the costs for installation, protection, 

 and maintenance when selecting the de- 

 sign wave. On the Atlantic and Gulf 

 coasts of the United States, hurricanes 

 may provide the design wave criteria; 

 whereas on the north Pacific coast, it 

 may be provided by annually occurring 

 severe storms (U.S. Army Corps of 

 Engineers 1973b). It may not be econom- 

 ically feasible, however, to design a 

 structure which will withstand a hur- 

 ricane which may occur once every 20 

 to 100 yr. Structures located in areas 

 with frequent storms should be built to 

 withstand the storms and to avoid high 

 annual maintenance costs. McCartney 

 (1975) selected the relatively short de- 

 sign life of 5 to 10 yr for the upper 

 beach revetments discussed in his 

 study. This design life is economical 

 and "compatible with erosion protection 

 needs for high lake levels in the Great 

 Lakes" (McCartney 1975). Gantt (1975) 

 has described riprap revetments, if cor- 

 rectly designed and constructed, as be- 

 ing relatively permanent structures. 

 However, very little quantitative data 

 are available to assess the actual dura- 

 bility of riprap or other revetment 

 types. 



Summary of Physical and Biological 

 Impacts 



Construction effects. Construction 



of revetments involves transporting ma- 

 terials to the site, preparing the em- 

 bankment to be protected, laying filter 

 materials, placing armor units, and pro- 

 viding toe protection. These activities 

 involve a truck for material transport 

 and a front-end loader for construction. 

 This heavy equipment causes noise, vi- 

 bration, and air pollution at the site. 

 Carstea et al. (1975a) noted that con- 

 struction time is relatively short for 

 structures such as riprap revetments. 

 They also commented that air pollution 

 is well below Federal air quality stand- 

 ards and that noise from construction 

 activities will only have an effect on 

 areas within about 100 ft (30 m) of the 

 site. However, construction noise and 

 activity may be sufficient to disrupt 

 waterfowl which may be nesting or rest- 

 ing at or near the site. Construction 

 activities also disrupt vegetation direct- 

 ly behind revetments (Knutson 1977). 



Habitat is lost due to the struc- 

 ture being placed over the previously 

 existing substrate (Gantt 1975). Estab- 

 lished intertidal flora and fauna are 

 often buried during the revetment con- 

 struction (Coastal Plains Center for Ma- 

 rine Development Service 1973). All 

 plant and animal communities from behind 

 the revetment to beyond the revetment 

 toe are therefore affected by the con- 

 struction of revetments. However, in 

 many cases, such as the construction of 

 riprap revetments, a new and different 

 type of habitat is created. 



Construction activities will cause 

 local erosion and new sediment deposits 

 in the vicinity of the revetment (Orto- 

 lano and Hill 1972). This will occur 

 from disturbance of bottom sediments and 

 erosion of exposed substrate. New sedi- 

 ment deposits are often silty and can 

 "destroy spawning areas, smother benthic 

 organisms, and reduce bottom habitat di- 

 versity and food supply" (Carstea et al. 

 1975). 



Several authors noted that distur- 

 bance of bottom sediments and erosion 

 results in increased turbidity and water 

 quality decradation (Boberschmidt et al. 

 1976; Cars"tea et al. 1975b; U.S. Army 

 Engineer District, Buffalo undated a; 

 Virginia Institute of Marine Science 

 1976). Resuspension of bottom sediments 

 may release trapped nutrients, heavy 

 metals, and other toxic substances into 

 the water column. Suspended materials 

 can also interfere with respiratory and 

 feeding mechanisms of aquatic organisms. 

 The extent of impacts from construction 

 activities has not been well documented. 

 The type of revetment, its location on 

 the shoreline, construction methods, and 

 type of substrate all play a role in de- 

 termining construction effects. For ex- 

 ample, turbidity from construction ac- 

 tivities is greater and lasts longer in 

 areas with finer sediments (Carstea et 

 al. 1975a). Even with a fine grain type 

 of substrate, riprap revetment construc- 

 tion should not lead to levels of the 

 resuspended sediments which exceed those 

 required for the protection of aquatic 

 life (Carstea et al. 1975a). The effects 

 of revetment construction must be evalu- 

 ated in light of the duration of the 



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