Ibadan city is generally drained by three North South flowing river systems namely: Ogunpa River (Central), Ona River (Western) and Ogbere Rivers (Eastern) that flow through the city. Ibadan is highly exposed to frequent flooding. Notable of these events was the disaster of 1980 which resulted in the death of 500 people (IUFMP ESMF, January 2014).The Ogunpa River basin drains the central area of the city and joins to the Ona River in the south of the city. This river is the smallest of the three, with a catchment size of approximately 50 sq.km. Although its tributaries consist of natural river channels within an active floodplain, the main Ogunpa river channel is largely canalized through the centre of the city. All three rivers have cross drainage structures CDS like culverts, sluices and bridges that are meant for safe passage of torrential floods when coming down from surrounding watersheds through the city. In some cases unsized CDSs become obstructions with heavy depositions of solid waste. The latest flood event on August 26, 2011 took place after a downpour rainfall of 187.5 mm (about 7.38”) that occurred in about 4-5 hours accentuated by the overflow from Eleyele reservoir causing the death of more than 120 people and serious damages to infrastructure (many bridges collapsed, roads washed away, and substantial property losses).