Modelling and Mapping of Hydrological Flood Risk Areas: A Case Study of Chókwè City, Mozambique

Abstract

With flooding on the rise in low-lying areas of the Chókwè city, as well as flooding on some access roads as a result of rising water levels in stormwater drainage basins, these flood-related problems bring a series of challenges to society. In recent years, various regions of the world, countries, cities or municipalities have faced problems with flooding in urban areas. The Chókwè City Municipality has shown itself to be prone to flooding. This study aims to contribute to flood management in the Chókwè city Municipality by providing information for decision-making. To this end, the relief was characterized by generating a Digital Elevation Model (DEM) using programmes related to Geographic Information Systems (GIS). Hydrological simulations were carried out in the region using the HEC-RAS hydrodynamic model. This made it possible to map the neighbourhoods most prone to flooding and their respective areas. The results show flood indices for the urban perimeter, with the 4th neighbourhood standing out, with an average flooded area of 25.2% and an elevation of 2.6 metres according to the return periods of 2, 5, 10 and 25 years. The 3rd neighbourhood, with an average flooded area of 2.7%, was the least prone neighbourhood compared to the 5th and 6th neighbourhoods, with a flooded area of 10.3% and 8% respectively. The mapping of flood areas generated by HEC-RAS was crucial in obtaining and exporting the results to geographic information software, allowing detailed mapping of flood spots according to the neighbourhoods under study, making it an important tool to help control and monitor scenarios arising from flood management in the urban area under study.