Reconciling flood-risk reduction and wetland resilience behind coastal floodgates

Abstract Coastal urban areas face increasing threats from sea-level rise and extreme weather events. Where population relocation is not feasible, hard-engineering defence measures are adopted to mitigate flooding. However, the implications of such interventions for surrounding coastal ecosystems remain poorly understood. Here we explored the effects of the recently inaugurated Mo.S.E. storm-surge barriers on hydrodynamics and wetland resilience within the Venice Lagoon—a highly anthropized environment that may foreshadow future adaptation in other coastal cities. Our analysis demonstrates that while the floodgates successfully protect urban areas, the barriers presently operate at the expense of wetland ecosystems, reducing tidal inundation and the associated delivery of mineral sediments essential to sustain vertical accretion and maintain elevation with rising sea levels. Comparison with optimized management scenarios shows that subtle adjustments to the timing of floodgate activation can markedly reduce these negative eco-geomorphological impacts, promoting a more sustainable balance between urban flood protection and ecosystem integrity.