Evaluation of Urban Stormwater Management Systems in Enugu City: Towards a Best Practice Framework

Urban stormwater management in Nigerian secondary cities is characterised by ageing colonial-era drainage infrastructure, rapid impervious surface expansion, and limited institutional capacity for maintenance and planning. This study evaluates the performance of stormwater management systems in Enugu City, South East Nigeria, with the aim of developing a contextually appropriate best practice framework. Using hydraulic performance assessment, field inspection of 42 kilometres of primary and secondary drains, and GIS-based catchment analysis, the study benchmarks current system capacity against design rainfall events. Institutional assessment interviews were conducted with Enugu State Ministry of Environment and Enugu Capital Territory Development Authority officials. Annual flood incident mapping based on emergency response records from 2018 to 2024 is used to identify persistent problem zones and quantify consequences of system failure. Findings indicate that system-wide capacity has been reduced to approximately 60 percent of original design specification through siltation, structural deterioration, and encroachment by informal construction. High-risk drainage corridors in Ogui New Layout and Trans-Ekulu receive the highest maintenance backlog. The study benchmarks findings against stormwater management practice in comparable African cities and derives a twelve-element best practice framework covering governance, maintenance financing, design standards, community engagement, and climate adaptation. Adoption of the framework is estimated to reduce annual flood damage costs in Enugu City by 40 to 55 percent within a ten-year implementation horizon. Keywords: stormwater management, urban drainage, Enugu City, flood risk, best practice framework.