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COASTAL MAPPING HANDBOOK

The coastal zone consists of open water, salt marshes, mudflats, twisting tidal channels, intracoastal waterways, islands, bays, natural and manmade levees, mosquito ditches, oceanfront and intracoastal developments, and estuaries. The coastal wetlands are generally composed of coastal vegetation and are under the influence, if not the daily flood, of the tide. They are the transition zone between the uplands and the sea and are influenced by both. The coastal wetlands are classified according to State and Federal definitions and interpretations.

DELIMITING THE COASTAL ZONE The Coastal Zone Management Act of 1972, as amended (see app. 5), defines the coastal zone as:

... the coastal waters (including the lands therein and thereunder) and the adjacent shorelands (including the waters therein and thereunder), strongly influenced by each other and in proximity to the shorelines of the several coastal states, and includes transitional and intertidal areas, salt marshes, wetlands, and beaches. The zone extends, in Great Lakes waters, to the international boundary between the United States and Canada and, in other areas, seaward to the outer limit of the United States territorial sea. The zone extends inland from the shorelines only to the extent necessary to control shorelands, the uses of which have a direct and significant impact on the coastal waters. Excluded from the coastal zone are lands the use of which is by law subject solely to the discretion of or which is held in trust by the Federal Government, its officers, or agents.

The complex part of this definition lies in the sentence, "The zone extends inland from the shorelines only to the extent necessary to control shorelands, the uses of which have a direct and significant impact on the coastal waters." Selecting boundary lines based on this definition is not an easy task. The definition implies an inland boundary of the coastal zone which is basically delineated along natural features, especially rivers, streams, marshes, and their watersheds. When establishing boundaries along natural features, the interrelations of those features and their relations to the coastal resource

system should be explored because of the dynamic nature of the features.

Tides sometimes cover the wetlands and may be of different phase and amplitude than the tide on open beach only a few kilometers away. Tidal rivers, streams, and freshwater surface runoff mix with the ocean water to form a brackish zone of changing salinity with a relatively few species of vegetation. The freshwater flow causes a hydrodynamic stage related more to the hydrologic cycle than to the lunar cycle. Marsh grasses a meter tall preclude photogrammetric measurement of the ground surface where elevation differences of a few centimeters are critical. It is not unusual for grass tops on the levees to be level with grass tops on lower ground behind the levee, giving the appearance of a continuous level surface. Tidal flow may reach an area by a long circuitous path through channels and breaks in natural levees.

A number of studies have attempted to relate mean high water lines to vegetative boundaries. The change between high vigor spartina alterniflora (resulting from a daily flooding by saline water) and a lower vigor form (resulting from occasional flooding) probably indicates a biological mean high water line. A similar effect has been noted between red and black mangrove. This close relationship is probably correct in many areas, but it is deficient in two operational criteria. First, establishing cadastral boundaries by engineering tidal surveys is an accepted legal procedure, and a biological survey may be supportive but not sufficient evidence in court. Second, the wetlands as defined by the growth of several species of vegetation often extend above the mean high water line. The regulation of wetlands is an exercise in the Government's authority to zone land and control use regardless of ownership. Therefore, the time, expense, and difficult ground surveying required to relate a vegetation boundary to a tidal datum may be unwarranted. If the only purpose of the mapping is to delineate the wetlands for regulatory action, then vegetative boundaries are appropriate. A cadastral survey re

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quires a tidal datum and is more costly; however,

it provides legal boundaries.

The species composition of a coastal marsh reflects the salinity, soil characteristics, frequency of inundation, and elevation. Saline marshes contain Spartina alterniflora in three growth forms-the largest up to 3 m tall. Other species are found where the elevation is higher or the tidal inundation less frequent. The different species can usually be clearly identified on color infrared film.

The upper wetland boundary is often sharply defined by an abrupt change in topography. The marsh may extend as much as 10 m under the canopy of large trees in the border zone. Where a broad and gradual transition occurs with a mixture of plant species present, the upper wetland boundary is more difficult to define. With a knowledge of the plant species, the morphology of the land, the tidal cycle, and applicable laws, one can usually position the upper wetland boundary within 3-5 m horizontally during field inspection. The task is easier and equally accurate when the boundary is delineated from color infrared aerial photographs offering a much larger view. For 5-10 percent of the area, the task is more difficult than normal, whichever method is used. The transition in these areas may be very gradual and indistinct and require more judgment, careful surveys, and intelligent legislation. Litigation may be necessary because there is no one technique for providing unequivocal solutions to wetland boundary problems.

In practice, some coastal States may define the landward boundaries of their coastal zone along other than purely natural features. For example, a State may determine that the most feasible boundary might be based on a line, such as a 10-ft vertical distance above mean high water, that may roughly approximate a flood-plain level. The line would then be modified to correspond to the nearest township line or paved road. This modification would greatly simplify the administration of such a coastal zone boundary. Another approach might be to draw boundaries at a fixed horizontal distance inland from the MHW line.

For the purpose of planning topographic mapping in the coastal zone, the U.S. Geological Survey defines the inland edge of the zone as the landward boundaries of the coastal counties, townships, or parishes within the States and Territories eligible for grants under the CZMA. Alaska's coastal area is defined separately as the first two 15-min quadrangles inland from the shore, because the State is not organized by counties.

Other approaches to delimiting the coastal zone beyond those specified in the CZMA might include a concept of the seaward limit as the edge of the continental shelf rather than the outer limits of the territorial seas. This might be a more logical way to define the coastal zone if natural considerations and features are most important.

The coastal zone might also include those areas where the water influences the land, the reverse of the concept cited in the CZMA. It might be easier to delineate the extent of the water's influence on the land, for example, by using the 100yr flood plain for the boundaries of coastal wetlands such as marshes and bogs. Numerous other schemes could be devised to define the coastal zone, each with its own advantages and disadvantages. However, in this handbook the CZMA definition is used.

COASTAL MAPS AND CHARTS

A map is a pictorial or graphical representation of a portion of the Earth's surface. In general, a coastal chart is a map that shows water depths, coastlines, and land features in a narrow band along the coast. Charts are generally used for navigation, but they have many other uses.

Maps and charts may be classified as either metric or nonmetric in quality. Most road maps, pictorial maps, and many atlas maps are for general information only and are not of metric quality, that is, they cannot be relied upon to provide accurate measurements. Only metric quality maps are considered in the handbook.

A metric quality map usually contains a graticule of meridians and parallels and a plane rectangular coordinate system to define specific locations, and it portrays the various map features in precise relation to each other and to the graticule or grid (except in cases of deliberate misplacement of symbols to avoid overcrowding). Distances and directions between features can be measured precisely, either on a single map sheet or between adjoining sheets on the same reference system and datum. A particular feature will have the same geographic position on other maps of the same area regardless of scale.

Map scale is the ratio between a unit distance (for example, 1 in or 1 cm) on the map and the corresponding distance on the ground. The scale of 1:24,000 means that 1 unit on the map represents 24,000 of the same units on the ground. Thus, 1 cm on the map represents 24,000 cm (240 m) on

the ground. This rule applies to all units of linear measurement.

The larger the denominator of the scale ratio, the smaller the map scale; for example, a 1:10,000scale map has a larger scale than a 1:24,000-scale map. A large-scale map usually portrays a smaller area than a small-scale map, and the detail is greater. The scale is generally given in the legend or margin of the map.

PLANNING USES

The CZMA of 1972 provides a new mechanism for planning and managing activities in the coastal zone. Coastal planners at the Federal, State, and local levels will need maps of the coastal zone covering their areas of interest. A set of maps for the entire coastal zone of the United States (including the Great Lakes) and Territories is fundamental for an overview perspective. Federal and State planners will need maps at scales ranging from 1:10,000 to 1:250,000. Local government coastal zone planners also will need planning maps to relate their activities to others in the State. Such maps may be at scale ranging from of 1:2,400 to 1:24,000.

Effective planning can be simplified considerably if the data and results of resource inventories of the coastal zone are displayed graphically on the planning maps. These inventories can include natural resources such as woodlands, estuarine areas, freshwater marshes, beaches, wildlife, geologic features, and marine life and minerals. Also, planning maps can include statistical distributions, residential housing, commercial and industrial facilities, transportation routes, flood plains, cultural features, archeological sites, esthetic resources, and parks and other recreation areas. Furthermore, these maps can depict land and water use classifications and such phenomena as estuarine circulation patterns and predominant coastal currents.

The different types of information needed for planning can be shown on maps in a variety of ways. Sometimes the information is printed as a part of the base map, sometimes as an overprint on the base map, and sometimes as overlays keyed to the base map. The method used often depends upon the availability of existing maps, the variety and quantity of information to be displayed, the time allotted to display the information in cartographic form, and budget constraints.

The sections on "Sources of assistance and advice" and "Product and data sources" are included

to assist coastal planners to develop effective coastal mapping programs tailored to their needs.

MANAGEMENT USES

Maps for coastal management generally would be of larger scale than general planning maps. Whereas the small-scale maps suitable for planning are frequently available from Federal agencies, the basic responsibility for producing large-scale maps for management of the coastal zone rests with the users-State and local governments. State coastal maps might range in scale from 1:2,400 to 1:24,000, depending on the geographic area of concern, the intensity of its development, and the length of the coastline to be mapped. Local governments may need maps of even larger scale for more detailed regulation and management of their coastal zone; perhaps in the range of 1:600 to 1:10,000. Large-scale maps for the entire coastline would be quite expensive. They should be made first for areas where immediate concentrated management is necessary, while somewhat smaller scale maps would suffice for areas needing less rigorous management. As the coastal management program evolves, larger scale management maps could be produced to cover the gaps. Management maps would be useful for monitoring, inventory, analysis, documentation, regulation, and enforcement. However, detailed maps can sometimes be a liability for management if they are misleading or if they do not define the precise location of the area being regulated. Maps are useful for indicating key natural areas or regulatory boundaries, but maps used as management or regulatory tools must be at an appropriately large scale, meet National Map Accuracy Standards (app. 6), and be up-to-date.

Large-scale maps, on which boundaries and other information can be delineated accurately, will also be needed in legal proceedings resulting from regulating land and water use. Maps submitted as evidence in court are subject to critical review. The need for accuracy and up-to-date information cannot be overemphasized. Old photographs are often compared with newer photographs of the same geographic area (sometimes in the form of orthophotomaps) to demonstrate how change has occurred. Obviously, adequate documentation of when and under what conditions the photographs were taken is vital. Accurate large-scale maps can also be used in court to indicate the proximity of proposed construction projects to valuable natural, esthetic, recreational, or economic resources that may be

affected by the proposed project. In these cases maps are best used in conjunction with such evidence as expert testimony, actual site visits, and other historical records and photographs.

Maps used in a group presentation must be large enough to be seen easily. Attempting to communicate a concept with an overly complex map can be counterproductive, especially if highly detailed keys are used. Managers may want to use a simplified version of the map or perhaps a sketch of the key information. Transparencies, slides, and overhead projectors are often effective in enlarging a portion of a map so the audience is not distracted by irrelevant information. In addition, the use of successive overlays on a base map can be most effective for some types of presentation. A planner or manager attempting to communicate with a diverse audience should use maps that are simple, clear, and to the point. Complex maps tend to confuse and overwhelm the general public. Obviously, those with specific interests such as coastal developers, local government officials, and members of public or private interest groups will be concerned with selected aspects of the coastal area and consequently with maps dealing with those aspects. In essence, considerable thought should be given to the type, format, content, scale, accuracy, and frequency of revision of the maps included in State or local planning and management programs.

It is important to note that coastal areas are dynamic biologically, geologically, demographically, and legally, and therefore, maps depicting coastal information have to be updated frequently. Using overlays on a good base map makes updating easier. (See the section "Overprints and overlays.")

Recent dramatic advances in remote-sensing technology have provided methods for revising maps of dynamic coastal areas. A variety of options exist with a wide cost range.

In the past, charts of water areas were used basically for navigation. However, as coastal programs evolve water and land use management will increase significantly, and new maps and charts will be needed.

MAPPING THE COASTAL WETLANDS

A review of present and proposed coastal wetland regulations of several States reveals that:

There is a requirement to provide an accurate cartographic base on which upper wetland

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boundaries and other coastal features can be accurately plotted.

It is desirable to give map users an orthophotobase showing more information about features that are not specifically delineated or that are necessarily generalized on the conventional map.

Vegetative boundaries can be identified and delineated on color infrared film and transferred to the orthophoto.

Selected areas of the coastal zone require map scales larger than 1:24,000.

There are no universal conversion factors for relating tide, vegetation, contours, and cadastral boundaries.

In many areas, available USGS 1:24,000-scale topographic maps could be used as cartographic bases. The upper wetland boundary could be interpreted from recent color infrared photographs according to the applicable regulations and compiled on the map. This procedure would serve as a practical inventory at minimum cost and would satisfy general zoning regulations. It would provide a zone boundary between marsh and upland with a horizontal accuracy of about 12 m (40 ft), which is within the National Map Accuracy Standards. However, the increasingly popular orthophoto cartographic products have proved invaluable for mapping swamps, marshes, and other regions of overwhelming detail usually lost in conventional map symbolization. Compared with line-map portrayal, the orthophoto of a coastal marsh provides more information on the many features associated with identifying the boundary between upland and marsh. Besides matching the accuracy of conventional maps, the orthophotos show the actual pattern of vegetation and woodland, all visible roads and trails, the intricate meanderings of waterways, and other detail useful for determining position. Information on current land use can be derived from tonal differences in the photograph.

The Geological Survey has recently prepared several experimental color-image maps using two synchronized cartographic cameras in a single aircraft. One camera contains black-and-white panchromatic film and the other black-and-white infrared film. The two sets of photographs are processed into orthophotos at the correct scale. During printing, the two images are in perfect register. Through the use of various inks, several different color renditions are possible. These simulated color infrared composites represent a new dimension in the interpretation and delineation of coastal wetlands.

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