fore dunes are protected, and beach 

 width can be increased by careful 

 placement of groins (Berg and Watts 

 1971, Pallet and Dobbie 1969). Down- 

 drift beach starvation results when 

 groins completely obstruct littoral drift. 

 Downdrift beaches will recede until the 

 groins are filled and sand bypassing 

 occurs (Schijf 1959). If groins are used 

 to widen beaches, they can be filled with 

 sand after construction thereby lessen- 

 ing the potential impact downdrift. 



Among the problems that accom- 

 pany groins is scour on the lee side. 

 This can often be minimized by includ- 

 ing weirs along the length of a groin or 

 by making the structure permeable 

 (Horikawa and Sonu 1968; U.S. Army 

 Corps of Engineers 1973b). 



The appearance of a shoreline on 

 which groins have been built changes 

 from one with long, fairly straight 

 stretches of sand to one with a series 

 of indentations downdrift of each groin. 

 This is due to pattern of erosion and 

 accretion caused by the alteration of 

 longshore drift (Horikawa and Sonu 

 1968). If the structures are permeable, 

 this recurring series of arcs is less 

 pronounced than if they are imperme- 

 able. 



The accretion of sand behind 

 groins buries those bottom organisms 

 which cannot move away from the area. 

 However, this disadvantage is usually 

 offset by the increased sand surface 

 area provided (Ortolano and Hill 1972). 

 The surface of groins serves as an at- 

 tachment site for sessile organisms 

 (Cronin et al. 1969), and groins often 

 provide a protected area for establish- 

 ment of beach vegetation (Garbisch et 

 al. 1975). Groins also attract fishes and 

 often provide excellent fishing spots. 

 Before a stable shoreline is achieved, 

 scouring and filling around groins af- 

 fects productivity by keeping the water 

 turbid and by providing a poor habitat 

 for marine plants and animals (Cronin 

 et al. 1969, Garbisch et al. 1975). 



C umulative effects . Cumulative ef- 

 fects of numerous groins in an area are 

 similar to the summation of effects caus- 

 ed by single groins. They are, however, 

 more widespread. Because oroins tend 



to accelerate downdrift beach erosion by 

 reducing the amount of sand transported 

 to them, the placement of one qroin 

 often leads to the need for another a 

 distance away. A series of groins will 

 take longer to fill, prolonging the pe- 

 riod in which downdrift shorelines are 

 exposed to erosive factors. 



Structural and Nonstructural 

 Alternatives 



The function of groins is either to 

 stabilize a beach by preventing movement 

 of sand, or to trap littoral sand which 

 would otherwise move past the area under 

 consideration. There are few alterna- 

 tives available which will accomplish 

 these functions. The most obvious is an 

 offshore or parallel breakwater which, 

 by diminishing wave energy, will disrupt 

 the movement of sand along the beach and 

 thereby cause an accumulation of sand in 

 the lee of the breakwater. 



Besides the immediate function of 

 the groin, two other purposes are imme- 

 diately apparent: 



o to provide a wider beach for aes- 

 thetic or recreational purposes; 



o to provide a wider beach to pro- 

 tect land or structures landward 

 of the beach. 



Both of these objectives can be ac- 

 complished by the nonstructural alterna- 

 tive of beach nourishment. The beach is 

 built up by artifically adding sand from 

 offshore or onshore sand sources. There 

 are numerous examples of this construc- 

 tion practice, particularly along the 

 east coast of the United States. " This 

 process is generally a continuous one 

 since the forces that eroded the beach 

 initially are probably still at work and 

 will erode it after nourishment. Thus, 

 further nourishment is required at a 

 later date. 



If the purpose of the wider beach 

 is for protection, there are several 

 structural alternatives available. A 

 breakwater will tend to widen the beach 

 in its lee. It will also assist in dis- 

 sipating energy from wave attack, thus 

 providing protection to structures or 

 land in its lee. If the purpose of the 



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