Detection and Monitoring of Very Slow Landslides in Vicinity of an
Artificial Reservoir using Advanced Differential SAR Interferometry: A
Case Study of Tehri Region, India
Abstract
Persistent Scatterer Interferometry (PSI) is a novel remote sensing
technique for monitoring land deformation on large scale. It is economic
and can be used for detection of land surface deformation in the past
given that the sensor should have passed over the area. The millimetric
precision of the technique makes it very useful. One of its application
is monitoring of slow moving landslides. In this study we have focused
upon monitoring of slow moving landslides in Tehri region of Uttarakhand
state of India. This area is landslide prone. Its susceptibility to
landslide has increased due to construction of artificial reservoir in
the region. The variation in reservoir drawdown level can be cited as
one of the reasons. In this study we have applied Persistent Scatterer
Interferometry on the stack of 20 Single Look Complex (SLC) scenes of
Envisat satellite of European Space Agency. We have performed
time-series analysis for period starting from 12 May 2008 to 26 July
2010. The methodology consists of selection of master image,
coregistration of other slave images to master image, calculation of
amplitude stability index, generation of reflectivity map. After this 19
interferograms were generated. On basis of this selection of Persistent
Scatterers (PS) is done. After that estimation and removal of
Atmospheric Phase Screen (APS) was done. In the end calculation of
time-series displacement of PSs is performed. From this analysis we are
able to identify the spatial location of slow moving landslides. In this
study we have identified PSs having nearly 40 mm/year of velocity.
Detected areas showing land movement away from the line of sight of
satellite, can be found on the rim of reservoir as well as areas 4
kilometres interior, away from the boundary of reservoir. These areas
are located near roads and places where anthropogenic interference is
there.