Wave attenuation in Sonneratia apetala mangroves during extreme wave—a field study in Southern China
摘要
Assessing the wave attenuation capacity of mangroves under extreme weather conditions is of great practical significance for enhancing coastal resilience. This study quantitatively analyzed the wave attenuation characteristics of Sonneratia apetala under drag forces through field observations at the mangrove demonstration area on the east coast of Leizhou Bay, Zhanjiang City, Guangdong Province, China, during super typhoon Yagi. The maximum wind speed reached 68 m/s (equivalent to Beaufort scale 17), with a maximum wave height of 1.2 m. The results indicated that the wave attenuation rate increased from 0.001 m−1 at the forest edge to 0.005 m−1 in the dense vegetation behind the forest. The average wave attenuation rate was 0.004 m−1, with an average wave height reduction of 66.01% over a transmission distance of 180 m. In contrast, within the mudflat, the average wave attenuation rate was only 0.001 m−1, leading to a 11.36% decrease in average wave height over a transmission distance of 200 m. Wave attenuation resulting from bottom friction and viscous dissipation in bare mudflats was considerably less pronounced than that observed in mangrove ecosystems. Due to its unique vertical structure, with dense pneumatophores and tall trunks with sparse branches, Sonneratia apetala forms a layered pattern. Wave attenuation varies significantly with tidal level, and the attenuation rate decreases as relative water depth increases. The main reason for wave attenuation is vegetation drag.