Evaluating sustainable coastal management strategies following Spartina alterniflora eradication: Insights from typhoon-induced hydro-sedimentary responses

Salt marshes play a critical role in buffering the impacts of extreme events, stabilizing coastlines, and regulating sediment transport. Along the eastern coast of China, various restoration and management strategies have been widely implemented under the national Special Action Plan for the Comprehensive Control of Spartina alterniflora. However, the effectiveness of these management strategies under extreme climate events remains unclear. This study evaluated the hydrodynamic–sedimentary–morphological responses of four sites representing three post-eradication management types (engineering-based restoration with breakwaters, native vegetation restoration, and untreated bare flats) during typhoon events. During the typhoon events, the breakwater protected site experienced the strongest hydrodynamic forcing, with peak significant wave height exceeding 0.5 m and wave energy >200 J m⁻², whereas vegetation restoration sites generally maintained lower energy conditions, with wave height remaining below 0.3 m. The untreated bare flat showed the most intense sediment disturbance, with turbidity peaks >2000 FTU, compared with <1000 FTU at vegetation restoration sites, and bottom shear stress peaks >1.0 N m⁻²at engineering and bare flat sites. Morphological analyses indicated that the engineering restoration site showed the strongest resistance to erosion, with elevation changes constrained within ±0.1 m, whereas the untreated bare flat experienced severe erosion, with local elevation loss peaks >0.5 m. Vegetation restoration sites exhibited intermediate geomorphological stability and post-storm sediment retention within vegetated areas (0.1 – 0.2 m deposition). Overall, these results demonstrate divergent hydrodynamic–sedimentary–morphological responses among management strategies under extreme disturbances, highlighting the importance of integrated ecological and engineering design for coastal wetland management and climate adaptation following large scale S. alterniflora eradication.