Tectonic and structural controlled landslide: a case study of Hardiya Nala Landslide, Inner Kumaun Lesser Himalaya (Uttarakhand), India

The study was carried out in the Inner Lesser Himalaya along the Karnprayag-Gwaldam-Jauljibi state highway near Thal (town) district Pithoragarh, Uttarakhand (India). This highway is of significance as it connects the interior part of the Kumaun region to other parts of the state. In the past, several landslides have occurred along Hardiya Nala, damaging the road and highway bridge, and even now, it poses a threat. This study is vital for designing the stability measures for the treatment of the landslide. Different rock mass classifications, rock mass ratings (RMR), slope mass rating (SMR), Q system and factor of safety (FOS), are co-relatable with the geological structural damage zone (GSDZ) for the landslide study area. Stromatolitic dolomite and variegated slates are the main lithologies in the area belonging to the Damtha Group. Field mapping marks the ductile and brittle-ductile damage zone in this area. In these GSDZ, SMR values vary from class III to class V, and Q values range from 0.08 to 3.27. SMR and Q values are justified by kinematic analysis at different elevations and FOS. This study shows that different rock mass classifications give similar results for the landslide investigation.