At a restored mangrove forest site on the coast of Zhanjiang, China, scientists recorded a 44–70% reduction in storm wave height. During Typhoon Yagi in September 2024, waves nearly 0.9 meters high at the seaward edge of the mangroves decreased to 0.36 meters after passing through a forest belt about the length of a football field, Mongabay reports.
The M5 laboratory team led by Zhang Hu at Sun Yat-sen University used the HU method to predict how much mangrove forests weaken waves. The researchers used measurements taken in calm weather to retrospectively assess the effect of mangroves on waves that were record-high for such an ecosystem during Typhoon Yagi, which passed through the Philippines and southern China in early September 2024.
The HU method takes into account relative wave height and the Ursell number, a parameter calculated from wave height and length as well as water depth. According to the study’s authors, the model’s predictions closely matched field observations during the typhoon, while other models showed significant deviations. The results were published online in the journal Climate Risk Management.
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The scientists also created an online tool into which wave data or storm modeling can be entered to calculate the expected weakening of waves by mangrove forests. The tool also makes it possible to estimate how many mangroves a restoration project may need to achieve the desired level of wave attenuation.
The authors believe the development could be useful for ecological restoration and coastal engineering, particularly for assessing the vulnerability of coastal areas and combining natural protection with engineering structures. At the same time, Monash University professor Ruth Reef, who was not involved in the work, noted that the method has so far been tested at a specific coastal site. Its performance under other conditions may be affected, among other factors, by high water levels at which mangrove trees are completely submerged.
Source: UA
