a subsurface root structure that helps to hold the soil in place. Vegetative marsh conservation 

 measures have been shown to reduce erosion more cost-effectively than alternative methods 

 (Table 1). 



The moderate to high wave-energy environments common to erosion-prone situations often limit 

 the number of planting techniques available. Seeds are not practical because they can be washed 

 away. Thus, transplant materials are required. In some areas a temporary wave-dampening 

 structure may be necessary (Figure 1) to protect a stand of vegetation until it is sufficiently robust. 

 At a certain threshold of increasing wave energy, vegetation may not be practical at all and 

 permanent physical barriers may be required to alleviate erosion. Research is needed to determine 

 the wave energy likely to be generated on water bodies with different sizes, shapes, depths, 

 shoreline configurations, and boat traffic; and the effect various wave-dampening structures and 

 plant species have on the wave energy (see Knutson et al. 1982). 



Succession Acceleration 



If an environment changes faster than the natural plant succession can recolonize the area with 

 species adapted to the new conditions, valuable marsh land will be converted to open water. 

 Potential marsh loss may be prevented by accelerating succession with the introduction of the 

 appropriate species. For example, when increasing amounts of marine water enter brackish and 

 intermediate marshes, the existing vegetation dies, leaving mud flats (Sasser et al. 1986). Tidal 

 action removes the sediment from these areas, and they can deepen rapidly until they are too deep 

 to support vegetation. It is important to prevent the final phase of this process because it is 

 usually irreversible. Smooth cordgrass (Spartina alterniflora) may well be the best plant to stabilize 

 these areas. Work under way by the author suggests that cordgrass may successfully colonize an 

 organic substrate in a denuded brackish marsh. 



Succession acceleration can also be used in freshwater areas where higher water levels resulting 

 from subsidence, impoundment, or other causes result in conditions unfavorable to existing flora. 

 Often these conditions are also unfavorable to seed germination. In these instances, transplants 

 of a species tolerant of fairly deep water, such as cutgrass (Zizaniopsis miliaceae), may speed up 

 recolonization sufficiently to stabilize the site. 



Table 1. Comparative costs per 3 m of erosion control methods. 



Plants only $3.70 a 



Plants through fiber mat $38.40 a 



Plants behind floating-tire breakwater $46.90* 



Rock revetment $200.00-390.00 b 



Fiberglass bulkhead $101.13 c 



Creosote lumber bulkhead $113.31 c 



"Allen et al. (1986) assume 20-m centers and 0.5-m spacing 

 "Gray and Leiser 1982 

 C R.A.W. Corp. 1987 



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