Figure 7. Stone rubble revetment at 



Jacksonville Beach, Florida. 



face of the breakwater. The armor stone must be designed against the force 

 of breaking waves, nonbroken waves, or broken waves. The design size of 

 armor stone will be a function of density, slope, and wave height. In 

 contrast to some breakwaters, almost all seawalls or revetments must be 

 designed to an elevation to prevent wave overtopping. Care must also be 

 taken to construct an adequate toe structure to prevent undermining of the 

 structure during severe wave action. This may not be a serious problem in 

 lakes or bays where advantage can be taken of prolonged periods of small or 

 no wave action to construct the toe trench. Conversely, along the open 

 seacoast, where the action of the surf is continuous, it is generally not 

 possible to excavate to a sufficient depth to reduce scouring velocities. 

 The usual alternative is to overbuild the toe structure in the anticipation 

 that as sand is scoured from under the toe, the excess rock will drop into 

 place and maintain toe support of the structure. 



Fixed structures generally have smooth and vertical, or near vertical, 

 faces on the seaward side. The effects of turbulence due to wave action or 

 scouring velocities due to currents can be stronger and more serious on 

 these structures than on rubble structures. In these cases the toe struc- 

 ture can serve two functions: 



(1) Designed as a submerged rubble structure, it may rise an 

 appreciable height above the natural bottom and serve to reduce 

 wave or current stresses on the fixed or solid structure (U.S. 

 Army, Corps of Engineers, CERC, 1977); or 



49 



