Breaker Travel and Choice of Design Wave Height

Experiments on three-plane laboratory beaches show that plunging waves travel a horizontal distance of from four to eight times breaker height during the breaking process. This suggests that the potentially damaging effect of breaking waves may be spread over a significant horizontal distance. The experiments, as well as previously available data, show that breaker depth-to-height ratios for plunging waves decrease from above 1.3 to below 0.9 as beach slope increases, so that higher waves on steeper slopes may approach nearer to shore before breaking. The combined effect of breaker travel and breaker depth-to-height ratio is such that structures sited in shallow water on moderate or steep slopes can be subject to breaking wave heights significantly larger than the design heights computed according to accepted practice. The experimental results are consistent with a solitary wave description of oscillatory waves at breaking, if the breaker depths of oscillatory waves are appropriately defined, and they are consistent with the limiting heights of breaking waves measured on rubble-mound breakwaters.