Urban growth or urban risk? Unraveling the flood paradox in Kumasi (Ghana) through the lens of natural factors and spatial decision modeling

Abstract

Amid accelerating urbanization across the global landscape, urban sustainability finds itself in a precarious balance, particularly in the face of increasing flood risks. As such, this study aims to assess and map flood risk in Kumasi. Methodologically, this study is grounded in the analytical hierarchy process (AHP) spatial decision modelling approach to unearth the varied impacts of natural and urban factors on flood susceptibility in the city. Consequently, the resulting model reveals that approximately 98 % of the city is moderately to highly susceptible to flooding. This model result is supported by a validation assessment with an overall accuracy of 95 % and a Kappa coefficient of 0.91, emphasizing the urgency for actionable flood management and resilient urban planning. The model also points out that natural terrain variables including elevation (β = 0.1324, p < 0.001), slope (β = 0.0707, p < 0.001), topographic wetness index (β = 0.1062, p < 0.001), drainage density, and proximity to rivers and urban development dynamics (Normalized Difference Vegetation Index: β = 0.0402, p < 0.001, and Land use and land cover: β = 0.0201, p < 0.046) are major predictors of flood susceptibility. Consequently, this study calls for a paradigm shift toward spatially integrated urban governance, anchored in proactive spatial planning, informed land use policies, and hydrologically responsive infrastructure design for the city.