Assessment of Flood Risk and Mapping of Flood Risk Zones in Yenagoa, Bayelsa State, Nigeria

Abstract

In recent years, most Nigerian cities have experienced several major flood episodes with serious catastrophes. Hence, this study was carried out to assess and map flood risk zones in Yenagoa. The Geographic Information System (GIS) and remote sensing technologies were used in generating and analyzing data to identify the different flood risk zones in Yenagoa. Environmental indices such as flood heights, land elevation and land cover images were analyzed using geo-statistical tools such as map overlay operations to produce a flood risk map. The flood risk map produced and the ground truthing carried out confirmed that the highest flood risk are located within residential areas where about 32% of the built-up area was vulnerable to moderate or high risk of flooding. The study revealed that both natural and anthropogenic factors are responsible for the severe flooding experienced in Yenagoa, especially due to heavy precipitation, elevation of the area, poor waste disposal, and inadequate urban development control amongst other factors. The city was classified into three flood risk zones-high, moderate and low, with about 48% of the area being either at moderate or high risk of flooding. It is therefore recommended that the Ministry of Physical and Urban Development should carryout proper urban development control, which will prevent building on flood plains, wetlands and natural drainage channels.