台风等极端天气会使淤泥质潮滩发生数十厘米的冲淤变化. 在全球变暖导致台风强度及频率增大的背景下, 厘清台风影响下潮滩冲淤变化及其机制, 对潮滩保护与生态系统完整性维持具有重要意义. 本文借助基于运动恢复结构算法的无人机(unmanned aerial vehicle, UAV)摄影测量方法, 于2021年7月“烟花”台风前后对崇明东滩典型样地进行滩面高程测量, 并在盐沼-光滩过渡带现场采集水动力泥沙数据. 结果表明: 无人机摄影测量精度为4.1 cm; 台风影响下光滩区域侵蚀、盐沼区域淤积, 变幅达 ±32 cm. 其原因是: 台风影响下, 光滩区域在天文大潮时波高及水深增大, 达到波浪破碎条件后表层沉积物被侵蚀并被强潮流搬运; 涨潮流携带悬浮泥沙进入盐沼后, 因盐沼缓流消浪作用导致水体挟沙能力下降, 泥沙在盐沼区域沉积. 因此, 盐沼-光滩过渡带呈现光滩区域侵蚀、盐沼区域沉积的冲淤分带性. 本文将无人机摄影测量与同步水动力泥沙现场观测结合, 为深刻认识台风事件对潮滩冲淤的影响提供了新视角.

Extreme events such as typhoons can change mudflats by tens of centimeters. It is important for coastal management and ecosystem maintenance to recognize changes in accretion-erosion during typhoons and to understand the mechanisms driving it. In this study, Unmanned Aerial Vehicle (UAV) photogrammetry based on the Structure-from-Motion (SfM) algorithm was used to generate Digital Elevation Models (DEM) of a mudflat in Eastern Chongming, Yangtze Estuary, before and after the passage of Typhoon “In-Fa” (July 2021). Hydrodynamic measurements were conducted from bare flats to marshes to explore the mechanisms of DEM changes. Changes in accretion-erosion observed by UAV photogrammetry presented an obvious zonation of eroded bare flats and accreted marshes. The accuracy of the DEMs is 4.1 cm. Under the impact of the typhoon, the erosion of the bare flat and the accretion of the marsh have a amplitude of ±32 cm. During typhoons, the wave height and water depth in the bare flat increases to the condition of wave breaking, and the surface sediment is eroded and carried by rising tides. But in marshes, the sediment carrying capacity of water columns decreases, and the sediments are deposited. Consequently, the mudflat presents an obvious zonation of accretion-erosion. This study provides a new perspective for deeply understanding the impact of typhoons on the accretion-erosion of mudflats by combining UAV photogrammetry and hydrodynamic measurements.