Identification of 3-D Landslide Displacement in the Outer Himalayas from Temporal High-Resolution Digital Surface Models Obtained Using Terrestrial Laser Scans

Uttarakhand is a state in India and is prone to landslides of different types and sizes, predominantly in the monsoon season. In particular, landslides in the Outer Himalayas (Shivaliks) are man-made due to the construction of roadways and highways. Our aim was to ascertain the 3-D displacement of man-made landslides during the tourist season that falls between June and September of each year coinciding with the monsoon season in the region. We selected two epochs, separated by ten days, to study the displacement due to a landslide along the national highway NH-7 in Uttarakhand. The field methodology was the same for both epochs: positioning terrestrial laser scanner (TLS) at equal intervals parallel to the landslide scarp and away from the landslide equal to the road width at each position. The scanning angles were kept 0–360° and − 60° to 90° in horizontal and vertical direction, respectively. For better identification of features within the scan, laser points were collected by the TLS four times at each location within the scan. We collected 10 scans which were subsequently co-registered to create a point cloud of the whole landslide for each of the two epochs. We removed artifacts to clip the point cloud corresponding to the landslide scarp. Finally, we applied the M3C2 method to the two epochs to identify landslide displacements in the x, y, and z directions. Collectively, we were able to show the potential of TLS to study landslide displacements in the Indian Himalayas. This work will be useful in understanding displacement rates of debris outflows in the Himalayas.