Urban Expansion Amplifies Hydro-Saline Processes and Infrastructure Vulnerability in an Arid Coastal City: A Long-Term, Field-Calibrated Remote-Sensing Assessment

Abstract

In arid coastal environments, urban expansion alters land–water interactions, leading to increased soil salinity and moisture accumulation across urban landscapes. This study examines the spatiotemporal evolution of soil salinity and moisture, and land-use/land-cover (LULC) changes in Port Sudan, an arid coastal city that experienced rapid expansion from 2008 to 2024. The limited vegetation cover enables effective shortwave infrared (SWIR)-based assessment of salinity and moisture, facilitating multi-temporal analysis of LULC change and hydro-saline impacts. The findings demonstrate significant landscape transformation driven by urbanization, with built-up areas nearly doubling, substantial rangeland expansion, and a pronounced reduction in bare ground. These land-use transitions are accompanied by a marked inland expansion of salinity and moisture-affected areas, increasing from 8.12 to 40.36 km2 and from 120.15 to 245.49 km2, respectively, particularly within low-lying and reclaimed sabkha terrains. Urban growth exhibits strong correlations with hydro-saline intensification (R2 = 0.77 and 0.82), as increased surface impermeability and disrupted drainage promote salt accumulation and subsurface water retention. Field observations in representative urban areas confirm that persistent hydro-saline ground conditions are linked to salt crust formation, sustained surface moisture, and progressive corrosion of building materials and foundations. Time-series forecasting indicates that continued urbanization is likely to further extend hydro-salinity-affected areas through 2040, with projections suggesting a substantial spatial increase under current development trajectories, although with uncertainty related to environmental variability and temporal resolution. Overall, this study presents a field-calibrated, earth observation-based framework that connects urban expansion with hydro-saline processes and related coastal infrastructure vulnerability, supporting risk-informed planning and management in arid coastal regions.