Engineering Management of Urban Stormwater Infrastructure in Ibadan During Climate Change-Intensified Rainfall

This study addresses the engineering management challenges of urban stormwater infrastructure in Ibadan, South West Nigeria, under conditions of climate change-intensified rainfall that is increasing the frequency and magnitude of extreme precipitation events beyond the design standards of existing drainage infrastructure. Ibadan has experienced a series of damaging flood events in recent years, and engineering assessment indicates that much of the existing drainage network is already operating beyond its original design capacity, a problem that will worsen under projected climate trajectories. The study employs an engineering management assessment approach, combining hydraulic modelling of three major drainage catchments in Ibadan using SWMM software with an infrastructure condition audit of primary channels, culverts, and outlet structures, and an analysis of the institutional management arrangements governing stormwater infrastructure maintenance. Design storm inputs are derived from updated intensity-duration-frequency relationships incorporating the most recent thirty years of rainfall records. Model results confirm that all three catchments experience significant hydraulic surcharging under the ten-year design storm event, with modelled flood extents closely matching flood damage records. Infrastructure condition assessment identifies silted channels, undersized culverts, and encroached drainage reserves as the dominant hydraulic deficiencies. Institutional assessment reveals fragmented responsibility between Ibadan North Local Government and the Oyo State Ministry of Works. Recommendations include a catch-up capital programme for the three highest-risk catchments, a stormwater governance protocol consolidating maintenance responsibility, and mandatory upstream detention requirements for new major developments. Keywords: urban stormwater, flood management, Ibadan, hydraulic modelling, climate adaptation.