Spatial and Temporal Characteristics of Land Deformation in Northern Saudi Arabia: Inferences from Radar Interferometric Applications

Over the past two decades, land deformation phenomena and related losses in public and private property were reported from the northern part of the Kingdom of Saudi Arabia in Al Jowf region (100,212 km²; from lat: 29.25°N to 30.90°N, from long: 37.60°E to 40.70°E). We applied an integrated approach (geotechnical, geology, remote sensing, geodesy, hydrogeology, and GIS) to identify areas affected by these phenomena, quantify the nature and magnitude of deformation, investigate the factors controlling the deformation, and recommend solutions for these problems. We applied a three-fold approach in three different areas (Alisawiyah, Wadi Alsarhan, and Sakaka areas) to accomplish the following: (1) assess the spatial distribution of land deformation and quantify deformation rates using InSAR methods Persistent Scatterer Interferometry (PSI) and Small BAseline Subsets (SBAS); (2) generate a GIS database to encompass all relevant data and derived products (e.g., remote sensing, geology, geotechnical, GPS, groundwater extraction rates, distribution of urban areas, etc.), and (3) correlate findings from the InSAR exercise with relevant spatial and temporal datasets in search of causal effects. Findings revealed the following: (1) high and consistent subsidence rates (5 to 13 mm/yr) from multiple interferometric techniques; (2) subsided areas correlated largely with the distribution of irrigated agricultural land over alluvial and unconfined aquifers (e.g., Tawil and Jauf aquifers), areas characterized by high and a progressive increase in groundwater extraction (1.2 bcm/yr) as evidenced from the satellite-based temporal distribution of irrigated lands (area irrigated lands: 1998: 37,737 ha; 2013: 70,869 ha); (3) high subsidence rates ( 8 mm/yr) were also detected over urban areas (e.g., Sakaka, Dumat Aljandal, and Tubarjal ), subsidence being caused by disposal of wastewater in the subsurface leading to rise in water tables, dissolution of substrate rocks/sediments (e.g., carbonates, evaporates, sabkhas), and settling of buildings and infrastructures; (4) presence of numerous sinkholes within the Aruma formation (limestone and dolomite) that appear as incoherent circular domains (diameter range: 20 to 50 m) on the derived radar products within subsiding areas (subsidence rates: up to 6 mm/yr).