Assessing urban sprawl dynamics in Abidjan's peri-urban area (Cocody and Bingerville) using Spot imagery and fractal analysis (1988–2017)

Urban expansion in sub-Saharan Africa is accelerating, particularly in peri-urban areas surrounding major metropolises. This study assesses the dynamics of urban expansion in the municipalities of Cocody and Bingerville, located in the peri-urban fringe of Abidjan, Côte d'Ivoire, over the 1988–2017 period. Using multi-date SPOT satellite imagery (SPOT-1, SPOT-6, and SPOT-7), we applied an object-oriented classification approach in eCognition to map land use/land cover changes, followed by fractal analysis using the box-counting method in Fractalyse-3.0 to characterize the morphological complexity of urban sprawl. Results show that the built-up area increased from 15 km 2 in 1988 to over 85 km 2 in 2017, a fivefold expansion occurring primarily at the expense of vegetation cover, which declined from 53% to 37% of the total area. The fractal dimension D rose from 1.456 in 1988 to 1.613 in 2014 and 1.670 in 2017, indicating a progressive morphological complexification of the urban fabric, shifting from a relatively compact monocentric structure to a more diffuse, fragmented, and polycentric configuration. This increase in D reflects both densification and spatial diffusion, driven by demographic pressure, improved road accessibility, and land speculation. The study demonstrates the effectiveness of combining object-oriented classification with fractal analysis for monitoring urban expansion in data-scarce environments. These findings provide a robust methodological framework for urban planning and highlight the urgent need for sustainable land management strategies in the rapidly urbanising peri-urban zones of West African cities.