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

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. [Display omitted] •PWL in the offshore regime decrease the most when an OLU is implemented on Sheyang coast of WYS.•OLUs are more effective on PWL damping if set upstream of an open coast, where tide propagates parallel to shore.•OLUs are classified into three types for PWL damping: Far-reaching Impact, Tidal Energy Absorption, and Local Reduction.•Internal friction of OLUs adjust local PWL, and external friction of OLUs affects overall energy absorption. Although many efforts have been made in recent years for ecological restoration in China, many challenges, such as the lack of effective legal constraints and the absence of nationwide criteria, remain for the coastal regime. For example, little is known about how to spatially implement natural shoreline restoration and whether the ‘green’ shoreline policy can meet the needs for preventing coastal floods. It is well known that coastal flood risks are highly dependent on local landscapes. In this study, a concept of “Operational Landscape Units” (OLUs), based on a county scale and first implemented in San Francisco Bay