Urban Sprawl and Changes in Landscape Patterns: The Case of Kisangani City and Its Periphery (DR Congo)

The rapid population growth in sub-Saharan Africa requires regular monitoring of the spatial expansion of cities in order to facilitate efficient urban planning. In this study, we quantified the dynamics of urban and peri-urban areas in the city of Kisangani from 1987 to 2021, based on morphological criteria. Results demonstrate continuous urban and peri-urban growth, with respective average annual change rates of 8.2% and 7.6%. The urban core area expanded from 13.49 km2 to 100.49 km2, resulting from an alternating process of diffusion and coalescence. Peri-urbanization indexes developed to assess the trend of the decline in urban densities indicate a phase of urban densification over the period 1987–2010 succeeded by a decline in urban density over the period 2010–2021 that is characterized by a large expansion of the peri-urban area. However, despite this trend observed between 2010 and 2021, the decrease in urban density was not effective between 1987 and 2021 in Kisangani, as the fraction of peri-urban area observed in 1987 remains equivalent to that observed in 2021. This suggests a continuity of urban densification despite increasing peri-urbanization.