Regional assessment of ground deformation in Greater Khartoum, Sudan, using Sentinel-1 SBAS-InSAR

Ground deformation monitoring is essential for understanding geohazards in rapidly urbanizing regions, yet regional-scale deformation assessments remain limited across Sudan. This study presents a regional Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) assessment of ground deformation across Greater Khartoum using 36 Sentinel-1 Single Look Complex (SLC) acquisitions obtained between January 2018 and December 2021. A network of 138 interferometric pairs was processed to derive a multi-temporal line-of-sight (LOS) deformation velocity field. The results reveal a spatially heterogeneous median-referenced LOS deformation field characterized by localized negative deformation, near-stable conditions, and positive LOS motion. The regional mean LOS velocity was −2.03 mm yr⁻¹, while median-referenced local LOS velocities ranged from −107.73 to +59.23 mm yr⁻¹. Velocity-class analysis showed that negative-LOS classes occupied 43.15% of the study area, the near-stable class 13.77%, and positive-LOS classes 43.08%. These proportions represent relative LOS motion within the adopted median-referenced frame and should not be interpreted as equivalent fractions of true vertical subsidence and uplift. Among the seven non-overlapping administrative units, Karrari exhibited the most negative mean LOS velocity (−14.61 mm yr⁻¹), while the separately evaluated Hilla Kuku nested analysis zone within Sharg An Neel showed a pronounced concentration of negative LOS deformation, with a mean velocity of −21.33 mm yr⁻¹. Hotspot sensitivity analysis using thresholds of −15, −20, and −25 mm yr⁻¹ showed systematic changes in mapped hotspot extent while preserving the dominant spatial concentration of strong negative LOS deformation. The results demonstrate that substantial localized deformation can occur within a region exhibiting a comparatively low mean LOS velocity, highlighting the importance of spatially resolved time-series analysis rather than reliance on regional averages alone. Beyond establishing a regional SBAS-InSAR deformation baseline for Greater Khartoum, this study provides a transferable multi-scale framework integrating LOS-velocity mapping, deformation classification, hotspot delineation and sensitivity testing, representative time-series analysis, and administrative-scale assessment for deformation monitoring in data-scarce urban environments.