Enhancing flood resilience in large regulated rivers. fighting flood with flood

Large regulated rivers across Europe have progressively lost floodplain connectivity due to channelization and longitudinal levees. This has led to increased flood risk, higher flow velocities, and recurrent economic damage in agricultural areas. In the middle reach of the Ebro River (NE Spain), decades of river confinement have resulted in frequent levee overtopping and failures during medium-magnitude floods, despite extensive structural defences.

This contribution presents the implementation of Lateral Flow Buffering Zones (ZAFL, Spanish acronym), developed within the LIFE Ebro Resilience project, as an adaptive flood risk management measure for non-urban floodplains. The approach combines setback levees, controlled overflow sections, and compartmentalized agricultural areas that allow pre-inundation and temporary water storage, reducing flow velocities and erosive forces during flood events.

Two-dimensional hydraulic modelling was applied to evaluate multiple design scenarios under a 10-year return period flood (Q ≈ 2,300 m³/s). Results show that the selected configuration—covering approximately 630 ha and subdivided into 14 buffering units—delays the onset of overtopping, increases the conveyance capacity of the main channel by more than 200 m³/s in constricted sections, and significantly reduces flow velocities over cultivated land. Additionally, the system stabilizes levees by balancing hydraulic pressures and enables rapid, controlled drainage after flood recession.

Beyond flood risk reduction, the intervention promotes river–floodplain reconnection, supports riparian habitat restoration, and aligns with the objectives of the EU Habitats and Floods Directives by applying Nature-Based Solutions. The Ebro River case demonstrates how adaptive floodplain management can provide a resilient, multifunctional alternative to traditional flood defences in large regulated rivers under climate change pressures.