Functional performance of modular porous reef breakwaters

Abstract

Reef breakwaters are submerged structures usually made out of rubble mound construction. Wave attenuation could be achieved off-shore by the introduction of such reef breakwaters. This offshore wave attenuation helps to protect a coast subjected to erosion. Such submerged structures are suitable when moderate wave transmission is acceptable on the lee side of the structure. This present work aims at providing a basis for the design of reef breakwaters using results from physical model tests. The hydrodynamic performance characteristics of the reef breakwaters, namely the transmission and reflection coefficients are examined in the study for varying wave parameters and geometric configurations of the reef. Further, the present experiments have helped shed light on Reef Induced wave Breaking (RIB) and its role in the hydrodynamic performance of the reef breakwater. The present investigations bring out those parameters which are involved in RIB so that a designer would be able to identify and provide-for the RIB. Design equations for prediction of transmission and reflection coefficients for submerged porous reef breakwaters in regular and random waves are proposed and compared with other such equations. It is shown that the present equations reproduce dependence of hydrodynamic performance on reef and wave parameters.