to even mature marshes. Breaking waves may erode the vulnerable leading edge 

 of the marsh forming a scarp or bank. In addition, long-terra sea level rise 

 and land subsidence may drown the seawardmost plants in the marsh, further 

 reducing the stability of this zone. Once a scarp is established it is 

 subject to continued erosion and the plants behind it can no longer spread 

 seaward. This is particularly critical in sediment-poor situations where 

 sediment accumulation cannot keep pace with subsidence and the marsh edges do 

 not recover and rebuild between storms. Most coastal marshes show evidence of 

 erosion because of these processes (Fig. 6). Once destroyed, the marsh will 

 not reestablish until the events which led to its origin (the presence of 

 plant fragments or seed and an absence of waves) are repeated. 



v'SSSKSs*^ '.s«»'i*»r- 



Figure 6. Scarp or bank on seaward edge of an eroding 



coastal marsh (San Francisco Bay, California). 



b. Planting to Encourage Establishment . With the use of agricultural 

 techniques, plants can often be established on shorelines where natural 

 processes of invasion have failed to produce plant cover. Marshes established 

 in this manner may greatly improve the shore's stability and resistance to 

 erosion. This erosion control alternative has been used successfully for many 

 years in the United States. In the winter of 1928, a property owner on the 

 eastern shore of Chesapeake Bay planted smooth cordgrass along more than 1 

 kilometer of shoreline in an attempt to reduce erosion. This shoreline has 

 remained stable for more than 50 years and is the oldest reported example of 

 shore stabilization with salt marsh vegetation in the United States (Knutson, 

 et al., 1981) (Fig. 7). Similarly in 1946, a landowner on the Rappahannock 

 River in Virginia graded an eroding shoreline and planted several varieties of 

 salt-tolerant plants. This planting has prevented erosion for more than 30 

 years (Phillips and Eastman, 1959; Sharp and Vaden, 1970; Sharp, Belcher, and 

 Oyler, 1981). 



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