mainly by structural considerations. No general criteria have been es- 

 tablished for determining their potential effectiveness in protecting 

 the land behind them. 



This report -raill deal with the determination of the efficiency of 

 vertical face and curved re-entrant face seawalls in tiirning back 

 damaging wave action. The results should not be applied to stepped 

 face or sloping face walls. The controlling factor in this problem is 

 the type of wave attack expected at th© structure , which may be de- 

 termined by observational data or if these are not available, by making 

 use of hindcasting techniques^ establishing, from historical weather 

 charts, a deep water design wavej and with that, a design wave at the 

 structure. Because the placement of a seawall is ordinarily determined 

 by terrain ca* economic considerations, water depths and beach slopes at 

 and before the wall's position will almost always be known. With these, 

 wave characteristics at the structure may be determined through con- 

 struction of refraction diagrams and the application of pertinent sections 

 of this report. 



The remainder of this report is divided into seven sections i 



Section II deals with the types of water level fluctuation 

 which may be eaqsected at a seawall's location. 



Section III establishes a criterion for a seawall to be totally 

 effective in turning back damaging waves. 



In Sections IV and V, the two problems of seawalls located in 

 and seaward of the breaker zone are discussed. Each of these sections 

 is divided into three jarts^ a general discussion of the means of de- 

 termining wave characteristics at the wall if only deep Tirater wave 

 characteristics are known (though the construction and interpretation 

 of refraction diagrams is not discussed): a determination of the height 

 of wall which will be totally effective in terms of the height of an 

 impinging wavej and a determination of the relative effectiveness of 

 lower walls. 



Section VI is a discussion of the problem of a seawall shore- 

 ward of the breaker zone. 



Section VII is a summary of Sections IV, V, and VI. 



Section VIII applies some of these results to an actual case. 



II, Factors Involved in Water Depth Variations at a Seawall 



As noted previously, if observational data are not sufficient, wave 

 characteristics at a seawall's locations will have to be determined from 

 deep water design waves through use of refraction diagrams. Construction 

 of these, their interpretation, and ultimately, the type of wave attack 



