Stability of Reef Breakwaters

Abstract

This paper discusses the stability of a class of rubble mounds referred to as reef breakwaters. Reef breakwaters do riot have a multilayer cross section like conventional breakwaters but are a homogeneous pile of stone. Individual stone weights are similar to those used in the armor or first underlayer of traditional breakwaters. Findings are based on a study which includes an extensive series of physical model tests conducted with irregular waves. An unusual method to quantify reef stability is presented. The method is unusual because it measures stability in terms of reduction in crest height due to wave attack. Reduction in crest height has less scatter than damage measured by number of stones displaced. Such an approach directly links stability to the primary performance characteristic of wave transmission. A stability model is developed which can accurately predict damage to the reef from very minor to very severe levels. The model also works for both submerged and subaerial mounds and for a wide range of wave conditions including those with heavy overtopping.