[From the U.S. Government Printing Office, www.gpo.gov]
The eology of Maine's oastline kv, io QE 119 .G46 1983 <ecutive Department Maine State Planning Of f ice June 19B3 The eology of Maine s Coastline A Handbook for Resource Rlanners, Developers, and Managers Executive Department Maine State Rlanning Off ice June 1983 VS Department of Commerce NOAA Coastal Services Center Library 2234 South Baboon Avenue Charleston* SC 29405-2413 Financial assistance for preparation of this document was provided by the U.S. Department of Com- merce, Office of Coastal Zone Management, under the Coastal Zone Management Act of 1972, as amended. ii - PREFACE Since 1977, as part of Maine's Coastal Program, the State Planning Office has published a series of handbooks to assist private citizens and developers, as well as members of local planning boards and professional planners, with convenient guides to the management of coastal resources. These handbooks provide the reader with sufficient technical background to communicate suc- cessfully with specialized scientists and technicians when considering developments proposed for shoreline and intertidal sites. They also serve as users' guides to specialized maps displaying coastal data. Non-technical language is used as much as possible without diminishing the accuracy of the information. This particular handbook, The Geology of Maine's Coastline, is the product of work undertaken by the State Planning Office through a contract with the Maine Geological Survey in,the Maine Depart- ment of Conservation. Barry S. Timson, a geologist formerly with the Maine Geological Survey, did the mapping of the numerous marine geologic units making up the coast and authored the analysis upon which this book is based. Subsequently, his work was reviewed and supplemented by other geologists including Robert Gerber, who added material on planning considerations for various geologic units and the impacts of human activities. The hand drawn illustrations for Chapter 3 were done by artist Jon Luoma. Mary Griffith, a Massachusetts Audubon Society Environmental Intern, edited and circulated various interim and review drafts of the work. Finally, environmental writer, Robert Deis, performed the task of editing the extensive technical text into a shortened version more readily understood by non-geologists. State Planning Office staff who contributed substantially to the project include: R. Alec Giffen, Director of the Natural Resource Division; Joseph Chaisson who developed the initial concept; Richard Kelly who designed the publication and did the layout; and Harold Kimball who coordinated the publication process. CONTENTS Page List of Figures vi Introduction: The Geological Connection 1 Chapter 1: Using the Marine Environments Maps 5 Chapter 2: Perspectives of the Maine Coast 11 Geologic Process Agents 13 Currents 13 Waves and Winds 14 Precipitation 16 Biological Activity 17 The Human Factors 18 Coastal Physiography: The Big Picture 20 Depositional Systems: The Interdependence of Environments 22 Chapter 3: The Building Blocks of Maine's Coast 39 Supratidal Environments 40 Intertidal Environments 45 Subtidal Environments Ro Chapter 4: The Disappearing Shoreline Beach Erosion 65 Dealing with Shoreline Erosion Some Basic Considerations an Preventing Erosion of Beaches and Dunes 70 Promoting Dune Growth 70 Seawalls 71 Revetments 72 Rock-filled Timber Cribbing 72 Beach Replenishment 72 Preventing Erosion of Channel Banks 73 Pre venting Erosion of Scarps or Bank Slopes 73 Geologic Hazard Zoning 74 Where to Go for Help 75 Some Planning Considerations for Development in Coastal Geologic Environments 76 Land Use Laws of Special Interest to Individual Coastal Property Owners 78 v LIST OF FIGURES Figure Page 1 Marine Geologic Environment Map and Legend 6 2 Natural Variables Affecting Sedimentation Within an Estuary 7 3 Surficial Deposits in the Coastal Zone 12 4 Landward Migration of a Barrier Beach 13 5 Past Sea-level Variations 13 6 Beach Profile-related Terms 14 7 Schematic Diagram of Waves in the Breaker Zone 14 8 Wave Terminology 15. 9 Wave Spectrum off Penobscot Bay 15 10 Development Activities - Environmental Suitability Index -19 11 Bedrock Control of Shoreline Physiography 20 12 Depositional Systems Index Map 22 12a The Arcuate Bay Shoreline 23 12b The Indented Embayments Shoreline 23 12c The Island-Bay Complex 24 12d The Eastern Cliff Shoreline 24 13 Profile View, Beach and Dune Features 25 14 Seasonal Cycle of Foreclune Erosion 26 15 Marine Environment Map: Wells, Maine 28 16 Little River: Coarse Grained Estuary Systems 29 17 Marine Environment Map: Addison, Maine 30 18 West River: Wave-dominated Embayment and Indian River Fine-grained Estuary- 31 19 Marine Environment Map: Lubec, Maine 32 20 So. Lubec: Wave-dominated Embayment 33 21 Marine Environment Map: Yarmouth, Maine 34 22 Royal River: Constructional Delta System 35 23 Marine Environment Map: Small Point, Maine 36 24 Popham Beach Destructional Delta System 37 25 Overview of Coastal Geologic Units 40-41 26 Unhealed Frontal Dune Scarp 40 27 Seaside Goldenrod and American Beach Grass 41 28 Beach Pea -41 29 Fresh to Brackish Marsh 42 30 Blue Winged Teal 42 31 Fluvial Marsh 44 32 Wild Rice 44 vi Figure Page 33 Salt Marsh Cross Section 45 34 Snowy Egret; Salt Meadow Grass; Salt Marsh Cord Grass; Black Rush 45 35 Salt Marsh 46-47 36 Plan View; Typical Transition Zone Salt Marsh to Fluvial Marsh 47 37 Marsh Levee, Two Views .48 38 Beach Types 49 39 Gravel Beach 50 40 Boulder Beach 50 41 Washover Fan, Plan View 51 42 Channel Levee 52 43 Red-winged Blackbird (male) 53 44 Common Loon 53 45 Mud Flat 53 46 Ledge 54 47 Ospreys 55 48 Point Bars 55 49 Aerial Perspective; Lateral Bars 56 50 Swash Bars 56 51 Flood Tidal, Ebb Tidal and Fan Deltas 57 52 Oblique Aerial View; Flood Tide Delta and Spillover Lobe 58 53 Yellowlegs (Sandpiper) 58 54 Sand Beach Profiles 66 55 Gravel Beach Profiles 67 56 Section of Concave Faced Seawall 71 57 How Seawalls Can Accelerate Beach Erosion 72 58 Schematic Sections of Two Types of Rock-filled Timber Crib Seawalls 72 59 Typical Stone Rip-rap Revetment 72 vii Monhegan Island Cliffs photo Harold Kimball Aw. *W"* ? T@ Ti Ali- INTRODUCTION: THE GEOLOGICAL CONNECTION in this environmental ly-aware era, it has be- ments are more subtle. Yet, whether subtle or come increasingly obvious to residents of simple, the links are there, and their importance Maine's coastal towns that geological factors is becoming more and more apparent each year. can have far reaching effects on their lives and Two major needs have resulted from our grow- their community. Especially along the coast, the ing awareness of this "geological connection." lay of the land, what it is made of and how it is First, faced with'the complex tasks of long range affected by natural processes and human activ- planning and assessing the feasibility or poten- ities determines much more than simply what tial impacts of various activities and projects, kinds of plants and animals can live in a given coastal planners, developers and residents are place. Ultimately, these factors determine how feeling an ever greater need for detailed geologi- people will view, value and utilize that place. For, -cal information about their towns. The second in very basic ways, the geological aspects of an need follows from the first. In order for non- area both create and limit opportunities for such scientists to use detailed geological informa- things as resource use and residential or com- tion, they must also be given an understanding of mercial development. what this information means and a working The existence of a mudflat, for instance, pre- knowledge of its implications. sents you with an opportunity to go clam- During the past few years, under the adminis- ming-but you wouldn't want to build your house tration of the State Planning Office, Maine's there. Marine sand and silt, the same geologic Coastal Program has made substantial progress materials that create a perfect habitat for clams, toward meeting these needs. As a beginning also limit the possibilities for construction be- step, it has put together an exhaustive inventory cause of their unstable nature and location in an of Maine's coastal resources, including a con- environment flooded daily by the tides. In addi- stantly-expanding data base on the geology of tion, the effects of construction, even if it were our state's coastline. Equally important, the practical, might conflict with the more valuable Coastal Program has gone on to create a con- long-term use of the spot as a commercially tinuing series of Coastal Inventory Maps and harvestable clarnflat. publications relating to various aspects of re- That's a simple example, of course. Many of source development or management in Maine's the interrelationships between people and the coastal areas. geological characteristics of coastal environ- This handbook is one such publication. Its Finally, in Chapter 4, a geological phenomenon purpose is to provide the layperson with a gen- that has become more and more troublesome to eral introduction to the geology of Maine's coast coastal residents in recent years is discussed- and a better understanding of how geological shoreline erosion. Our treatment of this special factors figure in resource utilization, develop- problem begins'with some background on how ment and planning decisions. and why shoreline erosion occurs, and then goes As a source of basic information, the book on to describe some common and effective ways stands on its own. However, it is important to of dealing with it. note that this handbook is particularly useful as Before going further, it should be explained a complement to a set of Coastal Program re- that since the focus of this handbook is on source maps formally titled the Coastal Marine geology, the amount of information given about Geologic Environments Maps. Simply put, the the biological aspects of Maine's coast is lim- Marine Environments maps show the locations of ited. Only the most relevant or outstanding de- distinct coastal environments, such as a mud- tails about the plants and animals who live in or flats and beaches. The features and uses of depend on marine environments are mentioned. these maps are described in the next section of For a more thorough look at the diverse bio- the handbook, Chapter 1. logical resources of our state's coast, readers In Chapter 3, entitled "The Geologic Environ- can refer to the companion volume to this book, ments of Maine's Coast", each of the 55 kinds of titled, A Planner's Handbook for Maine's Inter- environments shown on the maps is described, tidal Habitats (available from the State Planning along with some of the planning considerations Office). relating to them. This is the essential body of in- By using these two handbooks in conjunction formation needed to understand just what the with the Marine Environments maps, coastal individual environments are, why they are impor- residents, developers and planners should gain a tant and how human activities may affect them. clearer idea of what the ultimate benefits and To better comprehend coastal geology, how- effects of their decisions concerning resource ever, it is helpful to begin with a broader view- use or development may be. Hopefully, they will a look at the way all these small geologic units also have a better basis for making those de- fit together. Such an overview is provided in cisions in the first place. Chapter 2, called "Perspectives on Maine's Coast." It describes the interesting, complex links between marine environments, explains how natural forces affect coastal landforms, and summarizes some of the changes our coastline has gone through since the last great Ice Age. 2 Popham Beach, Dune and Marsh System photo Harold Kimball -tft ym 46 -k2r' CHAPTER 1: USING THE MARINE ENVIRONMENTS MAPS As mentioned in the introduction, much of the use of the maps is to determine the geological information in this handbook is particularly use- characteristics of particular sites in their town. ful in conjunction with a set of Coastal Program Though verification by on-site inspection should resource maps called the Coastal Marine Geo- always back up any important decision, a quick logic Environments Maps. These maps are not look at the appropriate map will show with rea- hard to understand. In a number of ways, they sonable accuracy what kind of environment ex- are similar to the Soil Conservation Service soil ists at any given spot in the shoreland zone. It maps with which most land use planners are will show, for example, whether a certain inter- already familiar. tidal area is a "coarse-grained flat" or a "sea- Soil maps are often used in regional or town weed covered flat." Even such relatively similar planning for purposes such as locating areas geologic environments have certain significant suitable for subsurface sewage disposal or sani- differences. Each has its own characteristic sedi- tary landfill sites and for identifying prime agri- ment composition; each supports a unique set of cultural land. The Marine Environments maps plant and animal life; and, each has a different can also be helpful for this-kind of generalized potential for meeting human needs. Of equal, planning. In addition, because of their larger perhaps greater, importance is the fact that each scale, they can be used for more detailed plan- reacts differently to various natural or man-made ning and environmental impact assessment. influences. Basically, the Marine Environments maps indi- The pinpointing and identification of these dis- cate the size and location of individual geologi- tinct environments is especially advantageous to cal environments, or "units", (a beach, a mudflat, developers, town planners, industrial researchers a tidal channel, etc.) as they occur along the and other people for resource utilization plan- Maine coast. Altogether, 109 maps have been ning. For instance, by using the maps, efforts to produced, covering land along the state's entire locate suitable sites for piers, houses, com- coastline between the nearshore uplands and mercial facilities, industrial plants and other de- shallow subtidal depths of about 8-10 meters, or velopments are made much easier. Places where roughly 25-30 feet below the low tide mark. On unstable soils or other geological conditions them, 55 different types of marine environments make a project unfeasible can be quickly identi- are distinguished with simple letter codes. fied and ruled out. The proximity of sensitive, To coastal residents, the most fundamental ecologically valuable environments to a site can 5 FIGURE 1 Marine Geologic Environment Map and Legend MAP SYMBOL GEOLOGIC ENVIRONMENT SUPRATIDAL ENVIRONMENTS Tidal Creeks Sd Dunes & Vegetated Beach Ridges Sw Fresh-Brackish Water Sm Fresh-Brackish Marsh Marsh Drainage Ditch Sz Man-Made Land Sx Landslide Excavation & Deposits INTERTIDAL ENVIRONMENTS Unit Boundary Marsh Environments M1 High Salt Marsh M2 Low Salt Marsh Approximate Unit-Boundary M3 Marsh Levee M4 Salt Pannes & Salt Ponds Beaches Approximate Transition 'Boundary Between Bi Sand Beach Estuarine and Marine (30 ppt salinity) B2 Mixed Sand & Gravel Beach Waters and between Estuarine and River B3 Gravel Beach (0.5 ppt salinity) Waters. B4 Boulder Beach B5 Low-Energy Beach Br Boulder Ramps Bw Washover Fan lee X Bs Spits Flat Environments F Mud Flats F1 Coarse-Grained Flat Ise, F2 Seaweed-Covered Coarse Flat F3 Mussel Bar @F4 Channel Levee Af F5 Algal Flats F6 Veneered Ramp Miscellaneous Environments 6 M Ledge 9-Ir Mc Fluvial-Estuarine Channel Mp Point or Lateral Bars Ms Swash Bars Mf Flood-Tidal Delta Me Ebb-Tidal Delta Mb Fan Delta Md Spillover Lobe Ire SUBTIDAL ENVIRONMENTS Flat Environments Fm Mud Flat Fc Coarse-Grained Flat 2 Fe Eelgrass Flat Fs Seaweed Community gr Fb Upper Shoreface N4 Fp Lower Shoreface N Channel Environments C1 High-Velocity Tidal Channel C2 Medium-Velocity Tidal Channel C3 Low-Velocity Tidal Channel C4 Estuarine Channel C5 Estuarine Flood Channel C6 Estuarine Ebb Channel C7 Inlet Channel C8 Dredged Channel Cs Channel Slope _j 6 be noted. And the possibilities for expanding a undertake this type of analysis, it is possible- project in the future can be estimated by look- and often necessary-for the layperson to make ing at the locations, sizes and nature of the judgements about potential environmental im- environments in the area. pacts for themselves. Similarly, the detailed information on the Mar- Members of municipal planning boards, for ine Environments maps can facilitate the loca- example, spend considerable time reviewing de- tion of potential aquaculture sites, commercially velopments proposed for their towns, a process harvestable mussel or seaweed beds, and other that usually involves some kind of environmental marine resources. It can help in creating effective impact assessment. For their part, developers strategies to combat shoreline erosion problems, generally have to study and report the potential or in the development of zoning guidelines. Re- environmental effects of their projects in order to cently, the maps have been used to help form- get needed permits and fulfill application require- ulate the clean-up plans that would be imple- ments. mented in case of a major oil spill off Maine's As a rule, the sophistication of impact assess- coast. ments varies with the size or expected environ- Because the differences between individual mental influence of the project in question, rang- sites are also crucial in determining the effects ing from simple common sense judgements to an activity or project may have on the environ- highly involved computerized simulations and ment, another basic use of these maps is for technical studies. Any type of impact assess- environmental impact assessment. While in ment, however, should take into consideration many cases professional advice is needed to the fact that the connections between human FIGURE 2 Natural Variables Affecting Sedimentation Within an Estuary external estuar precip. runoff orneIr wind 7 ic -loa-d r5p"h in ischar sed. te p. 2 ocean river [email protected] ..te water to oa ad hemistr d Note depth 2 2.4 12,3.4 7 \A biota '-L- I A" w. coastal estuary SEDIMENTATION - - "rren15 iEROSIO L substrate BIOTA i SEDIMENT TYPE Figure 2 illustrates the complex interactions between factors affecting estuarine biologic organ- isms. The emphasis is restricted to those factors which affect sediments. The primary factors acting on benthic organisms (those living in or near the bottom) are the processes of Sedimentation/ erosion and substrate sediment type. These two factors, in turn, are influenced by secondary factors (numbered 1-7) within the estuary. The secondary variables influence each other as indicated by the small numbers within and at the bottom of the secondary factor circles. The secondary factors and tertiary (third level) factors are influenced in turn by those processes within environments adjacent to the estuary itself. 7 activities and marine environments are extremely In terms of land use planning, particularly complex and that the links between the living and with respect to Maine's complex and highly val-' non-living components of those environments are uable coastal environments, the many intercon- equally intricate. nections between geological and biological com- Figure 2 is a good illustration of this point. ponents tend to support the conclusion that the It is a "process interaction diagram" showing the less basic changes made, the better. If not taken interrelationships between the various living and to an extreme, this view is generally a sound one. non-living components of a typical Maine estuary Almost all of Maine's major coastal industries, (a water body where fresh water mixes with from commercial fishing to tourism, depend ul- ocean water). Each component is labeled, with timately for their existence on healthy, attractive plant and animal life combined under the head- marine environments. ing of "biota," and each is linked with lines to Changes to the Maine coast are inevitable, in other components. In theory, if any one of the view of the heavy developmental pressures on- components is altered in some way due to natur- and great potential of-our state's coastline. But al or man-made causes, there will be some effect effective management and careful development on the other components it is linked to, and that minimizes adverse impacts is both wise and those components in turn will influence another possible. In many ways, the Marine Geologic set of components. The basic idea, at least, is Environments Maps and an understanding of plain. Few, if any, environmental systems are their implications can be very useful tools in simple, and everything in one is intricately con- working toward this goal. nected to many other parts of the system. Marine Environments Maps may be obtained from The Maine Geological Survey, Department of Conservation, Augusta, ME 04333 (telephone 1-207-289-2801). 8 Hermit Island and Head Beach, Phippsburg photo Harold Kimball HIRE 11, 7`9 CHAPTER 2: PERSPECTIVES ON THE MAINE COAST It's often said that Maine has a "rockbound force that had particularly significant effects on coast," a phrase suggesting shorelines that are Maine's landscape is both possible and rele- massive, solid and unmoveable. But in addition vant-the last great glacial advance. to rugged ledges, the physical structure of our The most recent in a series of continental coast is also made up of a significant amount glaciations that have covered Maine began about of sediments-accumulations of gravel, sand, 28,000 years ago, during a period when the cli- silt and clay, or combinations of these particles mate of North America became much cooler than as well as organic matter. And, in fact, our coast- it is today. That cooling trend created a three- line is constantly being altered and rearranged mile-thick ice sheet which eventually blanketed due to the influence of "process agents," those all parts of the state and extended out to what natural forces of the sea, the earth's weather are now the Georges Bank fishing grounds on the systems and the general climate of the north- edge of the present continental shelf. west Atlantic region. About 18,000 years ago, the climate began to Waves, tides and other process agents move warm again and the ice began to melt. By 10,000 sediments on a daily basis, transporting particles years ago the glaciers had receded from Maine. into and out of bays, along beaches and up and The geological effects the ice had during its "life down the length of the shoreline. Over longer span," however, are primarily responsible for the periods, process agents also affect bedrock Maine landscape we see today. For, among other ledge. Rock surfaces are weathered by wind and things, the last great ice sheet, known as the wave; blocks of stone are loosened by the alter- Laurentide Advance, actually removed or re- nate freezing and thawing of moisture in cracks, worked most of the surficial sediments and soils and may at times be dislodged and moved by covering the entire state. storm waves. . As the glaciers advanced over the land, they Geological studies show that in the past other became embedded with and carried along enor- natural forces besides those we see now have mous loads of sand, gravel, mud and boulders. affected the lay of the land. To describe them all, Over the centuries the ice mass moved slowly and all of the changes Maine's coastal geology southward, transporting more and more surface has gone through, would go far beyond the scope materials and scouring some areas (such as of this book. But before discussing existing pro- mountain peaks) all the way down to the bed- cess agents in more depth, a brief look at a past rock. 11 FIGURE 3 Surficial Deposits in the Coastal Zone WISCONSIN DRIFT, OTHER THAN END MORAINES AND OUTWASH, CHIEFLY TILL INCLUDES BEDROCK AND OLDER DRIFT. ICE-CONTACT STRATIFIED DRIFT, MAINLY SAND AND GRAVEL, OCCURRING AS ESKERS, KAMES, KAME TERRACES, PITTED OUTWASH PLAINS, AND COLLAPSED STRATIFIED DRIFT OUTWASH SEDIMENTS, MAINLY SAND AND GRAVEL DEPOSITED BY PROGLACIAL STREAMS POSTGLACIAL MARINE SEDIMENTS, CHIEFLY CLAYS AND SILTS, WITH SOME BEACH FEATURES Jr Here and there, the moving ice deposited composed of fine-grained sediments like silt and materials transported from elsewhere, creating clay, which were deposited in the ocean at the new landforms or altering old ones. One common glaciers' seaward margins. These are called type of glacial deposit is called "glacial till," "glaciomarine deposits." a mixture of boulders, cobbles, gravel, sand, silt Besides changing the topography and makeup and clay compacted together by the weight of of the land, the glaciers also affected our coast- the ice. Another kind of glacial debris is termed line in another very significant way. As the vast "ice contact deposits." These are hill-like sand ice sheet grew to cover the northern United and gravel formations such as eskers, deltas States, Canada, Europe and northern Asia, it and moraines, deposited by meltwater streams locked up large quantities of the earth's water flowing on, below or adjacent to stagnant or ac- supplies. This caused a world-wide lowering in tive ice. Outwash deposits of sand and gravel sea level height of about 300 feet. At the same were deposited away from the ice by meltwater time, however, the great weight of the ice mass streams. (Most of Maine's sand and gravel pits depressed the earth's surface in many coastal owe their existence to these types of deposits.) regions, making the drop in sea level less ap- A third general type of formation left by the ice is parent and causing parts of the coast to be flooded. 12 When the glaciers finally melted, the water ied by increasing shoreline erosion and mounting they contained was returned to the sea, causing threats of damage to property and buildings in the sea level around the world to rise. But then, some areas that are located near the edge of the with the weight of the ice removed, many areas sea. of the coastline rose rapidly, bringing land that Though it may seem paradoxical in view of the had been under water to a new elevation above effects described above, process agents on the the ocean. (Thus, glaciomarine deposits can be whole are far more beneficial than destructive found in what are now inland areas.) with respect to Maine's coastal environments. In Until about 8,500 years ago, the coastline of fact, they are the primary natural forces that Maine continued to rise more rapidly than the maintain the integrity of environments in the level of the sea. Since then, sea level has been nearshore zone. To understand this positive role, steadily overtaking land level at an average rate it is necessary to look closer at how process of around one inch per decade. This phenomenon agents work. Besides relative sea level rise, the is one of,the process agents acting on our coast five major process agents that most influence today. In fact, though the general public hears shoreline environments are currents, waves, little about it, the current progressive rise in sea winds, precipitation, and biological activity. Their level has a marked influence on shoreline effects on coastal geology and relevance to geology. coastal development and planning are the sub- FIGURE 4 ject of the next section of this chapter. Landward Migration of a Barrier Beach FIGURE5 Past Sea-level Variations 6,000 yrs 8P YEAR upland PRESENT FOREDUNE IN POSITION 19110 210 310 410 510 610 19170 3,000 BP Eastport Me. -20 __10 PRESENT .21 4) -5 Portland Me. 10 L FUTURE [1,000 yrs?l GEOLOGIC PROCESS AGENTS Currents It is the slow rise of the sea level that is Currents are one of the most common and responsible for the steady landward migration of most influential process agents affecting the coastal environments. As the sea level gets ever Maine coast. Able to both build and erode, they higher, the point where the land and sea meet are extremely important factors in the transport moves further and further inland. So too, do many and deposit of sediments from one geological non-bedrock nearshore environments, such as environment to another. beaches, marshes and mudflats. In addition, as This is particularly true of tidal currents, which the sea level continues to rise, waves, tides and result from the twice daily rise and fall of the other marine process agents are increasingly ocean as it responds to the gravitational pulls likely and able to impact upland areas. The re- of the sun and moon. Tidal currents erode sedi- sults? A slow drowning of the coast, accompan- ments from the bottoms of shoreline environ- 13 ments when tidal flow attains the necessary line structures, it is always wise to investigate "current threshold velocity"-the current speed the flow patterns of local currents in order to required to pick up and carry away sediments of avoid future erosion problems. a given size. As current velocities decrease to- FIGURE 6 Beach Profile-related Terms ward the peak of low or high tide, transport stops and the sediments carried by a current are deposited some distance away from their original position. 1 -0 The constant moving of sediments that results 1,112't or Shor.foce _W.-. ;..... ...... from tidal current action plays a major role in the 9 h F- maintenance of mudflats, low salt marshes and many other marine environments. And, on the B"Ch '"'P whole, its role is much more constructive than C-1 .1 destructive. In fact, in the absence of tidal cur- rents, many intertidal and subtidal areas might quickly become "sediment starved." Non-tidal currents may also supply nearshore environments with sediments. Coastal currents generated by large-scale water movements in the Waves and Winds Gulf of Maine generally flow southerly along the The marine process agent that causes the offshore, transferring river-delivered sediments or most nearshore erosion and its opposite, deposi- suspended sediments eroded from the shallow tion, is wave action. And, because waves are ocean bottom from one nearshore location to an- primarily generated by the frictional drag of other. winds, it is appropriate to discuss both of these One type of non-tidal current, known as the agents together. littoral current, has particularly great influence on Although wave action is probably best known the sediment budget of beaches. This current is for its destructive power, waves, like currents, generated by wave action and usually flows par- can both build and erode coastal landforms. allel to the coast in the surf zone. Most notably, Studies show, for example, that the stormy con- littoral currents are involved in the distribution of ditions of a Maine winter usually result in a net sand along the foreshore, or seaward margin, of offshore transport of sand from beaches, while beaches. Their movement often determines how the long, low swells prevailing in the summer wide a beach will be, and where sand eroded cause a net landward movement of sand back from beaches by waves will be carried. onto beaches. River currents, flowing seaward, also have a FIGURE 7 Schematic Diagram of significant influence on the sand budget of those Waves in the Breaker Zone beaches located near the mouths of major estu- aries (for example, Popham Beach, at the mouth of the Kennebec River). These currents may carry sediments eroded from upland areas to coastal R' - d 0__ geologic environments. Since the volume of sedi- ment transported varies with the current velocity and volume of water, the amount of sediment a- 3. delivered to the sea is greatest in spring. How- ever, almost all year round rivers bring sedi- ments that help maintain such environments as mud flats, deltas and marshes. D- W In terms of coastal planning and development, the role of tidal and non-tidal currents supports Whether waves will build or destroy isn't the following principle: simply put, any environ- necessarily related to the time of year. Wave ment that depends for its maintenance on a sup- effects are dependent on a complex set of vari- ply of sediments carried by currents may be ables including such things as the height and threatened with slow destruction if the natural length of the waves, the type of sediments in- flow of these currents is cut off or altered. Shore- volved, the depth and slope of the ocean floor, line construction is the activity most likely to and the shape of the shoreline. Another especi- have this effect. Thus, in planning the placement ally important factor is the direction of the wind, of piers, breakwaters, seawalls and other shore- which, along Maine's coast, usually comes from 14 one of four general bearings: the south-south- cession (less than two weeks), beaches may east, the southwest, the northeast, and the erode far back into adjacent dunefields. northwest. In the absence of nor'easters, northwest winds FIGURE8 WaveTerminology usually predominate along our coast in the fall and winter. Under their influence, incoming wave D,,,,,,,n at Wave Tr1,11 vi"', eng 'n heights are reduced and less able to cause se wave C-1 H= Wave Height vere erosion. Sand and other sediments tend to move shoreward, and beach aces are restore CreSt Length @e Tra.gh In addition, northwest winds often blow sand Region Wov Still,vater Level Tr-gh Lir qlh__@ from devegetated dunes seaward, onto or across Region dDepth Ocean Batiom beaches. 7-7-7-77771 In Maine, relatively mild south-southeast and FIGURE 9 Wave Spectrum off Penobscot Bay southwest winds prevail during the spring, sum- mer and early fall. They are responsible for the 25% formation of low sea waves that tend to carry Feet sediments onshore and are an extremely impor- 16 &over 20% 14-16 tant factor in the maintenance of beaches. It is 12- 14 810 15% r under the influence of these winds that the wide 8 seasonal "berms" are built along the seaward 4.. 10% margins of Maine's sand beaches. 2 -4 Northeast winds, on the other hand, are us- 5% ually associated with heavy storms and are re- 0.5-2 sponsible for the most destructive waves affect- 0 NE ing the Maine coast. They are generated by the Calm or Height Less The"E familiar "Nor'easters" which occur primarily in 0. , .at the late fall and winter months. Waves from such 37.2% SE storms cause the majority of shoreline erosion S problems that occur along our coastline. Nor'easters are low pressure systems fre- quently accompanied by "storm surges"-ele- vated ocean levels created by a combination of low atmospheric pressure and heavy winds. Northeast storm surges elevate tides an average of one to two feet above the daily predicted height, but during heavy nor'easters surges of While on the subject of winds and waves, four or more feet may occur. some mention should be made of hurricanes. Damage from storm waves and surges is least Though not really common along Maine's coast, when a nor'easter strikes the coast during low they do occur and can have significant effects tides. It is greatest when a storm coincides with on shoreline environments. high spring tides. If this happens, tide levels may Hurricanes are heavy storms characterized by be five or more feet above their normal height, their tropical origin and strong counterclockwise subjecting upland areas to severe wave attack. wind systems. Waves generated by these winds (This was the case during the record Nor'easter can cause erosion problems. But because their of February 7, 1978, which elevated tide levels up direction often parallels Maine's coast, they usu- to 5.3 feet above mean high water marks. As most ally lead to much less erosion than storm waves coastal residents remember, that storm caused associated with nor'easters. millions of dollars worth of damage to property The greatest danger from hurricanes generally and serious shoreline erosion problems along comes, not from waves, but from high winds and Maine's southern and central coast.) "storm surges." The latter effect, resulting from Overall, the extent of winter erosion along a combination of wind conditions, tide levels and Maine shores, particularly on sand beaches, is low afm-cispheric-pressure, can pose particularly roughly proportional to the number of nor'easters serious problems for--coastal residents. Storm that hit the coast that year. Although beaches surges created by hurricanes are-oftenjwo or usually regain sand eroded by storms in a rela- more feet higher than those generated by the tively short time as waves and winds return to strongest nor'easter and can cause severe coast- normal, if two heavy storms pass in rapid suc- al flooding. 15 Fortunately, hurricanes rarely reach Maine, Precipitation and they are far less frequent than northeast storms. Statistical studies indicate that the aver- Precipitation of all kinds-rain, snow, sleet, age probability of a hurricane hitting our coast hail-has many basic influences on the land. As annually is less than 5%, while an average of a process agent affecting geology, it can cause two damaging nor'easters are likely to occur both erosion and deposition. For example, rain each winter. and meltwater from snow play important roles in bringing new sediments from upland areas to Broadly speaking, coastal residents should be marine environments. (They also carry along or- aware of two basic planning considerations with ganic nutrients vital to ocean food chains.) On respect to winds and waves. On the one hand, the other hand, heavy rainfall can cause severe because wave and wind action is vital to the erosion when it flows over unvegetated river maintenance of beaches and certain other mar- banks and other sloping terrain lacking in plant ine environments, activities or projects that cover. In most, but not all, cases, erosion prob- might interfere with this role should be carefully lems develop as a result of human activities that assessed. This would primarily include develop- destroy existing vegetation. However, regardless ment on or near dunes and the construction of of the cause, severe erosion can also lead to sec- shoreline structures. On the other hand, the de- ondary problems resulting from the release of a structive potential of waves should also be con- heavy load of sediments. As these sediments are sidered in the planning and placement of piers, transported downslope they may cause serious buildings and any other kind of shoreline de- silt pollution of nearby waterways or smother velopment. shellfish beds and other valuable marine environ- One strategy for dealing with the adverse.ef- ments. fects of waves is the construction of man-made Relevant planning considerations can be or- shoreline protection devices, such as seawalls iented either to preventing erosion before it oc- (discussed in more detail in Chapter 4). In some curs or dealing with it afterwards. Severe erosion cases, this can be an effective way of preventing problems are most likely to develop where soils shoreline erosion and property damage. Unfor- become denuded of plant life by foot traffic, tunately, under certain conditions, seawalls and motor vehicles, development activities (such as similar structures can actually make erosion bulldozing) or herbicides. They are most easily problems worse instead of better, by cutting off prevented when the erosional potential of such the shoreward transport of sediments and inten- activities is carefully studied before they take sifying the effects of storm waves on adjacent place. shore areas. Because of this, and because sea- In the case of construction, plans can often be wall construction is now subject to State regu- formulated to reduce erosion using various com- lations, thorough studies should always be con- mon procedures. But in some instances studies ducted to determine the potential long-range may show that the activity should be sited in a impacts of any shoreline protection device being shoreline area less prone to erosion than the one considered. proposed, or even entirely beyond the shoreline area. A very attractive alternative strategy for deal- In general, solutions to existing erosion prob- ing with the erosional and destructive power of lems along the coast are basically the same as waves is simply to locate all structures and those employed inland. Revegetation with an ap- buildings in the nearshore zone above the area propriate plant cover, careful management of that will be affected by storm waves. Houses, foot traffic and, if necessary, physical reduction roads and other development situated well be- of the degree of slope are the most effective hind beaches, marshes, dunes and other near- .,after the fact" tactics. shore environments are least likely to be in It should be noted that not all erosion prob- danger during-heavy storms, which will continue lems related to precipitation are man-made. High, to impact areas further and further inland as sea steep shoreline banks composed of sediments level rises. This is a relatively easy, and com- other than bedrock are often prone to steady in- paratively inexpensive, tactic to employ. How- land recession. This is due in part to wave action ever, since each part of the Maine coast is sub- at the toe of the slope, which continually eats ject to different conditions, it is best to get away lower bank sediments. At the same time, expert help in making decisions about just how precipitation weathers away surface sediments far away from the shore development should be at the top and on the face of the bank. These placed. (See page 74 for more information on processes can lead to both a steady-or an this "hazard zoning" strategy.) abrupt- recession of shoreline banks and scarps 16 (depending on the sediment composition). How- cal environment. Probably the best known ex- ever, though the rate varies from site to site, ample of how "biological activity" works as a pro- some recession is almost sure to occur. cess agent in terms of coastal geology is the In certain cases banks may be stabilized with role of vegetation in preventing erosion. terracing and vegetation programs. But since The ability of plant roots to hold unconsoli- shoreline recession is partly an inescapable re- dated soil materials in place is a vital factor in sult of progressive sea level rise, the most basic the stability of many geologic environments, and planning response to this phenomenon is pre- along the coast this function is apparent in en- ventative. That is, whenever possible, shoreline vironments situated both on uplands and under- development should be placed far enough away water. Salt-tolerant grasses, for example, are from naturally receding embankments to prevent crucial to the maintenance of dunefields and salt future threats to property or human safety. (See marshes. Similarly, in some intertidal (between pages 73 for a more thorough discussion of bank the low and high tide mark) and subticlal (below recession and related planning considerations.) the low tide mark) environments, aquatic plants Another precipitation-related subject that play a critical role in preventing drastic erosion should be studied by developers and town plan- by waves and currents. ners is the hazard of construction on river flood Interestingly, in clunefields, marshes, vege- plains. In the spring, rain and snow meltwater tated subtidal flats, and certain other shoreline swell streams and rivers to levels much higher environments, plants not only hold sediments in than common during the rest of the year. Though place, but also facilitate the deposition of new it may happen only a few times every century, sediments. Their stems and leaves decrease the this occasionally leads to severe flooding of the velocity of winds and waters flowing over them, lowlands on either side of a river, a danger to causing sediments to be deposited-thus, actu- both property and people that might happen to ally building up the plants'own habitat. be there. For this reason, any new development Although the role of animal activity as a coast- in flood-prone areas, as well as the rebuilding of al process agent is not as well known as that of structures damaged by floods, should always be plants, it does affect the deposition and erosion carefully considered. (This is why the federal rates of some environments in several ways. Bur- flood insurance program requires towns to have rowing and bottom-dwelling organisms in sand flood hazard ordinances regulating new construc- and mud flats, such as clams, tend to excrete tion in flood-prone areas for private property to be fecal pellets that are bigger than the tiny sus- eligible for federal ly-subsid ized flood insurance pended particulates they ingest while feeding. and disaster assistance.) Because these pellets are relatively large, they Ice can also act as a process agent in some are deposited on the bottom rather than being re- coastal environments. Ice plays a minor role, for suspended in the water column. This is one of example, in the transport of intertidal flat and the best examples of how the biological activities salt marsh sediments when sediments bound up of animals builds aryd maintains a marine en- in ice floes are deposited as the floes melt. It vironment. can also act as an inhibitor of erosion. This hap- Certain types of fish and other large organisms pens when the tiny spaces between sediments that feed on the ocean bottom have the opposite are filled with water that then freezes as temper- effect. Their feeding habits tend to stir up bottom atures drop. The ice "cements" the sediments sediments and cause them to float away in the together, inhibiting erosion on beaches, dunes water '. Although this may have the effect of re- and some other shoreline environments. leasing nutrients needed to fuel ocean food Generally, though, the most important thing chains, it can also accelerate the erosion of fine- coastal residents should keep in mind about ice grained environments. However, on the whole, is its tremendous crushing force. Any piers, biological activity must be considered part of the wharves or other structures built wholly or partly process that maintains the balance of geological below the high water mark can be exposed to systems. impacts of 10 to 12 tons per square foot from The geologic function of coastal plants and floating ice, and should be designed accordingly animals is, of course, only one of the reasons in coastal areas prone to winter icing. why efforts should be made to minimize adverse effects human activities and projects may have on them. Almost all plant and animal species Biological Activity have some kind of commercial, aesthetic, or eco- Just as the physical environment can affect logic value as well. For coastal residents, many the lives of the plants and animals that live in it, of whose livelihoods depend on fish, shellfish, so too can plants and animals affect the physi- seaweed and other marine species, the impor- 17 tance of our native flora and fauna is especially localized areas around scattered trading posts apparent. Even so, it cannot be denied that pro- and fishing stations. tecting plants and animals from the many threats When settlers came to Maine in increasing that exist in the modern world can be difficult. numbers during the 19th century, the human im- To prevent devegetation on a sand dune, for pact on coastal geology began to be more pro- instance, a town planner might have to tackle the nounced. As forests were harvested for shipbuild- adverse effects of many different human activ- ing and agricultural purposes, for example, soil Wes-from the heavy foot traffic of beach goers erosion and the movement of sediments from the and direct destruction by development to off road uplands to marine environments was acceler- vehicles and the purposeful or accidental spray- ated. The damming of streams and rivers for in- ing of herbicides. To protect the clams, he may dustrial power caused further changes in the have to deal with threats ranging from dredging run-off, sediment transport and coastal deposi- and upland erosion to overharvesting and pollu- tional processes. tion by sewage, oil or toxic chemicals. In the present century, industrialization and ur- The companion volume to this handbook, A banization, marked by increased resident and Planner's Handbook for Maine's Intertidal Habi- seasonal populations, burgeoning construction tats, is one source of information relating to the activity and pollution, have made even more planning considerations involved in protecting changes in the geology of the shoreline. The plants and animals in marine environments. coast attracts people, both for its valuable re- Here, it is possible only to stress that for sources and as a place to live. And as almost geologic, economic and ecologic reasons, all coastal residents are aware, solutions to some adverse effects on plant and animal species as of the adverse side effects of residential and a result of human activities and projects should industrial growth are becoming more and more be avoided, or at least minimized, whenever complex. possible. Most coastal residents also realize, however, The Human Factor that finding ways to minimize undesirable en- Overall, the geological makeup of Maine's vironmental impacts is extremely important if the coastline has probably affected past and present resources that made the coast attractive in the coastal residents as much or more than those first place are to retain their aesthetic and econ- residents have affected coastal geology. Among omic value. If the productive potential of the land many other things, it has controlled where people and ocean are destroyed, if its beauty is marred, built their homes, how they traveled from one we are the ultimate losers. Undoubtedly, to pro- place to another, and how they have made their tect this potential and beauty and at the same livings. Unquestionably, the geology of Maine's time meet the growing demands of society is one coast is a basic factor that makes not only our of the greatest challenges we will face in the state, but also the people who live here, unique. coming decades. , But although man's total influence on the The key element in meeting this challenge is shoreline of Maine may be less than the shore- knowledge. In order to avoid environmental prob- line's influence on Mainers, we have definitely lems we must understand how the natural world had our effects. Fortunately, they have not been works and how our own activities and projects as extensive, on the whole, as those evident in affect the natural scheme of things. That, of more developed states. Even so, they cannot be course, is one of the primary purposes of this discounted or ignored. For better or worse, man handbook-to help coastal residents understand has become a kind of process agent. Perhaps not how developments may affect the intricate bal- a "natural" one, or a particularly powerful one in ance among shoreline environments. comparison to such things as waves or rising sea Figure 10 is a list of common human activities levels, but one that is just as real. along with descriptions of how those activities In many ways, modern coastal residents are may affect various nearshore geological environ- still more affected by geology than they affect ments. It should be stressed that these are only it. However, as our technology and population potential effects. They do not always occur. The has grown, the "geological connection" has in- list is given not to show what activities are creasingly become a two-way affair. "wrong;" it is given as an aid to planners, de- In the beginning, man had very little impact on velopers and others involved in resource utiliza- the geologic conditions along the shoreline. In- tion and development along the coast of Maine. dian populations were too small to have much ef- Hopefully, the information will be useful to them fect, and even at its height, early resource util- in assessing the possible effects of projects they ization during the colonial era by European fur may be considering. For a more thorough look at traders and fishermen was minimal, limited to how human activities and projects may affect 18 specific coastal environments, readers should re- fer to the planning considerations described under each of the 55 individual geologic environ- ments discussed in the next chapter. The relative suitability of particular environments for various human activities is summarized in Figure 10. FIGURE 10 Development Activities - Environmental Suitability Index ACrrIVITIFS - ENVIRON,4ENT SNITABILITY INDEX X11-it@bl, c d highe, co,t, U, K .1 E E I E E K C ASTAL WINE GEOLOGIC ENVNDNMENTS SUPRATIDAL ENVIR-TNTS: 1,,,Itd R-11, Ridg- xWAII i -[x A xI oAX1 A X1 II Ao o bb,i osist I O[XD oAA A A A F-h--ki@h Na,11 101XIX I.. XA A A A SS A I S La,dslid, E@ a,ati- & D,p-i,@ oA Ax Ao o E@bli- Fl@t AA A o A A @ h-, Fl- AAIX @A Xsx. A olAIx AA A FI-i.1 [email protected] S.-P o I oo- 2 xIx oo A A o AA A INTERTIDAL ENVI-NMENTS: I "ill I'll "I'll AoIx Xx_x AA Aoo A.A A L- .11 M-D .I XA _fx@_ xA X o IAx-K N., @h L- oxlx II xXx Ax io Ao IxA A S:,Idt BF,_,h, & S.It P..d, II AA AA A Aol IA A ssso xxx_x- o .A o o 5sso AAAx Ax o D s AAsx s AX,, xA o o L_ sssx oxoA Wx o o 13..1d- oxA Aix o o @-h-l F.. AAA A A s A AA x o o F"" I oAso [olo ool Ix A A o s o A A so oAsol lo o1ol Ix AIX --s A AI o I I Ix AIX El- A'ol oW I. AI s IB- W loln Ojol 19 A A o A A s ch11.1 I L_', I oAlol loo I I II o IA AI A1@11 F1111 AX101 00 o1ol IX A X o. o A AI V_,bb '..P I ossiol loo AA A 11 o A AI [."9@ I S0SISI 0o II I s SI F1'i.1-E-11i Chb-1 S jX 0Ajol 00 0A o II I Io 0 1 P ilt 11 LI-al B", __Sss A X AAJAI oAx oA A Isl o Io o I V` g,t,t,d P,i- 11 Lltlll@ 88- Ss A t oAJAI 0oA I oxio I I o o o Ab-dolld P.i- .1 1-1- SS S 1 0o101 0oA I ol I I o S s @ -h @- A 1 0X1 0 1 1 1@1 0 0 Fl-d-Tid,1 D@It. I" oJAI o I o o Ebb-Tldl,D11ta o s X 0JAI o o S 1 0101 01 0 0 0 0 A Ix 01XI 0 0 SUBTIDAL ENVNDN,11ENTS: F1111 lo @o o1ol A AX1 o I II IIx AI II I FI- 0 01 .0 01 A AA I II IIA AI I A01 101ol A AA 0 1 1AI I _S 001 1 lol IA AI Upp- Sho-f-, A 01 o[o I JAI 10 o I S L - Sh... f.- A ol 0 1 101 1o 01 S lig -V,1-ity Tid.1 Ch ... @1 5XIS11 0S 01 0 S101o o IoI oI sx1sl 11 SS ool o slolo o i"_"""iT'Y Til" 1": .. I o o L1. lbllily N., soisl ill So 0 oJXJA o o o F o OIXIX 0 Ch sx1stI so o 01 01 F1 sAS o co ooo o A A o 0 o F.--i- Ebb M--I tAS 0o 02220- XA 0 X x X o '@x o 0 SA s A 7 0 o o S S o S0 - 0 D-d@, 1 1: SA S S 0 C5 _R __6 A 0 0 Abbbd,-@ Tpe a' `1-71 0 0 T-1 FI-i @ 1 'N' -'1 0 S 10 0 A 0 Tidli C ... k, 0o AA - @E 0 0 o A -'h D-i-'@ @-h XR..w A 010 19 FIGURE 11 Bedrock Control of Shoreline Physiography PLUTONIC ROCKS P. PERMIAN TO CRETACEOUS (WHITE MOUNTAIN PLUTONIC- VOLCANIC SERIES) NDDLE TO LATE DEVONIAN (NEW HAMPSHIRE PWTONIC SERIES) 0 ORDOVICIAN STRATIFIED ROCKS D. M.DEVONIAN TO MISSISSIPPIAN (?) DL EARLY DEVONIAN (INCLUDES SOME ROCKS MAPPED AS SILURO - DEVONIAN). S SILURIAN (INCLUDES SOME ROCKS MAPPED AS SILURO - DEVONIAN). 0 ORDOVICIAN (INCLUDES SOME ROCKS MAPPED AS CAMIBRO- ORDOVICIAN AND SILURO- ORDOVICIAN). C, C CAMBRIAN (?) P PRECAMBRIAN a - CONTACT S n G. ,00' FAULT UL S 0 DL EASTERN 0 S CLIFF Ga DL SHORELINE L 0 G 0 1j. S S 0 0 4S L S DL ISLAND -BAY 0. COMPLEX S DL INDENTED IL EMBAYMENTS S P, ARCUATE BAYS COASTAL PHYSIOGRAPHY: THE BIG PICTURE of bedrock formations, and the past and present effects of the geologic process agents discussed earlier in this chapter. If you could view the coast of Maine from a The cumulative influence of these various ele- point far above the earth-from a satellite, per- ments has created a coastline that can be roughly haps-you would be able to discern certain broad divided into four large segments. Geologists have divisions of the shoreline that geologists call given these physiographic subsections names "physiographic subsections." An approximation based on their individual characteristics. of this view is provided by your Maine road map. Even a quick glance at it will show you that the They are, going from west to east: Maine coast is not the same along its entire 1) The Arcuate Bay Shoreline length. 2) The Indented Embayments Shoreline The geographic configuration that you see is a 3) The Island-Bay Complex, and result of two basic factors: the nature and location 4) The Eastern Cliff Shoreline 20 Although general physiography is not a primary The peninsulas, which are commonly 10 to 20 consideration in all planning decisions, it is the miles long here, closely parallel a layered struc- underlying factor in why certain areas have more ture of supporting bedrock chiefly composed of beaches and others have more rocky shores. Like hard crystalline rocks of metamorphic origin. other geological factors, it is one of the basic in- Where sections of these metamorphic rocks are fluences that both limit and make possible relatively soft, they have been substantially resource utilization or development. eroded, leaving elongated valleys now flooded by Here, then, in a nutshell, is the "big picture" into the ocean. Although much of the shoreline in this which all of the smaller individual segments of region is exposed bedrock, there are also a num- Maine's long coastline fit... ber of small beaches in narrow coves and, at Popham and Reid State Parks, sand beach areas The Arcuate Bays Shoreline of considerable size. The southernmost division of Maine's coast, the Arcuate Bays Shoreline, extends for about 42 miles north-northwest from Kittery to Cape The Island-Bay Complex Shoreline Elizabeth. It includes a series of three bluff The Island-Bay Complex Shoreline section of headlands separated by two wide, arc-shaped Maine's coast extends for about 105 miles east- bays widely noted for their fine sand beaches northeast from Port Clyde to Machias Bay. It con- (such as Old Orchard). sists primarily of numerous irregular bays and The first headland, from Kittery to Ogunquit, islands of many sizes. The largest bay is Penob- and the next, from Kennebunkport to Biddeford scot Bay, extending for more than 30 miles north- Pool, are supported mostly by erosion-resistant south and up to 20 miles east-west. The largest types of bedrock. The third headland, at Cape island is Mt. Desert, with a total area of over 100 Elizabeth, is underlain by a variety of slow-erod- square miles. Ing bedrock types. Along each of these head- The scattered distribution of a number of large lands there are a number of small local indenta- granite "plutons," or intrusions, is primarily res- tions cut into formations of more easily eroded ponsible for the hilly physiography of the region. sedimentary rocks, where isolated sandy or Where such erosion-resistant granite bulges rise gravelly beach deposits can often be found. high above the surrounding land they form moun- In the two great arcuate bays of this subsec- tains called "monadnocks," the most famous of tion-from Ogunquit to Kennebunkport and from which in this area is Cadillac Mountain. Biddeford Pool to Cape Elizabeth-most of the bedrock surface has been eroded to elevations The Eastern Cliff Shoreline below present day sea levels and buried beneath Extending for about 23 miles north-easterly beach sands, clay-silts, or glacial till. from Machias Bay to West Quoddy Head, the Eastern Cliff Shoreline consists primarily of hard The Indented Embayments Shoreline volcanic and igneous rocks which rise in cliffs The Indented Embayments Shoreline extends for 30 to 50 meters directly out of the sea. Be- for about 55 miles east-northeast from Cape Eliz- sides the steep cliffs, this area of shoreline is abeth to Port Clyde. It is characterized by a con- noted for its relative lack of harbors and inlets. tinuous series of long, narrow bays, inlets, rivers A major northeast-trending fault zone, called the and estuaries running north and south and sep- Fundy Fault, passes close offshore. The Fundy arated by numerous bedrock peninsulas and Fault is thought to be responsible for the char- islands extending southward. acteristic abruptness of this shoreline. 21 DEPOSITIONAL SYSTEMS: agents. In fact, nearly every coastal environment THE INTERDEPENDENCE OF ENVIRONMENTS that consists of mud, sand, gravel or any other "unconsolidated" sediments (as opposed to bed- If we look a bit closer at Maine's coastline, rock) ultimately depends on some other environ- focusing on areas smaller than major physio- ment for its sediment supply. This interdepen- graphic subsections but larger than individual dence can be traced along the pathways over geologic environments, we enter a realm many which process agents carry sediment from one laypeople are unaware of. It's a level at which environment to another. These geological net- certain intriguing similarities between geology works, marked by the flow of sediments among and the relatively new science of ecology begin environments in a nearly equal system of give to become apparent. and take, are termed, "depositional systems." In recent years, the important ecological con- The depositional systems concept has pro- cept of the interdependence of all living things found significance to coastal residents, develop- has come to the attention of the general public ers and planners. It is both a key to understand- through widespread media coverage of various ing coastal geology and a.crucial consideration environmental dilemmas. Few people yet realize, whenever assessments must be made concern- however, that most geological environments, or ing the potential impacts an activity or project "units," also exist only because of complex inter- may have on coastal environments. It is the dependent relationships with other units, or that underlying explanation of how and why changes such relationships are especially common along made in one geologic environment can affect the coast. other environments in the area. In the next few Each major coastal feature-a bay, for exam- pages we'll take a closer look at the depositional pie-is made up of a group of individual environ- systems common to Maine's coastline and some ments (mud flats, beaches, marshes, etc.) linked of the basic planning considerations relating to together by waves, currents, and other process them. FIGURE 12 Depositional Systems Index Map Calais Machias EASTERN CLIFFS 09 4 0 See Fig. 12d Rockland 9*1 Q ISLAND-BAY COMPLEX See Fig. 12c Portland J INDENTED EMBAYMENTS See Fig. 12b ARCUATE BAYS See Fig. 12a Kittery 22 FIGURE 12a The Arcuate Bay Shoreline LEGEND PORTLAND BEACH SYSTEMS Bb Barrier Beach Bs Strand Plain Beach Bsh Beach Shoreface ESTUARINE-NEARSHORE EMBAYMENT SYSTEMS Ec Coarse-Grained Estuaries Ef Fine-Grained Estuaries NEUTRAL EMBAYMENTS: NE, NEw Wave-Domina'ted NEt Tide-Dominated E@ 0. DELTA SYSTEMS Dc Constructional Dd Destructional Df Fan Deltas OFFSHORE SYSTEMS KJTTER 5b 0. Ow Wave-Shoal Platforms Op Platform-incised Channels COASTAL MARSH SYSTEMS Cm Coastal Marsh FIGURE12b The Indented Embayments Shoreline AUGUSTA E, KLAND C. WISCASSET E .,C. C. OP & 0. BRUNSWICK OTH ip .0w )C3 01- NE, 0 Od LEGEND See Figure 12a 23 FIGURE 12c The Island-Bay Complex BANGOR MACHIAS 0 Eff of CHERRYFIELD E, C. ELLSWORTH E,\C %. BELFAST Ef HE ME % 0. C OW 0. Op 0. op OP 0. ROCK NO NE -P LEGEND O@ See Figure 12a e FIGURE 12d The Eastern Cliff Shoreline The discussion covers the four basic types of depositional systems found along our coast: CALAIS beach systems, estuarine-nearshore embayment systems, delta systems, and offshore systems. These major categories are further divided into Of subsystems having their own unique character- istics. Finally, each subsystem can be broken down into groups of the geologic environments E@ E. that are described in Chapter 3. EASTPORT E Beach Systems Old Orchard, Popham, Reid-we've all been to Ef a few of Maine's beautiful beaches at one time or IE, ME'. another. Yet, very few visitors ever realize how MACHIAS $cl fragile or complex these popular environments E, IE,\ are. 0. In most cases, a beach is part of a larger sys- tem of environments characterized by its near- ness to the uplands, its dependence on a steady source of sediments, and the importance of LEGEND waves and winds in its formation and mainten- See Figure 12a ance. Along the Maine coast, two major types of beach systems occur: barrier beaches and strandplain beaches. 24 Barrier beaches are made up of beaches, transported in a northeasterly direction. Con- dunes (storm ridges, in the case of gravelly versely, nor'easters transport sand in a southerly beaches), shoreface deposits and other associ- direction. This bi-directional alongshore move- ated features that are completely separated from ment tends to retain the sand within each beach the upland shore by marshes. Such systems exist system (though some sand may be lost by being where offshore deposits of sand and gravel, now transported into inlets or along to, and offshore submerged, have provided sufficient sediments from, headlands where deeper waters occur). for their creation; Less commonly, barrier The basic planning consideration relating to beaches occur at the mouths of large rivers, the cyclical flow of sediments within barrier where great volumes of sediment have been beach systems is clear: almost any activity or transported from inland. project that significantly interferes with the nor- All barrier beach systems are maintained pri- mal onshore-off shore transport of a beach sys- marily by wave and wind (or "eolian") action, the tem's sediments threatens the continued exist- process agents that link together all of the in- ence of the entire system. dividual environments involved. The low waves A classic example is dune devegetation. Thick and southerly winds of spring, summer and fall growths of salt-tolerant grasses and shrubs are transport large quantities of sand and gravel from crucial to the formation and maintenance of sand foreshore deposits onto beaches and dunes. dunes. Their stems and leaves slow down and Northwest winds may also carry sand from sand capture wind-transported sand, thus making the flats behind the beach onto dunefields. Sand dunes higher; their roots hold the sand in place, thus stockpiled in the frontal dunes and beach effectively reducing erosion. When the plant life area of the system is later removed to the fore- on dunes is destroyed by heavy foot traffic or shore (subtidal) portions of the beach by winter construction, the dunes are open to severe ero- storms. This process reduces the slope of the sion by waves and winds. In a short time, this beach, causing more of the storm wave energy may result in the permanent loss of significant to be dissipated in the foreshore area rather than stockpiles of sand needed for the maintenance on the beach itself. When calmer conditions re- of the beach systems as a whole, ultimately lead- turn, this sand is again gradually transported ing to a sediment-starved, erosion-prone beach. back onto the beach and frontal dunes, thus com- Barrier beach systems may also be threatened pleting the cycle. if seawalls, revetments or other shoreline struc- Sand is also transported alongshore by waves. tures interfere with the natural cycle of erosion During periods of southerly winds, beach sand is and deposition within the systems. When the FIGURE 13 Profile View, Beach and Dune Features seasonal transport of sediments is cut off or The planning response is again clear. Any altered, severe erosion of beach areas and dunes roads, buildings or other structures built too may result or existing erosion problems may be close to a barrier beach may someday be buried accelerated. A sediment-starved beach can also in sand or washed away. This has, in fact, oc- result when the flow of sand delivered from in- curred in a number of places, both in Maine and land by a river is restricted by damming, dredging elsewhere along the Atlantic coast. Because the or some other activity. rate of inland movement varies from beach to beach, it is often wise to get expert advice when FIGURE 14 making decisions about how far away from Seasonal Cycle of Foredune Erosion beach areas development will be allowed. (See Appendix for a list of relevant agencies.) SEASONAL CYCLE OF The basic differences between barrier beaches North" FOREDUNE EROSION BY and strandplain beaches is that no marsh or es- (D Late Fall Windsst NORTHEAST WINDS AND STORM WAVES AND ACCRETION OF tuary separates the latter from the upland. And, WINDBLOWN SAND BY except for the fact that strandplain systems mi- Dun.. SOUTHERLY WINDS we grate inland at a much slower rate or not at all, GROWTH OF DEFLATIONARY we # Foredun PARABOLIC DUNE TO INTERSECT general planning considerations are the same. FOREDUNE BY EROSIONAL Parabolic NORTHWEST WINDS Ber. Dune Lobe Beach Face Estua ri ne-N ears hore Embayment Systems Estuarine nearshore embayment systems in- @Winter clude two basic types of depositional systems: 1) estuarine embayments, areas of saltwater wet- lands and intertidal or subtidal flats where fresh EROSION OF FOREOUNE AND and salt water intermix, and 2) neutral embay- BREAC14ING At PARABOLIC DUNE LOSE BY NORTHEAST ments, which though basically similar to estu- STORM WAVES arine systems in many ways, do not receive sub- Beach Face or Northeast stantial volumes of fresh water. Storm Waves Coarse-grained estuaries are estuarine embay- Summ Northeast ments which develop behind barrier beaches. inds The major sediment is sand, derived from nearby SOUTHERLY WINDS TRANSPORT beach systems or shallow offshore deposits. SAND FROM BERM SURFACE TO LD RAMP OFrSAND AT FOOT Among the geological units usually associated _WMJEam2__ 0 FOREDUNE 'CARP. NORTHWEST WINDS TRANSPORT with coarse-grained estuaries are salt marshes, X1, AND REWORK WASHOVER FAN Sou herly SAND TO BUILD DUNES AND Winds SEAL FOREDUNE BREACH. estuarine channels, subtidal flats, barrier sand Beach Face NEW GROWTH OF aEACH GRASS ON RAMP AND WASHOVER FAN spits, ebb- and flood-tidal deltas, and point or Early Fall DUNE. lateral bars. The process agents that most strongly influence this system are tides, rivers, waves and currents. RAMP 01 SAND E.TENDS TO TO' Flood tides bring sediment from beaches, tidal OF FOREDUNE AND OVERTOPS deltas, or offshore deposits into the estuaries. we CREST. ADDS HEIGHT AND WIDTH TO 'OREDUNE. Ebb tide currents return part of the sediment to I'V-11 Beach Face VEGETATION STABILIZES WASHOVER FAN. the ebb-tidal deltas near the marshes and sub- _J sequently back to beaches or offshore deposits. Finer deposits of mud and silt occur in the upper reaches of the estuaries as a result of upland Another important planning consideration runoff. stems from the fact that barrier beaches tend to A similar type of estuarine embayment system, migrate inland over the years. This slow but fine-grained estuaries, develop at the mouths of steady landward movement is accomplished by rivers that have moderate to large flows and rela- washovers during heavy storms and by eolian tively unprotected mouths at the ocean (such as transport of sand landward over the dune fields. the Sheepscot River). The basic difference is that It is usually accompanied by erosion of the front- major sediments are silt and clay, transported al beach area and foredunes by storm waves. as suspended sediments in the river or brought in Thus, as the beach migrates, its width remains by the tide from offshore deposits. fairly constant. (As previously explained, land- Wave-dominated neutral embayments are shal- ward migration is a result of the progressive sea low, curved bays generally found on the seaward level rise occurring along world coastlines.) side of estuaries. Here there is little or no fresh 26 water influx and wave action, rather than tidal these environments are very sensitive to action, sustains the system. changes, particularly to any alterations in the vol- These embayments are composed primarily ume of water that flows into and out of them. A of shallow, subtidal environments that receive dam constructed on the river entering an estuary, sediment only from wave erosion of glacial de- for example, can prevent sediments from reach- posits on the shores of islands or the mainland. ing it, leading to a shortage of material needed Fine-grained sediments are usually transported to replace sediments lost to waves and ebb tides out of the shallow parts of wave-dominated neu- and a lack of nutrients upon which the food tral embayments, while coarser sediments tend chains of the estuary are based. Constructing a to remain. The shallowest areas are often ex- breakwater at the mouth of an estuary can cause posed at low tide. increased sedimentation in interticlal and sub- Tide-dominated neutral embayments are shal- tidal areas, which could cover shellfish beds and low, very narrow bays in whicti tidal action is block navigation. more important than waves in depositional pro- Filling for residential or commercial develop- cesses. (The exposure to wave action is reduced ment, ditching, draining, impounding, diking or because of the narrow, sheltered shape of the any other activity that directly destroys an es- mouth of such bays.) Tide-dominated embay- tuarine wetland or interferes with the normal cir- ments receive little or no fresh water discharge. culation of water in an embayment system can Sedimentation and transport in this system is have significant adverse effects on the many similar to that in fine-grained estuaries, except commercially valuable species that live, feed or that most sediments come from offshore de- breed there. And even though coastal wetlands posits rather than from upland runoff. Tide-dom- can safely soak up a reasonable amount of con- inated embayments characteristically contain a taminants, they should be protected from exces- number of different flat environments, estuarine sive pollution by sewage or toxic chemicals. marshes along their landward margins and plat- (Both types of pollutants can also have drastic form incised channels at their seaward margin. effects on clam flats and other interticlal or sub- Many of the geologic environments associated tidal environments found in embayment sys- with Maine's estuarine-nearshore embayment tems.) systems are extremely valuable, both economi- cally and ecologically. The nutrient-rich saltwater wetland and subtidal or intertidal flat areas, for example, are major feeding, breeding, and "nurs- Mid-Coast and Eastern Coastlines Delta Systems ery" habitats for our most important fish and A number of different kinds of delta systems shellfish, such as clams, mussels, crabs, striped occur in Maine, each of which has its own par- bass, flounder, alewives and salmon. In fact, ticular attributes. Constructional deltas, for most of the commercial fish and shellfish example, are ever-growing accumulations of species in the Atlantic are directly dependent sediment found at the mouths of some rivers. on the existence of estuarine embayment sys- Very large constructional deltas, like the one at tems at some stage of their lives. They also the mouth of the Mississippi River, don't occur in provide crucial habitat to untold thousands of Maine because our rivers drain much smaller ducks, geese, wading birds and other water- areas and carry much less sediment than the fowl, as well as to a great diversity of game and Mississippi. Several smaller examples are found non-game animals. here, however, where rivers carry relatively large Beyond this, the wetland portions of estuarine amounts of sediment to areas of the shoreline embayments serve as natural barriers against the protected from heavy waves. Examples include erosion of adjacent upland by absorbing the deltas along the inner portions of Casco Bay and brunt of heavy storm waves. Equally important, in Merrymeeting Bay. Like other constructional marshes help to regulate the flow of runoff from deltas, these are similar to fine-grained estuarine the mainland, storing water and releasing it slow- deposits except that the rate of sedimentation is iy thus reducing the incidence and severity of higher. coastal flooding. The dense marshland vegeta- Destructional deltas are accumulations of sed- tion also acts as a natural water purifier that iment at the mouths of rivers that are exposed removes toxic materials from polluted water and to relatively high wave and tidal action. As a- re- traps sediments which might otherwise smother sult, fine sediments are quickly winnowed out of shellfish beds and fill in navigation channels. this type of delta leaving mostly coarse-grained Protecting the valuable geologic environments sediments such as sand which may be a source in embayment systems often entails numerous of material feeding nearby beaches and river- and complex planning considerations. Most of mouth bars. 27 Destructional deltas are maintained in a deli- upriver may cut off crucial supplies of new sedi- cate balance depending on levels of sediment ment and threaten the entire system with slow supply and the degree of wave and tide energy. destruction. Generally, sediments are removed from this sys- tem as fast or sometimes faster than new sedi- ments arrive. Offshore Systems A different kind of delta, called a fan delta, Offshore systems occur in the outer portions occurs where a stream delivers sediment to tidal of the nearshore zone and consist of two basic flats in areas where the tidal range (the difference types: wave shoal platform systems and platform between low and high tide levels) is relatively incised channels. great. In this delta subsystem, deposition of sedi- Wave shoal platforms are submerged offshore ments takes place at the mouths of streams dur- glacial deposits found in water less than 30 ing low tide. Erosion of these sediments then oc- meters deep, from which islands may or may not curs during high tide. The rising tides allow project. The major force acting on this deposi- waves to rework delta sediments dumped onto tional system is intense wave energy, which is tidal flats, depositing coarse-grained sediments continually reworking and transporting the shoal as sandy swash bars and dispersing fine-grained sediments. sediments to mud flats at the fan margin. Platform incised channels are deeply sub- Because beaches, salt marshes, mud flats and merged, low-velocity tidal channels connecting other recreationally or commercially valuable tide-dominated embayments or estuaries to geologic environments are often associated with shoreface deposits or subtidal flats. Such chan- delta systems, the maintenance or destruction of nels transport sediments landward and seaward, a delta can have far reaching effects on coastal depending on local conditions. residents. In terms of planning, one of the most Both types of offshore systems can be found important considerations is that the continued along Maine's entire coast. Where offshore sys- existence of deltas is dependent on the contin- tems provide habitat, e.g. for lobster or ground- ued delivery of wave-, river- or stream-borne sedi- fish, location of dredge spoil and other waste ments to the delta system. Changes in conditions disposal is an important planning consideration. FIGURE 15 Marine Environment Map: Wells, Maine C. S_ S a - S, S. S@ S M. C@ M, M, F M P M, Sd P K S@ S@ 5d M. B. Fb LEGEND See Page 6 Sd C. Fb Sf P B, S@ Mf F, S, S@ M, Sd F S S, F M, M. S, A14 S 28 Figure 15. Reproduction of a portion of the coastal marine geologic map of Wells, Maine, illustrating the geologic units associated with the Little River estuary, Drake's Island Beach and Parsons Beach. Figure 16 illustrates schematically the sedimentation processes associated with a barrier beach- coarse-grai ned estuary system. Large black arrows indicate magnitude and direction of wave transport on flood-tidal delta, ebb-tidal delta, beach, and shoreface. Small black arrows illus- trate tidal current transport of sediment; and open arrows indicate wind transport of dessicated sand. FIGURE 16 Little River: Coarse Grained Estuary Systems N Figure 17. Reproduction of a portion of the coastal marine geologic map of Addison, Me. illustrating the units of the Indian River estuary and the West River embayment. Figure 18 schematically illustrates depositional conditions and processes. Broad black arrows indicate magnitude and sources of suspended sediment to the systems. Small black arrows indicate estuarine and tidal flow directions. White arrows indicate addition of sediment to the embayments from shoreline erosion. FIGURE 17 Marine Environment Map: Addison, Maine 30 White areas are flats of low sedimentation rates; shaded areas - flats of moderate sedimentation rates; vertical-lined areas of high sedimentation and marsh deposition. Slant-lined area is area of estuarine mixing and induced deposition due to estuarine processes. Dotted margin areas are ero- sional shoreline areas. FIGURE 18 West River: Wave-dominated Embayment and Indian River Fine-grained Estuary Figure 19. Reproduction of a portion of the coastal marine geologic map of the Lubec, Me. quadrangle illustrating the geologic units of the wave-dominated embayment of South Lubec. Figure 20 illustrates, schematically, the depositional processes influencing the environments of the bay. Broad black arrows indicate tidal current flow; broad white arrows- mag n itude and direction of wave transport. Medium black arrows indicate general sediment dispersal, away from the shoreline; FIGURE 19 Marine Environment Map: Lubec, Maine 32 small black arrows along beaches indicate lateral sediment transport by littoral currents. Remaining black arrows indicate tidal transport within the bay. Shaded areas are accretional barrier beach sub-systems associated with the wave-dominated erosional embayment. FIGURE 20 So. Lubec: Wave-dominated Embayment L-LA @ec, Wave - r>OMMAtm . . . . . . . . . . . . bokmer 5vb,5y6tcm5 33 Figure 21. Reproduction of a portion of the coastal marine geologic map of Yarmouth, Me. quadrangle. Figure 22 illustrates the environments of the Royal River constructional delta subsystem at the inner margins of Casco Bay. Figure 22 illustrates the active processes maintaining the delta. Large, broad black arrow indicates sediment source to the system. Small, broad black arrows indicate suspended sediment dispersal within the basin during spring flooding of the Royal River, while broad white arrows, indicate sediment FIGURE21 Marine Environment Map: Yarmouth, Maine M M. M. S. M M, M, F@ C. M. S. M. M. M, M, C. I M M. M. M. C. M, M. F M. W F F. K F, S@ FF. F@ M M. M, M, F, F. F F F M F. F F S: M. F' F, F. F M M, F M. FF F j C. F F F \ , I , F. F F 11 M M. F M. M S@ FF F F, F F. F F. F 1, C M, S. C. F F F C F F rF F, S M. M MI W'M F F F, M F M'FF F. M F, L F F F F F M F C F F I C F F I F M.. F FF F F F -A F F F F M F MF F, F F, F I F, F, C' FF, -- F@ F. M. F, F F' M I LEGEND S,F F @-F F. F,. F. M B, See Page 6 IA F F@ F IC. C,F M F F@ F, a F, F, F. F F, F F. F. F. F M F, M 34 dispersal by flooding tidal currents during normal river flow conditions. Small, narrow black arrows indicate tidal current transport in channels; triangular arrows indicate sediment introduction to the delta system from eroding shorelines. Shaded areas are constructional portions of the delta plain; slant-lined areas are eroding portions of the delta system. Vertical-lined area is under the influence of processes typical of fine-grained estuaries. FIGURE 22 Royal River: Constructional Delta System N Royal Rivr_r COM5*1ACtive Delta '5ptem . . . . . . . . ...... . . . . .. .......... 35 c F m F s. FM' 5. s c. F., m m, lz@ M, F c. m W ,F c, m "F LEGEND See Page 6 sediment dispersal during spring floods; large white arrows indicate reworking of sediment by wave processes. Shaded areas are barrier beach systems; vertical-lined areas are associated coarse-grained estuarine systems. FIGURE24 Popham Beach Destructional Delta System 4E@ 4- <U E Cf :S 4- ......... . ................. . ... ...... ..... . . . . . . . . 37 Great South Beach, Roque Island photo Harold Kimball ` @w- *A CHAPTER 3: THE BUILDING BLOCKS OF MAINE'S COAST If you were to walk along the coast of Maine mark); intertidal environments (those located be- from one end to the other, you would travel con- tween the average low and high tide marks), and; siderably farther than "the crow flies." Though subtidal environments (those situated below the the distance isn't much more than 200 miles in mean low tide mark). Readers should realize, a straight line, there are well over 4000 miles of however, that in a depositional system, combin- shoreline between Kittery and Calais. ations of environments from each of these groups may occur. This shoreline-the longest of any state bor- dering the Atlantic-is made up of literally thou- It should also be noted that the planning con- sands of individual geologic environments, or siderations discussed deal primarily with the re- "units." It is a great patchwork quilt of beaches, lationships between people and the geological mud flats, bedrock ledges, marshes, and many aspects of an environment. For more complete other types of landforms. One system of classifi- information on how human activities and proj- cation currently in use distinguishes 55 different ects affect marine plants and animals readers are kinds of coastal environments found along urged, once again, to consult the Coastal Pro- Maine's shores, each characterized by a unique gram handbook entitled A Planner's Handbook set of attributes. for Maine's Intertidal Habitats. These environments are the subject of this Finally, a word about the color codes men- chapter. They are also, as explained in Chapter tioned as part of the description of each environ- 1, the basis for the Coastal Program's Marine ment. The Marine Environments maps are not, Geologic Environments Maps. Thus, the informa- themselves, color coded. Geologic units are indi- tion given here is particularly relevant to the sub- cated only by borderlines and letter codes. How- stance and use of those maps. It is a basic in- ever, if a planner or developer wants a more troduction to each of the 55 units and the geol- graphic delineation of coastal environments for ogy-related planning considerations pertaining to purposes of study, to help in creating zoning them. maps, for meetings or some other reason, the environments can be hand-colored with-"Prisma- For this discussion the environments have color" marking pencils. The appropriate colors ,been sorted into three groups: supratidal environ- are specified so that maps colored by one user ments (those located above the mean high water can be coordinated with those used by others. 39 FIGURE25 Overview of Coastal Geologic Units UrlAriel I-,'h LOW Tidal CMt1"Cl aoljqt1 Fiat 13Ack Dwre6 Salt marsh MuOlat 7W K ri AM4W I _A@ AL:-Z ..... .. LL --AL - 5UY INTER INMRTIPAL_ 6UPRATIPAL +PDA - TIDAI SUPRATIDAL ENVIRONMENTS Importance: Dunes play a crucial role in the main- Dunes and Vegetated Beach Ridges tenance of barrier or strandplain beach systems Map Legend - Sd by serving as a major "stockpile" that replen- Color - True Green ishes the sand beaches lose through storm wave Percentage of Total Coast Area Mapped-1.00% action. They are, in addition, important natural buffers against erosion of adjacent uplands. Dur- Characteristics: Dunes are vegetated, or in some ing a storm, the destructive energy of heavy cases devegetated, mounds of sand or sand and waves is expended on the dune fields, effectively gravel that border the landward margin of sandy shielding the land of the upper shore (and any beaches. Though they'sometimes lack plant life, man-made structures located there) from dam- dunes usually develop and continue to exist only age. Dunes also provide habitat, for a wide variety where salt spray-tolerant plants- particularly of plant and animal species. Dune plants include beach grass-grow thickly enough to act as a beach grass, Virginia rose, beach plum, bayberry, "sand trap." The stems and leaves of dune plants seaside goldenrod, beach heather, pitch pine and slow down and capture windblown beach sand; red oak. Among the animals that live or feed their interwoven root systems hold the sand in among dune fields are the least tern, piping place and resist wind and wave erosion. Where plover, killdeer, sanderling, herring gull, chip- long, continuous lines of dunes form, they are muhk, red squirrel, and white-tailed deer. Be- called "vegetated beach ridges." A very rare land- cause some of the species associated with form in Maine, the best examples are found at dunes live or breed in no other geologic environ- Popham Beach in Phippsburg. ment (e.g. the locally rare least tern), and be- FIGURE 26 Unhealed Frontal Dune Scarp . . . . . . . . . .. . . . . . . 7 4: 40-74 40 Fore DL4mes 1pilet to mamh Beack 13errn Led!3e 77 77' 7. Low TICIC INTtRTIPAl- 5V5T1PA1_ cause dune fields are relatively uncommon in Maine, this unit is considered to be a very im- portant type of wildlife habitat in our state. FIGURE 27 Seaside Goldenrod and American Beach Grass FIGURE 28 Beach Pea r other. Scientists have recently determined that seawalls and other man-made shoreline protec- tion structures tend to accelerate rather than slow down beachfront erosion by 1) cutting off supplies of sand that would naturally flow in to rebuild and maintain dune fields from beaches; 2) preventing sand stored in dunes from replacing sand lost to beaches during storms, and; 3) inter- Planning Considerations: Aside from their rela- fering with the influx of new sand to beaches tive rarity, their beauty, and their function as a and dunes from offshore deposits. By requiring wildlife habitat, the role of dunes in maintaining that all new structu'res and roads be built well valuable beach areas and in preventing upland behind dune fields (the exact distance depends storm damage lends considerable weight to argu- on the particular beach system in question), both ments for their protection or, when damaged, direct destruction and the need for man-made restoration. Direct destruction for purposes of shoreline protection structures can be avoided. residential or commercial development has long The fact that many beach systems may tend to been one major threat to this goal which should migrate inland over time provides further reason be avoided when possible. Construction of sea- for keeping buildings and other "improvements" walls built to protect beachside structures is an- relatively far away from dunes. 41 Fresh to Brackish Water the mean high water mark. Fresh-brackish Map Legend - Sw marshes represent a stage between salt marsh Color - Yellow Ochre and upland, forming where sediment is deposited Percentage of Total Coast Area Mapped-2.00% from mainland drainage or marine flooding. Most tracts are subject to occasional tidal flow and Characteristics: By definition, this unit includes submergence during floods. areas of standing water with a salinity of less than 5 parts per thousand (sea water offshore has FIGURE30 BlueWingedTeal a salinity of about 35 ppt). This type of water usu- ally occurs where beach ridges form natural "dams," at the heads of marsh tracts, and behind man-made barriers which have restricted tidal flow. Importance: Fresh to brackish water bodies tem- porarily store runoff flood water, thus reducing Al the effects of flooding on surrounding environ- ments. They are also important habitats in the life cycle of many waterfowl and anadromous fish (e.g. salmon, alewives and shad). Planning Considerations: The most suitable uses of fresh to brackish water as far as man is con- cerned are fishing and hunting. After careful an- alysis of the effects, some types of construction may be suitable (such as piers) though generally this will involve special engineering consider- Importance: Fresh to brackish marshes are an im- ations and higher costs than when undertaken on portant segment of a number of depositional sys- more appropriate sites. On the whole, most types tems, including coarse- and fine-grained estuar- of light or heavy development, dam construction ies, tide-dominated neutral embayments, con- and filling are considered unsuitable in this en- structional and destructional deltas, and coastal vironment. marshes. They provide significant habitat for many species of ducks and other waterfowl and Fresh to Brackish Marsh for some valuable game animals, such as beaver Map Legend - Sm and muskrat. Because they are able to tempor- Color - Silver arily store flood waters, these units help reduce Percentage of Total Coast Area Mapped-4.00% the effects of coastal flooding. FIGURE 29 Fresh to Brackish Marsh Planning Considerations: Fresh to brackish marshes are generally unsuitable for any kind of development, agricultural use or waste"disposal. They are particularly sensitive to drainage, ditch- . . . . . . Ing or filling. Though it has been practiced in the Of past, applications of pesticides or herbicides on fresh-brackish marshes poses a grave threat to I W@f 1`14411 their environmental health and can have serious adverse consequences for the valuable wildlife species who live in them. In many cases, how- ever, such marshes can be suitably used for some human activities, most notably, recreation- al fishing, hunting, and bird watching. Characteristics: Fresh to brackish marshes are Man-made land wetland adjacent to salt marsh or in coastal im- Map legend - Sz poundments where waters maintain a relatively Color - (no color) low salinity of less than 5 parts per thousand. Percentage of Total Coast Area Mapped-1.00% These marshes generally support lush growths of aquatic vegetation and have surfaces which are Characteristics: Although man-made land is not often several centimeters to one-half meter above a natural feature of the Maine coast, it does exist 42 in a significant number of places and thus must Eolian Flat be considered as an environmental unit. It in- Map Legend - Se cludes all structures and fill that have been Color - Grass Green placed in the nearshore coastal zone by humans, Percentage of Total Coast Area Mapped-0.01 % extending in some cases into the interticial zone. Importance: Basically, man-made land is geologi- Characteristics: Eolian flats are partly vegetated cally important only in the sense that its creation or devegetated sand flats extending behind may alter natural environments or interfere with coastal sand dunes onto back-barrier marshes or the maintenance of coastal depositional sys- onto coarse-grained estuarine channels where tems. It can, however, be considered important to marshes are not present. They originate as either people insofar as it provides a place for various washover fan deposits that are carried over the human activities, such as development or pier dune fields by storm waves or as windblown de- and wharf construction. posits eroded from devegetated dunes. Planning Considerations: The creation of new Importance: Although rare, eolian flats are impor- man-made land should always be carefully an- tant to the maintenance of the dune and sand alyzed to determine impacts on more important beach systems in which they occur. These sys- geologic units and is, understandably, subject to tems provide feeding and breeding habitat for numerous legal restrictions. Existing man-made terns, sanderlings, piping plovers and other lands are often suitable for many types of activ- shorebirds. ities, including pier and storm barrier construc- Planning Considerations: Eolian flats are gener- tion, light or heavy development, and placement ally unsuitable for any kind of development or of pipelines, though any such undertaking should coastal construction. Their role in helping to be carefully examined to avoid adverse effects on maintain beach systems also leads to certain nearby environments. other planning considerations similar to those for beaches and dunes (see pages 41 and 49). They can be indirectly affected, for example, by the construction of sea walls nearby. Like other units associated with beach systems, eolian Landslide Excavation and Deposits flats tend to migrate landward over time. Thus, Map Legend - Sx any man-made structures should be carefully Color - Crimson R .ed designed or excluded.to avoid future problems. Percentage of Total Coast Area Mapped-0.01 % Characteristics: This relatively rare unit consists of deposits of upland soil materials that have moved clownslope from their original position, Washover Flat causing an excavation of the shoreland by their Map Legend - Sf movement. The deposits are usually subject to Color - Sand further slumping and sliding due to gravity, wave Percentage of Total Coast Area Mapped-0.01 % erosion, undercutting and groundwater seepage. Occasionally, portions of landslide deposits and Characteristics: Washover flats are sand sheets excavations will revegetate with upland grasses deposited by waves over salt marsh behind inlet and trees, and may stabilize. mouths and landward of floodtide deltas. They, Importance: May contribute silt and clay to inter- are sometimes inundated by spring tides and tidal mud flats. storm flood water, as well as by wave shoaling during northeast storms. Planning Considerations: Obviously, the unstable Importance: Since these environments are so nature of these units make them unsuitable for small in area, they have relatively little signifi- any kind of development and for most kinds of cance to either the estuarine systems where they coastal construction. They also pose a consider- are found or to wildlife. able safety threat to pedestrians. A common method of minimizing the risks associated with Planning Considerations: The unstable, landslide excavations and deposits is to classify flood-prone nature of washover flats and their the area as a "hazard zone." In a few instances, close association with environmental ly-sensitive after careful consideration, filling and/or excava- salt marshes, make them unsuitable for nearly tion may be suitable activities in these units. any kind of development or construction. 43 FIGURE 31 Fluvial Marsh .4 k'Oh waifier Iff @FrC5;1 WA fet- M(4d FlAr Mud PlAt- Fluvial Marsh Map Legend - Sr Color - Slate gray Percentage of Total Coast Area Mapped-1.00% Characteristics: Fluvial marshes include sparse- FIGURE 32 Wild Rice ly-to-mode rate I y vegetated tidal river flats and floodplains of sandy mud or mud. They are sub- ject to flooding twice daily by fresh water backed up by tides, and occasionally by flooding rivers, which deposit the river sediments that make up this unit. Importance: Fluvial marshes are a significant part of many constructional delta systems, serv- ing as a "storage area" for sediments eventually transported to other geologic environments. They also provide feeding and breeding habitat to var- ious valuable wildlife species, including beaver, muskrat, otter, great blue heron, and numerous ducks and geese. Planning Considerations: Like other geologic units found in delta systems, fluvial marshes may be adversely affected by the construction of dams on rivers entering them due to a loss of sediments (see page 18).Their role in maintaining delta systems and as important wildlife habitats can also be destroyed by any dredging, filling or draining activities in the area. They may be suit- able sites for some types of activities, such as hunting and fishing, pier construction and place- ment of pipelines after careful consideration of potential impacts. Generally, however, waste dis- posal and light or heavy development are unsuit- able in fluvial marshes. 44 FIGURE 33 Salt Marsh Cross Section INTERTIDAL ENVIRONMENTS High Salt Marsh mainland from severe erosion. And the dense Map Legend - M1 vegetation that grows here acts as a kind of giant Color - Peacock Green natural water purifier by capturing and holding Percentage of Total Coast Area Mapped-5.00% pollutants and sediments that could otherwise degrade shellfish beds or fill navigational chan- Characteristics: This estuarine environment con- nels. sists of peat, mud or sand flats densely over- grown with salt-tolerant grasses and situated at FIGURE34 Snowy Egret; Salt Meadow Grass; or slightly above the mean high water mark. Wet- Salt Marsh Cord Grass; Black Rush land vegetation plays a key role in the creation and maintenance of a high salt marsh by slowing down and capturing sediments brought in by streams, rivers, and tides. Such marshes com- monly occur behind barrier beaches or along and at the mouth of river estuaries. Low salt marsh (Map Legend - M2) becomes high salt marsh as sedimentation builds up on intertidal flats, rais- ing them to the mean high water level. As rela- tive sea level rises (see page 13) coastal salt marshes rise with it, slowly migrating landward. Importance: The environmental and economic significance of high salt marshes is difficult to overstate. As a wildlife habitat, they are particu- larly valuable to migratory ducks and geese, numerous shorebird species, many colorful song- birds, ospreys and bald eagles. A great variety of animals important to marine food chains also live here, such as mud snails, copepods and flat- worms. Tidal channels and streams running through high salt marshes are breeding and nurs- ery grounds for dozens of commercially impor- tant fish and shellfish species. Marsh food chains are heavily dependent on the nutrients and bacteria absorbed and held by marsh vege- tation. Beyond its function as a habitat, a high salt marsh temporarily stores flood waters, thus reducing the severity of coastal flooding. Wide bands of marsh in front of upland shores absorb the brunt of heavy storm waves, protecting the 45 FIGURE 35 Salt Marsh 777 V1, . ...... ... 77: A- W 0. Q, Q Z,%p 'A@ r 14- Planning Considerations: Like other estuarine en- Characteristics: Low salt marshes are sparsely vironments, high salt marshes are very sensitive to densely vegetated sand or mud tidal flats lo- to changes in the volume of water flowing into cated between mean tide and the high water or out of them. Any kind of draining, ditching, mark. They generally have a slope of from 50 to dredging or filling activities on or near a high 200 and lead up to areas of high salt marsh, salt marsh can have detrimental consequences though isolated strands of low salt marsh are in terms of the maintenance and productivity of sometimes found. The vegetation here consists this environment. Light or heavy development, solely of salt cord grass (Spartina alterniflora), roadbuilding, and most other types of construc- which grows in stands up to one meter in height. tion are not considered suitable here; nor, despite The substrate between stands is bare mud or a high marsh's purifying capabilities, is the dis- sand. posal of solid or liquid waste. On the whole, the Importance: Although they are associated with a most appropriate human activities in this unit are variety of coastal depositional systems, includ- recreational, such as birdwatching, hunting, and ing coarse- and fine-grained estuaries, tide- canoeing. Even these activities can have adverse dominated neutral embayments, and construc- impacts on a high marsh since erosion-prone tional deltas, low salt marshes are a relatively spots on marsh plots and heavy foot traffic scarce geological environment in Maine. They along channel banks can cause devegetation are, nevertheless, one of the most important in and accelerated bank erosion. In some cases, terms of economy and ecology because of their changes made in nearby environments can af- crucial role as habitat for numerous comt@hercial fect a high salt marsh significantly. A dam con- fish and shellfish species. Indeed, nearly three- structed on a river entering a marsh can cut off fourths of Maine's fisheries resources are directly sustaining sediment supplies; a breakwater or indirectly dependent on the existence of low constructed offshore can cause increased sedi- salt marsh environments as a source of nutrients mentation that could smother parts of the or as a breeding and nursery ground. Over 60 marsh surface; and development of adjacent important commercial species, from clams and barrier beaches often results in restriction of crabs to menhaden and flounder, live, feed or the tidal channels feeding into marsh systems, grow up in these units. leading to a slow destruction of these produc- Planning Considerations: Like the high salt tive wetlands. marsh environment, low salt marshes are ad- versely affected by dredging, draining, filling and any other activity that alters the natural flow of water into and out of them. Dredging of nearby high salt marsh areas can disrupt the natural Low Salt Marsh transport of sediments in a low marsh, increasing Map Legend - M2 turbidity and sedimentation. Dredging on the Color - Peacock Green high marsh can also release chemicals or heavy Percentage of Total Coast Area Mapped-0.10% metals formerly bound up in the high marsh sedi- 46 ments which may be toxic to the many fish and experts agree that nearly all construction or de- shellfish species that live in low salt marsh en- velopment is inappropriate here. Even recreation vironment, or decrease their commercial value. should be limited, since waves caused by power Pesticides and sewage wastes can have similarly boats, for example, can erode stream banks and adverse effects on low marsh organisms. Most increase water turbidity. FIGURE36 Plan View; Typical Transition Zone -Salt Marsh to Fluvial Marsh 47 FIGURE 37 Marsh Levee, Two Views rRrSH-TO- SPACKIS14 MAKS" E@XTRA miaH WATp-P, HI&H TIM 7 T., ES14- To- BRACK1514 WFLSH SALT MARSH TIDAL CAANNEL, Ut4V9&E_rATEP LEM- vE&ermp LF-VCE Marsh Levees spring tide flooding fora while each year, but Map Legend - M3 during the summer it gradually evaporates, event- Color - Peacock Green ually leaving a dry panne covered by mats of Percentage of Total Coast Area Mapped-0.01 % algae (the only plants that can grow in this highly saline environment). Characteristics: Marsh levees form as deposits of sand or silt along the margins of tidal chan- Importance: Salt pannes were once used as a nels in high salt marshes. The levee surfaces are source of sea salt. generally up to ten centimeters higher than the Planning Considerations: None, other than those mean high water mark and surrounding marsh given for high salt marsh environments. surfaces. These units are created when storm waters overflow channel banks and spread onto the high salt marsh. The sudden reduction of cur- Sand Beaches rent velocity as the water hits the vegetated Map Legend - 131 marsh surface causes rapid sedimentation of Color - Lemon Yellow sand and silt, building the marsh levees. Percentage of Total Coast Area Mapped-1.00% Importance: Marsh levees provide dry walkways Characteristics: These are beaches consisting through a marsh. entirely of sand which are exposed to high wave Planning Considerations: There are no spec 'ial energy. They extend from the mean low water planning considerations associated with marsh mark to the uplands or to dune fields, where levees other than those relating to the mainten- inland vegetation is established. Fine-sand ance of the high marsh environment as a whole beaches are usually flatter than coarse-sand (see page 46). beaches, and remain more stable when exposed to large waves. Medium-to-coarse grained sand Salt Pannes and Ponds beaches exhibit wide, ridgelike beach "berms" Map Legend - M4 along their lower margins. Sediments involved Color - True Blue are generally @vashed in from offshore deposits of Percentage of Total Coast Area Mapped-0.05% glacial material, transported by river from inland areas, or derived from alongshore erosion of sur- Characteristics: Circular unvegetated depres- ficial sediments. sions existing on high salt marsh surfaces are called salt pannes or salt ponds. They are Importance: Recreationally, sand beaches are thought to form where bare, rotten spots occur one of Maine's most valuable and most popular on marshes or in segments of "abandoned" tidal environments despite their relative rarity in this channels. Pannes usually contain seawater from state. Many wildlife species feed or live on a 48 FIGURE 38 Beach Types beach, including surf clams, sand dollars, striped Mixed Sand and Gravel Beaches bass, sand pipers, sanderlings, gulls, terns, and Map Legend - B2 ruddy turnstones Dune fields are dependent on Color - Yellow Orange beaches as a source of sand, in turn acting as a Percentage of Total Coast Area Mapped- 1 50% stockpile of sand which replaces material beaches lose to winter storm waves Barrier Characteristics These are beaches very similar beaches form a protective buffer between valu- to sand beaches which consist of both sand and able salt marsh systems and the full force of gravel deposits In most cases, gravel is concen- the ocean trated on the upper portion of such beaches Planning Considerations Due to rising sea level Beach sediments here originate from wave-re- beaches tend to move inland over time Develop- working of glacial tills or outwash sands and ment close to beach areas is therefore not rec- gravels either immediately behind or adjacent to ommended Residential or commercial develop- the beach, or from shallow subtidal deposits ment behind sand beaches on dune areas can, Sand and gravel beaches are generally exposed in addition, disrupt the natural cyclical transport to heavy wave action and are thus classified as of sand between beaches and dunes, thus threat- "high energy" beaches ening the whole system with sediment "starv- Importance Like sand beaches, mixed sand and ation " Seawalls or other shoreline protection gravel beaches are highly valued as a recreation- structures built to protect beachfront property al resource They also provide habitat for various are another common threat In many cases, such shellfish and shorebird species, including clams, structures accelerate rather than slow erosion sanderlings, gulls, and terns rates on sand beaches Beaches that depend on river sediments as a source of sand may be ad- Planning Considerations Construction of dwell- versely impacted by dams built inland In a sim- ings and other development on or close behind ilar fashion, seawalls and other retaining walls sand and gravel beaches is generally considered can prevent the influx of new sand to a beach unwise, since they are subject to the effects of dependent on offshore deposits transported onto progressive sea level rise This slow but steady or along the shore by waves, tides and currents inland recession is often accompanied by ero- Devegetation and subsequent erosion of adja- sion of scarps backing these beaches, thus de- cent dune fields also lead to erosional problems velopment there should be given ample setback on sand beaches (Also see page 70) from the edge of the bank 49 FIGURE 39 Gravel Beach rise (see page 13) constant repair of these roads is often necessary due to the effects of continual washover. Thus, when possible, roads or other construction should be set back from gravel beaches and storm ridges far enough to avoid such problems. FIGURE40 BoulderBeach -7 Gravel Beaches Boulder Beaches Map Legend - B3 Map Legend - B3 Color - Non-photo Blue Color - Non-photo Blue Percentage of Total Coast Area Mapped-3.00% Percentage of Total Coast Area Mapped-0.50% Characteristics: These are beaches consisting Characteristics: Boulder beaches consist primar- solely of pebbles and boulders which were de- ily of boulders derived from glacial till or jointed rived from offshore or shoreline deposits of bedrock ledge exposed to very heavy waves. glacial till or outwash reworked and transported by high-energy waves. Gravel beach faces are Importance and Planning Considerations: (Sim- usually narrow and steep. The profile generally ilar to gravel beaches) includes gravel berms, or low ridges, along the lower beach margin and high gravel storm ridges Low Energy Beaches on the landward side. Such beaches occupy Map Legend - B5 shallow indentations of the shoreline where near- Color - Magenta by uplands are composed of glacial sediments. Percentage of Total Coast Area Mapped-4.00% They are characteristically small and are backed by either salt marshes or low or high scarps, or Characteristics: These are beaches composed of banks. a wide variety of sediment sizes, from mud to Importance: Though not as sought after as sandy gravel, that form in sheltered coves and other beaches, 6ravel beaches are often used for rec- parts of the shoreline protected from the force of reational purposes and considered very attrac- heavy waves. The sediments are usually derived tive. They also provide habitat for shorebirds, from wave erosion and weathering of scarps be- such as gulls and terns, and other wildlife. hind the beach. Low energy beaches are narrow and do not exhibit the significant changes in Planning Considerations: Gravel beaches are seasonal profiles shown by high energy beaches rarely developed except for the construction of (see page 66). The lower beach surfaces gen- roads sometimes built directly behind the storm erally grade seaward into intertidal mud flats ridges. Because gravel beaches are subject to and during the summer months salt marsh landward migration due to progressive sea level grasses may grow in some areas. 50 Importance: Though rarely used for recreational Washover Fans purposes, low energy beaches do provide habitat Map Legend - Bw for a number of wildlife species, such as terns, Color - Copper sandpipers, clams, and marine worms, as well as Percentage of Total Coast Area Mapped-0.01 to juvenile fishes. Finer sediments winnowed from low energy beaches are transported to near- Characteristics: Washover fans are low, fan- by mud flats, which often harbor valuable shell- shaped deposits of gravel located behind gravel fish beds. beach ridges and covering part of the marshes Planning Considerations: Low energy beaches or upland beyond. Washovers sometimes occur and banks backing them are subject to some re- on sand beaches but with much less frequency. cession due to sea level rise. This occurs, how- They are created when high waves overtop gravel ever, at a much slower rate than on high energy or dune ridges, carrying along loads of beach beaches. Although development should be set sediment. back a reasonable distance, the width of this Importance: Washover fans constitute part of the safety margin need not be as great as in areas stockpile of sediments that will eventually be re- where wave energy is heavier. cycled within the beach system. They are also the major way in which beach systems migrate Boulder Ramp inland in response to sea level rise. Map Legend - Br Color - Non-photo Blue Planning Considerations: Where seawalls or Percentage of Total Coast Area Mapped-2.00% other structures prevent the formation of wash- over fans beaches may erode at a faster rate. Characteristics: A boulder ramp is a gently slop- Other considerations are similar to those for ing, boulder-covered surface in the lower'inter- dunes and gravel beaches or ridges of which tidal zone that generally occurs seaward of gravel washover fans are a part. or boulder beaches on shorelines exposed to Spits heavy waves. They develop on top of ledge sur- Map Legend - Bs faces or on wave-worked glacial till. In the pro- Color - Gold cess of reworking till deposits, waves wash clay Percentage of Total Coast Area Mapped-0.04% and other fine sediments offshore, transporting sand, gravel and boulders onshore to form beach- Characteristics: Spits are sandy beach deposits es. Boulder ramps are made up of boulders too in the form of a peninsula attached at one end large to be moved by average waves. to the shoreline. Those which join islands to the Importance: Boulder ramps provide habitat for mainland are called tombolos. Spits originate by rockweeds and other shoreline plants important deposition of sand at the mouths of rivers or to marine food chains, as well as to tenacious where waves approach protruding areas of sandy animals such as the starfish, barnacle and mus- shoreline from opposite directions. sels. To many people they also have an aesthetic Importance: Spits are often the forerunners of value, due to the polished roundness of their beaches. Many barrier beaches in Maine, for ex- boulders and the sounds they make when im- ample, started out long ago as spits. As sand pacted by waves. deposition on the original spits continued, they Planning Considerations: Boulder ramps are gen- grew, eventually impounding large salt marshes erally unsuitable for any type of development. and tidal lagoons behind them. Spits often have FIGURE 41 Washover Fan, Plan View SAJ.T WASH 'MM,_ CHANNEL- . .. . . ..... SAC-KDV?4eS AVIA/or eOUAR FLAT F01ZFJ>VNF_ OR S-Ikm IkIDSE A FA 14 BEACH OCEAN 51 rather unstable tips, subject to continual wave Importance: The blue mussels that abound here reworking, and are favorite nesting sites of the are an important source of food to marine and locally rare least tern and piping plover. Where bird life. They are also a food source for humans, such tern and plover colonies occur in Maine and as their popularity with seafood lovers con- they are usually considered to be critical habi- tinues to increase, the value of mussel bars is tats. likely to become more widely appreciated. Planning Considerations: Spits are so closely Planning Considerations: Dredging and filling on allied to beachrenvironments that planning con- or near a mussel bar is the niost common threat siderations are much the same as those listed to this unit. A frequent result is increased sedi- for sand beaches (seepage 49). Generally, any mentation that can smother and kill the mussels changes in the characteristics of impinging or a release of toxic chemicals and heavy metals waves or the natural transport cycles of sand to which these organisms are very sensitive. supplies in the area will alter this unit. Only a few least tern colonies exist in Maine, thus spits on which they nest deserve special protection. ChannelLevee Mussel Bar Map Legend - F4 Map Legend - F3 Color - Cold Dark Grey Color - Scarlet Red Percentage of Total Coast Area Mapped-0.01 % Percentage of Total Coast Area Mapped-0.04% Characteristics: These are ridges of fine-grained Characteristics: Mussel Bars are low mounds or sediment several tens of centimeters high, de- "reefs" of living mussels (Mytilus edulis) and posited along the margins of tidal channels in shell debris deposited by wave shoaling. They intertidal flat areas (similar in form to marsh occur in relatively sheltered areas at the mouths levees). of bays or estuaries not receiving significant Importance: Channel levees provide habitat for freshwater input. The mussels expel sediments clams, marine worms and other marine species. they extract from the water in' feeding. These Many shorebirds, such as the great blue heron sediments settle between individual organisms and snowy egret feed here. On the whole, the in the bar, eventually raising the surface of the limited size and occurrence of channel levees bar above the level of the surrounding intertidal make them relatively rare intertidal flat environ- environments. ments. FIGURE 42 Channel Levee CRANNF-L- LF-VF-E /41 /Z oo 00 52 Planning Considerations: The most common Importance: Mud flats are usually valued most threats to channel levees are dredging and filling highly for the clam and marine worm popula- operations, both of which may affect surround- tions that abound there. They are the basis of ing flats. Maine's multi-million dollar clamming and mar- ine worm industries. Mud flats exposed at low FIGURE 43 Red-winged Blackbird (male) tide also provide a rich source of food for great blue herons, snowy egrets, sandpipers and other shorebirds. At high tide, numerous species of waterfowl feed in these environments, including black ducks and loons. Many kinds of fish are dependent on mud flats as a habitat, such as striped bass, alewives, killifish and smelt. FIGURE 44 Common Loon Planning Considerations: Mud flats may be dis- turbed or destroyed by dredging and filling on Mud Flats (Intertidal) the flats or on nearby environments. Dredging of Map Legend - F adjacent wetlands or agricultural activities and Color - Dark Brown construction on nearby uplands can release an Percentage of Total Coast Area Mapped- unnatural influx of sediments that may smother 27.00% shellfish beds and introduce toxic chemicals or heavy metals that are poisonous to clams and Characteristics: These are flat environments situ- marine worms. The commercial usefulness of ated between the low and high tide lines in this environment as a clamming resource can relatively sheltered waters. Major sediments are also be destroyed by sewage wastes, a problem sand, silt and clay, depositedby tidal currents. all too common along the Maine coast. FIGURE 45 Mud Flat SHEJ-TF-REP 5AY MEAN MI&H WATF-R MEAN I-ON WATE@R AAU 0 FLAi.-.- SAND 53 Coarse-grained Flat (Intertidal) Veneered Ramp Map Legend - F1 Map Legend - F6 Color - Dark Brown Color - Dark Brown Percentage of Total Coast Area Mapped-4.70% Percentage of Total Coast Area Mapped-0.05% Characteristics: These are flat environments be- Characteristics: These are boulder ramps or bed- tween low and high tide composed of sand and rock ledge surfaces shoreward of intertidal flat other sediments coarser than those found on areas which are covered by a layer of mud sev- units classified as mud flats. They occur along eral centimeters thick. Veneered ramps result shorelines exposed to greater tidal and wave from an increased influx of suspended sediments energies than fine-grained flats, but often exist in to tidal bays, typically due to agricultural activ- proximity to them. Coarse-grained flats exist at ity or construction on nearby uplands. lower elevations than mud flats and are thus Importance: Though veneered ramps have rela- subject to longer periods of tidal inundation. tively little importance to natural ecological bal- Importance: Like mud flats, coarse-grained flats ances in intertidal environments, they may pro- are important shellfish and marine worm beds, vide new habitat for a variety of mud-dwelling though because of their less stable nature, they lifeforms, such as clams and marine worms. are somewhat less productive. They also provide Planning Considerations: Veneered ramps can be habitat for various commercially important fish suitable sites for certain types of coastal con- species and food sources for waterfowl. struction, such as piers and retaining walls. It Planning Considerations: (Similar to those for should be noted that although veneered ramps Mud Flats - page 53). may provide new habitat for shellfish, their ap- pearance is often a sign that human activities on nearby uplands are causing increased sedi- mentation loads to flow into intertidal areas. This Seaweed-Covered Coarse-grained Flats increase in sedimentation may have an adverse Map Legend - F2 effect on more productive environments, such as Color - Light Green clam flats, adjacent to the ramps. Percentage of Total Coast Area Mapped-1.00% Ledge Characteristics: These are coarse-grained flats Map Legend - M extending into the intertidal and subtidal zones, Color - Warm Light Grey which support growths of marine algae such as Percentage of Total Coast Area Mapped- Ulva, Enteromorpha, and Ascophyllum. 12.00% Importance: These flats, like others, are produc- Characteristics: The ledge environment consists tive shellfish habitats and feeding grounds for of bedrock with little or no sediment cover. It various waterfowl and fin fish species. is relatively resistant to erosion, although per- Planning Considerations: (Similar to those for sistent wave action and freeze-thaw cycles may Mud Flats) loosen and remove small or large pieces of ledge shoreline. Below the high tide line, rocky shore- lines are characteristically covered with dense growths of marine seaweeds and algae. Algal Flats FIGURE 46 Ledge Map Legend - F5 Color - Green Bice Percentage of Total Coast Area Mapped-0.08% - _nx,O.. Characteristics: These are fine-grained flats in the upper intertidal zone that support growths of marine algae. This is a relatively rare flat environ ment on the Maine coast, occurring mostly north ...... of Frenchman's Bay. Importance and Planning Considerations: (Sim- ilar to Mud Flats). 54 importance: Rocky shores are not only aesthet- FIGURE 47 Ospreys ically pleasing but often superior places for man- made construction. They also support abundant growths of intertidal plants and animals along their lower margins which are important to many marine food chains. Species found here include rockweed, kelp, Irish moss, barnacles, mussels, starfish and periwinkles. Ledge outcrops along the shoreline, which may also be isolated from the mainland as islands, provide feeding and breeding habitat for many higher life forms as well, such as eider ducks, black ducks, and other waterfowl, razorbills, petrels, gulls, terns, and harbor seals. Planning Considerations: Rocky shoreline areas that are not significant breeding areas for birds and seals are some of the best sites for shore- Planning Considerations: Like other parts of es- line construction and development (excluding tuarine systems, preservation of these channels conventional septic systems), since they are both is important to the productivity of Maine's com- solid and rarely prone to erosion problems. They mercial fishing industry. The-basic threats are also offer opportunities for harvesting of mus- pollution, dredging, filling, and other activities sels and seaweeds, which are commercially im- that disrupt natural water circulation in the area. portant in some areas. One basic threat to these (For more information on planning considera- and other ledge-dwelling species is an increased tions relating to estuarine environments see influx of sediments, sometimes caused by agri- pages 60 and 61). cultural activities or construction on nearby up- lands. Such increases in sediment load may Vegetated Point or Lateral Bars smother productive ledge habitats, a problem Map Legend - My which can also develop when man-made con- Color - Dark Green struction along the shoreline alters current and Percentage of Total Coast Area mapped-0.01 % wave patterns. Pollution by oil or toxic chemi- cals can also reduce the productivity of ledge Characteristics: These are accumulations of environments and their suitability as habitat for sand and mud in tidal or estuarine channels birds or seals. adjacent to channel margins (point bars) or along straight channel segments (lateral bars) which Fluvial-Estuarine Channels are often stabilized by salt marsh or river bank Map Legend - Mc vegetation during the summer and fall. Sedimen- Color - Lavender tation here is due to deposition of sand and mud Percentage of Total Coast Area Mapped-0.03% as flood-tide currents flow across the surface of the bar. Characteristics: Fluvial-estuarine channels oc- FIGURE 48 Point Bars cupy the upper reaches of an estuary, carrying either river water or estuarine water, depending on the tidal range, river discharge in the area, and incidence of coastal flooding. They are the major link between rivers and estuarine chan- nels, forming a transitional channel through which waters in the estuarine environment flow. Importance: These channels are an important part of Maine's immensely productive estuarine Importance: Many valuable wildlife species live environments as regulators of outgoing fresh and or feed on point or lateral bars, including clams, incoming estuarine waters. Like other estuarine muskrats, raccoons, deer, great blue heron, units, they provide crucial habitat for many com- snowy egrets, ospreys, bald eagles and ducks. mercially valuable food fish species. Many shore- They are thus often prime hunting and clamming birds, loons, waterfowl, bald eagles and osprey areas, besides being a very productive part of forage in and adjacent to the channels. Maine's important estuarine systems. 55 Planning Considerations: Besides hunting and Swash Bars clamming, most other human activities, partic- Map Legend - Ms ularly construction or development, are not suit- Color - Light Violet able on these units. Basic threats to the main- Percentage of Total Coast Area Mapped-0.01 % tenance of point and lateral bars are similar to those to estuarine systems in general (see page Characteristics: These are small, transitory sandy 60), including dredging, filling, draining, damming bars deposited by waves that are continually of incoming rivers, increased or decreased sedi- moved and reformed by wave action. Swash bars mentation loads, and pollution. are derived from sediments carried offshore dur- ing winter storms. When the long, low waves of summer move this sediment shoreward again, swash bars are formed on ebb-tidal deltas and the margins of intertidal sand flats. FIGURE 49 Aerial Perspective; Lateral Bars Importance: Sand swash bars are important parts @* :-:@ @ of beach systems, serving to replenish sand lost .01 to beaches during storms. They also help dis- sipate wave energy that may erode beaches and R N provide more beach area for recreational use. Swash bars provide habitat for both clams and seaworms which are often abundant enough to ME be commercially haIrvested. Shorebirds frequent ly forage here, including ruddy turnstones, terns, plovers and gulls. Planning Considerations: Though swash bars are not suitable or commonly used as sites for con- struct ion or development, they are an integral part of sand beach systems and can be ad- versely affected by beachfront development. (See page 49 for other planning considerations re- lating to beach systems.) FIGURE 50 Swash Bars Abandoned Point or Lateral Bars ............. .. .. .... .. . MT Map Legend - Mt :NN1 Color - Sky Blue Percentage of Total Coast Area Mapped-0.01 % Characteristics: These are a type of vegetated point or lateral bars where flood-plain vegetation, including hardwood growth,. has succeeded marsh and river bank plants. They occur where Fbb-TIPAL- ... .... .... ::@ DE4ZA ............. accumulations of sand and mud develop in or . .... ../ .................. ............ along the margins of estuarine channels, grow- ....... . . ing, by continual deposition, beyond the vege ........................ .................. tated point or lateral bar stage (see previous unit). importance and Planning Considerations: Sim- HiON WATER ilar to those for vegetated point and lateral I@OW WATER bars and others generally given for estuarine sys- ........... SWAS@4 JD-ARS s' terns (see pages 55 and 26). 56 FIGURE 51 Flood Tidal, Ebb Tidal and Fan Deltas . . . . . .. . . . . . nDAI- :4:_ r-wop -nPAL. ..... . .... .............. Flood Tidal Deltas Ebb-tidal Deltas Map Legend - Mf Map Legend - Me Color - Flesh Color - Flesh Percentage of Total Coast Area Mapped-0.03% Percentage of Total Coast Area Mapped-0.03% Characteristics: These are lobate sand bars at Characteristics: These are similar to flood-tidal the mouths of lagoons or enclosed embayments. deltas except that ebb-tide currents play a larger During incoming tides sediments are transported role in their creation and maintenance. They ap- from barrier beaches adjacent to the inlet into pear as lobate sand bars seaward of embayment the estuary. They are deposited as current vel- inlet mouths that separate back-barrier beaches ocities rapidly decrease where the current enters from the open ocean. Sediments originate as the still waters of the back barrier estuary. Such sand transported out of the estuary by ebb tides deltas are actively reworked by waves and cur- or from nearby beaches by littoral transport. Ebb- rents, and often show migrating sand "ripples" tidal deltas exhibit swash bars on their surfaces on their surf ace. which migrate across the surface and into inlet Importance: Deltas are an integral part of many channels or onto adjacent shores. valuable sand beach systems, due to their in- Importance and Planning Considerations: Sim- volvement in the seasonal transport of sand to ilar to those for flood-tidal deltas (see above). and from beaches. They also regulate the flow of water into and out of estuaries. Thus, disturb- ance of deltas or their sediment sources may affect the productive estuaries with which they are associated by changing the natural flushing Fan Deltas time and volume. These units can provide habi- Map Legend - Mb tat for many beneficial and valuable species, Color - Tuscan Red including clams, horseshoe crabs, marine Percentage of Total Coast Area Mapped-0.01 % worms, striped bass, sanderlings, terns, eider ducks and loons. Characteristics: These are fan-shaped accumu- Planning Considerations: Maintenance of deltas lations of sand deposited by streams draining is dependent on a continued influx of wave-, into intertidal areas with high tidal ranges. The current- or river-borne sediments. These sedi- apex, or head, of the fan is located at the point ment supplies can be cut off by dams built where the stream enters the nearshore zone from upriver or by construction on nearby beaches. the upland. Stream water migrates from side to The ever-changing nature of deltas and their side across the fan surfaces at low tide, and close association with sensitive beach systems swash bars form on the margins as fan sedi- and estuaries make them unsuitable for develop- ment is reworked by waves. ment or construction, though clamming, hunting Importance and Planning Considerations: Sim- and fishing may be appropriate. ilar to those for flood-tidal deltas (see above). 57 FIGURE52 Oblique Aerial View; Flood Tide Delta and Spillover Lobe M", 5PIL-LOV X s 4X K 'it Si@ 8i X:: g ii@ 'Iik g@& Spillover Lobes Map Legend - Md Color - Flesh Percentage of Total Coast Area Mapped-0.01 % Characteristics: These are lobe-shaped sand bars extending from flood-tidal deltas into deeper channels or lagoons along flood-tidal delta mar- gins. Spillover lobes tend to migrate up the estuary and may extend to marsh surfaces, form- ing washover flats (see page 43). Importance and Planning Considerations: Similar to those for flood-tidal deltas (see page 57). FIGURE 53 Yellowlegs (Sandpiper) 58 SUBTIDAL ENVIRONMENTS Eelgrass Flats Map Legend - Fe Mud Flats (Subtidal) Color - Apple Green Map Legend - Fm Percentage of Total Coast Area Mapped-3.00% Color - Burnt Ochre Percentage of Total Coast Area Mapped-9.00% Characteristics: These are shallow, subtidal flats which support growths of eelgrass, Zostera mar- Characteristics: These are fine-grained flats be- ina. Eelgrass creates a current baffle, slowing the low the low tide mark that are similar to and flow of water and inducing the deposition of usually adjacent to intertidal mud flats. They tend fine- to coarse-grained sediments. Most eelgrass to occur in embayments or other places shel- in Maine was destroyed by a blight in the tered from heavy wave action where sediments 1930's, but in recent years many flats have been derived from offshore deposits, river transport recovering, particularly in upper Casco Bay. and eroding shorelines are brought in by tides Importance: Eelgrass flats provide habitat for and currents. commercially exploitable populations of clams Importance: Though subtidal flats are often too and marine worms, as well as for many other far underwater to be harvested regularly, they are bottom-dwelling species. Various species of fish, important habitats for clams and marine worms. waterfowl and shorebirds feed here, and the As such they comprise a reservoir of these com- nutrients released by the decay of the eelgrass mercially valuable species that provides stock for stands are important to a number of ocean food replenishing heavily utilized intertidal flats. Sub- chains. tidal flats are also crucial habitat for many of Planning Considerations: Similar to those given the food fish species caught by Maine fishermen. for subtidal mud flats (see above). Planning Considerations: Like intertidal flats, subtidal flats can be adversely impacted by any Seaweed Community dredging or filling operations in the vicinity or by Map Legend - Fs poor farming or construction practices on nearby Color - Light Green uplands. Such activities can release an unnatural Percentage of Total Coast Area Mapped-2.30% influx of sediments that may smother shellfish beds and toxic chemicals or heavy metals that Characteristics: These are subtidal coarse- are poisonous to marine organisms. Sewage dis- grained flats and bedrock ledges that support charges may increase the turbidity and lower relatively dense growths of seaweeds. the oxygen levels of the water above flats, often Importance: Seaweed communities thrive with reducing the productivity of these environ- many species of valuable fish and shellfish, such ments as habitat forvaluable fish and shellfish. as clams, mussels, and mackerel. In some areas of the state, various types of seaweed. are com- mercially harvested from these environments. Coarse-grained Subtidal Flats Planning Considerations: Similar to those given Map Legend - Fc for subtidal and flats (see above). Color - Burnt Ochre Percentage of Total Coast Area Mapped-5.00% Characteristics: These are coarse-grained flats Upper Shoref ace below the low tide mark that are similar to inter- Map Legend - Fb tidal coarse-grained flats and often exist adja- Color - Sand cent to them or to mud flats. They are formed Percentage of Total Coast Area Mapped-2.00% from submerged glacial deposits reworked by Characteristics: The upper shoreface consists storm waves. of subtidal sand flats on the seaward margin of Importance: These units provide habitat for large sand beaches, extending from the mean clams, marine worms, fin fish and other valuable low water mark to depths of about ten meters. marine species, though they are generally less It is an environment in which sediments are in productive than mud flats due to the coarser constant movement due to wave activity. nature of their sediments. Importance: The upper shoreface is a crucial Planning Considerations: Similar to those for component of sand beach systems, alternately subtidal mud flats (see above). receiving and stockpiling sand lost from beaches 59 during storms and resupplying sand to the beach- selves, habitat for many commercially valuable front during periods of lower waves. It is also an shellfish and fish, including clams, striped bass, important habitat for various marine shellfish and alewives, and crabs. fish, including striped bass, surf and razor clams, Planning Considerations: The most basic threat sand dollars, and quahogs. As Maine's shell- to tidal channels is man-made obstruction of the fishing industry expands its utilization of clams flow of water through them, which can be caused other than soft-shells, the commercial value of by dams inland, by seawalls and other shore- upper shoreface environments is likely to be- line structures built along the shores, or by come more widely appreciated. (Further south dredging and filling operations. along the Atlantic coast, surf and razor clams are both intensely harvested by clammers.) These Medium-Velocity Tidal Channel are also prime areas for recreational surf fishing. Map Legend - C1 Planning Considerations: The upper shoreface Color - Purple is so closely tied to the fate of sand beaches Percentage of Total Coast Area Mapped-0.90% that the planning considerations are identical (see page 48). Characteristics: These are similar to high-velocity tidal channels except that they are usually lined Lower Shoref ace with mud, sand or bedrock and exhibit water Map Legend - Fp flows of between one and two meters per second. Color - Aquamarine Importance and Planning Considerations: Similar Percentage of Total Coast Area Mapped-4.00% to those given for High-Velocity Tidal Channels Characteristics: The lower shoreface is the deep- (see above). er, subtidal slope seaward of the upper shore- Low-Velocity Tidal Channels face beyond sand beaches. It grades from about Map Legend - C3 ten meters below the low tide mark, where sedi- Color - Pink ments are mostly sand, to about twenty meters Percentage of Total Coast Area Mapped-1.50% down, where silt and clay predominate. Importance and Planning Considerations: Similar Characteristics: These are similar to high-velocity to those given for the upper shoreface and sub- tidal channels except that they are usually lined tidal mud flats (see above). with mud and exhibit water flows of less than one meter per second. High-Velocity Tidal Channel Importance and Planning Considerations: Similar Map Legend - C1 to those given for high-velocity tidal channels Color - Violet (see above). Percentage of Total Coast Area Mapped-0.02% Characteristics: Tidal channels are low troughs Estuarine Channel running through intertidal and subtidal environ- Map Legend - C4 ments along which tidal waters flow as a current Color - Cream during ebb and flood tides. They generally de- Percentage of Total Coast Area Mapped-0.70% velop in river channels submerged by rising sea Characteristics: These are tidal channels at the levels or by headward erosion of currents into mouths of rivers and streams that contain mixed subtidal and intertidal flats. High-velocity tidal or stratified salt and fresh waters flowing at low channels are those in which water velocities or high velocities, depending on the particular exceed two meters per second. They are usually conditions. lined with pebbles and cobbles or bedrock. Importance: Tidal channels play a critical role.in Importance: Estuarine channels are one of the carrying salt or mixed salt-and-fresh waters an .d most important components of our productive es- the organic nutrients suspended in them to and tuarine systems, providing feeding, breeding and between various nearshore environments, par- nursery grounds for dozens of valuable marine ticularly in estuarine systems. Thus, by affecting species including herring, smelt, flounder, pol- both salinity levels and nutrient levels, these lack, shad, menhaden, alewives, clams, mussels, channels can have profound influences on shell- lobsters and crabs. fish and fish productivity in the areas through Planning Considerations: Like other environ- which they flow. They also provide, in them- ments making up estuarine systems, estuarine 60 channels are very sensitive to alterations in the travel for est u ari ne-de pendent fish and shellfish volume of water flowing into and through them, species moving between the sea and estuaries such as can be caused by dams upriver, seawalls or lagoons. and other structures built along the shoreline, or Planning Considerations: Similar to those for dredging, filling and draining activities. The pro- estuarine channels (see above). ductivity of these channels as a habitat for com- mercially important fish and shellfish may also Dredged Channel be imperiled by sewage, chemical and pesticide Map Legend - Cs pollution as well as by increased sediment loads Color - Purple resulting from logging, agricultural activities or Percentage of Total Coast Area Mapped-0.03% construction on nearby uplands. Estuarine Ebb Channel Characteristics: These are man-made or enlarged Map Legend - C6 and deepened inlet, tidal and estuarine channels Color - Blue Violet that exist in their present form as a result of Percentage of Total Coast Area Mapped-0.08% mechanical dredging. Importance: Most dredged channels are primarily Characteristics: These are estuarine channels important as navigable waterways, the basic pur- carrying mixed salt-and-fresh waters in which pose behind such alterations. water flow is dominated by ebb-tide currents. Planning Considerations: Dredged channels may Importance and Planning Considerations: Similar have severe adverse effects on surrounding to those given for Estuarine Channels (see natural environments if they significantly alter above). sedimentation rates, water flow or other pro- cesses. Dredging can be desirable to increase Estuarine Flood Channel the flushing rate of an embayment; however, be- Map Legend - C5 fore any dredging project is begun, careful in- Color - Blue Violet vestigation of potential environmental side- Percentage of Total Coast Area Mapped-0.08% effects is both wise and legally required. Characteristics: These are estuarine channels carrying mixed salt-and-fresh waters in which water flow is dominated by flood-tide currents. Abandoned Tidal Channels Map Legend -Cb Importance and Planning Considerations: Similar Color - Orange to those given for Estuarine Channels (see Percentage of Total Coast Area Mapped-0.01 % above). Characteristics: These are the remains of former Inlet Channel tidal channels no longer transporting enough Map Legend - C7 water to erode or maintain the channel bound- Color - White aries. Some abandoned channels are isolated Percentage of Total Coast Area Mapped-0.05% because of human alterations to the course of the active main channel. They also occur natur- Characteristics: These are high-velocity tidal ally in salt marsh tracts where the main channel channels that cut through barrier beaches to con- has meandered, taking a "short cut" and by- nect back barrier marshes or lagoons with the passing a formerly active channel segment. open ocean. Inlet channels terminate landward Importance: If not entirely cut off from the main on flood-tidal deltas and seaward on ebb-tidal channel, abandoned tidal channels may provide deltas. Their shape and width varies with the habitat foe juvenile fishes and feeding grounds local tidal, wave and current characteristics; the for wading birds. bottoms are usually lined with sand and gravel. Planning Considerations: In time, abandoned Importance: Inlet channels maintain sediment channels may become a salt panne or fill in transport between coarse-grained estuaries and with marsh plants and become part of the sur- beach systems. They are an integral part of the rounding high salt marsh. Either way, they are so beach sediment supply, maintaining equilibrium closely tied to the high salt marsh that general between sand supplies in the lower estuary and planning considerations are the same as for that the beach system. They also serve as lanes of unit (see page 45). 61 Channel Slope Tidal Creeks Map Legend - Cs (No Map Symbol or Color) Color- Cold Medium Grey Percentage of Total Coast Area Mapped-0.01 % Percentage of Total Coast Area Mapped-0.01 % Characteristics: These are small channels or Characteristics: These are moderately sloping creeks draining intertidal flats and salt marsh margins of subtidal channels which occur where areas which are dominated by ebb-tidal flow. deposition of mud and silt builds up on the sides Ti.dal creeks are usually lined with mud or sand. of a channel. (Most channel walls are too steeply Importance: Though small in area and extent, sloping and too erosional to exhibit channel tidal creeks provide crucial habitat for many slopes.) species of juvenile marine fishes (including her- Importance: Channel slopes provide additional ring, flounder, pollack, shad, menhaden, and ale- habitat,for clams, marine worms and other bot- wives), various shellfish and marine worm tom dwelling organisms. Exposed upper slopes species, and feeding grounds for many types provide feeding grounds for great blue herons, of waterfowl, shorebirds and wading birds. snowy egrets and other wading birds. Planning Considerations: Similar to those given Planning Considerations: Depend on the type of for high marsh environments (see page 45). channel where the channel slope occurs. Tidal Fluvial Channel Marsh Drainage Ditch Map Legend - Cf (No Map Symbol or Color) Color - Olive Green Percentage of Total Coast Area Mapped-0.01 % Percentage of Total Coast Area Mapped-0.01 % Characteristics: These are man-made rectilinear Characteristics: These are tidal channels in the channels dug in saltmarsh tracts during the lower segments of rivers entering large estuar- 1930's and 1940's to eliminate mosquito breeding ies. They are subject to the rise and fall of the habitat by drying up marsh tracts. tides, but carry only fresh water. (The Kennebec Importance: Undetermined. River between Merrymeeting Bay and Augusta is a good example.) Planning Considerations: The practice of drain- Importance: Tidal fluvial channels provide habitat ing salt marshes to reduce mosquito populations or feeding grounds for a great variety of wild- was generally replaced by pesticide application life, particularly waterfowl. Black ducks, golden- after WW 11. Both methods threaten the pro- eye ducks, mergansers, loons, Canada geese, ductivity of salt marsh environments, upon which ospreys and eagles are among the many species Maine's commercial fishing and shellfishing in- found here at some time during the year. Such dustries ultimately depend (seepage 46), and are now subject to strict regulations. In time channels are also important to various fresh- these ditches will naturally fill in with mud and water and anadromous fish, including alewives, salt marsh vegetation again, though various shad and salmon. tactics can be used to speed up this healing Planning Considerations: Dams can block the en- process. trance of anadromous fish to this environment unless fishways are incorporated into them. Another common problem is pollution by sewage effluent, toxic-chemicals and pesticides, which can drastically reduce the productivity of tidal fluvial channels and associated estuaries. A particularly insidious effect of pesticides is that they tend to accumulate in the tissue of water- fowl, osprey and eagles, often reducing breeding success. 62 Beach Erosion, Popham-1976 photo Ken Fink iL ft 1411 CHAPTER 4: THE DISAPPEARING SHORELINE The final part of our discussion of Maine's Copies of the Shoreline Erosion Maps may be coastal geology deals with a special geology- obtained from the Maine Geological Survey, related problem-shoreline erosion. It is a prob- Department of Conservation, Augusta, ME lem that has affected millions of dollars worth 04333. of shorefront property in Maine over the years and one that will probably continue to concern Beach Erosion coastal residents for a long time to come. The way erosional process agents such as The primary concern of most coastal residents, winds and waves will affect a beach depends of course, is the erosion of shoreline environ- largely on: 1) the size of the "constituent par- ments that lie above the mean high water mark. ticles" making up the beach (which can range Thus, the following discussion is limited to the from tiny sand grains to sizeable boulders), and three basic types of erosional shores common to 2) the amount of wave action that reaches the Maine: beaches, scarped shorelines of uncon- area. So-called "high energy beaches" are those solidated materials, and bedrock ledge. exposed to the full force of storm waves gen- For very useful additional information regard- erated in the Gulf of Maine. These generally ing the erosion of various shoreline types, plan- consist of sand or gravel and boulders. "Low ners should consult the Coastal Program's energy beaches" border relatively protected "Shoreline Erosion Inventory Maps." This series bays, where wave heights and strengths are far of twenty-nine 1:48,000 scale maps indicates the less than those generated in the open Gulf. various erosional conditions that generally exist The makeup of such beaches ranges from pure along segments of the Maine coast. By revealing sand to small-sized gravel or mixtures of both. the general rates of erosion in a given segment, In terms of human use, the most valuable the maps can be of great help in indicating the Maine beaches are those in which the major scope of erosion problems and in designing site sediment is sand. The bulk of our large, recre- studies of local conditions for solutions that ational sand beaches is found along the state's conserve shoreline property, prevent damage to southwest coast, from the Sheepscot River to structures, and avoid the unnecessary loss of Kittery. Most are barrier spits, separating large natural shoreline resources. Like the Marine En- saltmarshes from the open ocean. Almost all are vironments Maps, they can also be useful for subject to seasonal erosion and some are more long range planning. subject to long term erosion. 65 I The seasonal variations can be seen by com- During the spring, summer and early fall paring the summer and winter profiles of sand months, sand beach profiles are built up rather beaches. After a heavy winter storm, sand than eroded (or, as scientists would say, they are beaches tend to have a smooth, concave profile. "accretional" rather than "erosional"). The long, Wave action often cuts a broad scarp, or bank, low waves common during the less stormy, into the foredune ridges and sand eroded from warmer months transport sand deposited off- the beach and dunes is transported a short shore by winter storms back to the beach. The distance offshore. southerly winds that predominate at this time Most of the time, the majority of this sand is tend to blow sand from the fully recovered beach returned to a beach by the lower wave action and berm onto the foredunes, eventually filling of calmer weather when the storm is over. Such in the characteristic scarp cut by severe winter "post-storm beach recovery" is usually associ- storms. Soon, if the beach system is a balanced ated with the building of a berm, or ridgelike one, the foredunes are widened and heightened strip of sand, on the upper portions of the beach. back to their pre-winter dimensions. Renewal of this berm usually takes about two Beyond this seasonal erosion cycle, there is weeks. It is a natural process that works to also long term erosion occurring on Maine protect the foredunes from severe erosion, since beaches as a result of the slow rise in sea level wave ' energy from succeeding storms is ex- and storm processes. As the sea level rises (at pended on the renewed berm and not on the dune the almost imperceptible rate of about one inch fields. If a beach has not fully recovered its berm per decade) marine process agents encroach by the time the next istorm passes along the further into the dune-beach system. Sand is coast, much more severe erosion of the fore- removed from the frontal beach and foredunes dunes is likely to occur. and is transported by wave washover to the FIGURE 54 Sand Beach Profiles FOREDUNE RIDGE SALTMARSH BACKDLINES BEACH FACE MEAN HIGH WATER LOW -TIDE TERRACE STORM BEACH PROFILE BERM BEACH FACE MEAN LOW WATER RECOVERY (ACCRETION) MHW RIDGE RECOVERY BEACH PR FILE MLW BERM BEACH FACE RECOVERY (ACCRETION) WIND- DEPOSITED MHW SAND RIDGE FLILLY- RECOVERED POST- STORM BEACH PROFILE _M L_W_ HIG @BEACH @FAC E @@LOW -@TIDE TE@RRACE MEA N@ _@H BEACH P@ROFILE LOW @ME@AN @.H W RID.@ 1Y B@EAH @PROIFIL@E MLW V V E@R Y TIO @E N) @@WINDDE OS P SA.D@@ WIND- ACCRETION 66 back of the dune field, causing a progressive an almost instantaneous wave energy barrier, landward migration of the entire system. If this that makes gravel beaches much less prone to migration is not interfered with by coastal de- severe erosion than sand beaches. velopment, the size of the beach and the dune Long term erosion of gravel beaches parallels fields remains about the same over time. that of dune-beach systems. As sea level rises, To people who have built summer homes or the gravel beach and storm ridge "migrates" other structures along the beachfront, however, inland slowly but steadily. -However, washover is the natural process of landward migration is far more frequent than on sand beaches. often viewed as a severe erosion problem that Although gravel beaches are not often de- should be stopped. In the past, this has usually veloped by man, roads are sometimes built di- led to the construction of seawalls, built in the rectly behind storm ridges as a means of access hope of stabilizing the naturally dynamic dune- to points of land. The washover phenomenon beach system. frequently necessitates constant repair of these Unfortunately, scientists have determined that roads. Obviously, in planning the locations of seawalls often speed up beach erosion (see future roads and other shoreline structures, page 71). Thus, landowners who build sea- problems can be avoided if gravel beaches are walls to protect their property must realize that, given a wide berth. depite their intentions, they are probably ac- A similar kind of environment, mixed sand and celerating rather than slowing down the loss of gravel beaches, occurs just seaward of shore- valuable sand beaches. line margins eroded into thick deposits of glacial. Another serious threat to beach systems is sands and gravels where wave energy levels are devegetation of dunes. Devegetated dunes are far less than on the open ocean. The profile of far more vulnerable to erosion by winds and this type of beach responds to seasonal wave waves than those protected by a thick cover of action much like gravel beaches do. Storm waves natural vegetation. And the increased mobility lower the beach profile temporarily, but beach of loose sand raises the chance of its being material is soon returned in calmer weather by permanently lost from the beach system. wave transport as well as by weathering of the Although devegetation of dunes sometimes scarp, or bank, above the beach. occurs when stands of beach grass die from FIGURE 55 Gravel Beach Profiles diseases, unmanaged foot traffic and develop- ment are the most common causes. Fortunately, dunes can often be saved by revegetation pro- grams (seepage 70) that may involve nothing CRAVEL BEACH PROFILE - LATE SUMMER more complex than restricting pedestrian traffic to controlled access points. SALTMARSH STORM RIDGE MULTIPLE BERMS BEACH FACE Gravel beaches generally occupy shallow in- dentations of the shoreline where nearby uplands STORM %ATER LEVEL are composed of glacial sediments, or "till." GRAVEL MEAN HIGH WATER These beaches are characteristically small and GLACIAL TILL are backed by either saltmarsh or by low or high banks, or scarps. STOW PROFILE The profiles and erosional cycles of gravel WASHMR BEACH FACE d. beaches are much like those of sand beach MN 5@ systems, but the greater size of the constituent particles creates a steeper, narrower beach that STORM VATER LEVEL responds more quickly to changing wave action. ------ MEM HIGH MTER A gravel beach is made up of a storm ridge RECESSIO1 (similar to the foredune ridge on sand beaches) STOW Rlli--:@ and the beach proper. The force of winter storm waves erodes the POST STORM RECOVERY PROFILE storm ridge and beach, giving the whole a smooth, concave profile similar to that of dune- beach systems. Within a week after a storm WASHOVER MEAN HIGH WATER passes, gravel beaches recover to a prof I le of two GRAVEL to three berms, as most of the gravel removed MEAN C_ @G.AVEL T" @ VELER G by storm waves is returned immediately to the beach from offshore. This quick recovery creates 67 Long term recession of sand and gravel beach- Glacial till escarpments, composed of,a com- scarp shorelines is accomplished by wave ero- pacted mixture of sediments ranging in size from Sion of material at the bottom, or "toe," of the clay particles to boulders, tend to erode at a scarp accompanied by erosion of the upper sur- slower rate than those made of sand and gravel. face due to rain and other weathering processes. The cohesiveness of the sediments make such As sea level rise continues, so too will shoreline banks more stable, allowing vegetation to take recession in such areas, thus any buildings or hold and increase stability even further. other structures built too close to the scarp Nevertheless, constant undercutting by waves may someday be in danger of resting on un- and currents can create unstable conditions on stable ground. the upper slopes, often causing glacial till banks The last type of beach common to Maine to recede at rates of one to several feet an- shores are low energy beaches. They occur in nually. relatively protected places where the shoreline Embankments composed of marine clay-the intersects unconsolidated surficial deposits of most common type of shoreline scarps in sand and gravel. Maine-are also subject to steady erosion and Low energy beaches exhibit very low reces- recession. In contrast to other scarps, however, sional rates. Continued sea level rise and weath- banks of marine clay also exhibit extreme ero- ering causes some erosion, but it is much slower Sion hazard due to occasional small- and large- than on other beaches, since banks bordering scale landslides. low energy beaches are rarely impacted by heavy Landslides on clay scarps may occur instan- waves. taneously and without warning, especially during Erosion exhibited by Maine beaches in the the wet late winter and spring months. This is recent past has varied greatly, at times reaching usually a response to oversteepening of the lower up to 185 feet of dune line recession annually. scarp as a result of wave action. Generally, however, low energy beaches recede For example, three days after a late January at a rate of less than one foot per year; oc- thaw in 1973, some 75,QOO square feet of resi- casionally, up to five feet. High energy sand dential upland abruotly,'slid into the northern beaches recede at an annual rate of about two margin of Rockland Harbor when five large feet, though storms may cause recession,in high blocks of marine clay slumped onto the tidal flats erosion areas to exceed 25 feet annually. below with no previous warning or obvious sign. Fortunately, no loss of life or damage to build- Erosion of Scarped Shorelines ings occurred. But where one resident once had The erosion and subsequent recession of an expansive back yard of 200 feet between his shoreline scarps, or embankments, presents a house and the edge of the bank, he now has constant but often unrealized hazard to coastal less than 50 feet. residents. One reason for this lack of awareness The planning considerations that revolve is the fact that the instability of a piece of shore- around shoreline scarps made of marine clay are line property is not always apparent upon cursory rather evident, and hold true for banks made of inspection by potential buyers or builders. Also, sand and gravel of glacial till as well. As a general the potentia.1 for drastic shoreline bank erosion rule, it is unwise-and possibly dangerous-to can increase significantly as an indirect result of build near the edge of scarps, though the safety development levels in the immediate area. margin deemed appropriate varies greatly from In the natural scheme, shoreline scarp erosion site to site. (Expert advice should be sought in rates are related to two basic factors: the degree making such decisions about the appropriate of exposure to heavy waves and the "erodi- amount of setback.) In the case of extremely bility" of the material the bank is made of. Gen- unstable or landslide-prone banks, it may even be erally, the less consolidated the material and a good idea to prohibit pedestrian traffic for the more exposed it is to the open ocean, the safety's sake. faster and more severely it will erode. Scarps made of loosely packed sand and gravel, for example, are extremely sensitive to Erosion of Rocky Shorelines gravity and weathering forces. They tend to re- Many people think of the rocky shores com- spond to dislodgement and undercutting by mon to many parts of Maine's coast as shore- waves very rapidly. Because of particle instabil- lines in equilibrium that neither erode nor recede. ity, most sand and gravel scarps are bare of In actuality, shorelines composed of ledge are vegetation. There is too much down-slope move- weathering and eroding, but at extremely slow ment of the substrate for plants to take root and rates which pose almost no hazards along the stabilize the slope. lines of those associated with scarps. 68 Recession of bedrock shores is primarily de- Coastal properties in different areas are sub- pendent on the amount, spacing and direction of ject to different shoreline erosion conditions. fracturing within the bedrock. As ice freezes and They also exhibit different rates of shoreline expands in these fractures it loosens bedrock recession, ranging from negligible on bedrock fragments, sometimes allowing them to be dis- headlands to extremely variable and unpredict- lodged and moved by heavy waves. The rate of able on beach and dune systems. Severe erosion bedrock recession is so slow, however, that it of beaches and dunes may not occur at a steady, can usually only be measured over long spans predictable annual rate; more likely, it will occur of time-hundreds and thousands of years. Thus, unexpectedly, as a result of an especially severe rocky shorelines create erosional hazards requir- winter storm coupled with an unusually high tide. ing a planning Tesponse only in extremely rare Moreover, a beach and dune system which has cases. been stable or even growing for a number of years may respond to disturbances or changes DEALING WITH SHORELINE EROSION in its source of sand supplies, in the pattern and strength of littoral currents transporting that in recent decades, efforts to prevent or "miti- sand, or in the shape and location of shoreface gate" erosion of shoreline beaches, dunes and deposits, such as sand bars, just offshore. Thus, scarps have taken many forms. The techniques particularly during a winter storm, the beach's devefoped have had varying success. Some have response may be to show severe erosion in had no success at all. Some have even had places where it has not been evident in the re- the opposite effect of what the builders intended, cent past. making erosional problems worse instead of bet- The safest course of action for a property ter. The costs involved have also varied greatly. owner in this uncertain environment is either to The techniques described in this section are make plans for moving structures of value to those which are most commonly used in Maine. more solid ground if necessary, or to be pre- They have also been chosen with an eye toward pared for eventual destruction of their buildings affordability. Each is within the realm of being at some unpredictable future time. financed by either private individuals or towns, Seawalls and other man-made shoreline pro- or is the kind of project for which municipal- tection devices are expensive alternative respon- ities can receive financial assistance from fed- ses, and they may be ineffectual during severe eral agencies. storms when they are needed most. In many It should be stressed that whether an erosion cases they accentuate, erosion problems. As a mitigation technique will be effective depends on result, protective structures must usually be the particular conditions existing at each shore- viewed as temporary solutions at best. line site. Thus, a very complex array of variables Some coastal properties are located on shore- must be taken into consideration in choosing and line environments that are eroding at a more planning the most appropriate solution for an ero- constant, and therefore more predictable, rate sion problem. The reader should also be aware than beaches and dunes. These rates can be, that the implementation of most of these tech- estimated by measuring the distance from a fixed niques is subject to state regulation. point (the corner of a building or a stake) to the Near the end of this chapter are lists of state top of the shoreline bank and maintaining an and federal agencies that can provide expert annual record of shorefront recession. advice and assistance to individuals and towns After three to five years, such records will considering some kind of erosion mitigation pro- make it possible to estimate the average annual gram. It is strongly urged that before any of the recession rate in feet or inches. Then, the re- techniques described-or any others-are tried maining distance between the edge of the shore- or even considered, the relevant agencies be con- line and any buildings can be divided by the tacted. annual recession rate to give the approximate number of years before the structures will be Some Basic Considerations threatened by erosion. (The Shoreline Erosion Because erosion of the shoreline is a natural Maps described on page 65 can also be helpful and continuing process, it is an extremely impor- in making these estimates.) tant factor to owners or potential owners of In some cases, various factors may affect the shorefront property. In fact, the local rate of reliability of a property owner's estimates, includ- shoreline recession is one of the first things that ing any projects in the vicinity that involve should be investigated by anyone considering shoreline alteration, protection, or dredging. the purchase of a piece of land along the shore. Such projects can accelerate or slow down ero- 69 sion rates of the shorefront by disrupting natural and discuss their interests with the board de- sediment transport and altering wave effects at ciding on an application. And under current laws, the shoreline. As a result, it is wise to get the the burden of proof showing that a project will help of a certified geologist at this stage. A have no adverse effects on the property of nearby geologist can ascertain the exact type of erosion landowners rests with the permit applicant. problem or problems bei 'ng faced, and confirm the magnitude and rate of the erosion threat. Preventing Erosion of Beaches and Dunes He will also be able to suggest appropriate miti- One of the most frequent and frustrating ero- gation techniques and estimate what their side sion problems facing Maine's coastal residents effects on the physical environment might be. is the erosion of sand beaches and dunes. Often, Next, the services of a professional engineer it is a problem complicated by the fact that should be obtained if the erosion problem re- valuable private property and buildings are threat- quires the construction of some kind of pro- ened as the beach system recedes landward, and tective device, like a seawall or revetment. The by the fact that former attempts to slow down engineer, working closely with the geologist, erosion have instead accelerated it. may be able to design a structure that is ap- The three most commonly employed tech- propriate to the conditions of the site and which niques of mitigating erosion of this nature are: will withstand the forces creating the erosion 1) promoting the growth of dune vegetation; 2) without unnecessary or continual maintenance. constructing some kind of shoreline protection However, it is possible that the geologist and device, such as a seawall or revetment, and; 3) engineer will decide that the erosion problem replenishing the sand lost to erosion with new cannot be dealt with in an environmentally or sand. economically acceptable way. In such cases, the PROMOTING DUNE GROWTH owner may have to consider other alternatives: moving his structure back from the shoreline, seeking financial and technical assistance from Whenever possible, one of the most attractive State or Federal agencies, or-in a few in- and effective ways of preventing shoreline ero- stances- abandon I ng the property. sion is to take advantage of the natural barriers If an erosion mitigation technique is attempted that already exist-coastal sand dunes. Scien- by a shorefront property owner, certain steps tists have determined that beaches, dunes and must be taken in the planning stages. Before any the sea maintain a delicate balance of give and alteration of an intertidal area can be made, take. In the natural scheme, the dunes resupply permits must be secured from the town in which the beaches with sand through wave action, the project will be located, from the Department while the sea and wind carries in new sand to of Environmental Protection's Bureau of Land restore the dunes. During a storm, the energy of Quality, and from the U.S. Army Corps of En- heavy waves is expended on the lower, or fore- gineers. In making the proper applications, the dune, ridges. The upper, or secondary, dune property owner should be able to describe exact- ridges are protected from severe erosion in part ly what he or she proposes to do. It will be neces- by the foredunes and, to an even greater degree sary to provide information, for example, about by the surprisingly strong, interwoven root mats the specific nature and dimensions of proposed of the beach grass that grows on them, holding projects or activities as well as details of any the bulk of the sand firmly in place. these sec- potential environmental side effects. Once again, ondary dunes, extending up to twenty feet above this suggests the need for expert help. the high tide line and fifty feet in width, ef- fectively shield the land of the upper shore from The interests of owners of property next to erosion. Equally important, any permanent struc- development sites, as well as those of the gen- tures placed well behind the dune fields will eral public, are recognized in existing land use -also be protected. laws. Shoreland zoning, coastal dune and wet- Unfortunately, this natural barrier cannot per- land, aquaculture lease and fish weir laws all manently prevent wave breaching or continual provide for notice to abutting owners and tra- erosion where sources of sand are lacking or ditional users through direct notification, public have been cut off by man made obstructions notice and public hearings. Applicants for a per- such as seawalls. Nor can they continue to main- mit under these lease or license laws must pro- tain their protective role if the crucial, anchoring vide specific information about their plans. Pub- growths of beach grass are destroyed. But in lic notices and public hearings provide every- areas where development has not completely one- particularly neighbors and traditional users disrupted the dynamic balance between sea, of an area-opportunities to present their views beach, and dunes, it is possible to successfully 70 work with nature toward forestalling serious Seawalls may be vertical or concave-faced shoreline erosion and resulting property damage. walls constructed of poured concrete and rein- In terms of preventing erosion, the key element forcing steel, stone, or stone-filled pile-and-tim- in this technique is the promotion of beach ber cribworks that are situated on the landward grass growth. It can be accomplished most margin of the beach in front of any dune fields easily over several consecutive summer seasons that might exist. Past experience by the builders by installing snow fence around sparsely vege- of such structures has led to the formation of tated dune areas. Snow fencing prevents foot a number of general guidelines for seawall con- traffic from trampling and eventually killing the struction. grass. At the same time, it allows the wind to Generally, for example, seawalls should ex- blow dry sand from the beaches onto the dunes. tend into the sand below the surface of the Such windblown deposits of sand are very im- beach at least one-and-a-half times farther than portant. They tend to promote beach grass the exposed height of the wall. The face of the growth, which entraps even more windblown wall should be smooth, with no protruding corn- sand, thus heightening and widening the ero- ers, angles or buttresses. Irregular faces tend to sion-combating dune ridges. break down under the force of heavy waves In dune areas where beach grass is nearly much faster and should be avoided. or totally absent, it may be necessary to begin When new seawalls are constructed next to the process by planting beach grass "springs." existing ones, they should be placed so that the (Springs of beach grass, Ammophila breviliqu- wall faces are oriented in the same direction. lata, are available in quantity from commercial Isolated walls should be flanked by "wing walls" greenhouses in New Jersey. Planning assistance extending well back from the front to prevent, for a dune vegetation program can be obtained or at least reduce, the severe erosion of sand from the Maine Geological Survey (State Office that sometimes takes place at the ends of sea- Building; Augusta, Maine 04333; Tel. 289-2801), walls. the U.S. Soil Conservation Service (U.S.D.A. Build- The shape of the wall face is also important. ing; Orono, Maine 04473; Tel. 866-2132), and the Straight vertical walls tend to reflect wave energy Ira C. Darling Center (Walpole, Maine 04573; back over the beach, thereby accelerating ero- 563-3146). sion in many cases. A concave wall face can TECHNIQUE COSTS: from $3.00 per running foot diminish wave overtopping, but still focuses for snow fencing, posts and installation. wave energy on a small area of the beach. On the whole, vertical planarfaced seawalls are no long- Seawalls er recommended as erosion prevention struc- In the past, one of the most frequently used tures due to their adverse effects on beach sys- tactics aimed at mitigating beach erosion has tems. been the construction of seawalls. Although this Under some conditions, seawalls and other can sometimes be an effective technique, sea- shoreline protection devices can actually accel- walls often speed up rather than slow erosion erate rather than slow down beach erosion. This problems (see below). For this reason, it is unintended side effect may occur for a number always wise to study alternative solutions and of reasons: the specific conditions of the site before plan- 1) seawalls can reflect storm waves back over ning or building a seawall to make sure it is the a beach area for second time, causing a greater best possible response to the situation. amount of sediments to be eroded by the same FIGURE 56 wave; Section of Concave Faced Seawall 2) seawalls may prevent low summer waves from replenishing the beach with sand from off- El. 1700' shore deposits; 1 3) seawalls constructed at the dune-beach 6-kfill 34 boundary may prevent sand stored in the dunes -eroded beach sand and 26- 0' 27 - 0' 8 ... h from replenishing storm 4-0' 4`0 4'.0'- keep back beach sand from replacing sand eroded from the dunes by winds or waves; and, 4) isolated seawalls may concentrate storm -12' El. tO wave energy at each end of the structure, causing unprotected adjacent areas to erode Foondation Piles shis.1 Pile. much faster than if no seawall were present. Costs: $75-150 per linear foot. 71 FIGURE 57 to reflecting wave energy back over a beach, a How Seawalls Can Accelerate Beach Erosion phenomenon which can accelerate erosion dra- matically. FIGURE 59 Typical Stone Rip-rap Revetment PROFILE MAL BEAC N The drawbacks of revetments are that they are more susceptible to wave damage, due in part to the tendency for a wall to sink into the sand under its own weight and because individual blocks of stone are sometimes dislodged by in- tense storm waves. In building a revetment, these drawbacks should be taken into consideration. For example, walls constructed of very large blocks should be buried five to eight feet below the beach sur- face, and strategic blocks at wall corners should be pinned to prevent dislodgement. As in the case of seawalls, wing walls are also recom- mended for revetments, extending landward from Revetments each end, in order to avoid erosion problems at Revetments- retaining walls built of large these points. Finally, the stones used should stone blocks-are another common structure be of variable size and heavy enough to resist used to mitigate beach erosion in Maine. This is being moved by storm waves. Stones in the 200 particularly true along the southern and mid- to 500 pound range are considered best. coast areas due to the availability of large blocks Costs: $75-100 per I! near foot of stone from nearby quarries. Many experts be- lieve stone revetments are a better choice than Rock-filled Timber Cribbing concrete seawalls in circumstances where a re- In some parts of Maine, rock-filled timber crib- taining wall is used. they are not only less ex- bing has been effectively used as an erosion miti- pensive than concrete walls, but also less prone gation technique. This is a type of retaining wall FIGURE 58 Schematic Sections of Two Types of Rock-filled Timber Crib Seawalls 72 framed with railroad ties and heavy industrial Although channel retaining walls tend to have fencing and filled with rocks ranging in weight fewer adverse side effects than seawalls, some from 30 to 50 pounds. Timber cribbing is rela- unintended impacts can occur. Such impacts tively inexpensive and reasonably attractive. In include transportation of backfill material onto addition, although the faces are vertical, their nearby environments by marine process agents boulder-filled walls generally absorb some wave and the accelerated erosion of adjoining unpro- energy, lessening the amount of energy reflected tected property. The latter effect is caused when back over the beach. current eddies created at the wall's ends lead to Costs: $50-75 per linear foot concentrated turbulence on nearby banks. Fortunately, both of these side effects can Beach Replenishment usually be avoided, or at least minimized, by: Beach replenishment is the addition of sand to 1) not constructing a channel retaining wall too an existing beach to widen and heighten it. It close to the shore, and 2) adding landward- is based on the concept that the best way of pointing wing walls at each end of the wall. preventing storm damage to shorefront struc- Costs: Timber Planking -$75-100 per linear foot tures is to maintain a wide, "healthy" beach be- Steel Bulkhead Ing -$300-350 per linear tween them and the ocean. Beaches absorb the f oot impact of heavy waves and reduce the amount of wave energy that can reach the uplands and Preventing Erosion of Scarps or Bank Slopes any buildings there. The erosion of shoreline slopes or scarps by Though beach replenishment programs can be waves and weathering (or "mass wasting") is a very effective, they are also quite expensive, problem that can be dealt with in a variety of usually requiring financial backing by state or ways. However, the best technique for mitigating federal agencies. The Army Corps of Engineers, slope erosion at a given site depends on many in particular, promotes and helps implement this complex factors, including the nature of the bank method as the best approach to shoreline pro- deposits, the amount of wave energy impacting tection that at the same time preserves the beach the area, and the surface and subsurface drain- as a recreational resource. age patterns in the vicinity. Sand for beach replenishment programs is One of the most common methods of miti- usually provided by excavating inland glacial de- gating erosion on scarps composed of com- posits, by dredging submerged sand from off- pacted glacial sand and gravel is to promote the shore deposits, or from channel and anchorage growth of existing vegetation or to establish such dredging in the vicinity of an eroding beach. growths where none exists. This is probably the Before a program begins, temporary protection of most attractive and least expensive means of backshore structures can be provided by bull- slowing the recession of sand and gravel banks. dozing sand from the lower beach up against the Along protected shorelines, an increased growth frontal dunes or a deteriorating seawall. This af- of grasses and other plants may be enough in fords protection, however, only for the duration itself to stabilize the scarp. In more open shores, of one northeast storm in most cases and re- where wave energy is high, revetments or bulk- quires a permit from the Department of En- heads may be needed to prevent erosion of vironmental Protection. the bottom of the slope. Costs: Variable-public assistance funding is In some states, a slightly more complex tech- usually required. nique called "terracing and vegetating" has been shown to be very successful in stabilizing sand Preventing Erosion of Channel Banks and gravel scarps up to eighty feet high. This Occasionally, due to adverse man-made or method employs the following procedures: natural causes, it may be necessary to employ 1) construction of a low revetment at the toe of erosion prevention techniques to stabilize tidal or the scarp to prevent storm wave erosion of estuarine channel banks. This is usually accom- the lower slope; plished by the construction of retaining walls 2) hand-grading of the slope to an angle of less designed to protect the banks from currents or than 45 0; waves generated by passing power boats. 3) terracing of the slope into consecutive levels Channel retaining walls are generally con- by means of posts and riser boards; structed of timber planking and piles or steel 4) seeding of the slope with both rye grass for bulkheads backfilled with gravel. Most are tied to quick vegetative cover and American beach an anchor post, or "deadman," well behind the grass, which provides a dense root systems wall to help prevent the structure from being to bind and stabilize slope soils in the long destroyed by heavy storm waves. term; and 73 5) shallow burial of dead reed grasses, such as Geologic Hazard Zoning low salt marsh grass (Spartina alterniflora) Shoreline areas subject to high rates of ero- or common reed (@hragmites communis) be- sion often pose a perplexing dilemma to munici- hind the terrace riser boardi-to -Provide im- palities and individuals. The alternatives are not mediate drainage of runoff water during the always attractive: large losses of valuable, tax- period before the grass seeds begin to germ- able property on the one hand and the imple- inate. mentation of costly erosion mitigation programs This technique can be very effective in re- which may have serious side effects on the en- ducing slope runoff and the erosion that it vironment on the other. Obviously, preventing causes. Grading the slope to an angle less than development on such shorelines before it occurs 450 and constructing a revetment to prevent is a very attractive remedy in avoiding hard wave erosion at the bottom of the scarp also aids choices between losses of property and the in decreasing the frequency of small-scale land- spending of large amounts of private or tax slides, or slumping, of the bank material. money. Terracing can be accomplished with a mini- This tactic can be accomplished by establish- mum of technical assistance from a geologist, ing municipal "geologic hazard zoning." It in- soil scientist or regional soil conservationist. Before trying such a project, interested property volves establishing a zoning line a reasonable owners should request and study the publication distance back from a fast-eroding shoreline be- How to Hold Up a Bank by Giorgina Reid, which yond which little or no development will be per- is available from A.S. Barnes Inc. & Co., Cran- mitted. Placement of the line can be arrived at bury, New Jersey. by getting expert help in determining the prob- able shoreline position 25 to 50 years in the Costs: For terracing (exclusive of revetment future. costs)- approximately $400-600 for an 80 In many cases, zoning an area as a geologic foot slope of 200 foot frontage (A vege- hazard because of erosion does not mean that it tation program without terracing will be cannot be used at all. Often, activities such as considerably less expensive, but often low-intensity recreation or agriculture may be less effective.) safe and appropriate. However, construction of Stabilizing scarps composed of marine clay permanent or semi-permanent structures should which are subject to small- or large-scale land- usually be avoided. slides is a very technical operation that should Where dwelling structures are already located be planned by experts who have a detailed near a shoreline threatened by accelerated ero- knowledge of sediment engineering properties, sion, a suitable alternative to hazard zoning or subsurface and surface drainage conditions, and the construction of expensive protective devices ground water hydrostatic conditions. This type is simply to move the structure further back from of program may require expensive runoff-drain- the shoreline. (Assuming, of course, that an ade- age networks and underground pumps to mod- quate amount of property setback is available.) ify ground water tables in the area of the scarp. Thus, mitigation of clay scarp erosion are usu- If relocation seems the best alternative, a thor- ally too costly and too complex for individuals ough analysis of the projected shoreline loss rate or towns without extensive State or Federal fi- should be made first by an engineer or geologist. nancial and technical assistance. Even then, ef- This will provide a sound setback distance based fective erosion mitigation may be too expensive on the probable future shoreline position. The to be worthwhile and alternative tactics, such as cost of moving a structure varies, but it is usually geologic hazard zoning (described below) may be under $2000-which is considerably less than more attractive. the cost of constructing a seawall or revetment. Costs: Variable- usually very expensive 74 WHERE TO GO FOR H ELP- and the techniques used to combat it, and names GOVERNMENT AGENCIES and addresses of technical experts needed in the planning of erosion mitigation projects. At the Individuals or towns involved in or concerned Federal level, both the U.S. Army Corps of En- about shoreline erosion mitigation projects gineers and the U.S. Soil Conservation Service should be aware of the assistance offered by can provide technical advice to private indi- various State and Federal agencies. At the State viduals and financial and technical assistance level, most help available will be in the form of to municipalities involved in the protection of information or technical advice. For example, publicly-owned shorelines. there are a number of State agencies which can The following list includes the most relevant provide guidance on permit requirements, gen- agencies that can be contacted along with a eral or specific information on shoreline erosion description of the type of assistance they offer. FEDERALAGENCIES Type of information or Title assistance given U.S. Army Corps of Engineers Technical information on the construction and ef- New England Division fects of shoreline erosion mitigation structures 424 Trapelo Road Financial assistance for erosion mitigation projects Waltham, Mass. 02154 on public shorelands. Tel. 1-617-894-2400 U.S. Department of Agriculture Technical information about coastal dune erosion Soil Conservation Service and agricultural effects on sediment loads to U.S.D.A. Building nearshore environments. University of Maine at Orono Orono, Maine 04473 Tel. 1-207-866-2132 U.S. Soil Conservation Districts Technical information on erosion mitigation tech- (located in each county seat) niques. Financial assistance under some circumstances U.S. Environmental Protection Agency General and technical information on the effects New England Region of human activities on coastal environments. J.F.K. Building Boston, Mass. 02203 Tel. 1-617-223-7223 STATE AGENCIES Type of information or Title assistance given Maine State Planning Office #38 Land use planning and zoning information Natural Resources Division Lists of consulting engineers August 'a, Maine 04333 Tel. 1-207-289-3261 or 1-207-289-3155 *Department of.Environmental Protection #17 Information on environmental problems, permits Bureau of Land Quality Control and impact assessment Augusta, Maine 04333 (Administers the Wetlands Law) Tel. 1-207-289-2111 Department of Marine Resources #21 Information on impacts of human activities on Stevens School coastlines Hallowell, Maine 04347 Coastal wardens and biologists can offer assist- Tel. 1-207-289-2291 ance and enforcement 75 Department of Conservation #22 Information on coastal geology, shoreline erosion, Maine Geological Survey and impacts of human activity on the shoreline. Hospital Street Shoreline Erosion Maps Augusta, Maine 04333 Marine geologic environments maps Tel. 1-207-289-2801 Lists of consulting geologists Land Use Regulation Commission (LURC) #22 Information on land use standards in Maine's Hospital Street wildlands (unorganized townships) Augusta, Maine 04333 Tel. 1-207-289-2631 Department of Inland Fisheries and Wildlife #41 Information on impacts of human activities on State Street - waterfowl, fish, and other wildlife Augusta, Maine 04333 Tel. 1-207-289-2766 University of Maine Information on impacts of human activities on Ira C. Darling Center marine ecosystems Walpole, Maine 04573 Tel. 1-207-563-3146 *(The DEP through its Citizen's Environmental Assistance Service also provides information con- cerning general environmental problems and laws-Tel. 1-800-452-1942) SOME PLANNING CONSIDERATIONS FOR DEVELOPMENT IN COASTAL GEOLOGIC ENVIRONMENT Land Use Activity Planning Considerations RECREATIONAL Boating Mitigating bank and bottom erosion and turbidity from waves, wakes and propellers. Foot Traffic Bridges, boardwalks, and traffic patterns can pro- tect dune vegetation and reduce wind/wave erosion. Fishing & Hunting Keeping activity levels within tolerance of vege- "All Terrain Vehicles" (ATVs) tation/substrate to prevent undue erosion. DREDGING; PIPELINES& CABLES Interruption of sediment transport critical to main- tenance of geologic units and depositional sys- tems, e.g. beaches; turbidity and sedimentation; spoil disposal and stifling life at the site; release of toxic heavy metals from disturbed sediments; (heavy metals can precipitate naturally or from in- dustrial waste-many shellfish and benthic organ- isms concentrate toxic metals) 76 CONSTRUCTION OF MARINE FACILITIES Piers, Wharves and Jetties Alteration of sediment transport by currents; relo- cating impact of wave energy. Roads Location to avoid storm damage; maintaining tidal flows over marshes; preservation of natural erosion controls, eg. vegetation on dunes, steep banks etc. Seawalls Locate and design to survive storm damage; avoid accelerating wave erosion; avoid interrupting sea- sonal sand cycle between dunes and foreshore. UPLAND CONSTRUCTION River Alterations Effect on sand supplies for coastal beaches e.g. dams, channelization Light Industry/Residential Natural shoreline recession rates vs. expected use- ful life of buildings and roads, sewers, water sup- ply, etc. Likelihood of slumping, accelerated erosion from storm runoff from paved areas, etc. Heavy Industry Changes in bay flushing rates due to stratifica- tion from freshwater/warm water effluents; sedi- mentation may be affected by changes in flushing action. AGRICULTURE Timber Harvesting Removal of trees may upset vegetative stabilizing influence on sand dune areas; logging equipment, operations and roads may cause erosion. Crop Farming Increased sedimentation from soil erosion. WASTE DISPOSAL Liquid Effluents Changes in water quality; scouring and channel (large discharges) cutting; stratification and changes in sedimentation and flushing rates. Solid Waste Erosion from alteration of currents and wave pat- (deposited into water bodies) terns; short term sedimentation and suspended solids. AQUACULTURE Impoundment Aquaculture Thermal and density stratification; sedimentation. PEST CONTROL Draining Wetlands Loss of floodwater storage capacity; nutrient trans- fer to open waters. Pesticides Shift in biologic processes. DEVEGETATION Erosion; accelerated storm runoff; reduced nutri- ents from estuaries. MINING SAND AND GRAVEL (In subtidal and intertidal areas) Beach starvation. FILLING Down-current sedimentation; suffocation of vege- tation and benthic organisms. 77 Land Use Laws of Special Interest to Indiv l1dual Coastal property Owners This chart summarizes some uses and activities regulated under local, state and federal law in the nearshore coastal area. Land, wetland, and water areas covered by these particular land use laws are listed, as well as the name and citation of each law, and the administering agency to contact for information. The administering agency is generally the place to learn the necessary procedures for making applications, obtaining' permits, making statements as an interested person at hearings on appli- cations by others, etc. Not all land use and environmental laws which may apply to a particular proposal are listed. For example, a residential subdivision or@ any kind of development involving more than 20 acres or disturbing more than 60,000 square feet of land above or below water is subject to the "Site Location Act" (T.38 S. 481-5, 488-90) administered by the Department of Environmental Protection, 1-800-452-1942. Some Uses and Areas Covered Law/Citation Administering Agency Construction of residences, docks, wharves, roads, sew- In municipalities, Shoreland Municipal Planning Board age systems, beaches, campgrounds, tree clearing, tim- Zoning Town Office/City Hall ber harvesting, agricultural operations. Area: Land 250 T. 12 S. 4811-14 feet back from normal high water mark. Same as above. In unorganized and deor- Department of Conservation #22 ganized areas, Land Use Land Use Regulation Commission Regulation Commission 289-2631 T. 12 S. 681-689 Dredging, draining, filling; construction of a causeway, Alteration of Coastal Wet- Department of Environmental bridge, marine, wharf, dock, or any other structure; lands Protection #17 bulldozing, moving, removing, adding to, or building any T. 38 S. 471-6,47B Bureau of Land Quality Control structure in, on, or over any coastal sand dune. Area: 1-800-452-1942; 289-2111 Coastal dunes and wetlands-all tidal and subtidal lands including lowlands subject to storm flowage (ex- cept during "maximum storm activity") also includes coastal sand dunes above high tide. 78 To dredge, fill, or erect permanent causeways, bridges, Submerged Lands Act Department of Conservation #22 marinas, wharves, docks or other permanent structures. T. 12 S. 558; T. 38 S. 1022 Bureau of Public Lands Area: Submerged lands (beyond mean low water) and 289-3061 intertidal lands owned by the State. Lease required. All overboard (into water) liquid waste discharges in- Protection & Improvement Department of Environmental cluding those from residences, seasonal cottages, of Waters Protection #17 boats, businesses, industries, municipal and private T. 38 Ch. 3 Bureau of Water Quality Control sewer systems. Area: All Waters-fresh, salt, surface, 1-800-452-1942; 289-2591 ground, tidal. Liquid wasteldisposal from residential or other land Minimum Lot Size (20,000 Department of Environmental use activity including septic tanks, surface spraying, sq. ft./100 foot shore front- Protection #17 drainage fields, holding ponds and tanks. Area: All age) T. 12 S. 4807, A,B,C,D,G Bureau of Land Quality Control land areas. 1-800-452-1942; 289-2111 Wastewater Disposal-all systems other than munici- State of Maine Plumbing Department of Human Services #11 pal sewer systems or discharges licensed under line (5) Code Part 11 Regulations Division of Health Engineering above (overboard liquid waste discharges). Areas: All T. 22 S. 42; T. 30 S. 3221 - 289-3826 land areas. 3225, 4359, 4453, T. 32 S. 3301, 2, 4, 3401-6; 3501, 3504,3507, T. 20 S. 2361 Deposit of waste or refuse: A) forest products, e.g. Dredging/Discharging Department of Environmental sawdust,. bark, slabs, etc., B) potatoes or parts, C) T. 38 S. 417 Protection #17 refuse, e.g., junk, sludge, etc. Area: All land and ice Bureau of Water Quality Control which drains or melts into tidal or any other waters 1-800-452-1942; 289-2591 of the State. Siting of all aquacultural (sea-farming) and marine Research and Aquaculture Department of Marine research facilities and related operations, such as rais- Leases Resources #21 ing mussels, oysters, salmon or trout. Area: All tidal T. 12 S. 6072 289-2291 waters, all intertidal and subtidal land. Construction, extension or maintenance of fishweirs, Wharves and Fish Weirs Municipal Officers traps and wharves. Area: Tidewaters within the limits (Ch 9) T. 38 S. 1021-1026 Town Office/City Hall of any city or town. Construction of any marine facilities, e.g. piers, Rivers & Harbors Act 1899; U. S. Army Corps of Engineers wharves, pipelines, power lines, bridges, breakwaters; Federal Water Pollution 424 Trapelo Road dredging or filling; ocean dumping of dredge spoil. Control Act of 1972; Marine Waltham, Massachusetts 02154 Some activities are already covered by nationwide or Protection- Research and 617-894-2400 general permits. Area: All navigable (tidal) waters of Sanctuaries Act of 1972 the U.S., all tributaries and adjacent wetlands, e.g. 33 CFR Parts 320-329 marshes, bogs, swamps. 79 3 6668 14100 5696