Nature-based solutions for coastal flood risk reduction on the Changhua Coast, Taiwan: Modelling the benefits of wetland restoration under climate change

Study region Changhua, Taiwan Study focus Estuarine wetlands are increasingly recognized as nature-based solutions that complement structural defenses by providing flood-regulation services and co-benefits such as carbon sequestration. Focusing on the Changhua coast at the Jhuoshuei River estuary in Taiwan, designated as a coastal protection zone under the Coastal Zone Management Act, we develop a coupled hydrodynamic and ecosystem-service framework. The framework links two-dimensional storm-surge modelling using SRH-Coast with ecosystem-service assessment using the InVEST Coastal Blue Carbon module to evaluate wetland loss and restoration under sea-level-rise scenarios. New hydrological insights for the region Our results show that sea-level rise and wetland contraction act as compounding drivers of coastal flood risk along the Changhua coast. Under the + 34.5 cm sea-level-rise scenario, intertidal wetland area decreases from 6063 ha to 4619 ha, while storm-surge inundation extent increases by 65%. Wetland restoration produces the strongest hydrodynamic benefit locally, reducing surge levels by up to 37% across coastal cross-sections, whereas the reduction in total inundation area under future conditions is more modest at about 3%. This scale-dependent response indicates that substantial local surge attenuation does not necessarily translate into an equivalent reduction in system-wide inundation. Projected wetland loss also decreases blue-carbon stocks by about 16.4%, while restoration increases storage by about 31.7% relative to present conditions. Together, these results provide region-specific evidence that wetland preservation and restoration can complement existing coastal protection by attenuating local surge propagation while maintaining blue-carbon storage, and offer a transferable framework for evaluating nature-based flood-risk-reduction strategies on other subsiding, wetland-fringed estuarine coasts.