5„2 SEAWALLS, BULKHEADS, AND REVETMENTS 



5.21 FUNCTIONS 



Seawalls, bulkheads, and revetments are structures placed parallel, 

 or nearly parallel, to the shoreline, to separate a land area from a water 

 area. The primary purpose of a bulkhead is to retain or prevent sliding 

 of the land, with the secondary purpose of affording protection to the 

 upland against damage by wave action. The primary purpose of a seawall 

 or revetment is to protect the land and upland property from damage by 

 waves, with incidental functions as a retaining wall or bulkhead. There 

 are no precise distinctions between the three structures, and often the 

 same type of structure in different localities bears a different name. 

 Thus, it is difficult to say whether a stone or concrete facing designed 

 to protect a vertical scarp is a seawall or a revetment, and often just 

 as difficult to determine whether a retaining wall subject to wave action 

 should be termed a seawall or bulkhead. All these structures, however, 

 have one feature in common, in that they separate land and water areas. 

 Tliese structures are generally used where it is necessary to maintain the 

 shore in an advanced position relative to that of adjacent shores, where 

 there is a scant supply of littoral material and little or no protective 

 beach, as along an eroding bluff, or where it is desired to maintain a 

 depth of water along the shoreline, as for a wharf. 



5.22 LIMITATIONS 



These structures afford protection only to the land immediately 

 behind them, and none to adjacent areas up- or doivncoast. When built on 

 a receding shoreline, the recession will continue and may be accelerated 

 on adjacent shores. Any tendency toward loss of beach material in front 

 of such a structure may well be intensified. Where it is desired to 

 maintain a beach in the immediate vicinity of such structures, companion 

 works may be necessary. 



5.23 FUNCTIONAL PLANNING OF THE STRUCTURE 



The planning of seawalls, bulkheads, and revetments is an elementary 

 process, since their functions are restricted to the maintenance of fixed 

 boundaries. Factors in designing such a structure are: use and overall 

 shape of the structure, location with respect to the shoreline, length, 

 height, and often stability of the soil and ground and water level seaward 

 and landward of the wall. 



5.24 USE AND SHAPE OF THE STRUCTURE 



The use of the structure dictitates the selection of the shape. 

 Face profile shapes may be classed roughly as vertical or nearly vertical, 

 sloping, convex curved, concave curved, reentrant, or stepped. Each cross 

 section has certain functional applications. If unusual functional cri- 

 teria are required, a combination of cross sections may be used. 



5-3 



