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Himalayan Geology, Vol. 41 (1), 2020, pp. 21-30, Printed in India

Geodetic Monitoring of Landslide Movement at two sites in the Garhwal Himalaya

RAJEEV K. YADAV1, V.K. GAHALAUT2, PARAM K. GAUTAM3, R. JAYANGONDAPERUMAL3*, K.M. SREEJITH4, ISHWAR SINGH3, AMIT KUMAR2, V. JOEVIVEK3,5, RITESH AGRAWAL4, JOSHI K. CATHERINE2, S.P. SATI6

1Institute of Seismological Research, Ahmadabad, India

2CSIR-National Geophysical Research Institute, Hyderabad, India

3Wadia Institute of Himalayan Geology, Dehradun, India

4ISRO-Space Applications Centre, Ahmadabad, India

5Akshaya college of Engineering and Technology, Kinathukadavu, Coimbatore, India

6Dept. of Basic and Social Science, V.C.S.G. Uttarakhand Univ. of Horticulture and Forestry, Bharsar, Pauri Garhwal, India

* Email (corresponding author): ramperu.jayan@gmail.com

Abstract: Three continuously operating GPS sites were established in the Garhwal region for monitoring landslides in the Main Central Thrust (MCT) region of climatically sensitive Bhagirathi and Mandakini Valleys. Two adjacent sites at Bhatwari (BHTW) and Raithal (RATH) villages in the landslide prone MCT zone in Bhagirathi valley, record time varying rapid eastward movement in the downhill slope and bedrock dip direction. The site RATH, located at the crown is moving at slower rate than the site BHTW in the toe, since 2006. The relative motion between these two sites appears to be increasing with time and it is consistent with the ground deformation features observed in the region. Another site at Guptkashi (GUPT) of Rudraprayag district in Mandakini valley, ~50 km southeast of Uttarkashi region, also show rapid horizontal movement. The geodetic motion at BHTW and RATH, are also complimented with Interferometric Synthetic Aperture Radar (InSAR) analysis. These results along with the high resolution field surveys using RTK (real time kinematic) and detailed field investigations suggest that BHTW and RATH sites, located on a gently sloping spur size of ~2×2 km2 exhibit a creep motion towards east since 2006 at a rate of 12 mm/year, which increased to 22 mm/year in 2016. However, it is not obvious whether the measured movements in this region may lead to catastrophic landslides during an earthquake or monsoon (seasonal or extreme event) and thus a detailed monitoring of the two identified regions is warranted to avoid the potential secondary effects such as the damming of Bhagirathi and Mandakini river and subsequent floods.

Keywords: NW Himalaya, GPS measurements, creep, SAR and Landslide.

 
 
 
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