Potential short wave attenuation function of disturbed mangroves

Abstract

Mangroves are able to protect coastal communities through their ability to attenuate incoming long and short waves. Evidence of wave attenuation function and the factors contributing to wave attenuation by mangroves are now well established, especially for undisturbed mangrove stands. However, as tropical coastlines continue to urbanize rapidly, there is interest in understanding the ability of mangroves in wave attenuation along such disturbed coastlines. This study models the potential wave attenuation capacity of disturbed mangroves along the urban coastline of Singapore. Short wave attenuation is estimated under both average and storm (elevated water level) conditions. The percentage of wave height reduction is higher under storm events compared to average conditions. Vegetation drag is the main mechanism of wave energy dissipation under both average and storm conditions, with additional wave dissipation caused by wave breaking under the latter. Mangrove density and width were found to be positively correlated to the percentage of wave height reduction during a storm event. Compared to trunks and canopies, mangrove roots contributed to a larger percentage of wave height reduction. No statistical differences in wave height reduction extent were found between mangrove types, incident wave heights, and water levels respectively. This study has illustrated the potential for the attenuation of short waves by disturbed mangroves, especially during elevated water levels associated with storm events. The findings imply the potential of disturbed mangroves in wave attenuation, and should encourage the stronger incorporation of mangroves into coastal management strategies designed to protect urban communities against coastal hazards.