A Simplified Numerical Framework for Diagnosing Storm-Induced Vegetation Lodging and Wave-Attenuation Recovery in Coastal Salt Marshes: Field Evidence from Consecutive Typhoon Events

Abstract

A Simplified Numerical Framework for Diagnosing Storm-Induced Vegetation Lodging and Wave-Attenuation Recovery in Coastal Salt Marshes: Field Evidence from Consecutive Typhoon Events
Chen Chen¹, Zhong Peng¹
1 State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200241, PR China
E-mail: 52293904022@stu.ecnu.edu.cn
Coastal salt marshes provide critical wave-attenuation services, yet how consecutive typhoons degrade and restore this capacity remains poorly constrained by field evidence. We present a back-calculation framework that continuously diagnoses vegetation-wave interaction strength directly from hydrodynamic monitoring data, applied to the unprecedented back-to-back landfalls of Typhoon Bebinca and Typhoon Pulasan at the Chongming Dongtan salt marsh, Yangtze Estuary, in September 2024.
The framework's key contribution is a numerical simplification of the nonlinear hydrodynamic term linking wave attenuation to vegetation drag, which allows the complete dissipation-efficiency parameter  to be solved explicitly from wave height, water depth, and decay length alone, without iterative inversion and, critically, without independently measuring vegetation structural traits (stem density, diameter, drag coefficient) in the field. This avoids the substantial errors typically introduced by destructive or visual vegetation surveys, particularly under storm conditions when direct measurement is impractical or unsafe.
The resulting  time series declines from a pre-typhoon mean of 0.313 to a typhoon-period mean of 0.176, an approximate 43.77% reduction in effective wave attenuation, followed by rapid post-storm recovery exceeding pre-typhoon levels.   collapses onto stable power-law/exponential relationships with several hydrodynamic controls , water depth (R² = 0.782), wave height (R² = 0.711), and near-bed orbital velocity (R² = 0.615) , with water depth showing the strongest control, identifying submergence depth as the dominant factor governing dissipation efficiency.
Relying solely on wave data, this framework offers a generalizable, real-time, measurement-error-free approach for quantifying vegetated coastal protection under extreme storms.
Keywords: salt marsh; wave attenuation; numerical approximation; consecutive typhoons; coastal protection