Integrated Approach for the Assessment of Land Deformation in the Jazan City and Surroundings, Saudi Arabia

Abstract:

Jazan City is a growing (in size and population) industrial city in the Jazan Province and an important port on the Red Sea coastline of Saudi Arabia. Parts of the city are built on sabkha deposits and others on a salt plateau (diaper) that intrudes overlying sedimentary sequences. Both areas are reported to experience various degrees of ground deformation, causing severe damages to buildings and infrastructure. An integrated study involving remote sensing (i.e. optical, multispectral, and radar) and geophysical (gravity) was applied to address the following objectives: (1) identification of the spatial distribution and areal extent of lithologic units in the study area, (2) assessment of the factors controlling the deformation, (3) locating the areas that are most susceptible to present and future deformation, and (4) quantifying the relative deformation rates in various parts of the city. The following methodology was adopted: (1) deformation rates were extracted applying both Persistent Scatterer (PS) and Small BAseline Subset (SBAS) radar interferometric techniques using seven Envisat scenes over a time span of six years (from 2003 to 2009), (2) the extracted deformation rates were correlated spatially in a GIS platform with relevant datasets (e.g. lithology, soil type, geologic structures, subsurface data) to identify the factors controlling land deformation, and (3) temporal datasets (e.g. Tropical Rainfall Measuring Mission; TRMM) were used to investigate whether deformation rates are affected by rainfall intensity. Our preliminary findings indicate a spatial correspondence between the PS results: (1) subsidence rates (-1.4 mm/yr) correlates with the distribution of the mapped sabkha units and uplift rates (0.95 mm/yr) with the mapped distribution of salt dome plateau outcrops. The sabkha subsidence could be associated with agricultural activities, poor waste management practices, and large rainfall events that induce salt removal from the sabkha soil. Inspection of regional airborne gravity data confirmed our findings (listed above) and suggest that the salt plateau extends beyond the surficial mapped unit to the south and north of the Jazan City.