The role of narrow fringing reefs in tsunami mitigation: a numerical modelling study along the Sanya coastline

This study assesses the tsunami mitigation capacity of narrow fringing reefs (50–200 m width) under varying ecological health states using a high-resolution implementation of the COMCOT model. Satellite-derived reef bathymetry (20 m resolution) and non-uniform bottom friction coefficients were incorporated to simulate tsunami propagation from four ∼Mw 9 earthquake scenarios along the Manila Subduction zone. The results indicate that healthy reefs can reduce the maximum on-platform current velocities by nearly 80% and delay wave arrival by 5–10 min – providing a critical window for early evacuation. While these narrow coral reefs exert limited influence on initial tsunami wave crests, they significantly attenuate subsequent waves, with up to 50% reduction in wave heights when the peak arrives after the first crest. These findings highlight the disproportionate protective value of healthy narrow fringing reefs, framing them as essential natural infrastructure for tsunami risk reduction. This study offers quantitative thresholds for targeted reef conservation and supports the integration of ecological parameters into computational tsunami hazard modelling frameworks.本研究采用高分辨率配置的COMCOT模型，针对不同生态健康状态下的窄型岸礁（宽度50~200米）的海啸减灾能力开展评估。研究纳入了卫星反演得到的礁体水深地形（分辨率20米）与非均匀底摩擦系数，以模拟马尼拉俯冲带沿线4个约Mw9级地震情景下的海啸传播过程。研究结果表明，健康状态的岸礁可将礁坪平台上的最大表层水流速度降低近80%，并将波浪抵达时间延后5至10分钟——这为早期疏散提供了关键时间窗口。尽管这类窄型珊瑚礁对初始海啸波峰的影响有限，但可显著削弱后续波浪，在首个波峰过后抵达的峰值波高可被降低至多50%。这些研究结果凸显了健康窄型岸礁不成比例的防护价值，将其定位为海啸风险防控不可或缺的自然基础设施。本研究为针对性的礁体保护工作提供了量化阈值，同时支持将生态参数纳入计算海啸灾害模拟框架。