Simulating coastal hydrodynamics: the role of seagrass in climate adaptation

Abstract This study investigates how future hydrodynamic and sediment transport may evolve in the Jade Bay, located in the southern Wadden Sea, by analyzing a historical baseline (1999–2003) as well as future projections (2090–2099) under the high-emission RCP8.5 scenario. We conducted 10-year simulations using the Semi-Implicit Cross-Scale Hydroscience Integrated System Model (SCHISM) for three distinct sea-level rise (SLR) trajectories corresponding to the 5th, 50th, and 95th percentiles of projected SLR to capture a realistic range of climate variability. Return periods of residual water levels were estimated to characterize extreme events and analyze the impact of SLR on the hydrodynamics and sediment transport. To assess ecological changes, we used European Nature Information System (EUNIS) habitat maps for the historical and projected periods. This allowed us to make a spatially explicit comparison of habitat distribution over time and highlight potential shifts in coastal ecosystems under changing hydrodynamic conditions. The results show that future SLR intensifies flow velocities and bed shear stress, increasing erosion risk and destabilizing sediments, particularly in high-energy zones. Habitat mapping revealed a contraction of intertidal areas and salt marshes by up to 62% and an expansion of aquatic habitats by up to 28%, with important implications for ecosystem services. Numerical experiments incorporating seagrass as a nature-based solution demonstrated their capacity to attenuate wave heights by up to 20% and decrease erosion by up to 60%, highlighting their potential role in enhancing coastal resilience under future sea-level rise scenarios.