Mapping seasonal soil deformation in expansive clay using synthetic aperture radar interferometry: A case study in Diamniadio, Senegal

Expansive clay soils, known for their moisture-driven volumetric changes, pose a critical challenge to infrastructure stability in rapidly urbanizing regions. This study presents the first quantitative assessment of seasonal soil deformation in Diamniadio, Senegal, using Persistent Scatterer and Distributed Scatterer Interferometric Synthetic Aperture Radar (PSDS-InSAR) techniques with Sentinel-1 data from March 2017 to July 2024. High-resolution time series and deformation maps were generated for 11 strategic urban sites using 793 interferograms processed via a wavelet-based InSAR approach. Results reveal a clear pattern of seasonal uplift during the wet season (July–October) and subsidence during the dry season (October–June), with vertical deformation amplitudes ranging from 0.5 to 5 mm. Localized subsidence was detected in key areas such as the United Nations House (−16.11 mm/year) and Dakar Arena (−2.28 mm/year), correlating with active construction and soil sensitivity. Angular distortion analysis identified critical zones where differential settlement exceeds empirical thresholds for structural damage, with total angular distortion values reaching up to 2.5 × 10 −3 . An exposure map combining deformation gradients and infrastructure distribution highlights high-risk zones, particularly in clay-rich soil areas. These findings provide a robust spatial and temporal characterization of soil behavior, offering essential insights for geotechnical hazard assessment and sustainable urban development in Diamniadio and similar contexts.