Numerical modeling of wave attenuation by different mangrove species

A coupled wave-current-vegetation model is used to study the wave attenuation of a mangrove wetland in Dongzhaigang Bay (DZG), Hainan, China, and in an idealized bay-shelf system. A new metric for the wave attenuation rate is developed based on numerical simulations, and then, it is applied to study the wave attenuation capabilities of four common mangrove species (<i>Avicennia marina</i>, <i>Bruguiera</i><i> gymnorrhiza</i>, <i>Ceriops tagal,</i> and <i>Rhizophora stylosa</i>) in DZG under a winter storm scenario and a super typhoon scenario. The mangroves in DZG could reduce the incoming waves by ~80% during the winter storm and by &gt;80% during the typhoon. Mangroves could reduce waves more effectively under high water level conditions (e.g., high tides or storm surges). The wave attenuation capabilities of <i>A. marina</i> and <i>B. gymnorrhiza</i> during the typhoon were significantly stronger than their respective performances during the winter storm, while <i>R. stylosa</i> and <i>C. tagal</i> had relatively stable wave attenuation capabilities under both scenarios. The idealized bay-shelf model results showed the existence of three types of relationships between the wave attenuation rate and the wave height, which are related to the morphological characteristics of the mangroves and the local water depth. Model results suggest that<i> C. tagal </i>and <i>R. stylosa </i>can provide better protection under low water level conditions, while <i>A. marina </i>and <i>B. gymnorrhiza</i> can provide better protection under high water level conditions. The wave attenuation performances of specific mangroves species should be considered in the conservation of mangrove ecosystems.