The influence of precipitation and land use change on flood incidence in Lagos Metropolis, Nigeria
Publication Date : 27/12/2022
This study investigates the flood impact of precipitation increase and land use change in Lagos megacity. It simulates the runoff, peak flow and area inundated for different climate change scenarios on systems 1, 2 and 5. This was achieved by using the Precipitation Water Inundation Model (PWIM) which integrates projections of precipitation from regional models and urbanization drivers from land use change to analyse future flood scenario of 25 years and 50 years return periods. Using 2008 as base year, future climate scenarios of 50 and 100 years of medium and high changes were analysed for three urban catchments in Lagos (system 1, system 2 and system 5). The urbanization driver of transforming storm runoff to flood in central Lagos was determined using trend analysis. In contrast, the projection of the precipitation driver was based on statistical downscaling of CAM-EULAG regional climate model. The results revealed that runoff and peak flow on system 1 would increase by 6.34%, 14.24%, and 20.36% for 50 years of medium climate change MCC, 50 years of high climate change HCC and 100 years HCC respectively, 10.88%, 13.52%, and 19.26% for 50 years MCC, 50 years HCC and 100 years HCC respectively on system 2 and 6.13%, 13.31%, and 18.91% for 50 years MCC, 50 years HCC and 100 years HCC respectively on system 5. On average, a 20% to 25% increase in urban flash flood due to high climate change will be recorded in the next 50 - 100 years. Adaptation and Mitigation measures through urban renewal and integration of future fluxes from climate change are imperative in reducing the vulnerability of people and property to flooding in Lagos.
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