An Agent-based Model to promote Nature-based Solutions for flood management in Algeria

International audience In recent decades, Algeria has faced an increasing frequency and intensity of extreme climatic events, particularly floods, which represent one of the natural hazards most amplified by climate change and have caused major disasters in several urban areas. Despite growing awareness, the implementation of innovative and sustainable flood risk management approaches, such as Nature-based Solutions (NbS), remains limited and insufficiently explored at the national level. To address this gap, this study employs a multi-agent simulation framework to evaluate the effectiveness of NbS compared to conventional strategies through flood scenario simulations. The model integrates multiple management strategies and assessment criteria focusing on potential human losses and environmental impacts. The approach is applied to the city of Chlef, a flood-prone area. Simulation results indicate that, without adequate mitigation, flooding could have catastrophic consequences, with an average of >32 fatalities and over 128 injured. Conventional structural measures, such as levee construction, significantly reduce impacts, lowering fatalities by approximately 50%, injuries by about 80%, and material losses by 20% to 60%. However, strategies combining urban nature and retention basins outperform other approaches by achieving equivalent results in terms of protection and maximizing social protection while enhancing environmental benefits. These findings demonstrate the strong potential of NbS to complement or surpass traditional flood management strategies, highlighting their relevance for sustainable urban resilience and supporting their integration into future national risk management policies.