In this example, although the highest significant deepwater waves approached 

 from directions ranging from W to NW, the refraction study indicated 

 that higher inshore significant waves may be expected from more southerly 

 directions. 



The accuracy of determining the shallow-water design wave by a refrac- 

 tion analysis is decreased by highly irregular bottom conditions. For 

 irregular bottom topography, field observations including the use of aerial 

 photos or hydraulic model tests may be required to obtain valid refraction 

 information. 



7.124 Bathymetry Changes at Structure Site . The effect of a proposed 

 structure on conditions influencing wave climate in its vicinity should 

 also be considered. The presence of a structure might cause significant 

 deepening of the water immediately in front of it. This deepening, result- 

 ing from scour during storms may increase the design depth and consequently 

 the design breaker height if a breaking wave condition is assumed for 

 design. If the material removed by scour at the structure is deposited 

 offshore as a bar, it may provide protection to the structure by causing 

 large waves to break farther seaward. Experiments by Russell and Inglis 

 (1953), van Weele (1965), Kadib (1962, 1963), and Chesnutt (1971), provide 

 information for estimating changes in depth. A general rule for estimat- 

 ing the scour at the toe of a wall is given in Section 5.28. 



7.125 Summary - Evaluating the Marine Environment . The design process of 

 evaluating wave and water level conditions at a structure site is summa- 

 rized in Figure 7-6. The path taken through the figure will generally 

 depend on the type, purpose, and location of a proposed structure and on 

 the availability of data. Design depths and wave conditions at a structure 

 can usually be determined concurrently. However, applying these design 

 conditions to structural design requires evaluation of water levels and 

 wave conditions that can reasonably be assumed to occur simultaneously at 

 the site. Where hurricanes cross the coast, high water levels resulting 

 from storm surge and extreme wave action generated by the storm occur 

 together, and usually provide critical design conditions. Design water 

 levels and wave conditions are needed for refraction and diffraction 

 analyses, and these analyses must follow establishment of design water 

 levels and design wave conditions. 



The frequency of occurrence of adopted design conditions and the 



frequency of occurrence and duration of reasonable combinations of water 



level and wave action are required for an adequate economic evaluation of 

 any proposed shore protection scheme. 



7.2 WAVE RUNUP, OVERTOPPING AND TRANSMISSION 



7.21 WAVE RUNUP 



The vertical height above the Stillwater level to which water from 

 an incident wave will run up the face of a structure determines the 

 required structure height, if wave overtopping cannot be permitted. 



7-15 



