How do peak-water-levels respond to natural shoreline restoration projects with progressive tide parallel to shore

Abstract

Facing strict control of natural shoreline retention and the urgent need for mitigation of oceanic hazards, amid climate change, challenges persist in the spatial allocation of nature-based and concrete-based measures in China's coastal protection and restoration plans. This study explores the feasibility of “Operational Landscape Units" (OLUs) and their impact on peak-water-levels (PWL) and tides on the western Yellow Sea inner shelf (WYS), considering the newly published “China Coastal Ecological Zoning on Land and Seas” in 2023. Numerical experiments with a single OLU of county-size operated along the WYS indicate the largest reduction of 10% (0.23m) in PWL on the coast happens when an OLU is set on the section closest to the tidal amphidrome and the shoreline is parallel to the tidal propagation direction. Furthermore, as the restoration section extends on both sides, the spatial scale of the changed PWL expands. Further investigation reveals that OLUs positioned upstream of the tidal propagational direction can more effectively mitigate coastal inundation risks. This is because local tidal damping through bottom friction inside the OLUs overweighs the tidal damping on the inner shelf outside the OLUs. Overall, this study provides insights into high-tidal-flooding mitigation through OLUs in China's coastal zones, offering references for future coastal plans and flood control deployments.