A window to the future: balancing urban protection and ecosystem preservation in flood-regulated shallow coastal areas, insights from the Lagoon of Venice

Low-lying coastal areas are vital hubs, hosting invaluable ecosystems and supporting large human populations for centuries. Nonetheless, these regions face growing threats from climate change, sea-level rise, and intensifying extreme weather events, negatively affecting the quality of life in coastal communities. In response, storm-surge barriers have been widely adopted as a global solution to mitigate coastal flooding risks, with numerous projects proposed and implemented over the past two decades, although questions arise on the long-term ecological response.

This study focuses on the flood-regulated Venice Lagoon (Italy), a pilot example of an artificially controlled estuarine system, to explore the future of urban coastal environments as they navigate the challenges of balancing wetland conservation with the resilience of coastal communities—two goals that are often interdependent yet conflicting. Using a custom-built two-dimensional numerical model, we investigate four years of floodgate operations (2020–2023) to compare different flood regulation scenarios and their effects on urban flooding risk and ecosystem health. Specifically, we simulated tidal and wind-wave-induced circulations across the Venice Lagoon and compared the results of the real-case flood-regulated condition with those of a hypothetically non-regulated scenario. Additionally, we examined a third, hypothetical, flood-regulated scenario in which floodgate closures are managed using an optimized approach to minimize their frequency and duration.

Our analysis shows that the current operational strategy, while effectively protecting Venice and surrounding urban settlements from flooding, significantly disrupts the submersion dynamics of salt marshes, thereby reducing sediment deposition and fostering ecosystem degradation. However, this study demonstrates the feasibility of adaptive, sustainable management strategies that balance the competing demands of mitigating flood risk while preserving valuable coastal ecosystems, enhancing their resilience to climate change as a whole.