Simulating the Effects of Urbanisation on Urban Flooding in Ashimowu Watershed, Lagos, Nigeria

Shakirudeen Odunuga; Lekan Oyebande; Ademola S. Omojola; Adebayo J. Adeloye

Shakirudeen Odunuga Department of Geography, University of Lagos, Akoka
Lekan Oyebande Department of Geography, University of Lagos, Akoka
Ademola S. Omojola Department of Geography, University of Lagos, Akoka
Adebayo J. Adeloye School of the Built Environment, Herriot-Watt University, Edinburgh

Keywords: Rainfall-runoff, Modelling, Inundation, Lagos (Nigeria)

Abstract

The paper studied the effects of urbanization on the extent of urban flooding in Lagos by using System 6c (Ashimowu Watershed) as a case study. The study utilized a scenario approach to simulate flooding processes for different land use scenarios (1965, 1975, 1987 and 2005) and 13 storm events recorded in 2005. For each scenario, the peak flow and area inundated were assessed using Precipitation Water Inundation Model (PWIM), a bespoke simple catchment water balance model with three components (Infiltration, runoff and digital surface) developed as part of the study. The results show that runoff and peak flow from precipitation increased by more than 200% between 1965 and 2005, due principally to urban impervious developments, causing the inundated area to increase by about 10% over the same period. Finally, Sustainable Urban Drainage Systems, (SUDS) that encourages natural groundwater recharge was recommended.