MONITORING THE UNSTABLE SLOPES ALONG THE RESERVOIR RIM OF KOLDAM IN HIMACHAL PRADESH USING TEMPORAL UAV SURVEY

Abstract

The functioning of dams and reservoirs is significantly impacted by landslide occurring along the reservoir rims. Occurrence of landslides inside a reservoir's watershed may lead to genera-tion of a significant amount of debris reducing the storage capacity of the reservoir. However, quantification of volume of debris is difficult. Therefore, in this work I have worked towards quantifying volume of debris mobilized from landslides along a reservoir rim. Two large land-slide locations were selected for this research. I have used temporal UAV survey for monitor-ing these landslides. I have used a micro category surveying UAV, a high-precision GNSS re-ceiver as the base station for temporal surveys. Then collected several overlapping, high-resolution photos that lead to the development of temporal point clouds and temporal digital elevation models. The raw GNSS data was corrected with the CORS data for increasing the lo-cational accuracy of digital elevation models. The first site is about 1.25km upstream at the left bank of Koldam along the reservoir rim. The second one is about 2.75 km downstream of Kol-dam at the right bank of Sutlej River. Field surveys were carried out at the two landslides with the help of Rhyno UAV in September 2023 and February 2024. Digital Elevation Models (DEMs) of the landslides were generated with aerial images obtained from the two different UAV flights with the help of Structure from Motion technique. I have then used the temporal DEMs for quantification of the volume change at the surface within the landslide area over a period of four months. The volume of the mass movement at site1 was 4784.78m3 and 1091.46m3 at site2. Results demonstrate the usefulness of temporal UAV surveys for examin-ing the dynamics of landslides along the reservoir rims.