Study on wave attenuation on a coral reef flat in SCS by in-situ measurement and simulation

Abstract

There has been no quantitative assessment of the wave attenuation coefficient on the coral reef flat in South China Sea (SCS) previously. Based on MIDAS DWR (Directional Wave Recorder), an in-situ experiment was carried out on a coral reef flat of Yongle Atoll, SCS. Waves and currents were measured at several locations on the reef flat, which were used to estimate wave attenuation due to bottom friction. A spectral wave model based on the action density balance equations is proposed to solve the wave attenuation coefficients on the coral reef flat, which can consider influence of currents. The wave attenuation coefficients due to bottom friction on the coral reef flat were found to be one order of magnitude greater than that recommended in most spectral wave models. Additionally, numerical simulation using a third-generation wave model SWAN was carried out. The simulation results verify in turn that the bottom friction plays a predominant role in the wave attenuation on the coral reef flat. It also captures the main characteristic of wave directional spectra with high precision. The study of the wave attenuation characteristics near islands and reefs will lay a foundation for the mechanism of wave propagating near islands and reefs.