The Indian Institute of Remote Sensing (IIRS), Dehradun has carried out a study on the incidents of landslides in the vicinity of hydro projects and has prepared a report on landslide studies in commissioned / under construction hydro projects utilising remote sensing and GIS technology. The study revealed that landslide activities around hydropower projects are not related to the construction activity of the project while the topography, geological conditions and rainfall have been found to be the major causative/ triggering factors of landslide activities.

According to official sources, the IIRS carried out the study in nine NHPC power stations/ projects which include Dhauliganga in Uttarakhand, Subansiri Lower in Arunachal Pradesh, Teesta-V and Rangit in Sikkim, Salal, Dulhasti and Uri-II in Jammu and Kashmir, Chamera-I and Parbat-II in Himachal Pradesh. The study undertook preparation of landslide inventory maps 10 years before the start of construction of the project upto the current status of the project/ power station. The report highlights that in most of the cases, the landslide area decreased considerably in comparison to the landslide area observed before construction of the project. According to the report, it appears from the temporal statistics that in most of the cases, the construction of hydropower projects and related activities and post commissioning hydrological condition might have helped in stabilising the area. Further, the size of hydropower projects, size of reservoir, local geology, soil and land cover conditions (especially vegetation cover) seem to play some slope stabilisation role for mitigating landslides in the project areas.

The report has been prepared with the help of satellite image-based interpretation, subject to resolution and availability of satellite image.