Mapping of deflection caused due to hydrostatic pressure using Differential SAR Interferometry (DInSAR) on Bhakhra dam

Abstract

Microwave remote sensing is truly the most rapidly emerging field of satellite remote sensing today. In a very short span of time, it has found variety of applications in almost every field which had seen optical remote sensing dominance. This shows that its both state of the art and a versatile non-evasive remote sensing tool. It has added advantage of all-weather availability and penetration abilities which the optical remote sensing lacks. Hence can be easily used for areas and months with dense cloud cover. Of the many applications of SAR (Synthetic Aperture RADAR) or Microwave remote sensing is its ability to map and monitor land surface deformations shown by both natural and man-made features over a period, which helps as an early warning for many possible disastrous events like structural failures in dams. The technique involved is Differential SAR Interferometry or DInSAR. DInSAR involves a repeat pass configuration of SAR Interferometry with minimum baseline. The presence of any random motion on the surface or surface features on earth, tends to decorrelate the backscatter signals and add noise to phase difference. Small change due to surface movements, causes change in phase difference which is measured precisely and accurately by this technique. This study aims to measure the deflection that has come over a period of one year on the walls of Bhakhra Dam in Himachal Pradesh in India, due to the change in water levels and pressure exerted by it. Using DInSAR, the deflection was measured to be around 0.952cm from August 2017 to October 2017.