Continuous monitoring of ground deformation in Qatar, using Sentinel-1 InSAR time series

In this study, we present ongoing research to develop a semi-automated system for continuous monitoring of ground deformation for the country of Qatar (11,571 km²), using Sentinel-1 InSAR time series. The system, upon completion, will enable automated extraction, update, and analysis of deformation time series, identification of the anomalous deformation trends, and monitoring the impacts of major ongoing engineering and infrastructural projects, and areas susceptible to subsidence and collapse (e.g., sinkhole locations). The system will build on our initial radar interferometric analysis of a stack of 80 ascending and 46 descending Sentinel-1 data acquired between May 2015 and January 2019.The extracted deformation products including deformation rates and time series were validated against continuously operating reference stations of Qatar (CORS-Qatar; 6 stations) and are made available via an interactive web application. The factors controlling the observed deformation were investigated by conducting spatial and temporal correlations of the extracted deformation rates with relevant datasets (e.g., temporal variations in groundwater levels, surface and subsurface lithologies, landuse and landcover, optical multi-temporal imagery, and distribution of subsurface openings such as caves, sinkholes, metro construction locations). Findings include: (1) high rates of subsidence (up to -15 mm/yr) along recently reclaimed coastal areas, and extreme subsidence rates (up to -40 mm/yr) over landfills, dumpsites, and backfilled construction areas, (2) moderate subsidence rates (up to -10 mm/yr) over 2 circular topographic depressions (area: 0.1 km² and 0.8 km²) that could represent old collapse structures, and (3) moderate regional uplift (4-5 mm/yr) over two locations (20 km² and 50 km²) in areas proximal to waste water injection operations, areas where an increase (average increase: 2 m) in ground water level was recorded during the investigated InSAR period.