Rainfall – Runoff Relationship and its Implications on Lagos Metropolis

Abstract

An insight into rainfall-runoff studies especially within a densely populated area such as Lagos becomes imperative in the light of global acceptance in building sustainable and resilient cities. The location of Lagos alongside other anthropogenic activities makes it difficult for rain water to drain off quickly into the surrounding Lagoons. Therefore this study was concerned with analyzing and establishing relationships between rainfall events and their implications on runoff generation within Lagos Metropolis. Monthly data on rainfall and temperature were obtained from Ikeja and Lagos Roof weather stations, while monthly river discharge data for Yewa River were obtained from Ogun-Oshun River Basin Development Authority, Abeokuta. The data on rainfall and temperature were used in computing water budget model for both stations. The model revealed that May and June are months of soil moisture recharge and that the months of water surplus are July, September and October with July leading the way as the month for the most surplus water received. Period of surplus rainwater are very crucial as they could serve as seasons for rainwater harvesting which most often than not helps in agricultural planning and reducing the risk of flood events especially in highly urbanized cities. This study therefore suggested sustainable solutions in channeling the increase in the volumes of runoff in order to create a city that is resilient and eco-friendly.