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 (Avicennia marina, Bruguiera gymnorrhiza, Ceriops tagal, and Rhizophora
stylosa) 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 >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 A.
marina and B. gymnorrhiza during
the typhoon were significantly stronger than their respective performances during
the winter storm, while R. stylosa
and C. tagal 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 C. tagal and R. stylosa can provide better
protection under low water level conditions, while A. marina and B.
gymnorrhiza 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.