3.2 million for the structural Olan to associated with the alternatives consid- in particular would also support this SO.9 million for the 25-year nonstructur- ered would be similar to those pre conclusion. Table 36 provides a compar- al plans. Table 39 includes a summary of viously discussed for Cambridge and ison of all beneficial and adverse impacts the annual benefits and costs associated Crisfield. An area of concern would be of the plans investigated. with the plans considered. the adverse environmental/ aesthetic impacts of a structural plan in the Byrd Virginia Communities Assessment and Evaluation Park area. Included as Table 32 is a comparative assessment of the benefi- Cape Charles A substantial portion of the Hampton cial and adverse impacts of all the plans Roads city complex is susceptible to considered. Economic Analysis tidal flood damage. There are tidal flood protection projects for the downtown St. Michaels An analysis was not conducted of the commercial areas of Norfolk and costs and benefits associated with the Portsmouth. Also the Corps has recently Economic Analysis modifications previously discussed. Such recommended the construction of a pro- accomplishment by the Corps would tective sand berm along the entire 7.3- The four plans investigated had first require the raising of the existing wooden mile Chesapeake Bay shoreline of the 47 TA BLE 26 COMPA RA TI VE A SSESSMENT A ND E VA L UA TION CRISFIELD, MAR YLAND Study Objective Plan Description of Plan Beneficial Effects Reduce flood Plan CR-1 22,600 feet of levee/wall beginning at Will reduce flood hazard and provide damages in Map Ref A-C high ground near Jacksonville Road and degree of protection indicated for most of Crisfield. running along the shoreline to exclude Somer's Crisfield and the surrounding area. Cove and tie-out at high ground near Johnson Creek Road (5' NG VD design elev.). Reduce flood Plan CR-2 23,300 feet of levee/wall with identical Will reduce flood hazard and provide damages in Map Ref A-C alignment as Plan CR-1. Degree of degree of protection indicated for most of Crisfield. protection increases to 400-year Crisfield and the surrounding area. recurrence level. Additional levee sections are needed to tie into higher ground (6' NG VD design elev.). Reduce flood Plan CR-3 20,900 feet of levee/wall beginning at Will reduce flood hazard and provide damages in Map Ref A-B high ground near Outten Road and degree of protection indicated for most of Crisfield. running along the shoreline to exclude Crisfield and the surrounding area. Somer's Cove and tie out at high ground near the intersection of Johnson Creek Rd. and Rt. 390 (5' NG VD design elev.). Reduce flood Plan CR-4 21,650 feet of levee/wall with identical Will reduce flood hazard and provide damages in Map Ref A-B alignment as Plan CR-3. Degree of degree of protection indicated for most of Crisfield. protection increases to 400-year Crisfield and the surrounding area. recurrence level. Additional levee sections are needed to tie into higher ground. (6' NG VD design elev.). Reduce flood Plan CR-5 Nonstructural protection to the 4' NG VD Will reduce flood hazard and provide damages in (12-year) flood level; includes utility degree of protection indicated for entire Crisfield. addition, acquisition and demolition, community. trailer relocation, structure raising, standard floodproofing, and floodproofing by floodwalls. Reduce flood Plan CR-6 Nonstructural protection to the 5' NGVD Will reduce flood hazard and provide damages in (80-year) flood level; includes utility degree of protection indicated for entire Crisfield. addition, acquisition and demolition, community. trailer relocation, structure raising, standard floodproofing, and floodproofing by floodwalls. 48 Adverse Effects Economics City of Norfolk. Although the studies in Destruction of fringe marsh areas near Woodson D. 0. P. = 80-year this and previous reports offer some High School (< 5 acres), near Collins Street west of F. C. = $7,018,000 insight to the feasibi .li-ty of-both structur- Main Street, (< 10 acres) and west of Wynnfall Ave A.A.C. = $543, 100 al and nonstructural alternatives, they (< 20 acres). Destruction of marsh area west of A.A. B. = $145,700 Jacksonville Road to the site of construction (< 25 B.C. R. = 0.27 are not sufficient to present conclusive acres). Temporary destruction of benthic organisms evidence of the economic feasibility of due to construction. Recolonization may occur tidal flood protection based on today's after completion of construction. Some permanent level of residential, commercial, and loss of habitat may also occur. Increased siltation industrial development. Further com- and turbidity due to construction which may effect submerged aquatic vegetation and fish. Use of prehensive consideration of both struc- shoreline will be severely restricted. Adverse effects tural and nonstructural measures for the to the aesthetic conditions of the area. protection of portions of the Hampton Same as above. D. 0. P. = 400-year Roads city complex - Norfolk, Ports- EC, = $7,333,200 mouth, Chesapeake, and Hampton - A.A.C. = $567,200 from tidal flooding is warranted. Table A.A. B. = $172,000 40 provides an assessment and evalua- B.C.R. = 0.30 tion of the plans considered. Same as above except excluding destruction of D. 0. P. = 80-year marsh area near Jacksonville Road. F. C. = $5,807,400 A.A. C. = $449, 100 A.A. B. = $128,300 B.C.R. = 0.29 Same as plan CR-3. D. 0. P. = 400-yea r F. C. = $7,215,000 A.A. C. = $558,200 A.A@B. = $164,200 B.C.R. = 0.29 Loss of unique social life style for those that are D.O.P. = 12-year relocated. Construction of floodwall may result in F. C. = $676,300 adverse environmental effects such as destruction of A.A. C. = $49,800 adjacent wetland areas, increased siltation and A.A.B. = $33,000 turbidity, and destruction of benthic organisms. Use B.C. R. = 0.66 of shoreline will be restricted. Adverse effects to the aesthetic conditions of the area. Temporary noise pollution. Same as above. D. 0. P. = 80-year F. C. = $6,294,300 A.A.C. = $463,300 A.A. B. = $158,600 B.C.R. = 0.34 49 TABLE27 SUMMARYECONOMIC ANALYSIS OFALTERNATIVE PLANS FOR POCOMOKE CITY (April 1980 Prices) ($I,000's) PLAN Item PC_l PC-2 PC-3 PC-4 PC-5 Costs First $ 3,543 S 4,323 $ 260 S 729 S 1,357 Annual I&A 253 308 19 54 100 O&M 22 27 0 0 0 Total $ 275 $ 335 $ 19 $ 54 $ 100 Benefits Intensification $ 0 $ 0 $ 0 $ 0 $ 0 Location 0 0 0 0 0 Employment 0 0 0 0 0 Inundation Reduction Existing 11 17 10 14 18 FutureO Total 11 $ 17 S 10 14 18 Net Benefits -$264 -$318 _$9 -$40 -$82 Benefit-Cost Ratio 0.0 0.1 0.5 0.3 0,2 Consists of affluence factor for residential contents only. TABLE 28 COMPARATIVEASSESSMENTAND EVALUATION POCOMOKE CITY MA R YLA ND Study Objective Plan Description of Plan Beneficial Effects Reduce flood Plan PC- 1 10, 190 feet of levee/ wall which runs Will reduce flood hazard and provide damages in Map Ref A-B along the eastern banks of the Pocomoke degree of protection indicated for the Pocomoke City River south of the Rt. 13 Bridge (6' portion of Pocomoke City south of the NG VD design elev.). Rt. 13 Bridge. Reduce flood Plan PC-2 10,500 feet of levee/wall which runs Will reduce flood hazard and provide damages in Map Ref A-B along the eastern banks of the Pocomoke degree of protection indicated for the Pocomoke City River south of the Rt. 13 Bridge (8' portion of Pocomoke City south of the NG VD design elev.). Rt. 13 Bridge. Reduce flood Plan PC-3 Nonstructural protection to the 5' NG VD Will reduce flood hazard and provide damages in (25-year) flood level; includes utility degree of protection indicated for entire Pocomoke City relocation, acquisition and demolition, community. and floodproofing by floodwall. Reduce flood Plan PC-4 Nonstructural protection to the 6' NG VD Will reduce flood hazard and provide damages in (70-year) flood level; includes utility degree of protection indicated for entire Pocomoke City relocation, structure raising, acquisition community. and demolition, trailer relocation, standard floodproofing, and floodproofing by floodwall. Reduce flood Plan PC-5 Nonstructural protection to the 7' NGVD Will reduce flood hazard and provide damages in (220-year) flood level; includes utility degree of protection indicated for entire Pocomoke City relocation, acquisition and demolition, communtiy. trailer relocation, structure raising, standard floodproofing, and floodproofing by floodwall, 50 TABLE 29 SUMMARYECONOMIC ANALYSIS OFALTERNATIVE PLANS FOR ROCK HALL (April 1980 Prices) ($1,00o) PLAN Item RH-1 RH-2 RH-3 RH-4 RH-5 RH-6 RH-7 RH-8 RH-9 RH-10 Costs First S 9,455 $ 13,514 $ 7,996 $ 10,308 S3,292 $ 4,797 S 1,093 $ 2,504 $ 4,832 $ 7,081 Annual I&A 674 964 570 735 235 342 81 184 356 521 O&M 58 82 49 63 20 29 0 0 0 0 Total $ 732 $ 1,046$ 619 $ 798 $ 255 $ 81 $ 184 $ 356 $ 521 Benefits Intensification $ 0 $ 0 0 0 $ 0 0 $ 0 $ 0 $ 0 $ 0 Location 0 0 0 0 0 0 0 0 0 0- Employment 97 139 82 106 34 49 11 26 50 73 Inundation Reduction Existing 39 53 23 32 15 21 12 24 40 50 Future' 1 2 1 1 1 1 0 1 2 2 Total $ 137 $ 194$ 106 $ 139 $ 50 $ 71 23 $ 51 $ 92 S 125 Net Benefits -$595 -$852 -$513 -$659 -$205 -$300 _$58 -$133 -$264 -$396 Benefit-Cost Ratio 0.2 0.2 0.2 0.2 0.2 0.2 0.3 0.3 0.3 0.2 Consists of affluence factor for residential contents only. Adverse Effects Economics Impact on the wooded wetland areas on the shore D. 0. P. = 70-yea r at the end of Laurel Street and northwest of Quinn F. C. = $3,542,600 Avenue (total area < 10 acres). Temporary A-A,C. = $274,800 destruction of benthic organisms due to A.A.B. = $11,000 construction. Recolonization may occur after &C.R. = 0.04 completion of construction. Some permanent loss of habitat may also occur. Same as above. D. 0. P. = stand. project flood F. C. = $4,322,700 A.A. C. = $335,300 XA.B. = $16,600 B.C. R. = 0.05 Construction of floodwall may result in adverse D. 0. P. = 25-year environmental effects such as destruction of F. C. =$259,700 adjacent wetland areas, increased siltation and A.A. C. = $19,100 turbidity, and destruction of benthic organisms. Use A.A.B. = $10,100 of shoreline will be restricted. Adverse effects to the B.C.R. = 0.53 aesthetic conditions of the area. Temporary noise pollution. Same as above with the addition of loss of unique D, 0. P. = 70-year social lifestyle for those that are relocated. F. C. =$728,500 A.A.C. = $53,600 A.A. B. = $13,000 B.C. R. = 0.24 Same as above, [email protected]. = 220-year F. C. = $1,357,200 A.A, C. = $99,900 A.A.B. = $18,000 B.C. R. = 0. 18 51 TA BLE 30 C OMPA RA TI VE A SSESSMEN T A ND E VA L UA TION ROCK HALL, MARYLAND Study Objective Plan Description of Plan Beneficial Effects Reduce flood Plan RH-I 22,400 feet of levee/wall "ringing" the Will reduce flood hazard and provide damages in Rock Map Ref A-E Rock Hall-Gratitude areas (9' NGVD degree of protection indicated for both Hall design elev.). Rock Hall and Gratitude. Reduce flood Plan RH-2 25,500 feet of levee/wall "ringing" the Will reduce flood hazard and provide damages in Rock Map Ref A-G Rock Hall-Gratitude areas. Includes degree of protection indicated for both Hall protection from flooding on Gray's Inn Rock Hall and Gratitude. Creek. (12'NG VD design elev.). Reduce flood Plan RH-3 16,000 feet of levee/wall encircling the Will reduce flood hazard and provide damages in Rock Map Ref B,C,D Gratitude area only (9' 1VG VD design degree of protection indicated for the Hall elev.). Gratitude area only. Reduce flood Plan RH-4 16,000 feet of levee/wall encircling the Will reduce flood hazard and provide damages in Rock Map Ref B,C, Gratitude area only (12' NG VD design degree of protection indicated for the Hall D elev.). Rock Hall area only. Reducenood Plan RH-5 9,900 feet of levee/wall encircling the Will reduce flood hazard and provide damages in Rock Map Ref A-B, Rock Hall area only (9' NG VD design degree of protection indicated for the Hall D-E elev.). Rock Hall area only. Reduce flood Plan RH-6 11,650 feet of levee /wall encircling the Will reduce flood hazard and provide damages in Rock Map Ref A-B- Rock Hall area only. Includes protection degree of protection indicated for the Hall D-E-F-G from flooding on Gray's Inn Creek (12' Rock Hall area only. NG VD design elev.). 52 Adverse Effects Economics Destruction of marsh areas along the shoreline in D.O.P.= 140-year Rock Hall Harbor (< 2 acres) northwest of F. C. = $9,454,800 Windmill Point (< 20 acres) and east of Rock Hall A.A.C. = $731,900 Harbor (< 10 acres). A portion of the marsh areas A.A.B. = $137, 100 in Gratitude near the Havens will be destroyed due B.C.R. = 0.19 to construction (< 20 acres). Use of shoreline will be severely restricted and access to existing piers and wharves difficult. Temporary destruction of benthic organisms due to construction. Recolonization may occur after completion of construction. Some permanent loss of habitat may also occur. Increased siltation and turbidity due to construction which may effect submerged aquatic vegetation and fish. Adverse effects to the aesthetic conditions of the area. Same as above with additional marsh destruction D.O.P.= stand. project flood near Gray's Inn Creek. (< 10 acres). F.C. = $13,513,800 A.A. C. = $1,046,300 A.A. B. = $194,500 B.C. R. = 0. 19 Destruction of marsh area along the shoreline in D. 0. P. = 140-yea r Rock Hall Harbor (< 2 acres), northwest of F. C. = $7,995,600 Windmill Point (< 20 acres), two areas near the A.A. C. = $619,200 Havens (< 20 acres) and a fringe area north of A.A.B. = $106,700 Caroline Avenue (< I acre). Temporary destruction B.C. R. = 0. 17 of benthic organisms due to construction. Recolonization may occur after completion of construction. Some permanent loss of habitat may also occur. Increased siltation and turbidity due to construction which may effect submerged vegetation and fish. Adverse effects to the aesthetic conditions of the area. Use of shoreline will be restricted. Same as above. D. 0. P. = stand. project flood F. C. = $10,308,200 A.A.C. = $798,500 A.A.B. = $139,000 B.C. R. = 0. 17 Partial destruction of marsh areas east of Rock D. 0. P. = 140-year Hall Harbor (< 20 acres) and on the eastern shore F. C. = $3,291,600 of the Havens (< 15 acres). Use of shoreline A,A. C. = $254,600 restricted. Adverse effects to the aesthetic A.A. B. = $50,400 conditions of the area. Temporary destruction of B.C. R@ = 0.20 benthic organisms due to construction. Recolonization may occur after completion of construction. Some permanent loss of habitat may also occur. Increased siltation and turbidity due to construction which may effect submerged aquatic vegetation and fish. Same as above with the addition of marsh D.O.P. =stand. project flood destruction along Gray's Inn Creek (< 10 acres). F.C. = $4,797,000 A.A.C. = $370,900 A.A.B. = $71,500 B.C. R. = 0. 19 53 TABLE 31 TA BLE 30 (Con td) SUMMARYECONOMIC ANALYSIS OF ALTERNATIVE PLANS FOR SNO W HILL (April 1980 Prices) (S1,000,S) PLAN Study Objective Plan ITEM SH-1 SH-2 SH-3 SH-4 SH-5 SH-6 SH-7 Reduce flood Plan RH-7 Costs damages in Rock First $3,011 $2,845 $3,742 $3,596 $304 $421 $1,210 Hall Annual I&A 215 203 267 256 22 38 89 O&M 19 18 23 23 0 0 0 Total $ 234 $ 221 $ 290 $ 279 $22 $ 38 $ 89 Benefits Reduce flood Plan RH-8 Intensification $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 damages in Rock Location 0 0 0 0 0 0 0 Hall Employment 0 0 0 0 0 0 Inundation Reduction Existing 5 5 9 8 3 6 8 Future] 0 0 0 0 0 0 0 Total S 5 $ 5 $ 9 $ 8 $ 3 $ 6 $ 8 Reduce flood Plan RH-9 Net Benefits damages in Rock -$229 4216 -$281 -$271 _$19 -$32 -$81 Hall Benefit-Cost Ratio 0.02 0.02 0.03 0.03 0.1 0.2 0.09 'Consists of affluence factor for residential contents only. Reduce flood Plan RH-10 damages in Rock Hall TABLE 32 COMPARA TIVEASSESSMENTAND EVALUA TION SNO W HILL, MA R YLA ND Study Objective Plan Description of Plan Beneficial Effects Reduce flood Plan SH-1 7,190 feet of levee/wall which runs along Will reduce flood hazard and provide damages in Snow Map Ref A-C the southern banks of the Pocomoke degree of protection indicated for the Hill River from north of the Rt. 12 Bridge to entire community. the city's southern limits (6' NG VD design elev.). Reduce flood Plan SH-2 5,080 feet of leveelwall which runs along Will reduce flood hazard and provide damages in Snow Map Ref A-B the southern banks of the Pocomoke degree of protection indicated for the Hill River frornJust north of the Rt. 12 entire community. Bridge to the city's southern limits (6' NG VD design elev.). Reduce flood Plan SH-3 7,920 feet of levee /wall which runs along Will reduce flood hazard and provide damages in Snow Map Ref A-D the southern banks of the Pocomoke degree of protection indicated for the Hill River from near the northern city limits entire community. to the city's southern limits (8' NGVD design elev.). Reduce flood Plan SH-4 6,460 feet of levee/wall which runs along Will reduce flood hazard and provide damages in Snow Map Ref A-B the southern banks of the Pocomoke degree of protection indicated for entire Hill River from north of the Rt. 12 Bridge to community. the city's southern limits. (8' NG VD design elev.). 54 COMPARATIVE ASSESSMENT AND EVALUATION ROCKHALL, MARYLAND Description of Plan Beneficial Effects Adverse Effects Economics Nonstructural protection to the 5' NG VD Will reduce flood hazard and provide Loss of unique social life style for those relocated. D.O.P,= 15-year (15-year) flood level; includes utility degree of protection indicated for entire Construction of floodwall may result in adverse F. C, = $1,093,000 addition, acquisition and demolition, community. environmental effects such as destruction of A.A.C. = $80,450 trailer relocation, standard ad 'jacent wetland areas, increased siltation and A@A-B. = $22,500 floodproofing, and floodproofing by turbidity, and destruction of benthic organisms. Use B.C. R. = 0.28 floodwalls. of shoreline will be restricted, Adverse effects to the aesthetic conditions of the area. Temporary noise pollution. Nonstructural protection to the 6' NGVD Will reduce flood hazard and provide Same as above. D. 0, P. = 25-year (25-year) flood level; includes utility degree of protection indicated for entire F. C. = $2,504,450 additions, house raising, trailer community. A-A.C.= $184,350 relocation, acquisition and demolition, A. X 8@ = $50,900 standard floodproofing, and B.C.R. = 0.26 floodproofing by floodwalls. Nonstructural protection to the T NG VD Will reduce flood hazard and provide Same as above. D, 0. P. = 50-year (50-year) flood level, includes utility degree of protection indicated for entire F. C. = $4,831,500 additions, house raising, trailer and community. [email protected]. = $355,650 house relocation, acquisition and A.A.B. = $91,500 demolition, standard floodproofing, and B.C.R. = 0.26 floodproofing by floodwalls. Nonstructural protection to the 8' NGVD Will reduce flood hazard and provide Same as above. D. 0. P. = 80-year (80-yeqr) flood level; includes utility degree of protection indicated for entire F.C. = $7,080,700 additions, house raising, house and community. A,A.C. = $521,200 trailer relocation, acquisition and A.A.B. = $125, 100 demolition, standard floodproofing, and &C.R. = 0.24 floodproofing by floodwalls. Adverse Effects Economics Construction will impact on the wooded areas D.O.P.= 70-year along the riverjust north of Green Street (< 2 F. C. = $3,010,800 acres). A fringe marsh area along the shore near A.A.C. = $233,500 Commerce Street will be destroyed (< 2 acres), A.A.B. = $5,500 Adverse effects to the aesthetic conditions of the B.C. R. = 0.02 areas especially at Byrd Park. Cypress trees in the park along the shoreline will be impacted due to construction. Temporary destruction of benthic organisms due to construction. Recolonization may occur after completion of construction. Increased siltation and turbidity due to construction which may effect submerged aquatic vegetation and fish. Use of the shoreline will be severely restricted. Same as above. D.O.P. = 70-year F. C. = $2,844,600 ' A.A.C. = $220,700 A.A.B. = $5,300 B. C. R. = 0.02 Same as above with the addition of extension of D. 0. P. = stand. project flood impacts on the w@oded area near the cemetery F. C. = $3,741,600 K 10 acres). A.A.C. = $290,300 A.A. B. = $9, 100 B.C.R. = 0.03 Same as SH-1. D.O. P. = approximate 500-year F, C. = $3,595,600 A.A.C. = $278,900 A.A.B. = $8,800 B.C. R. = 0,03 55 TABLE 32 (Cont'd) COMPARA TIVEASSESSMENTAND EVALUATION SNO W HILL, MA R YLA ND Study Objective Plan Description of Plan Beneficial Effects Reduce flood Plan SH-5 Nonstructural protection to the 5' NGVD Will reduce flood hazard and provide damages in Snow (25-year) flood level; includes structure degree of protection indicated for entire Hill raising, acquisition and demolition, community. standard floodproofing, and floodproofing by floodwall,, Reduce flood Plan SH-6 Nonstructural protection to the 6' NG VD Will reduce flood hazard and provide damages in Snow (70-year) flood level; includes structure degree of protection indicated for entire Hill raising, acquisition and demolition, community. standard floodproofing, and floodproofing by floodwall,. Reduce flood Plan SH-7 Nonstructural protection to the 7' NGVD Will reduce flood hazard and provide damages in Snow (220-year) flood level; includes structure degree of protection indicated for entire Hill raising, acquisition and demolition, community. standard floodproofing, and floodproofing by floodwall,- TABLE 34 TABLE 33 SUMMARY ECONOMIC ANALYSIS OF Study Objective Plan AL TERNA TIVE PLANS FOR ST. MICHAELS (April 1980 Prices) Reduce flood Plan SM-1 0110001s) damages in St. Map Ref A-B, Michaels D-C PLAN Item SM-1 SM-2 SM-3 SM-4 Costs First $7,224 $11,971 $730 $916 Annual I&A 515 854 54 67 O&M 44 73 0 0 Reduce flood Plan SM-2 Total $ 559 S 927 S 54 $67 damages in St. Map Ref A-D Michaels Benefits Intensification $ 0 $ 0 $ 0 $ 0 Location 0 0 0 0 Employment 0 0 0 0 Inundation Reduction Reduce flood Plan SM-3 Existing 10 17 8 11 damages in St. Future' 0 0 0 0 Michaels Total $ 10 $ 17 $ 8 $11 Net Benefits -$549 _$910 -$46 -$56 Benefit-Cost Ratio 0.02 0.02 0.1 0.2 Reduce flood Plan SM-4 damages in St. 'Consists of affluence factor for residential contents only. Michaels 56 Adverse Effects Economics Construction of floodwall may result in adverse D. 0. P. = 25-year environmental effects such as destruction of F. C. = $303,500 adjacent wetland areas increased siltation and A.A. C. = $22,300 turbidity, and destruction of benthic organisms. Use A.A.B. = $3,400 of the shoreline will be restricted. Adverse effects to B.C. R. = 0. 15 the aesthetic conditions of the area. Temporary noise pollution. Same as above. D. 0. P, = 70-year F. C. = $521,200 A.A.C. = $38,400 A.A. B, = $6,200 B.C.R. = 0.16 Same as above. D. 0. P. = 220-yea r F.C. = $1,210,200 A@A,C@ = $89, 100 A.A.B. = $8, 100 B.C. R. = 0.09 COMPA RA TI VE A SSESSMENT A ND E VA L UA TION S T MICHA ELS, MA R YLA ND Description of Plan Beneficial Effects Adverse Effects Economics 14,000 feet of levee/wall which begins Will reduce flood hazard and provide Use of the shoreline will be severely restricted and D.O.P. = 100-year near Rt. 33 at the town's northern limits, degree of protection indicated for area access to existing piers and wharves difficult. F. C. = $7,224,000 runs around St. Michaels Harbor, and within town's old city limits, Destruction of fringe marsh areas near Parrot Point A.A.C. = $559,300 ties into high ground near the southern and northwest of Navy Point (total area < 5 acres). A.A.B. = $10,200 town limits at Radcliffe Ave. (7' NG YD Temporary destruction of benthic organisms due to B.C.R. = 0,02 design elev.). construction. Recolonization may occur after completion of construction. Some permanent loss of habitat may also occur. Increased siltation and turbidity due to construction which may effect submerged aquatic vegetation and fish. Adverse effects to the aesthetic conditions of the town. 23,890 feet on levee/wall which begins Will reduce flood hazard and provide Same as above except for the addition of the D.O.P. = 450-year near Rt. 33 at the town's northern limits, degree of protection indicated for area destruction of a small marsh area at the end of San F-C. = $11,970,800 runs around St. Michaels Harbor to within town's old city limits as well as a Domingo Creek (end of Thompson Street). (Total A.A.C. = $926,600 Seymour St., and ties into the levee portion of the new development near Rio area less than 5 acres.) A.A.B. = $16,000 section near San Domingo Creek at Rt. Vista. B.C.R@ = 0.02 33 and the town's southern limits (9' NG VD design elev.). Nonstructural protection to the 6' NG VD duce flood hazard and provide Temporary, minor noise pollution and aesthetic D. 0. P. = 45-year (45-year) flood level; includes utility degree of protection indicated for entire disturbances. Construction of floodwall may result F.C. = $730,000 addition, acquisition and demolition, community. in adverse environmental effects such as destruction A.A.C. = $53,700 standard floodproofing, and of adjacent wetland areas, increased siltation and A.A.B. = $8,200 floodproofing by floodwall:,. turbidity, and destruction of benthic organisms. Use B-C. R. = 0. 15 of shoreline will be restricted. Adverse effects to the aesthetic conditions of the area. Nonstructural protection to the 7' NG VD Will reduce flood hazard and provide Same as above. D.O. P. = I 00-year (100-year) flood level; includes utility degree of protection indicated for entire F.C. = $916,300 addition, structure raising, acquisition community. A.A.C. = $67,400 and demolition, standard floodproofing, A.A.B. = $10,800 and floodproofing by floodwall-. B.C. R. = 0. 16 57 TABLE 35 SUMMARY ECONOMIC ANALYSIS OF ALTERNA TIVE PLANS FOR TILGHMANISLAND (April 1980 Prices) (S1,000,S) PLAN Item TI-1 TI-2 TI-3 T14 TI-5 TI-6 TI-7 Costs First $7,370 $2,342 $8,896 $2,878 $121 $1,038 $2,772 Annual I&A 526 167 635 205 9 76 204 O&M 45 Is 55 18 0 0 0 Total $ 571 $ 182 $ 690 $ 223 $ 9 $ 76 $ 204 Benfits Intensification $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Location 0 0 0 0 0 0 0 Employment 0 0 0 0 0 0 0 Inundation Reduction Existing 3 0 6 1 3 14 21 Future' 0 0 0 0 0 0 1 Total $ 3 $ 0 $ 6 $ 1 $ 3 $ 14 $ 22 Net Benefits -$568 -$182 -$684 -$222 -$6 -$62 4182 Benefit-Cost Ratio 0.0 0.0 0.0 0.0 0.3 0.2 0.1 'Consists of affluence factor for residential contents only. TABLE 36 COMPARATIVE ASSESSMENT AND EVALUATION TILGHMANISLAND, MARYLAND Study Objective Plan Description of Plan Beneficial Effects Reduce flood Plan TI- 1 17,560 feet of levee/wall encircling Will reduce flood hazard and damages on Map Ref the large area south of Knapp's provide degree of protection Tilghman Island Southern Narrows (6'NGVD design elev.). indicated for area south of Knapp's Section Narrows. Reduce flood Plan TI-2 5,350 feet of levee/wall encircling the Will reduce flood hazard and damages on Map Ref. small area north of Knapp's Narrows provide degree of protection Tilghman Island Northern (6' NG VD design elev.). indicated for area north of Knapp's Section Narrows Reduce flood Plan TI-3 17,560 feet of levee/wall encircling Will reduce flood hazard and damages on Map Ref. the large area south of Knapp's provide degree of protection Tilghman Island Southern Narrows (8'NG VD design elev.). indicated for area south of Knapp's Section Narrows. 58 Adverse Effects Feonomics Destruction of fringe marsh areas in scattered D.O.P. = 90-year patches alonR the eastern and western -hnre.- P.C. = $7,369,800 of Tilgham Island, (Total area < 10 acres). Use A-A.C, = S570,900 of the shoreline wilf be severely restricted' and A.A.B. z $3,300 access to public landings at Knapp's Narrows 8, C. R. = 0.00 and Dogwood Harbor will be difficult. Temporary destruction of benthic organisms due to construction. Recolonization may occur after completion of construction, Some permanent loss of habitat may also occur. Increased siltation and turbidity due to construction which may effect submerged aquatic vegetation and fish. Adverse effects to the aesthetic conditions of the town, Destruction of marsh area along the cove just D.O-P@ = 90-year north of Knapp's Narrows. (Total area less than F.C. = $2,342,400 20 acres). Access to shoreline at Ki)app's A.A.C. = $181,600 Narrows scverely restricted, A.A.B. = $400 O.C.P., 0.00 Same as TI-L [email protected]. stand, project flood FC. $8,896,360 A,A.C, $699,300 A.A.13, $6,400 B.C.R. 0.01 59 TABLE 36 (Contd) COMPARATIVE ASSESSMENT AND EVALUATION TILGHMANISLAND, MARYLAND Study Objective Plan Description of Plan Beneficial Effects Reduce flood Plan TI-4 5,350 feet of levee/wall encircling the Will reduce flood hazard and provide damages on Map Ref. small area north of Knapp's Narrows (8' degree of protection indicated for area Tilghman Island Northern Section NG VD design elev.), north of Knapp's Narrows. Reduce flood Plan TI-5 Nonstructural protection to 4' NGVD Will reduce flood hazard and provide damages on (15-year) flood"Ievel; includes trailer degree of protection indicated for entire Tilghman Island relocation, housing aquisition and community. demolition, and floodproofing by floodwall. Reduce flood Plan TI-6 Nonstructural protection to 5' NG VD Will reduce flood hazard and provide damages on (40-year) flood level; includes structure degree of protection indicated for entire Tilghman Island raising, home and trailer relocation, community. acquisition and demolition, standard floodproofing, and floodproofing by floodwall. Reduce flood Plan TI-7 Nonstructural protection to 6' NG VD Will reduce flood hazard and provide damages on (90-year) flood level; includes structure degree of protection indicated for entire Tilghman Island raising, home and trailer relocation, community. acquisition and demolition, standard floodproofing, and floodproofing by floodwall. TABLE 38 Beneficial Plan Description Effects Structural Recommend that town consider Ensure that entire town is construction of low dikes, in- protected to same tidal ele- stallation of flapgates or storm vation as top of existing drains. bulkhead. TABLE 37 Nonstructural CAPE CHARLES SUMMARY Plan A Raise buildings, construct utility Provide tidal flood ECONOMIC ANALYSIS additions and temporary closure. protection. (Based on January 1983 Price Levels) Plan B Raise buildings and construct utility additions. A verage Plan C Construct utility additions Annual Annual Net Benefal and temporary closures. Plan Cost Benefits Benefits Cost Ratio A $45,400 $5,000 -$40,400 0.11 Plan D Construct utility additions. B 41,500 5,200 -36,300 0.13 C 11,500 200 -11,300 0.02 1 Elevation 8. No wave action, runup, or freeboard considered. 2EIevation 7. D $ 9,300 $ 300 -$ 9,000 0 .03 60 Adverse Effects Economics Same as TI-2. D.O.P. = stand. project flood F.C. = $2,878,200 A.A.C. = $223,200 A.A.B. = $1,100 B.C.R. = 0.00 Loss of unique social life style for those relocated. D.O.P.= 15-year Temporary, minor noise pollution and aesthetic F. C. = $120,500 disturbances. Construction of floodwall may result A.A.C. = $8,900 in adverse environment effects such as destruction A.A. B. = $2,500 of ad 'jacent wetland areas, increased siltation and B.C.R. = 0.28 turbidity and destruction of benthic organisms. Use of the shoreline will be restricted. Adverse effects to the aesthetic conditions of the area. Same as above. D. 0. P. = 40-year F. C. = $1,038,150 A.A.C. = $76,400 A.A. B. = $12,500 B.C.R. = 0.16 Same as above. D. 0. P. = 90-year F. C. = $2,772, 100 A.A.C.= $204,100 A.A.B. = $21,000 B.C.R. = 0.10 CAPE CHARLES COMPARATIVE ASSESSMENT A ND EVALUATION (Based on January 1983 Price Levels) Economics Adverse Degree First Average Annual BIC Effects Protection Cost Costs Benefits Ratio Minor impact 100-year flood' Cost and benefits of dikes and flapgates not estimated - during construc- tion activitv. 100-year flood $502,000 $45,400 $5,000 0.11 100-year flood $458,000 $41,500 $5,200 0.13 35-year flood2 $127,000 $11,500 $ 200 0.02 35-year flood $103,000 $ 9,300 S 300 0.03 61 TABLE 39 ANNUAL BENEFITS, COSTS AND BIC RA TIOS FOR HAMPTON (Based on January 1983 Price Levels) Average Annual Average Annual Benefits Damages (Dollars) (Dollars) A verage Annual Alet Without With Inundation Affluence Costs Benefits Benefitl Cost Plan Project Project Reduction Factor Total (Dollars) (Dollars) Ratio Structural Plan for Protection to 100-year flood level $100,100 $13,600 $86,500 $20,400 $106,900 $352,000 -$245,100 0.30 Nonstructural Plan for Protection to 100-year flood level $100,100 $12,300 $87,800 $20,800 $108,600 $187,000 -S 78,400 0.58 Nonstructural Plan for Protection to 25-year flood level $100,100 $50,000 $50,100 $11,900 $ 62,000 $ 81,800 -$ 19,800 0.76 TABLE 40 COMPARA TIVE ASSESSMENT AND EVALUA TION FOX HILL AREA OF HAMPTON, VIRGINIA (Based on January 1983 Price Levels) Plan Description of Plan Beneficial Effects Adverse Effects Economics Structural 6,200 feet of floodwall to Provide tidal flood Environmental impact during D. 0. P. = 100-year 100-year protect 50 structures protection. construction activity. F. C. = $3,184,000 A. A. C. = $352,000 A. A. B. = $106,900 B.C.R@ = 030 Nonstructural Raise 59 structures. Provide tidal flood Minor environmental impact D. 0. P. = 100-year 100-year protection. during construction activity. F.C. = $2,065,000 Major social effects during A.A.C. = $187,000 construction activity. A. A. B. = $108,600 B. C. R. = 0.58 Nonstructural Raise 34 structures. Provide tidal flood Minor environmental impact D. 0. P. = 25-year 25-year protection. during construction activity. F.C. = $904,000 Major social effects during A.A.C = $81,800 construction activity. A. A. B. = $62.000 B. C. R, = 0.76 Poquoson rain and the potential danger of loss of level of a rare flood, Unfortunately, the life, it would appear that additional roads leading to the school are at a rela- Economic Analyst's study is warranted. tively low level making it necessary for the City of Poquoson to promptly warn A total of seven plans of protection were No attempt was made to estimate the its citizens of an impending major tidal considered for Poquoson. As shown in cost of protecting the Poquoson Middle flood, soon after a severe storm warning Table 41, the 25-year plan for area School wherein people and families can is issued. POQ-3 was found to be economically and do congregate during high water. feasible. Due to the low level of the ter- The school should be protected up to the 62 TABLE 41 POQUOSON ANNUAL COSTS, BENEFITS, AND BIC RATIOS (Based on January 1983 Price Levels) Average Annual A rea Plan Benefitl Cost Considered Considered Costs Benefits Net Benefits Ratio POQ-2 Complete relocation $ 71,700 15,000 -$56,700 0.21 POQ-3 100-year flood level 91,300 39,200 -52,100 0.43 POQ-3 25-year flood level 18,100 21,300 3,200 1.18 POQ-4 100-year flood level 792,800 362,000 -430,800 0.46 POQ-4 25-year flood level 353,400 223,800 -129,600 0.63 POQ-41 25-year flood level 381,200 253,200 -128,000 0.66 POQ-42 10-year flood level S 52,800 27,800 -$25,000 0.53 'Purchase and demolish structures. Raise others. 2Purchase and demolish structures. Assessment and Evaluation Tangier Island of Ta@gier topromTtly warn its citizens of an impending ti al flood. Eighty-five percent of the entire City of Economic Analysis Poquoson is below the level of the 25- Table 44 is the estimated cost of provid- year tidal flood as established by the Four lans of protection were consid- ing tidal flood protection via walls Corps. Construction of a wall which ered ?Or Tangier Island. Included in and/ or raising buildings. A comparison would encircle a large portion of the city Table 43 is a summary of the findings of of the annual costs and benefits indi- would separate it from adjacent areas. the economic analysis of the plans con- cates that economic justification is lack- Because this is not deemed to be in the sidered. The Corps 100-year structural ing except for the few structures encom- city's best interest, this measure was not plan is the least feasible with a B-C ratio passed within VIMS 100-year stage. considered. Data were approximated of only 0.17. Both the Corps 100-year Table 44 also presents an assessment for protection of the areas investigated and 25-year nonstructural plans ap- and evaluation of the effects of the p lans to 10-, 25-, and 100-year tidal flood lev- proach economic feasibility with B-C investigated. It does not take into ac- els. The studies indicate that such pro- ratios of 0.76 and 0.78, respectively. count the safety and/ or lives of the pop- jects are generally not economically ulation in the event that the waters of a feasible. major tidal storm overtop the island to a considerable depth. Escape to the main- As shown in Table 4 1, only Plan POQ-3 Assessment and Evaluation land by boat, helicopter, or plane would exceeds the requirements for economic not be practical. feasibility. However, only a segment of The entire community of Tangier is Poquoson has been sampled to deter- below the level of a major tidal flood. Any additional structures on Tan_gier, mine the desirability of further investi- An estimate was made of the cost of such as concrete walls, would further gations relative to the justification of protecting the Tangier School to the reduce the small amount of land avail- nonstructural measures by the Corps. level of the Corps Standard Project able to-tbe islanders. The raising of prac While it is believed that one or more Of Flood so that people could congregate tically all the houses on Tangier would the seriously affected areas has been there during high water. The school or have a major social and possibly an investigated, further detailed studies of another building should be protected up environmental effect on the community. this and other areas will have to be made to the level of a rare flood. No benefit- Undoubtedly, construction activities to obtain a comprehensive understand- c.ost ratio is presented for the construc- could create side effects on some of the ing of the entire tidal flood situation at t!on of a wall around the school building adjacent marshland through litter, the since this is considered a must to insure a Poquoson, particularly in view of the safe refuge for the people in the com- placement Of material thereon, and the low-lying terrain and the -potential for munity. Unfortunately, the roads lead- movement of vehicles. Noise during loss of life. ing to the school are at a relatively low construction activities would also con- level making it necessary for the officials 63 TABLE 42 POQUOSON COMPARATIVE ASSESSMENTAND EVALUATION (Based on January 1983 Price Levels) Nonstructural Beneficial Adverse Plan Description Effects Effects POQ-1 Commercial area on Wythe Since the average annual damages in this area are less than $1,240 at Creek Road near Hudgins Road the 100-year tidal flood stageJurther study of this area is not warranted POQ-2 Relocate 96 structures in a Provide tidal flood Minor impact trailer court protection during construction activity. Major social effects. POQ-3 Raise 45 buildings POQ-3 Raise 9 buildings POQ-4 Raise 383 buildings POQ-4 Raise 182 buildings POQ-4 Purchase and demolish 58 structures. Raise 124 structures POQ-4 Purchase and demoiisfi 25 structures. TABLE 43 TA NGID? ISLA ND ECONOMIC A NA L YSIS OF PLA NS (Based on January 1983 Price Levels) Annual Average Annual Net Annual Benefit/ Plan Costs Benefits Benefits Cost Ratio Structural 100-yr (Corps) $2,503,300 $419,000 42,084,300 0.17) Standard Project tribute to the temporary impacts asso- Flood (Corps) 170,600 -2 -2 -2 ciated with projects. Nonstructural West Point 100-yr (Corps) $704,800 $534,100 -170,700 0.763 25-yr (Corps) 473,400 370,500 -102,900 0.783 Economic Analysis 100-yr (VIMS) 16,300 23,800 7,500 1.464 'Affluence factor benefit not projected since b/c ratio is very small. Two plans of protection were consid- 2Not determined. ered for the Town of West Point. 'indicates effect of including affluence factor benefits. Included as Table 45 is a summary of the 4Affluence factor benefit not projected since b/c ratio is greater than 1. results of the economic analysis of the nonstructural plans based on Corps and VIMS frequencies. As shown, the 25- year plan of protection was found to approach economic feasibility in the Corps plan and was economically feasi- ble in the VIMS plan. Assessment and Evaluation Although West Point is exposed on 64 Economics Degree First Average Annual BIC Protection Cost Costs Benefits Ratio Complete 792,000 $ 71,700 15,000 0.21 100-year flood 1,008,000 91,300 39,200 0.43 25-year flood 199,000 18,100 21,300 1.18 100-year flood 8,754,000 792,800 362,000 0.46 25-year flood 3,902,000 353,400 223,800 0.63 25-ycar flood 5,127,000 381,200 253,200 0.66 10-year flood 978,000 52,800 27,800 0.53 three sides to water, the flood problem cal factors appear to be involved in along the Pamunkey River. The plant is there (exclusive of the Chesapeake Cor- connection with raising the houses. susceptible to tidal flooding; however, poration plant) is confined mostly to the Nonstructural measures involving the the company has a program in effect to areas around I st Street, at the south- raising of a maximum of 43 structures raise its equipment and machinery to ernmost edge of the town, and 14th were evaluated at the 25-and 100-year elevation 8.0. Therefore, it was decided Street, where State Route 33 crosses the flood levels and were found to be not that no further study of possible protec- peninsula on which the town is located. economically justified although the B-C tive measures for the plant was necessary. Structural measures to alleviate the ratio of the 25-year plan approached problem in the lower reaches of the town, unity. Table 46 presents a summary of including the construction of a wall and the effects of the plans investigated. the removal or demolition of some houses were found to be not feasible at Separate consideration was given to this time and were not considered Chesapeake Corporation's paper manu- further. A wall along the waterfront facturing plant north of 14th Street would require the removal of many of the houses along First Street and would be socially objectionable. The raising of residences would have little effect on the environment. However, it could incon- venience the residents during construc- tion. No environmental and/ or biologi- 65 TABLE 44 TANGIER ISLAND COMPARATIVE ASSESSMENT AND EVALUATION (Based on January 1983 Price Levels) Beneficial A dverse Plan Description Effects Effects Structural Construct concrete wall around Provide tidal flood Impact on marshland and ridges. protection adjacent areas during and following construction. Also social impacts. Structural Construct concrete walls around Provide tidal flood impact on marshland and buildings. protection adjacent areas during and following construction, Also social impacts. Nonstructural Raise buildings. Provide tidal flood impact on marshland and protection adjacent areas during and following construction. Also social impacts. Nonstructural Raise buildings. Provide tidal flood Impact on marshland and protection adjacent areas during and following construction. Also social impacts. I Affluence factor benefit not projected since b/c ratio is very small. 2 Not determined. Required for safety of public during severe tidal floods. 3 Indicates effects of including affluence factor benefit. 4 Affluence factor benefit not projected since b/c ratio is greater that 1.0. TABLE 45 WEST POINT ECONOMIC ANALYSIS (Based on January 1983 Price Levels) Stage A verage frequen(j, Level of Annual Annual Net Benefit- data Protection Costs Benefits Benefits Cost Ratio Corps 100-yr. $94,900 $40,200 -$54,700 0.42 Corps 25--vr. 42,100 38,300 -3,800 0.91 VIMS 100-yr. 30,800 11,200 -19,600 0.36 VIMS 25-yr. $ 8,200 $ 9,400 $1,200 1.15 66 Economics Degree First Average Annual BIC Protection Cost Costs Benefits Ratio Corps 100-year. $24,891,000 $2,503,300 $419,000 0.171 Corps Stand. $ 1,697,000 $ 170,600 - 2 - 2 Proj. Flood Corps 100-yr. $7,781,000 $704,800 $534,100 0.761 VIMS 100-yr. $ 180,000 $ 16,300 $ 23,800 1.464 Corps 25-yr. $5,227,000 $473,400 $370,500 0.78 3 67 TABLE 46 WESTPOINT COMPARATIVE ASSESSMENTAND EVALUATION (Based on January 1983 Price Levels) Stage Frequency Plan Beneficial Adverse Data Description Effects Effects Corps Raise 43 structures Provide tidal flood Minor environmental and protection social impact during construction Corps Raise 17 structures Provide tidal flood Minor environmental and protection social impact during construction VINIS Raise 15 structures Provide tidal flood Minor environmental and protection social impact during construction vims Raise 3 structures Provide tidal flood Minor environmental and protection social impact during construction 69 Economics Degree of First Average Annual BIC Protection Cost Costs Benefits Ratio I 00-yr. $1,048,000 $94,900 $40,200 0.42 25-yr, $ 465,000 $42,100 $38,300 0.91 1 00-yr. $ 340,000 $30,800 $11,200 0.36 25-yr. $ 90,000 $ 8,200 $ 9,400 1.15 69 CHAPTER V Summary and Conclusions Summary of screenings, to be critically flood- prone. As part of its comprehensive Chesa- peake Bay Study, the Corps of Engi- The communities selected for detailed neers conducted an analysis of tidal. study were done so as part of an iterative flooding and its impact on shoreline process which successively screened communities. This analysis addressed communities from further consideration. the Maryland and Virginia communities The initial step in this analysis identified that were determined, through a series all Bay communities with a population of TABLE 47 TIDAL FLOODING CRITICA L PR OBLEM A REA S Communities With Communities Facing Communities Critical Additional Critical Designated For Flood-prone Communities' Existing Problems2 Problems in Future3 Detailed Study MARYLAND Anne Arundel County Arundel on the Bay X X Avalon Shores X Broadwater Columbia Beach Deale X Eastport Franklin Manor on the Bay & Cape Anne Galesville Rose Haven Baltimore City X Baltimore County Back River Neck Dundalk X X Middle River Neck X Patapsco River Neck X Calvert County Cove Point North Beach on the Bay Solomons Island Caroline County Choptank Denton X Federalsburg Cecil County Elkton X Northeast X Charles County Cobb Island Dorchester County Cambridge X X 'Communities having at least 50 acres of existing development in the Standard Project Tidal Flood Plain. 2COMmunities having at least 25 acres of existing development in the 100-year tidal flood plain. 3COMMunities having at least 25 acres of additional proposed development in the 100-year tidal flood plain 71 at least 1,000 that were located within TABLE 47 (Cont'd) the Standard Project Tidal Flood Plain. The Standard Project Tidal Flood TIDAL FLOODING (SPTF) was defined as the flood event, CRITICAL PROBLEMAREAS resulting from the combination of tidal surge and wave action, which would Communities With Communities Facing Communities inundate areas up to an elevation of 20 Critical Additional Critical Designated For feet above NGVD. These areas were Flood-prone Communities' Existing Problems2 Problems in Future3 Detailed Studv identified as existing tidal flood areas. Harford County The next step in the tidal flooding analy- Harve de Grace sis was to determine the "flood-prone" Kent County communities. To designate an area as Rock Hall X X X "flood-prone" at least 50 acres of inten- Queen Anne's County sively developed land had to be inun- Dominion dated by the SPTF. Sixty communities Grasonville X X were identified as being "flood-prone" Stevensville X and these are listed in the first column of Table 47. St. Mary's County Colton Piney Point X A further examination of the flood St. Clement Shores prone communities was conducted to St. George Island determine whether the tidal flooding problem was of a "critical" nature The Somerset County Crisfield X X Intermediate Regional Tidal Flood Smith Island X X (IRTF) was selected as the determining factor. The I RTF is defined as that tidal Talbot County flood which has a one percent chance of Easton occurrence in any one year. This is gen- Oxford St. Michaels X X X erally referred to as the 100-year flood. Tilghman Island X X The tidal flood problem was considered to be critical if the I RTF inundated 25 or Wicomico County more acres of intensively developed land Bivalve Nanticoke and caused significant physical damage. Salisbury X X As a result of this iteration, 32 Bay communities were determined to be Worcester County 11 critically flood-prone." The communi- Pocomoke City X X X ties so designated are indicated in the Snow Hill X X second column of Table 47. 'Communities having at least 50 acres of existing development in the Standard Project Tidal Flood Plain. 'Communities having at least 25 acres of existing development in the 100-year tidal flood plain. A further iteration eliminated from con- 'Communities having at least 25 acres of additional proposed development in the 100-year tidal flood plain. sideration those "critical" communities where it was evident that flood protec- tion would not be desirable. This deter- tamed for detailed examination. These with important factors to be considered mination was based on the fact that communities are identified in column in developing detailed plans. The struc- many residential communities are lo- four of Table 47. Detailed flood damage tural measures considered included pro- cated along the Chesapeake Bay shore- analyses were conducted in 1979 to jects such as earth levees, concrete line solely for aesthetic and recreational establish relationships between flood floodwalls, dikes. The nonstructural reasons. Structural solutions would stages and damages in the critically measures included programs such as impact upon the use of the shoreline for flood-prone communities. Field surveys flood proofing, utility room additions, recreation and would cause visual dis- were also undertaken to determine the acquisition and demolition of certain ruption of the shoreline's environment. number of structures subject to tidal structures, relocation, and raising of Nonstructural solutions in these areas flooding. In 1983 these communities buildings. would also be inappropriate because were revisited to determine if the find- many structures are old and not suitable ings of the earlier analyses were still Several plans were developed for each of for flood proofing modifications. Sev- valid. the communities studied. All of the eral more communities were eliminated plans included some or all of the mea- from further analysis as detailed studies Once the severity and frequency of the sures previously identified. The plan of these same communities were already tidal flooding problem in each commu- designs themselves varied in size, degree being conducted by the Corps under nity had been defined, alternative plans of protection, and physical configura- separate authorizations. for reducing the magnitude of the prob- tion based on the area] extent of dam- lem were formulated. Potential structur- ages, the frequency of flooding, and the Based on this iterative process, 12 criti- al and nonstructural measures were economic severity of flooding. They cally flood-prone communities were re- first examined in general terms along emphasized both the structural and 72 TABLE 47 (Contd) highest benefit-cost ratio was 0.66 for Crisfield. An examination of these TIDAL FLOODING communities in the summer of 1983 CRITICAL PROBLEM AREAS indicated that minor growth had oc- curred in nearly all the communities, but Communities With Communities Facing Communities not to the degree necessary to substan- Critical Additional Critical Designated For tially alter any of the earlier findings. Flood-prone Communities' Existing Problems2 Problems in Future3 Detailed Study VIRGINIA Independent Cities Virginia Communities Chesapeake X X X Fredericksburg X GeneralIV, the Virginia communities Hampton X X X Newport News were found to be somewhat larger and Norfolk X X X of a broader economic base than those Poquoson X X X in Maryland. Significant growth is ex- Portsmouth X X pected in future years in some of these Virginia Beach X X communities. These communities are Accomack County also close to the Atlantic Ocean and Onancock exposed to potentially great damages as Saxis storms move along the coastline. Tangier Island X X King George County Dahlgren X Similar to the plan development process which was undertaken for the flood- King William County prone Maryland communities, alterna- West Point X X tive plans were formulated for each of Northampton County the Virginia communities facing critical Cape Charles X X tidal flooding problems. These plans Westmoreland County again included both structural and non- Colonial Beach X structural measures in various combina- tions as indicated in Table 49. It should WASHINGTON, D.C. X be noted that the intense level of devel- opment in the Hampton/ Norfolk/ 'Communities having at least 50 acres of existing development in the Standard Project Tidal Flood Plain. Chesapeake/ Portsmouth region pre- 'Communities having at least 25 acres of existing development in the 100-year tidal flood plain. clude a detailed examination of the area 3Communities having at least 25 acres of additional proposed development in the 100-year tidal flood plain during this study. Instead, only the selected sample area of Fox Hill was examined to determine if tidal flood reduction measures might be feasible. nonstructural protective measures. Costs the level of protection provided. In other for each alternative plan were also devel- communities, different levee and/ or Environmental and social effects of the oped and then annualized for compari- floodwall alginments were examined to various flood reduction measures were son to the benefits. furnish protection to different sections found to be similar to those in the Mary- in the town. land communities. In several of the Vir- Maryland Communities ginia communities, though, the prelimi- Adverse environmental effects were nary examinations conducted in 1978 For the most part, the Maryland com- found to range from minimal for most and 1979 revealed that some of the munities were found to be older village of the nonstructural measures to signifi- alternative plans were economically j us- centers with relatively stable popula- cant for the structural components such tified. Consequently, the Norfolk Dis- tions. The economy in most of the criti- as levees and floodwalls. Adverse social trict, Corps of Engineers conducted ad- cal Maryland communities is tied to the effects would occur if structures were ditional investigations in 1983 including seafood industry and other Bay-related relocated, or if certain buildings were reexaminations of the average annual trades. Little growth is projected for the acquired and demolished. Economic in- damages, new computations for the first coming years. Table 48 contains a list of formation was developed for each alter- costs and annual costs of the alternative the Maryland communities and a sum- native plan and is shown in the last plans and recomputation of the benefit mary of the structural and nonstructural several columns of Table 48. As is evi- to cost ratios. The results of this recent measures which were considered. Some dent from the data in the table, the eco- update of the economic analysis are plans contained only structural elements, nomic costs of providing tidal flood shown in the last several columns of some plans contained only nonstructu- damage protection far outweighed the Table 49. Confirming the earlier work, ral measures, and some plans contained potential economic benefits. In no in- certain combinations of tidal flood re- both structural and nonstructural mea- stance did the ratio of benefits to costs duction measures appear to be econom- sures. Alternative plans for a given exceed the 1.0 which would be necessary ically justified for Poquoson, Tangier community sometimes differed only in for economic justification. Indeed, the Island, and West Point. 73 TABLE 48 PLANS FOR TIDAL FLOOD REDUCTION MARYLAND COMMUNITIES Structural Nonstructural Measures Measures Earth Concrete Flood Utility Room A equisition Community Levee Floodwall Proofing Addition Demolition Relocation Raising Cambridge x x x x x (8 Plans) Crisfield x x x x x x x (6 Plans) Pocomoke City x x x x x x x (5 Plans) Rock Hall x x x x x x x (10 Plans) Snow Hill x x x x x (7 Plans) St. Michaels x x x x x x (4 Plans) Tilghman Island x x x x x x (7 Plans) I Economic information is based on July 1979 price levels and the fiscal year 1980 interest rate of 71/8 percent. 2 Figures for annual costs include operation and maintenance as well as interest and amortization. TABLE 49 PLANS FOR TIDAL FLOOD REDUCTION VIRGINIA COMMUNITIES Structural Nonstructural Measures Measures Earth Concrete Dikes, Flood Utility Room Acquisition & Community Levee Flood Wall Flapgates Proofing Addition Demolition Relocation Raising Cape Charles x x x (5 Plans) Hampton/ Norfolk/ x x Chesapeake/ Portsmouth 3 (3 Plans) Poquoson x x x (8 Plans) Tangier Island (4 Plans) x x West Point x (4 Plans) I Economic information based on January 1983 price levels and fiscal year 1983 interest rate of 7y8 percent. 2 Figures for annual costs include operation and maintenance as well as interest and amortization. 3 Figures are for the Fox Hill sample area only. 74@ Economic Information I A verage First Annual Annual Benefit Annual Cost Cost Benefits 10 Damages of Plans of Plans 2 of Plans Cost Ratios $ 18,400 $ 356,300 to $55,150 to 13,500 to 0. 14 to $ 9,120,600 $706,700 $103,800 0.5 $142,500 $ 676,300 to $49,800 to S 33,000 to 0.3 to $ 7,333,200 $567,200 $172,000 0.7 $ 23,900 $ 259,700 to $19, 100 to $ 10,100to 0 to $ 4,322,700 $335,300 $ 18,000 0.5 $ 73,500 $ 1,093,000 to $80,450 to $ 22,500 to 0.2 to $13,513,800 $1,046,300 $194,500 0,3 $ 11,400 $ 303,500 to $22,300 to $ 3,400 to 0 to $ 3,741,600 $290,000 $ 9,100 0.2 $ 26,300 $ 730,000 to $53,700 to $ 8,200 to 0 to $11,970,800 $926,600 $ 16,000 U $ 34,700 $ 120,500 to $8,900 to $ 400 to 0 to $ 8,896,360 $689,300 $ 21,000 0.3 Economic Information I A verage First Annual Annual Benefit Annual Cost Cost Benefits TO Damages of Plans of Plans 2 of Plans Cost Ratios $ 37,400 $ 103,000 tc $9,300 to $ 200 to 0.02 to $ 502,000 $45,400 $ 5,200 0.13 $100,100 $ 904,000 to $81,800 to S62,000 to 0.3 to S 3,184,000 $352,000 $108,600 0.8 $501,400 $ 199,000 to $18,100 to $ 15,000 to 0.2 to $ 8,754,000 $792,800 $362,000 1.2 $481,700 $ 180,000 to $16,300 to $ 23,800 to 0.2 to $24,891,000 $2,503,300 $534,100 1.5 $ 62,500 $ 90,000 to $8,200 to S 9,400 to 0.4 to $1,048,000 $94,900 S 40,200 1.2 75 Findings and Conclusions Although flood protection plans for the tionship does not exist. A stage-frequency Town of Cape Charles and the Hamp- analysis of Chesapeake Bay should be As a result of the tidal flooding analysis ton Roads city complex are not justi- conducted based on a numerical tidal conducted during the Chesapeake Bay fied, several findings did result from the surge model developed by the U.S. Study, several observations and find- analysis of these areas. The ground level Waterways Experiment Station at ings are noteworthy. Tidal flooding is a on the north and south sides of Cape Vicksburg, Mississippi, This should be problem that periodically affects all of Charles should be raised to the level of coordinated with the Federal Insurance Chesapeake Bay's shorelines at one time the existing bulkhead with flapgates Administration and the Virginia Insti- or another. Based on the screening crite- installed in the storm drains. tute of Marine Science so that the stage- ria, 60 day communities were identified frequency analysis for Tangier can be as having existing or potentiallv serious Existing flood damage surveys in the resolved. Further studies should then be tidal flooding problems. Less obvious Hampton Roads area are over 20 years made of structural and/ or nonstructur- perhaps, is that significant monetary loss o1c, and much new development along al protection measures based on the resulting from tidal flooding is incurred with substantial redevelopment has oc- results of the frequency analysis referred by only a few of these 60 communities curred in this particular area. Therefore, to above. This would be particularly which, because of topography and land further studies of the Hampton Roads desirable due to the isolation of the use pattern, are especially susceptible to city complex should be made to ascer- population from the mainland. Consid- damage in developed sections. tain the economic feasibility of structur- eration should also be given to flood al and/ or nonstructural measures. This proofing the Tangier School or another should take into account the effect of public building wherein the public could Both structural and nonstructural mea- wave action and runup, particularly in take shelter in the event of a major sures were considered for preventing or the exposed areas adjoining Chesapeake flood. The building should be flood reducing the adverse effects of tidal Bay, Emphasis should be placed on all proofed to a high level of protection. flooding in the 12 communities exam- factors-economic, environmental, social, ined in detail. Structural measures usu- and technological. Furthermore, city Another finding that is common to all of ally impact adversely on the environ- officials throu2hout the Harnnton Roads the Virginia communities is that the ment and are expensive. citv complex should insure that the first State, with the assistance 01 the Corps floor level of the numerous evacuation and local officials, should insure that Furthermore, residents dislike str.uctur- shelters are sufficiently reinforced and concrete or metal markers be placed to al measures for aesthetic reasons an at an elevation so as to protect occu- indicate to the public the height of because direct and easy access to the Bay pants from a major catastrophic flood future floods. The same program would shoreline may be hindered. Nonstructur- including the effect of wave action. The also have merit in Maryland. al measures, on the other hand, are ess Corps of Engineers should assist in this damaging to the environment and are, matter if so requested by local officials. Given the lack of historical tidal flood- usually, less expensive. However, to stage and frequency information, a co- make a nonstructural tidal flood protec- The analysis of Poquoson indicated that ordinated program should be instituted one plan for tidal flooding protection to collect and record stage-frequency tion program effective on a community- has a benefit-cost ratio greater than 1.0. data. This program should include ap- wide basis, voluntary participation b Y Because of the extent and seriousness of propriate state agencies as well as Fed- nearly all residents and businesse .s is its tidal flood problem, the Corps of eral agencies such as the Corps of Engi- required. Furthermore, these solutions Engineers should prepare a detailed neers, the Coastal Zone Agency of the usually require direct monetary outlays feasibility investigation of the entire city National Oceanographic and Atmo- by the residents. to establish the seriousness and extent of spheric Administration, the Federal the tidal flood problem, the need and Emergency Management Agency, the justification for the evacuation of indi- National Weather Service, and other Economic information developed dur- vidual houses from the flood plain par- appropriate agencies. This program ing the Tidal Flooding Study indicated ticularly those that are in serious jeo- should not limit its scope to the com- that protection programs were econOm- pardy, the justification for low levees or munities examined in this study but ically justified in only a few communi- walls for individual and/ or small groups should be Bay-wide in nature. Thus an ties. Of the 12 communities investigated of houses, the raising of escape roads effective Bay-wide data base can be only some the plans formulated for during high water, and the desirability established which will be of great benefit Poquoson, Tangier Island, and West of an urban renewal program in the in the future evaluation of tidal flooding. Point were found to have benefit-cOst extremely low-lying areas which FIA ratios greater than 1.0. The value and indicates are subject to major wave As much still is to be learned about the intensity of development in most flood- action. Consideration should also be intricacies of natural events which result prone areas was not great enough to given to flood proofing the Middle in tidal flooding, the completion of a warrant a full-scale tidal flooding pro- School or another building wherein the storm-surge model would be beneficial. gram. An additional observation is that public could congregate in the event of a A model of this type would permit more many residents of flood-prone commu- major flood. The building should be accurate forecasts of tidal flooding nities view tidal flooding as a temporary flood proofed or protected by a wall to a stages. A storm-surge model would also inconvenience which is a tolerable high level of protection. be useful in developing better stage- trade-off for the convenience of living frequency relationships on which to and working close to the waters of Ches- The analysis of Tangier Island indicated base the economic evaluation of flood apeake Bay. that a definitive stage-frequency rela- protection plans. A model of this nature, 76 if developed to represent surges Bay- weather and tidal stage forecasts, (2) flooding as a temporary inconvenience wide, could be of much benefit to all of communication networks to inform which is a traded off against the aesthe- the tidal communities. communities and residents of potential tics and benefits of living and working Despsite the fact that few of the plans flooding, (3) permanent markers placed near the Chesapeake Bay. It is also rec- in critical areas to indicate tidal flood ognized that development in some of for tidal flood protection are justified, heights, (4) identification of low-lying these areas may be faster than in others steps can be taken to reduce inconven- areas and planned evacuation routes attracting residents who may view tidal ience and damage in any community. from these same areas, and (5) designa flooding as a problem rather than as an Perhaps one of the most promising mea- tion of municipal buildings out of the inconvenience. Through the use of sures is the coordinated development of flood-prone areas for temporary shelter comprehensive planning documents, an accurate tidal ilood torecasting anu during flood events. While these actions land use designations, and zoning ordi- warning system. A measure of this type will not reduce the incidence or magni- nances- prudent use should be made of could be developed through the efforts tude of tidal flooding, inconvenience, flood-prone areas in such a way as to of the National Weather Service and physical damage, and personal injury minimize the loss that may result from state and local civil defense and disaster may be reduced. future tidal flooding events. preparedness departments. Included in a flood forecasting and warning system It is reco2nized that many residents of could be items such as: (1) advance flood-prone communities view tidal 77 CHAPTER VI Recommendations Based on the information gathered dur- (6) Development of a storm-surge model ing the Tidal Flooding Study, and the should be completed for use in estab- findings and conclusions resulting from lishing reliable stage-frequency rela- the tidal flooding analyses, the follow- tionships on which to base economic ing recommendations are made: evaluations of flood protection plans. (1) The ground level on the north and (7) Investigations should be conducted south sides of Cape Charles should to determine the feasibility of imple- be raised to the level of the existing menting a coordinated tidal flood bulkhead with flapgates installed in forecasting and warning system with- the storm drains. in the Bay Region communities. (2) Additional studies of the Hampton Roads city complex should be con- ducted to ascertain the economic feasibility of structural and/or non- structural measures to include the effect of wave action and runup. (3) Due to the extent and seriousness of the tidal flooding problem, the Corps of Engineers should conduct a de- tailed feasibility investigation of the entire City of Poquoson to fully determine the feasibility of construct- ing tidal flood protection measures. (4) Based on the positive results of the preliminary analysis of Tangier Island's tidal flooding problem, further detailed investigations should be made by the Corps of Engineers to determine the feasibility of imple- menting protective measures. (5) Given the lack of historical tidal floodstage and frequency informa- tion, a coordinated program should be instituted to collect and record stage-frequency data on a Bay-wide basis and should include appropriate state agencies as well as the Corps of Engineers, the Coastal Zone Agency, FEMA, and the National Weather Service. 79 LIST OF ABBREVIATIONS AAB -Average Annual Benefits NPDES - National Pollutant AAC -Average Annual Costs Discharge Elimination AC -Acre System NWS -U.S. National Weather BC1 -Building Construction Service Index BPT -Best Practicable OBERS -Acronym referring to the Treatment agencies responsible for BCR -Benefit-Cost Ratio demographic projections used in water resources CATV -Cable Antenna Television planning - the Bureau of CPCB -Citizens Program for the Economic Analysis Chesapeake Bay (formerly the Office of C.Y. -Cubic Yard Business Economics) and the Economic Research D.O.P. -Degree of Protection Service. D.O.T. -Department of O&M -Operations and Transportation Maintenance ENR -Engineering-News Record PPT -Parts Per Thousand FAA -Federal Aviation SMSA -Standard Metropolitan Administration Statistical Area F.C. -First Costs SPTF -Standard Project Tidal FEMA -Federal Emergency Flood Management Agency SY -Square Yard FIA -Flood Insurance Administration VIMS -Virginia Institute of FOR -Flood of Record Marine Science FWS -U.S. Fish and Wildlife Service WES -U.S. Army Corps of FY -Fiscal Year Engineers Waterways Experiment Station I&A -Interest and Amortization 1. W. R. -Institute for Water Resources U.S. Army Corps of Engineers JTU -Jackson Turbidity Units Lb -pound MGD -million gallons per day MPN -most probable number NASA -National Aeronautic and Space Administration NGVD -National Geodetic Vertical Datum NMFS -National Marine Fisheries Service NOAA -National Oceanic and Atmospheric Administration 81 GLOSSARY L Accretion - May be either natural or than a cove. artificial; Natural accretion is build- up of land, solely by the action of the Beach - The zone of unconsolidated forces of nature, on a beach, by depo- material that extends landward from sition of waterborne or airborne the mean low water line - unless material. Artificial accretion is a sim- otherwise specified - to the place ilar build-up of land by reason of an where there is marked change in act of man, such as the accretion material or physiographic form, or to formed by a groin, breakwater, or the line of permanent vegetation. beach fill deposited by mechanical means. Opposite of erosion. Beach Erosion - The carrying away of beach materials by wave action, tidal Amortization - The process of setting currents, or littoral currents, or by money aside at intervals for gradual wind. payment of a debt, etc. either at or before maturity; the economic pro- Benefit-Cost Ratio - The arithmetic cess of repaying or liquidating a debt proportion of estimated average an- or recovering the wealth invested in a nual benefits to average annual costs, project over a given period of time. insofar as the factors can be expressed in monetary terms. The relation of Armoring - The use of riprap material benefits to costs representsthe degree to protect the water side of levees. of tangible economic justification of a project. Astronomical Tide - The alternate rise and fall of the oceans, seas, and the Benefits - Increases or gains, net of bays, rivers, etc. connected with them; associated or induced costs, in the caused by the attraction of the moon value of goods and services which and sun; it occurs twice in each result from conditions with the pro- period of 24 hours and 50 minutes. ject as compared with conditions without the project. National eco- Atlantic Flyway - Flying route along nomic benefits include direct output the Atlantic seaboard taken regularly increases, use of unemployment or by migratory birds going to and from underemployed resources, and in- their breeding grounds. creases in output resulting from ex- ternal economies. Average Annual Equivalent Benefits - Term referring to the annual benefits Berm - Portion of a beach or back- estimated to be associated with plan/ shore that is formed by deposition of project implementation over the material by wave action; marks the period of analysis. limit of ordinary high tide. Average Annual Equivalent Charges - Biota - The plant and animal life of a Term referring to the annual pay- region. ment associated with project costs which include amortization of the investment costs, the annual opera- Breakwater - A structure for breaking tion and maintenance costs, and the the force of waves to protect craft annual equivalent of major replace- anchored in a harbor or to protect a ment costs. beach from erosion. An offshore bar- rier may be either an artificial struc- Bay - A recess in the shore or an inlet of ture or a natural formation. Some- a sea between two capes or head- times it is connected at one, or both lands, not as large as a gulf but larger ends, with the shore. 83 Building Construction Index (BCI) - a lake; its boundary is defined by the stant direction and spe .ed; sometimes Index published monthly by the ridge beyond which water flows in used synonymously with Fetch Engineering - News Record maga- the opposite direction - away from Length. zine which applies to general con- the basin. struction costs and how much it costs Fetch Length - The horizontal dis- to purchase a hypothetical package Dune - A mound or ridge of sand tance (in the direction of the wind) of goods and services compared to a formed, either in a desert or along the over which a wind generates seas or base year. The BCI includes skilled sea coast, through transportation by creates wind setup. labor for bricklayers, carpenters and wind. Sand particles are carried by structural ironworkers. wind and piled in a heap. Dunes often First Costs - The total project con- form around an obstacle. They change struction cost including costs of lands, Bulkhead - A low wall of stones, con- constantly in size, shape and location. relocations, engineering, design, crete or piling built to protect a shore, administration, and supervision. or fills, from wave erosion. A bulk- Ecology - The science which treats head may be built to protect naviga- orgariisms'in relation to their envi- Flood - An overflow of lands not nor- ble waters, and serve as a line, limit- ronment; frequently subdivided into mally covered by water and that are ing filling, or beyond which filling of human ecology, plant ecology, and used or are usable by man. Floods submerged lands is not permitted. A bioecology. The latter deals with the have two essential characteristics: the secondary purpose is to protect the interrelationships between animal life inundation of land is temporary and upland against damage from wave and plant life. the land is adjacent to an d- inundated action. by overflow from a river or stream or Ecosystem - A community and its (liv- an ocean, or other body of standing Coriolis Force - The inertial force ing and none-living) environment water. caused by the earth's rotation that considered collectively; the funda- deflects a moving body to the right in mental unit of ecology; the interact- Flood Plain - The relatively flat area or the Northern Hemisphere and to the ing system of things with their physi- low lands adjoining the channel of a left in the Southern Hemisphere; this cal and chemical environment. river, stream or watercourse or ocean, deflection (Coriolis Effect) is pro- bay, or other body of standing water, duced by the acceleration of any Embayment - A bay or a formation which has been or may be covered by body moving at a constant speed resembling a bay which offers protec- flood water. above the earth with respect to the tion and shelter. surface of the rotating earth. Flood-prone - For purposes of the Estuary - That portion of a stream or Tidal Flooding Study, having at least Critically Flood-prone - For purposes river influenced by the tide of the 50 acres of land developed for inten- of the Tidal Flooding Study, when 25 body of water into which it flows; a sive use inundated by the SPTF. acres or more of intensively devel- partially enclosed body of water, with oped land are inundated by the 100- a connection to the ocean, in which Flood Stage - The stage or elevation at year flood. freshwater from overland drainage is which overflow of natural banks of a mixed with saline water moving in stream or body of water begins in the Dike - Artificial embankment (techni- from the ocean. reach or area in which the elevation is cally neither dams or levees) con- measured. structed to hold bodies of water, Euphotic Zone - The uppermost por- mostly on relatively flat land. A body tion of a body of water, into which Floodwall - A structure built along a of water so retained may be in the light enters to a degree sufficient for water course to prevent flooding in nature of a reservoir, lake, pond, or photosynthesis and the consequent the adjacent land area. Primarily used flooding. Also dikes may be con- growth of plants. where levees are not feasible, either structed on the shores or borders of a due to space limitations or consider- lake either to prevent flooding, from Evapotranspiration - The total water able wave action. See Seawall. overflow of the lake, or adjacent loss from the soil, including that by land, or to prevent inflow into a lake direct evaporation and that by trans- Fluvial - That which is produced by a of undesirable water. Dike also has piration from the surfaces of plants. river. the meaning of a ditch which holds water, but such usage is rare. Extratropical Storm - See Northeaster. Freeboard - The vertical distance between a design maximum water Diurnal - Occurring once a day; i.e., Fall Line - The geographical line indi- level and the top of a structure. with a variation period of one day; cating the beginning of a plateau, having a period or cycle of approxi- usually marked by many waterfalls Frequency (Statistics) - The number of mately one Tidal Day. and rapids; the line east of the Appa- observations or measures in one of lachian Mountains marking the end the class intervals of a frequency dis- Drainage Area - The region which of the coastal plains and the begin- tribution. Also called frequency, class drains all the rain water that falls on ning of the Piedmont Plateau. size, and variate frequency. The it, apart from that removed by evap- number of observations or measures oration, into a river or stream, which Fetch - The area in which seas are gen- in one of the cells of a double entry then carries the water to the sea or to erated by a wind having a rather con- table. Also called cell frequency. 84 Groin - A low wall built out into the of once in 100 years although the Mean Tidal Range - Average differ- sea, more or less perpendicular to the tidal flood may occur in any year. It is ence between mean low water and coastline, to resist the travel of sand based on statistical analyses of tide mean high water. and shingle along a beach, or mini- records available for the "general mize erosion by the sea. region of the study area." Another Mean Tide - Mid-point between mean way to refer to a 100-year flood is to high and mean low water. Harbor of Refuge - A name given to say that it is a flood that has a one- havens along shorelines located percent chance of occurring during National Geodetic Vertical Datum of between commercial and recreational any year. 1929 (NGVD) - is a geodetic datum harbors; designed primarily to be a derived from a general adjustment of place of refuge for small craft during Intertidal Zone - Of or pertaining to a the first order level nets of both the storm periods. shore zone (line) bounded by the lev- United States and Canada. It was els of high and low tide. formerly called "Sea Level Datum of Head of Navigation - The farthest 1929" or "mean sea level." Although point up a river to be reached by ves- Jetty - On open seacoasts, a structure the datum was derived from the aver- sels for the purposes of trade. extending into a bay of water, and age sea level over a period of many designed to prevent shoaling of a years at 26 tide stations along the Hurricane - An intense tropical cyclone channel by littoral materials, and to Atlantic, Gulf of Mexico, and Pacific in which winds tend to spiral inward direct and confine the stream or tidal Coasts, it does not necessarily repre- toward a core of low pressure, with flow. Jetties are built at the mouth of sent local mean seal level at any maximum surface wind velocities that a river or tidal inlet to help deepen particular place. equal or exceed 75 mph (65 knots) for and stabilize a channel. several minutes or longer at some Northeaster - A cyclonic type storm points. Tropical Storm is the term Knot - A unit of speed of one nautical which developes near the Atlantic applied if maximum winds are less mile *(6,076. 10 feet) an hour;, same as Coast and is most common during than 75 mph. nautical mile. the winter months and early spring. Wind speeds are not as great and cen- Hydraulic Model - Anowsystem so Levee - A dike or embankment to pro- tral pressures are not as low as ordi- operated that the characteristics of tect land from inundation. nary hurricanes, but winds cover a another similar system may be pre- considerably greater area. dicted. A model is generally a small- Littoral - Of or pertaining to a shore, scale reproduction of the prototype, especially of the sea. but may be larger and/or geometri- Phytoplankton - Plankton consisting cally distorted. The Chesapeake Bay Littoral Current - Any current in the of plants; i.e. some forms of algae and Model is a hydraulic model. littoral zone caused primarily by wave diatoms. action, e.g., longshore current. Hydrodynamics - The study of the Port - A place where vessels may motion of and the forces acting on Littoral Drift - The sedimentary Mate- discharge or receive cargo; this may water. rial moved in the littoral zone under be the entire harbor including its the influence of waves and currents. approaches, or it may be the com- Hydrograph - A graph showing stage, mercial part of a harbor where the flow velocity or other properties Ot Littoral Transport - The movement of wharves and facilities for transfer of water with respect to time. littoral drift in the littoral zone by cargo, docks, and repair shops are waves and currents; includes move- situated. Hydrology - The scientific study of the ment parallel (longshore transport) waters of the earth, especially with and perpendicular (on-shore trans- Probable Maximum Tidal Flood - The relation to the effects of precipitation port) to the shore. tidal flood that can be expected from and evaporation upon the occurrence the most severe combination of and character of water in streams, Littoral Zone - In beach terminology, meteorological and hydrologic con- lakes, and on or below the land an indefinite zone extending seaward ditions reasonably possible in the surface. from the shoreline to just beyond the region. Breaker Zone. Hydrostatic Forces - Pressures due to Reaches - A straight section of res- the weight of a water column above a Lunar Day - 24.84 hours; within the tricted waterway of some extent; a given point. Chesapeake Bay Area, a period en- straight section of a stream or river. Impervious - Incapable of being passed compassing two tidal cycles; see Tidal Recurrence - The act or instance of through or penetrated; usually said Day. occurring again; often used inter- of material that is not penetrated by Macrophytes - large plants (visible to changeably with frequency to indi- water. the naked eye). cate the statistical probability of the occurrence of a particular hydrologic Intermediate Regional Tidal Flood - A Mean Low Water (mlw) -The average event; such as the 100-year flood tidal flood having an average fre- height of the low waters over a long event, or a recurrence interval of 100 quency of occurrence on the order period of time. years. 85 Revetments - A facing of stone, con- channel, or structure designed ex- Tidal Station (gage) - A place at which .crete, etc., built to protect a scrap, pressly or primarily to discharge tide observations are being taken. It embankment, or shore structure "excess" water from a reservoir. A is called a primary tide station when against erosion by wave action or "controlled" spillway is equipped with continuous observations are to be currents. crest gates, stoplogs, or other mova- taken over a number of years to ble structures to permit various obtain basic tidal data for the local- Riprap - A layer, facing, or protective degrees of variation in outflow rates, ity. A secondary tide station is one mound of stones randomly placed to operated over a short period of time prevent erosion, scour, or sloughing Stage - In hydrology, the height of the to obtain data for a specific purpose. of a structure or embankment; also water surface above or below an arbi- the stone so used. trary datum; a gage height. As a phY- Tide - The periodic rising and falling of siographic term as in the "stage of the water that results from gravita- Runup - The rush of water up a struc- development of a shoreline," stage tional attraction of the moon and sun ture or beach on the breaking of a refers to a period or phase in the cycle and other astronomical bodies acting wave. The amount of runup is the of erosion; for example, the youthful upon the rotating earth. vertical height above stillwater level stage or mature stage. The final period that the rush of water reaches. in the life history of a lake may be Topography - The configuration of a called a stage of extinction. Also surface, including its relief, the posi- Scour - Removal of underwater mate- former levels of a lake marking peri- tion of its streams, roads, building, rial by waves and currents, especially ods in its geological history are called etc. at the base or toe of a shore structure. stages and often given the geographic name of the ancient predecessor lake, Tributary - A stream or other body of Seawall - A structure separating land as for example, the Algonquin Stage water that contributes its water to and water areas, primarily designed of Lake Michigan. another and larger stream or body of to prevent erosion and other damage water. due to wave action. See Also Bulk- Standard Project Tidal Flood - The head and Floodwall. flood in coastal areas caused by a Tropical Cyclone - See Hurricane. storm surge that may be expected Semidiurnal- Of, lasting, or performed from the most severe combinations Tropical Disturbance - A cyclonic wind in half a day; coming twice a day, or of meteorological and hydrological storm of tropical origin with winds about every 12 hours, as do the tides. conditions that are con sidered rea- from 39 to 74 mph. sonably characteristic of the geo- Sheet Piling - A group of piles with a graphical area in which the drainage rurbidity - A condition of a liquid due generally slender flat cross section to basin is located, excluding extremely to fine visible material in suspension. be driven into the ground or seabed rare combinations. Such floods, as The particles may not be of sufficient and meshed or interlocked with like used by the Corps of Engineers, are size to be seen by the naked eye, but members to form a diaphragm, wall, intended as practicable expressions do prevent the passage of light through or bulkhead. of the degree of protection that should the liquid. A measure of fine sus- be sought in the design of flood con- pended material (usually colloidal) in Shoal - A shallow place in a river, sea, trol works, the failure of which might liquids. etc.; a sandbar or piece of rising be disastrous. ground forming a shallow place that Wind Setup - (1) The vertical rise in the is a danger to navigation. Storm Surge - A rise above normal stillwater level on the leeward side of water level on the open coast due to a body of water caused by wind Shore - The narrow strip of land in the action of wind stress on the water stresses on the surface of the water. immediate contact with the sea, in surface. Storm surge resulting from a (2) The difference in stillwater levels cluding the zone between high and hurricane also includes that rise in on the windward and the leeward low water lines. A shore of unconsol- level due to atmospheric pressure sides of a body of water caused by idated material is usually called a reduction as well as that due to wind wind stresses on the surface of the beach. stress. See Wind Setup water. (3) Synonymous with storm surge. Storm surge is usually reserved Shoreline - The intersection of a speci- Stratification - The state of a fluid that for use in referring to the ocean and fied plane of water with the shore or consists of two or more horizontal large bodies of water. Wind setup is beach (e.g., the highwater shoreline layers arranged according to their usually reserved for use in referring would be the intersection of the plane density, the lightest layer being on to reservoirs and smaller bodies of of a mean high water with the shore or top and the heaviest at the bottom. water. beach). The line delineating the shoreline on U.S. Coast and Geo- Wind Waves - Waves being formed detic Survey nautical charts and sur- Tidal Day - The time of the rotation of and built up by the wind. Loosely, veys approximates the mean high the earth with respect to the moon, or any wave generated by wind. water line. approximately 24.84 solar hours (24 hours and 50 minutes) or 1.035 times Spillway - In broad terms, a "spillway" the mean solar day. Also called lunar may be defined as any passageway, day. 86 Acknowledgements and Credits The Chesapeake Bay Study was per- report and the conduct of the Low formed by the Baltimore District, Freshwater Inflow and/or the Tidal Corps of Engineers, under the gen- Flooding Studies include: eral direction of the following Dis- Baltimore District: Brooke Alex- trict Engineers: ander, John M. Brzezenski, John C. Diering, Jr., Robert C. Gordon, J. COL Frank W. Rhea 1967-1968 William Haines, George W. Har- COL William J. Love 1968-1971 man, Clifford J. Kidd, Edward S. COL Louis W. Prentiss, Jr. 1971-1973 Musial, Peter A. Pellissier, Steven BG Robert S. McGarry 1973-1976 R. Stegner, Stanley Synowczynski, COL G.K. Withers 1976-1979 Charles E. Yoe. Norfolk District: COL James W. Peck 1979-1982 Edward Andrews, Hyman J. Fine, COL Gerald C. Brown 1982-1984 Owen Reece, Frank T. Wootton, Jr. COL Martin W. Walsh, Jr. 1984 Other staff persons who contributed This study was performed under the to the Chesapeake Bay Study in- staff supervision of: clude: John T. Starr, Chief, Basin Planning Branch 1968-1970 Thomas L. Anderson, Kenneth L. William E. Trieschman, Jr., Chief, Beat, James E. Crews, Paul S. Danis, Planning Division 1970-1984 Linda K. Davidson, Kenneth L. Garner, James J. Guerrini, Kenneth The study was performed under the E. Hartzell, Martha R. Hayes, Henry immediate supervision of the follow- A. Hespenheide, Harry E. Kitch, C. ing: John Klein, 111, William L. Klesch, Michael A. Kolessar, Chief, David S. Ladd, Robert W. Lindner, Chesapeake Bay Herbert H. Linthicum, Carl D. Mat- Study Group 1967-1968 thias, Andrew Matuskey, David C. Alfred E. Robinson, Jr., Chief, Mitchell, Harold L. Nelson, John P. Chesapeake Bay O'Hagan, James E. O'Hara, James Study Branch 1971-1984 P. Rausch, Raymond C. Solomon, Noel E. Beegle, Chief, Study Claggett M. Wheeler, Jr., Thomas P. Coordination and Whelley, Jr., Leonard A. Zapalowski. Evaluation Section 1971-1981 Chief, Urban Studies Branch 1981-1984 Dr. James H. McKay, Chief, Advisory Group Technical Studies and Data Development Section 1971-1984 Department of Agriculture The U.S. Army Waterways Experi- Edward R. Keil, 1967-70 ment Station was responsible for the C. Douglas Hole, 1970-72 design, construction, operation and Graham T. Munkittrick, 1972-76 maintenance of the Chesapeake Bay Gerald R. Calhoun, 1977-84 Hydraulic Model under the staff supervision of the following: Department of Commerce Henry B. Simmons, Chief, Phillip K. Reiss, 1967-68 Hydraulic Laboratory Howard J. Marsden, 1968-70 Richard A. Sager, Chief, Estuaries Henry L. DeGraff, 1970-83 Division Department of Health, Staff persons who made significant Education, and Welfare contributions to the writing of this Gerald W. Ferguson, 1967-70 87 Department of Housing National Science Foundation and Urban Development Dr. William A. Niering, 1968 Steering Committee for Mark Keane, 1967 Dr. Edward Chin, 1968-70 Liaison and Basic Research Jerome E. Parker, 1967-68 Dr. Richard C. Kolf, 1970-74 Thomas M. Croke, 1968-76 Dr. Edward H. Bryan, 1974-84 U. S. Army Corps of Engineers Lawrence Levine, 1976-84 Smithsonian Institution Michael A. Kolessar Department of the Interior Dr. 1. Eugene Wallen, 1968-71 (Chairman 1968-70) Eugene T. Jensen, 1967-68 Dr. Francis S. L. Williamson, William E. Trieschman, Jr. Lloyd W. Gebhard, 1968 1971-75 (Chairman 1970-72) Mark Abelson, 1968-73 Dr. J. Kevin Sullivan, 1975-83 Alfred E. Robinson, Jr. Ellen Jensen, 1973 Dr. David L. Correll, 1983-84 (Chairman 1972-84) J. David Breslin, 1973-75 Department of Commerce Roger S. Babb, 1975-78 U. S. Navy Russell T. Norris, 1968-76 William Patterson, 1978-83 Anita Miller, 1983-84 CDR J. A. D'Emidio, 1967-70 William Gordon, 1976-78 LCDR P. J. Parisius, 1970-71 Dr. Robert L. Lippson, 1978-84 Department of Transportation Edward W. Johnson, 1971-84 Department of the Interior Philip E. Franklin, 1967-70 Albert H. Swartz, 1968-71 ADM E. C. Allen, Jr., 1971 Capt. Winford W. Barrow, 1971-72 Delaware John T. Gharrett, 1968-70 Capt. G. H. Patrick Bursley, BG Norman M. Lack, 1967-68 Dr. Oliver B. Cope, 1971-74 1972-74 Austin N. Heller, 1970-73 Dr. Daniel L. Leedy, 1974-76 Capt. Keith B. Schumacher, John C. Bryson, 1973-78 Dr. W. Sherman Gillam, 1976-78 1974-78 John E. Wilson, 111, 1978-84 Dr. Glenn Kinser, 1978-84 Capt. J. W. Kime, 1978-81 Capt. J. C. Carlton, 1981-84 Atomic Energy Commission District of Columbia Dr. Jeff Swinebroad, 1971-73 Atomic Energy Commission LTC Tom H. Reynolds, 1967 Dr. Ford A. Cross, 1973-75 Dr. Jeff Swinebroad, 1968-73 LTC Louis W. Prentiss, Jr., Dr. Ford A. Cross, 1973-75 1967-68 Department of Energy Department of Energy Roy L. Orndorff, 1968 Dr. W. Roland Taylor, 1975 Norman E. Jackson, 1968-72 Dr. Jackson 0. Blanton, 1975-76 Dr. W. Roland Taylor, 1975 Paul V. Freese, 1972-73 Dr. D. Heyward Hamilton, 1976-84 Dr. Jackson 0. Blanton, 1975-76 Robert R. Perry, 1973-75 Dr. D. Heyward Hamilton, 1976-84 William C. McKinney, 1975-76 Environmental Protection Agency Herbert L. Tucker, 1976-80 Environmental Protection Agency Lloyd W. Gebhard, 1971 William B. Johnson, 1980-84 Dr. Tudor T. Davies, 1979-80 William M. Blankenship, 1971-73 Dr. David A. Flemer, 1980-84 Larry S. Miller, 1973-74 Maryland Green Jones, 1974-76 Joseph H. Manning, 1967-71 National Science Foundation Leonard Mangiaracina, 1976-79 John R. Capper, 1971-73 Dr. William A. Niering, 1968 Dr. Tudor T. Davies, 1979-83 James B. Coulter, 1973-82 Dr. Edward Chin, 1968-70 Thomas P. Eichler, 1983-84 Dr. Torrey C. Brown, 1982-84 Dr. Richard C. Kolf, 1970-74 Dr. Edward H. Bryan, 1974-84 Federal Energy Regulatory Pennsylvania Commission Clifford H. McConnell, 1967-83 Smithsonian Institution (Federal Power Commission) Nicholas DeBenedictis, 1983-84 Dr. 1. Eugene Wallen, 1968-71 Paul H. Shore, 1967-72 Dr. Francis S. L. Williamson, John H. Spellman, 1972-74 Virginia 1971-75 Angelo Monaco, 1974-76 Dr. William J. Hargis, Jr., 1967-83 Dr. J. Kevin Sullivan, 1975-83 .James D. Hebson, 1976-84 Betty J. Diener, 1983-84 Dr. David L. Correll, 1983-84 88 Delaware Environmental Protection Agency U. S. Navy BG Norman M. Lack, 1968 Daniel K. Donnelly, Robert D. C. L. Hamilton, Edward T. Kinney, Norman G. Wilder, 1971-73 Kaiser, Frederick D. Knapp, Jr., G. Liberatore, Harold Singerman, John C. Bryson, 1973-78 Thomas H. Pheiffer, Dorothy A. Jack Wilson, Carl Zillig. John E. Wilson, 111, 1978-84 Possehl, Orterio Villa, Gail Mac Kiernan. Smithsonian Institution District of Columbia William 1. Aron, Dale Jenkins, Steve Norman E. Jackson, 1968-72 Federal Emergency Kcely, David W. Kunhardt. Paul V. Freese, 1972-73 Management Agency Robert R. Perry, 1973-75 Walter P. Pierson Department of Transportation William C. McKinney, 1975-76 CPT Winfred W. Barrow, CPT G. H. Herbert L. Tucker, 1976-81 Patrick Bursley, LT Mark Grossetti, James H. McDermott, 1981-84 Federal Energy Regulatory CPT Lester A. Levine, CPT William Commission (Previously Federal A. Montgomery, CPT Harold B. Maryland Power Commission) Summey. Frederick W. Sieling, 1968-75 Martin Inwald, John Pazmino, Dr. L. Eugene Cronin, 1968-84 Charles Ramirez, Martin J. Thorpe. Dr. Donald W. Pritchard, 1968-84 State Agencies Albert E. Sanderson, 1968-79 Department of Health, Howard Wilson, 1979-80 Education and Welfare L. E. Zeni, 1975-84 Edwin C. Lippy Delaware Dr. Walter R. Taylor, 1979-84 Harry E. Derrickson, Charles Hat- Dr. Sarah J. Taylor, 1980-84 Department of Housing and field, William J. Hopkins, David R. Pennsylvania Urban Development Keifer, Edward Lane, Charles A. Marshall S. Goulding, Jr., 1968-70 Maureen Gottshalk, Richard Lesser, Frank Moorehead, James L. William N. Frazier, 1970-80 Lippold. Pase, John Sherman, Ronald A. Steve Runkel, 1980-84 Thomas. Virginia Department of Interior District of Columbia Dr. William J. Hargis, Jr., 1968-84 Robert H. Alexander, Milton Ander- John V. Brink, Robert H. Cousins, son, Ralph Andrews, Philip B. Aus, William B. Garlow, Jean B. Leves- In addition to the members of the Ellen P. Baldacchino, Frank M. que, George J. Moorehead, Kent above groups, the following indi- Basile, John W. Baumeister, Mountford, Paul W. Reed, Arnold viduals made substantial contribu- Frederick W. Bell, Ocrard Bentryn, B. Speiser, Richard B. Westbrook. tions to this study: Black, Edward B. Bradley, C. Ed- ward Carlson, Ken Chitwood, L. Maryland Cohen, William M. Colony, James Anthony Abar, Jack Anderson, John Federal Agencies Comiskey, Kenneth Compton, Antenucci, Edwin M. Barry, Tyler George W. Davis, Robert K. Dodd, Bastian, Marvin J. Bennof, Dr. James J. Donoghue, Gary Estronick, Robert B. Biggs, Ralph A. Bitely, Stanley A. Feitler, Katherine Fitz- Charles R. Bostater, Jr., Earl Department of Agricutlure patrick, William Forrest, John R. Bradley, Carlo Brunori, Mark Bun- George, John T - Gharrett, Richard E. dy, Nick Carter, Thomas Chaney, David K. Bowden, P. Thomas Cox, Griffith, K. Hall, Kenneth Hanks, Marshall M. Cook, Robert B. Dan- David P. Doss, Charles B. England, Thomas R. Harman, David B. Harris, necker, Eugene F. Deems, Jr., Anthony M. Grano, John W. Green, Mickey Hayden, M. Honeycutt, Her- Spencer P. Ellis, Harold J. Elser, Mark A. Heiman, James E. Horse- bert A. Hunter, Frank D. Jones, Rob- Samuel W. Fowler, James Golds- field, John E. Hostetler, Harold E. ert D. Kaiser, Ralph Keel, Rob Kelsey, berry, Bernard F. Halla, Frank Scholl, W. M. Tinsley, Jr., William David A. Kimball, Howard Larson, Hamons, Sidney Hatkin, Edgar H. Weldon. Gordon Leaf, William F. Lichtler, J. Hollis, Jeffrey Hutchins, Randall T. Lowman, Kenneth McGinty, Robert Kerhin, Dr. Ted S. Y. Koo, Dr. Department of Commerce Munroe, Phillip J. Murphy, Paul H. George E. Krantz, Lester A. Levine, Donald D. Allen, Frederick W. Bell, Mutschler, Gary L. Nelson, Earl C. John R. Longwell, Raymond W. Marvin F. Boussu, Robert Brewer, Nichols, James P. Oland, Warren T. Ludlow, Richard Marasco, Paul Eleanor Curry, Ronald D. Gatton, Olds, Jr., Edmond G. Otton, Willard Massicott, Ruth M. Mathes, Kenneth Timothy E. Goodger, Dr. Robert Parker, Ralph Pisapia, Stephen H. E. McElroy, Jr., Roy G. Metzgar, Hanks, Steacy D. Hicks, Dr. Chester Porter, Ronald M. Pyle, E. R. Roach, Caldwell D. Meyers, Bob Miller, Fred P. Jelesnianski, Dr. Robert Kifer, K. Larry R. Shanks, Katherine Shaw, P. Miller, Steve Miller, Robert S. L. Kollar, Roger A. Matson, Patrick Marianne J. Smith, William Stolting, Norton, Jr., Chris Ostrom, Donald H. McAuley, James E. McShane, Jane Sundberg, Nelson Swink, David Outen, Kenneth E. Perkins, Duane Ronald J. Morris, Robert L. Schueler, Taliaferro, Robert L. Wait, Paul Pursley, Charles K. Rawls, Robert J. William N. Shaw, Robert C. Smith, Weiser, W. Finch White, James R. Rubelman, Josh Sandt, Alexander V. Robert Taylor, Robert R. Wilson. Whitehouse. Sandusky, Arnold Schiffman, David 89 A. Schultz, Scribner Sheafor, enmeyer, James L. Reveal, Carol R. Thomas W. Shives, Neil M. Shpritz, Shearer, J. Albert Sherk, Jr., Eugene Turbit H. Slaughter, William M. B. Small, Robert E. Stewart, Richard Sloan, Harley Speir, Vernon D. Swartz, Daniel E. Terlizzi, Shirley Stotts, Edwin Thomas, Noel C. Van Valkenburg, Marvin L. Wass, Valenza, Dr. John B. Williams, Martin L. Wiley, Austin B. Howard Wilson, Jen T. Yang. Williams. Pennsylvania Citizens Program for the V. M. Beard, Richard M. Boardman, Chesapeake Bay, Inc. Arthur D. Bradford, Wayne DeMoss, Edward W. Aiton, Charles W. Fritz Fichtner, George E. Fogg, Coale, Jr., Barbara Fine, Frances William C. Forrey, Ellis W. Harried, Flanigan, Germaine Gallagher, Betty John E. McSparran. Jane Gerber, John Gottshalk, E. Polk Kellam, John Harris Lane, IV, Virginia Thomas B. Lewis, William C. Michael A. Bellanca, Dr. Michael E. Lunsford, J. Douglas McAlister, W. Bender, Fred C. Biggs, Robert R. Cranston Morgan, John J. Ney, Blackmore, Dr. John Boon, Dr. Mor- William Park, William R. Prier, ris, L. Brehmer, Donald W. Budlong, Gord .on Riley, Arthur Sherwood, Robert Byrne, John Capito, Charles Ed Vinnicombe, J. Paul Williams. A. Christopherson, Arthur L. Col- lins, Elbert Cox, Dr. W. Jackson Biota Evaluation Panel Davis, James E. Douglas, Jr., Alex- ander M. Griffin, Dixie Griffin Dr. L_ Eugene Cronin, Dr. Herbert Robert J. Griffis, J. Gwynn, A. W M. Austin, Dr. Walter R. Boynton, Hadder, Milton T. Hickman, Carl Steve Early, Dr. David 'A. Flemer, Hobbs, Dale F. Jones, Robert H. Kir- Ron Gatton, Dr. William J. Hargis, by, John L. Knapp, Ken Lion, Jr., Dexter S. Haven, Dr. Anson H. Howard MacCord, James F. Mc- Hines, Dr. Glenn Kinser, Dr. Robert Inteer, Jr., Larry Minock, A. H. Lippson, Hayes T. Pfitzenmeyer, Paessler, Chester F. Phelps, Norman Dr. J. Kevin Sullivan. Phillips, Jr., John B. Pleasants, George V. Podelco, Donald B. Richwine, Glen Rehberger, Fairfax Susquehanna River Basin Settle, Jeff Sinclair, John Stockton, Commission Robert Swisher, T. Edward Temple, Robert J. Bielo Burton Tuxford, Cloyde W. Wiley. The preparation of the artwork and Others graphics for this report was under the supervisionof: Henry G. Dunn, Chief, Reports and Chesapeake Research Consortium Communications Branch. Richard Anderson, John W. Bishop, Donald F. Boesch, Russell G. Art and graphics for this report were Brown, Martin A. Buzas, Dale R. prepared by: Calder, D. G. Cargo, Sonya Cohen, Lynlee 1. Brock Rita R. Colwell, M. Kenneth Cor- G. Wayne Parker bett, Carol Feister, John M. Frazier, Jerry D. Hardy, Jr., Herbert Harris, Typing was accomplished by: Donald R. Heinle, Robert P. Hig- Lynn Airey, Joann Downs, Ruby gins, Daniel Higman, Linda L. Hud- Jones, Patricia D. Kuta, Christine son, Rogers Huff, Robert J. Hug- Ralph, Mary Rhode, Paula Schultz, gett, Catherine Kerby, Lar.ry Marla Smith. Kohlenstein, Robert W. Krauss, Richard J. Marasco, Andy McEr- lean, Robert E. Miller, Leo L. Mina- sian, Richard A. Mulford, Thomas Credit is also due to many others who A. Munson, John Musick, Patricia contributed to the Chesapeake Bay Orris, Franklyn D. Ott, Robin M. Study and to this report. Overstreet, Anna Belle Owens, For- res E. Payne, Hayes T. Pfitz- 90 3 6668 00001 3146