Storm sequences reduce the wave attenuation capacity of salt marshes

Abstract

Salt marshes provide critical coastal protection by attenuating waves, yet their performance under extreme storm conditions and subsequent recovery have lacked quantitative assessment. This study quantifies temporal variations in wave attenuation capacity across a complete storm cycle (before-during-after) at a Scirpus mariqueter marsh in the Yangtze Estuary, and evaluates cumulative impacts under storm sequences through numerical modeling. Our results show: (1) Storm landfall led to significant reduction in wave attenuation capacity of salt marshes, with wave damping coefficient (β) decreasing substantially in the post-storm period; (2) The weakened wave attenuation capacity of salt marshes was attributed to storm-induced vegetation damage in stem density, with recovery taking more than a few weeks; (3) Under the scenario of storm sequences, cumulative damage in stem density caused significant decline in wave attenuation capacity of salt marshes, with β gradually decreasing until the vegetation disappeared completely. This study reveals the vulnerability of salt marsh wave attenuation to storm disturbances, particularly under storm sequences, providing critical insights for coastal wetland management under increasing storm frequency.