Albert Nii Moe Allotey

Climate change seriously threatens human systems, properties and livelihoods. Global projections suggest a continuous increase in the frequency and severity of weather events, with severe outcomes. Although the trends and impacts are highly variable depending on location, most studies tend to concentrate on either the urban or rural areas, with little focus on peri-urban areas. Yet, in Sub-Saharan Africa, peri-urban areas display unique characteristics: inadequate infrastructure, unplanned development, weak governance, and environmental degradation, all of which exacerbate flood impact and thus need academic attention. This study contributes to filling this gap by assessing the flood vulnerability of roads in peri-urban Accra and its implications for mobility. Based on the fieldwork, the study delineated and analysed potential zones within the research locations. The researchers calculated roads’ absolute and relative lengths, using a spatial overlay (intersection) of potentially flooded roads with the total road network within the grid cells of 500 m by 500 m. These measures were adopted and used as exposure measures. The findings revealed that over 80% of roads with lengths between 100 m and 500 m were exposed to floods. Some areas had higher exposure indices, with absolute road lengths ranging from 1.5 km to 3.2 km and relative road lengths between 0.8 and 1.0. There were significant variations in road exposure between and within neighbourhoods. Depending on the depth and duration of the floodwater, residents may be unable to access their homes or carry out their daily activities. In conclusion, this study highlights the differential vulnerability of peri-urban areas to road flooding and recommends targeted provision of flood-resilient infrastructure to promote sustainable development.

Urban flood risk is significantly shaped by ground conditions and the built environment, which are constantly modified and transformed by human actions. This paper examines the intertwinement of flood risk and unregulated urban expansion processes in three selected sites in Accra’s expanding periphery. All three sites have been included in Accra’s urban extent since the 1990s, but differ with regard to the timing of development and socio-economic characteristics of residents. The research illuminates how flood risk is produced and “built-in” to the urban fabric through widespread practices associated with unregulated urban expansion processes, especially the persistent encroachment on water retention areas, wetlands and riparian zones and the highly fragmented provision of transport infrastructure in emerging residential areas in the periphery. Such harmful development practices are neither confined to homebuilders from poorer segments of the urban population nor spatially concentrated in low-income areas. The research highlights how the actions and inactions of a wide range of social groups and actors engaged in urban land administration and development contribute to flood risk in various ways, making flooding an increasingly alarming issue of citywide concern. Different stakeholders highlight fragmented urban governance as an underlying root cause for the obstruction of sustainable land and water management. Overall, the study calls for a more robust recognition of spatial planning and transport infrastructure provision in flood risk mitigation and highlights the urgent need for planning and governance practices that challenge the existing fragmentation of urban governance systems.

Data on the extension of urban areas are important for analyzing growth dynamics and to support the planning of transport and service provision. Satellite-based remote sensing has proven extremely useful, especially in cities that experience fast spatial growth. Different approaches to satellite-based mapping may, however, produce different results concerning urban categorization and delineation, often making direct comparison misleading. This study analyses four different satellite-based studies of urban land cover in Accra, Ghana and presents a new land cover map based on visual interpretation of segmented Sentinel-2 imagery. The methods and results, as well as the underlying definition of “urban”, are compared and discussed. One method identifies exclusively areas with man-made, impervious surfaces, such as roads and buildings, as proxies for urban extent. Other methods aim to identify a broader set of land cover types, including green spaces, which are treated as part of the mixed urban fabric. Further differences are found in the way urban fringe areas under development are classified depending on their degree of urbanization, and in the distance threshold values used for defining the urban agglomeration. For the most recent maps we identify a difference in the measured size of the Accra agglomeration of almost 100%.