Evaluation of Nature-Based Solutions for Flood Risk Reduction in Benin City, Edo State, South South Nigeria

Benin City in Edo State experiences recurrent urban flooding exacerbated by rapid impervious surface expansion, deteriorating drainage infrastructure, and loss of natural water retention areas. This study evaluated the potential of nature-based solutions, including urban wetland restoration, vegetated swales, and permeable pavement systems, to reduce flood risk in selected flood-prone districts of Benin City. Hydrological modelling using the Storm Water Management Model was applied to two subcatchments to simulate flood peak reduction achievable through different nature-based solution scenarios. Community vulnerability assessments were conducted through household interviews in flood-affected areas to document flood frequency, damage patterns, and community risk perceptions. Site suitability analysis using geographic information system mapping identified optimal locations for nature-based solution implementation based on topography, soil permeability, and land availability. Modelling results indicated that implementing vegetated swales and restoring degraded wetland patches could reduce peak flood discharge by 18 to 31 percent in the modelled subcatchments. Community surveys confirmed high willingness to support green infrastructure improvements near residential areas. The study recommends prioritising nature-based solutions in Benin City's drainage master plan revision, establishing a multidisciplinary urban ecology and engineering task force, and piloting implementation in two high-risk wards before citywide scaling. Keywords: nature-based solutions, flood risk, Benin City, urban hydrology, stormwater management.