construction period and the severity of 

 disturbance. 



C hronic effects. The presence of a re- 

 vetment in an area leads to a number of 

 physical and biological changes at the 

 site and in the surrounding shoreline. 

 A revetment, when adequately designed 

 and constructed, will control erosion of 

 the shoreline on which the structure 

 sits; however, it will not stabilize ad- 

 jacent beaches or the foreshore in front 

 of the structure. 



Alterations in the foreshore follow- 

 ing revetment construction are site-spe- 

 cific and difficult to predict. Unlike the 

 groins, revetments generally do not fa- 

 cilitate beach accretion in either the 

 backshore or foreshore regions and may 

 promote beach erosion in front of the 

 revetment (Brater 1950, Michigan Sea 

 Grant Advisory Program undated ). Fore- 

 shore erosion, however, will be less 

 from a revetment than if a bulkhead or 

 seawall had been constructed because 

 wave energy tends to be dissipated 

 rather than reflected as waves run up 

 revetment faces (Pallet and Dobbie 

 1969). In fact, construction of revet- 

 ments on severely eroding shorelines 

 can actually improve water quality by 

 reducing turbulence (Carstea et al. 

 1975a, U.S. Army Engineer District, 

 Buffalo undated a). Erosion of the fore- 

 shore can result from toe scour, increas- 

 ed backwash during severe storms 

 (Brater 195C), and seasonal and long- 

 term fluctuations in the beach profile in 

 front of the structure. G if ford (1977) 

 has noted bottom changes in front of 

 revetments in Florida which usually in- 

 volve deepening near the shore and 

 parallel offshore bar formation. 



Well-designed and properly placed 

 revetments typically do not promote the 

 beach growth as they offer very little 

 obstruction to littoral drift. Poorly de- 

 signed or placed revetments can cause 

 increased erosion of adjacent beaches 

 (Herbich and Ko 1968, Herbich and 

 Schiller 1976). Erosion of adjacent 

 beaches may result from alterations in 

 water circulation patterns or from the 

 structure intruding into the littoral 

 zone and obstructinq littoral drift (Car- 

 stea et al. 1975a, Gifford 1977). 



Construction of a revetment is a 

 physical alteration of the shoreline 

 which brings with it many biological 

 changes. The structure itself buries 

 established flora and fauna. The revet- 

 ment facing affords a new and different 

 type of substrate. A revetment thus pro- 

 vides a new habitat for various terres- 

 trial, benthic, and aquatic organisms. 

 The plant and animal communities which 

 colonize a revetment will have a commu- 

 nity structure which is different from 

 the one in existence prior to construc- 

 tion. 



The diversity and abundance of or- 

 ganisms living in and around a revetment 

 will vary, depending upon the type of 

 revetment facing, energy conditions, its 

 location on the beach, and the type of 

 substrate on which the revetment was 

 built. In some instances, a revetment 

 can increase species diversity and abun- 

 dance compared to what was previously in 

 the area. An example of such an area is 

 Rincon Island, an offshore man-made is- 

 land in California which is protected by 

 rock and tetrapod revetments. Rincon 

 Island's revetments support a diverse 

 population of over 225 species of plants 

 and animals while the mainland, an area 

 one-half mile distant with sandy beach- 

 es, has fewer than 12 species (Brisby 

 1977). Prior to construction, about 20 

 to 25 different species lived in the 

 Rincon Island area (Keith and Skjei 

 1974). In general, revetment facings 

 that are highly irregular and have a 

 shallow slope are favored biologically 

 over structures with smooth and/or 

 steeply sloped surfaces. Such structures 

 tend to dissipate wave energy better and 

 have greater ability to support various 

 organisms (Cantt 1975). 



A change in beach substrate, as a 

 result of revetment construction, may 

 alter the types of aquatic organisms 

 which are able to utilize the area for 

 growth, food, reproduction, and protec- 

 tion. For example, fish species requir- 

 ing rocky substrates for spawning will 

 be favored in the riprapped areas over 

 those requiring sand, gravel, or vege- 

 tated substrates (U.S. Army Engineer 

 District, Buffalo undated a). Heiser 

 and Finn (1970), in a study of chum and 

 pink salmon in marinas and bulkheaded 



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