Storm Surge Reduction by Mangroves

Background

Flooding and wave energy from storm surges can damage infrastructure and harm inhabitants of coastal communities. Climate change and sea level rise have the potential to increase or intensify storm surges, which necessitate investment in coastal defenses and disaster risk reduction. Mangroves can reduce the effects of storm surges through attenuating waves and wind, making mangroves an important form of nature-based protection for coastal communities.

Goals and Methods

The authors reviewed available data and literature on mangrove forests’ ability to reduce the effects of storm surges. They compiled this information into a report for the Natural Coastal Protection Series, which summarizes current information on nature-based coastal protection for scientists, coastal engineers, decision makers, site managers, and conservation advocates.

Conclusions and Takeaways

Mangroves can reduce storm surge peak water levels when extending over areas several kilometers wide, with peak water level reductions of 5 to 50 cm per km of mangrove forest. Smaller patches of mangroves can also decrease wave height and buffer strong winds, but significant reductions to peak water levels, flooding, and damage are found only in mangrove forests that are several kilometers wide. Therefore, it is important to conserve and restore mangrove forests to preserve mangroves’ coastal protection functions. However, the successful reduction of storm surges due to mangrove forest vegetation and topography varies greatly, due to complex mangrove communities, physical settings, and storm event characteristics that affect storm surge water levels and inundation. Due to these variabilities, combining mangroves as a form of coastal defense with other risk reduction measures (i.e., early warning systems, evacuation centers, sea walls, levees) would be the most effective during severe storm events.