marshes usually form on a gently sloping coast with a broad continental shelf, 

 under conditions of a sea slowly rising relative to the land. Western marshes 

 are mostly formed in relatively narrow river mouths which drain almost 

 directly onto a steeply sloping continental shelf along a slowly emerging 

 coastline (Cooper, 1969). Consequently, the western estuaries and their 

 marshes are more limited in development than those of the east and tend to 

 mature more rapidly. 



There are two types of coastal salt marshes: the regularly flooded low 

 marsh, which is considered to be the most valuable and usually the most 

 essential to erosion control, and the irregularly flooded high marsh. 



a. Eastern Region Marshes. Vegetation of eastern region marshes is 

 remarkably uniform. The inter tidal zone from New England to Texas is dominat- 

 ed by a single species, smooth cordgrass (Spartina altemiftova) (Fig. 2). 

 Two grasses, saltmeadow cordgrass (5. patens) and saltgrass {D'lst'tahlis 

 spiaata) , usually dominate the zone immediately above high tide along these 

 coasts with two rushes on slightly higher sites — black-grass (Junaus gevavdi) 

 north of the Virginia Capes and black needle rush (J. voemevianus) southward. 



Figure 2. Smooth cordgrass marsh (Virginia) . 



Eastern marshes divide into four general areas: north Atlantic, mid- 

 Atlantic, south Atlantic, and gulf. Typical north Atlantic marshes occur on 

 fibrous or silty peat because the shore is predominantly composed of hard 

 rock. The inter tidal zone of pure stands of smooth cordgrass is usually 

 relatively narrow with a well-developed upper zone of saltmeadow cordgrass 

 mixed with saltgrass (Fig. 3). Saltmeadow cordgrass often occupies a larger 

 area than smooth cordgrass. Pure stands of black-grass in the higher parts of 

 the zone often form a fringe at the edges of the marsh. 



17 



