Rising urban flood risk and exposure under shared socioeconomic pathways in Greater Accra Ghana

Abstract

This study assesses flood susceptibility in the Greater Accra Region of Ghana, one of West Africa’s most flood-prone areas by employing the Frequency Ratio (FR) model. The analysis integrates a range of environmental and meteorological variables alongside non-meteorological factors in the susceptibility mapping. The model yielded an Area Under the Curve (AUC) score of 0.82, indicating reliable flood susceptibility predictions. Various factors such as elevation, slope, geology, distance from urban, and stream power index significantly influence flood susceptibility. The spatial distribution of baseline susceptibility zones reveals coastal and northeastern areas as highly susceptible. Projections under different Shared Socioeconomic Pathway (SSP) scenarios depict a dynamic susceptibility landscape, emphasizing shifts in susceptibility levels. Notably, SSP2 and SSP3 foresee an increase in high and very high susceptibility zones. For district and town-level dynamics, districts like Weija Gbawe and towns along the coastline consistently exhibit very high susceptibility. The spatial distribution of building footprints shows a notable concentration within high and very high flood susceptibility zones, highlighting significant exposure risks to both the population and critical infrastructure. For example, over 780,000 and 810,000 building footprints, representing 3.12 million and 3.24 million people, are projected to experience high flood susceptibility under SSP2 and SSP3, respectively. This comprehensive assessment provides critical insights for flood management decisions in cities, emphasizing the importance of considering various factors in understanding and mitigating flood risks in West Africa and globally.