How Does Flooding Influence Intra-Urban Mobility? The Case of Accra

Abstract

This study analyzes how daily mobility may be disrupted or constrained due to the flooding of road infrastructure. The empirical focus is Accra, Ghana, a rapidly growing African city with frequent flood events due to heavy rainfall. In the context of very scarce mobility data availability from official sources, this study proposes a novel way to utilize data from a large survey of mobility patterns conducted through in-person interviews in four peri-urban neighbourhoods. The survey targeted economically active adults and provided spatially explicit data on frequent destinations within the city when travelling in relation to income-generating activities. Using survey data on mobility patterns and detailed population data, we present a transport model with estimates of daily traffic volumes. At the city-wide scale, we propose a method for combining this transport model with maps of flood-prone locations derived from digital terrain models. At the local scale, we propose a method for analyzing the impact of flood events that restrict access to and from urban neighbourhoods. The presented results include maps of flood locations with a high impact on overall mobility, as well as maps that illustrate the spatial extent of this impact within the Accra region. At the local scale, the results illustrate the degree of potential isolation of smaller urban areas during flooding and identify the flood locations with the most significant impact on this issue. It is argued that the presented methods for identifying hotspots of flood-induced mobility disruptions may assist planners and policymakers in providing more resilient infrastructure and mitigate the adverse effects of flooding on urban transport.