For STEPPED slopes, Stoa (1979) recommends using 70 to 75 percent of the smooth slope runup
if the risers are vertical, and 86 percent if the edges are rounded.
A rough approximation of the runup height can be obtained from Table 11. However, the values in
the table tend to represent the upper bound of the available data and may result in over design. Equations
(13) and (14) or the methods given in Stoa (1978) and (1979) are recommended.
If it is impossible or undesirable to build a structure to the recommended height, a splash apron
should be provided at the top of the structure. These are generally constructed of rock and they prevent
the ground at the top from being eroded and undermining that portion of the structure.
Environmental Factors
Many different materials can be used to construct shore protection structures, including rock,
concrete, timber, metal and plastics. The choice often depends on the desired permanence of the
protection. Durable materials usually cost considerably more than shorter-lived materials used for
temporary protection. The choice of materials is important because the coastal environment is a harsh
testing ground for all man-made structures. Aside from wave forces, which are formidable in and of
themselves, a host of chemical, biological and other factors can degrade structural
materials. A brief review of these follows.
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