areas in Puget Sound, found that the 

 spaces between rocks in riprap revetted 

 areas provided protection for salmon fry 

 avoiding predators. 



Revetments also affect the plant 

 and animal communities in the upper 

 foreshore and backshore zones. Revet- 

 ments constructed in wetland areas can 

 cause extensive damage to wildlife habi- 

 tat. Carstea et al. (1975a) have describ- 

 ed wetland destruction as the "most 

 significant ecological impact of riprap 

 construction." Revetments can damage 

 or destroy wetlands by covering up 

 narrow fringe marshes and altering wa- 

 ter circulation in larger shorefront 

 marsh areas. Wetlands are highly pro- 

 ductive areas which filter upland runoff 

 and function as the nutrient and sedi- 

 ment traps. Destruction of shorefront 

 wetlands eliminates waterfowl feeding, 

 resting, nesting, and nursery habitats 

 and destroys the habitat for other 

 birds, reptiles, and small mammals 

 (Bobersch midt et al. 1976, Carstea et 

 al. 1976, Herbich and Schiller 1976). 



Cumulative effects . No studies were 

 found that investigated cumulative phys- 

 ical and biological impacts due to the 

 existence of a number of revetments 

 within a coastal area. Revetments are 

 relatively small in size. The effects of 

 a single revetment may be relatively in- 

 significant in a coastal area due to the 

 size of the structure, the size of adja- 

 cent undisturbed areas, and even re- 

 cruitment into the revetment-produced 

 habitat. The physical and biological 

 impacts from the construction of a num- 

 ber of revetments in a coastal area may 

 have a synergistic effect. For example, 

 extensive riprap revetting of a sandy 

 coastline will change what once was a 

 sandy habitat into a rocky intertidal 

 habitat. Examination of the physical 

 and biological impacts of revetment con- 

 struction on a case-by-case basis ig- 

 nores a host of potential cumulative 

 physical, chemical, and biological impacts 

 (Fetterolf 1976). No information was 

 found regarding the cumulative effects 

 of revetments in connection with other 

 shoreline structures. All structures in 

 an area should be evaluated concomi- 

 tantly. 



Structural and Nonstructural Alterna- 

 tives 



There are numerous alternative 

 structures and materials available for 

 building revetments. They are described 

 earlier in this section and more com- 

 pletely in the Shore Protection Manual 

 (U.S. Army Corps of Engineers 1973b) and 

 the Survey of Coastal Revetment Types 

 (McCartney 1976). In addition to the 

 alternative designs and materials for 

 revetments, either offshore breakwaters, 

 groins, or bulkheads may constitute al- 

 ternatives depending on the conditions 

 at the site. 



A revetment generally protects the 

 landward area from erosion or scour due 

 to waves or currents. An offshore break- 

 water may accomplish this same purpose 

 by dissipating the wave energy before it 

 strikes the eroding land area. A break- 

 water may secondarily interrupt the 

 longshore littoral transport of sedi- 

 ments. This can buildup the beach which 

 further protects the adjacent uplands. 

 Objections to a breakwater as an alter- 

 native to a revetment are the cost, the 

 interruption of longshore transport and 

 possible impact on adjoining land areas, 

 and the visual impact. In addition, a 

 breakwater might constitute a hazard to 

 navigation. 



A groin or system of groins might 

 indirectly accomplish the same function 

 as a revetment by causing the accumula- 

 tion of littoral drift which widens the 

 beach cross section and ultimately pro- 

 tects uplands from wave attack. The 

 groins, might reduce wave attack depend- 

 ing on spacing, height of the groins 

 and angle of wave attack. The groins 

 can cause undesirable side effects due 

 to their tendency to interrupt longshore 

 transport with the resultant impact on 

 downdrift beaches. Erosion problems are, 

 in some instances, only displaced by 

 groins. 



A bulkhead or seawall could be used 

 as an alternative to a revetment. How- 

 ever, due to the greater expense and 

 lack of environmental advantages, bulk- 

 heads would normally not be selected as 

 alternatives to revetments. The circum- 

 stances under which bulkheads are used 

 are described in another section of this 

 report. 



There are a number of nonstructural 

 procedures which may constitute viable 



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