VALIDATION OF NEW APPLICATIONS FOR INTERFEROMETRIC SYNTHETIC APERTURE RADAR [INSAR] DATA: GEOHAZARDS AND INFRASTRUCTURE DISTRESS

As part of the USDOT-funded research program RITA-RS-11-H-UVA, “Sinkhole Detection and Bridge/Landslide Monitoring for Transportation Infrastructure by Automated Analysis of Interferometric Synthetic Aperture Radar [InSAR] Images,” the authors validated new applications of InSAR data as a tool for early detection of geological hazards and incipient infrastructure failures, including sinkhole development, potentially dangerous rock slopes, distressed bridges, rock buttresses, and other geotechnical assets. First, by bringing the InSAR dataset into a GIS dataframe and georeferencing to published maps of sinkhole locations, locations of repaired sinkholes, and karst terranes, the authors were able to detect differences in average displacement velocities of InSAR data points (“scatterers”) with respect to their proximity to karst geohazards. Second, the authors correlated the InSAR signal characteristics with kinematic analysis of rock slopes using point-cloud data generated using digital photogrammetry and LiDAR. Third, the authors used displacement time-series of various InSAR scatterers to screen for compromised geotechnical assets and deteriorating infrastructure, and the findings were strongly confirmed by field inspection of previously-unidentified distressed bridges and a failing rock buttress, with strongly positive correlation values. Lastly, the authors used points yielded by a new processing method, referred to as “temporary scatterers,” to reveal areas of sudden or variable motion, greatly expanding the nature and number of data points and adding yet greater value to InSAR data. The validation of InSAR data for these purposes thus allows generation of GIS-based geohazard and at-risk infrastructure/asset maps and provides the opportunity to augment or eventually replace a periodic field inspection-based infrastructure management system with continuous performance-based system. Initial cost-benefit analyses suggest that deployment of such a system would yield positive cost benefits if the system allowed early stabilization of only one geotechnical failure, rather than a repair subsequent to failure.