Figure 7. Oldest reported salt marsh planting in the 

 United States (Virginia). 



Most shoreline plantings do not have the longevity of these two examples. 

 Planted marshes proceed through a cycle which includes periods of establish- 

 ment, stability, and erosion, just as natural marshes do. The length of time 

 required for a planting to complete this cycle is its "functional life" (the 

 period over which it has functioned to reduce erosion) . The life of a plant- 

 ing is influenced by the severity of wave conditions which impinge upon the 

 shore. Areas subject to more severe wave conditions require longer to estab- 

 lish and have a shorter functional life. For example, Woodhouse, Seneca, and 

 Broome (1974) discuss a shoreline planting at Cedar Island, North Carolina. 

 This shoreline is subject to waves generated over a fetch of more than 20 

 kilometers. Because of these conditions, it would be anticipated that the 

 period of establishment for a planting would be relatively long and the period 

 of stability would be relatively short. The shore was planted in the spring 

 of 1973. After one growing season (Fig. 8) the plant cover was incomplete and 

 ineffective. However, by the end of the second growing season (Fig. 9), the 

 shoreline was well vegetated and stable. By 1980 (Fig. 10), much of the 

 planting had eroded away and the shoreline had returned to its preplanting 

 condition. Therefore, the functional life of the planting at the site was 

 about 6 to 8 years. Because erosion control plantings are made in difficult 

 environments where nature has failed to establish plant cover, the functional 

 life of plantings may be shorter than the life of typical natural marsh. How- 

 ever, this fact should not discourage the use of this alternative. Many cost- 

 ly shore protection structures function successfully for only 5 to 10 years. 



c. Research on Planting to Control Erosion. In the late 1960 's a major 



research program was initiated on stabilizing dredged material with marsh 



vegetation by scientists from North Carolina State University at Blaleigh 



(Woodhouse, Seneca, and Broom, 1972, 1974). These studies on establishing 



22 



