The Impacts of Ecological Restoration Engineering on the Seawall: The Protection Ability Assessment

Coastal zones are under the increasing threat of severe flooding caused by the rising sea level and increasing storm intensity. Ecosystem-based coastal defense promotes the ability to dissipate waves and elevates the seabed with the rising sea level. Therefore, ecosystem-based coastal protection is becoming one of the sustainable solutions for disaster prevention and mitigation in coastal zones. However, to what extent the ecological restoration measures can favor the seawall regarding the protection ability is still unclear. By taking the Dingshan Seawall on the Wenzhou Coast as an example, this study used the design tide level as the index to investigate the impacts of the coastal ecological restoration measures on the seawall protection ability under the background of sea level rise. We established a coupling model of wave-vegetation-seawall based on the non-hydrostatic wave model SWASH. A series of experiments have been carried out considering factors such as vegetation species, densities, locations, widths, and sea level rise rates. Under given numerical experimental conditions, when the sea level rises by 0.7 m with a Suaeda salsa area of 60 m width, the medium-density (350 individual plants per square meter) will increase the design tide level of the seawall with a non-vegetated area from 4 years return period to 12. Therefore, ecological restoration engineering can effectively enhance the protection ability of the seawall by attenuating waves.