Experimental Study on the Effectiveness of V-Type Breakwaters Against Infragravity Waves on Reef-Fringed Coasts

Abstract The infragravity waves are closely linked to flooding and shoreline erosion on reef-fringed coasts, particularly during typhoons. With the increasing frequency of extreme wave events and ongoing reef degradation, the reef-fringed coasts are becoming increasingly susceptible to the impact of infragravity waves. This highlights the urgent need for effective engineering solutions to mitigate the associated risks. This study investigates the performance of a perforated V-type breakwater in mitigating infragravity wave energy on reef-fringed coasts through extensive wave flume experiments. The experimental setup includes a reef model with a horizontal reef flat and a steep reef face with a slope of 1/1. The V-type breakwater, consisting of interlaced V-shaped columns facing the open sea, was positioned on the reef flat. Various incident wave conditions and breakwater configurations were tested. The generation, propagation, and reflection of infragravity waves were analyzed using cross-correlation between incident wave envelopes and the time series of the infragravity waves. Results show that the V-type breakwater effectively reduces the infragravity waves at the shoreline by up to 40%, primarily through wave reflection and dissipation.