Wetland Delineation

Federal and state laws and regulations now protect salt marshes and recognize their valuable features.  In many cases wetlands are now protected from disturbances such as development.  A wetland is defined in the Clean Water Act of 1972 as areas that are inundated or saturated by surface or ground water often enough so that they support a prevalence of vegetation typically adapted to life in saturated soils or sediments.  Often a buffer zone of 50 to 200 feet is required around their border if development is adjacent to a wetland.  This means that the boundary of the wetland must be determined as accurately as possible.  To achieve this, legal criteria have been established.  They vary depending on who has jurisdiction over the project, local, state or federal agencies.  The most explicit criteria are federal and administered by the US Army Corps of Engineers, or the US Fish and Wildlife.  The USACOE produced a manual on wetland delineation in 1987 that is still used to define these criteria. These agencies use three criteria to establish boundaries of wetlands; vegetation, hydrology and hydric soils.  All three criteria must be present to locate the boundary of a wetland.

1. Vegetation

Each state has a list of plants that they consider wetland indicators.  So does the federal government.  Obligate wetland species are found in wetlands 99% of the time.  An example would be smooth cordgrass (Spartina alterniflora).  Facultative wetland species are found in wetlands 66-99% of the time.  These types of categories continue until Upland is reached, where wetland species occur less than 1% of the time.

2. Hydrology

Hydrologic indicators are used to determine if the water table is at or near the surface for at least a week during the growing season.  Direct observation is the simplest way to do this.  Also, if a test pit immediately fills with water to within 4 inches of the surface, this also satisfies the hydrology requirement.  Vegetation and litter (called wrack) trapped in branches following flooding is also used to satisfy this criteria.  The presence of tidal flooding also satisfies the hydrology condition.

3. Soils

Hydric soils are saturated with water long enough during the year so that they develop anaerobic conditions.  They typically have a dark surface and at least 24% organic matter by weight.  Blue-gray coloration from reduced iron, and often iron or manganese concretions occur below the surface.  Both the States and the Federal government publish extensive information and maps about the occurrence of wetland soils.  Every County in the US has a detailed Soil Survey with maps.  They are available from the Cooperative Extension Service, an agency in every state.

Salt Marsh Restoration and Creation

            Because of the stringent regulations protecting salt marshes and other wetlands the loss rate of these kinds of habitats has been greatly reduced.  There are active efforts to restore degraded salt marshes and it is now becoming a regular process to create salt marsh habitat.  Both the creation and restoration of salt marshes are activities likely to increase in the coming decades.

            In the NYC area federal, state and private groups are involved in wetland creation and restoration.  Save the Sound, Inc. is a non-profit group based in Connecticut and New York that is dedicated to the restoration, protection and appreciation of Long Island Sound and its watersheds.  More information about this group and their activities can be found on the web at www.savethesound.org.