because it would have to withstand wave forces as "well as static pressure 

 forces. 



110. Seax^alls and bulkheads are used where there is little littoral 

 drift along the shore and little or no protective beach, as along an 

 eroding bluff, or ;jhere it is desired to maintain a depth of water along 

 the shore line as for a quay or pier line. 



111. Limitations . - In general, the seawall designed to withstand 

 the forces of high waves of the open ocean, or of the Great Lakes, is a 

 very costly structure. Because of its high cost, its use ordinarily is 

 limited to those areas where, because of the value of the upland, and 

 improvements thereon, it is essential to maintain and protect the shore 

 line in a fixed position. In many instances, the construction of a wall 

 may be accompanied by loss of beach since no seawall is a cure for the 

 cause of erosion but rather a defensive work to mitigate certain result- 

 ing effects without regard for other effects. VJhere the beach is of prime 

 importance, the seawall must be augmented by companion works, and may even 

 be undesirable. 



112. At those localities where minor fluctuation of the shore line 

 would not be harmful, the economic aspects of the high cost seawall should 

 be studied with a view to determining the desirability of some less costly 

 means of providing necessary protection. Further, the seawall provides 

 protection only to the area immediately behind it. On an eroding shore, 

 its construction tends to shift the focus of erosion to the downdrift end 



of the seawall. Extensions of the seawall have the same effect. "wTiere this 

 condition arises, consideration must be given to other methods to provide 

 the protection iiiroughout the entire littoral segment. 



113- Functional Planning of the Structure . - The planning of seawalls 

 and bulkheads is a relatively simple processes, since their functions are 

 restricted to the maintenance of fixed boundaries. The features which must 

 be analyzed in adequately planning such a structure are: the use of the 

 structure and its overall shape, its location with respect to the shore line, 

 its length, its height, and often the ground level in front of the wall. 



llU. Use of the Structure . - The shape to be chosen for a seawall 

 must be determined by consideration of collateral uses of the xfall. Wall 

 profile shapes may roughly be classed as: vertical or nearly vertical 

 face, sloping or curved convex seaward face, concave curved seai-iard and 

 re-entrant face, or stepped face. Each silhouette has certain functional 

 applications and so may be used in combination with any other if diverse 

 functional criteria are to be met. 



115. A vertical or nearly vertical face wall lends itself to use as 

 a quay wall or landing place, where other wall shapes need to be provided 

 with additional work to be so adapted. In addition, especially 

 with the lighter types of walls, a vertical face wall (sheet pile, for 

 example) may with one exception be constructed more quickly and often 



