The synergistic effect between engineering measures and ecological measures in coastal erosion prevention

Coastal areas, especially salt marshes, are key regions for ecological stability and coastal protection, but they are increasingly threatened by erosion, sea-level rise, and invasive species. This study focuses on the synergistic effects of engineering measures (soft mattresses) and ecological restoration (native Suaeda salsa ) on the coastal geomorphological evolution and ecosystem resilience in the Tiaozini tidal flat of Jiangsu Province, China. Through field measurements (using RTK-GPS, UAV terrain scanning, and vegetation plot sampling) and bio-morphodynamic coupling models, the hydrodynamic processes, sediment transport, vegetation growth, and morphological changes were studied. The results show that soft mattresses altered the flow field, reduced the hydrodynamic force in the sheltered areas, promoted sediment deposition, and transformed the sheltered areas from an erosive environment to a depositional one. The presence of Suaeda salsa enhanced the resilience of the coast by increasing bed roughness, weakening tidal energy, and stabilizing sediments, maintaining a stable sedimentation rate even under strong tidal dynamics. The synergy between soft mattresses and Suaeda salsa significantly improved the restoration efficiency. In the high-tide flat, the cumulative sediment accumulation over four years reached 1.767×10 4 m 3 , which is 32.26% higher than the accumulation achieved by relying solely on engineering measures and 82.54% higher than that achieved by relying solely on ecological measures. Additionally, the artificial planting intensity and offshore sediment supply affected the coverage of Suaeda salsa . Moderate planting intensity and adequate sediment supply increased the survival rate and the resilience of the ecosystem. This study clarifies the biophysical feedback between Suaeda salsa and coastal geomorphology, providing a scientific basis for the engineering-ecological integrated strategy for coastal erosion control and ecological restoration.