Landslide occurred in the rock because of the intersection of  different set of joints and along joint planes. During heavy rainfall highly jointed and sheared rock mass started flowing down.

An Interim Report on Preliminary  Geological  Slope Stability Assessment of the Recent Disaster Affected Areas in Parts of Chamoli District, Uttarakhand by Bhupendra Singh, Bhupender Singh, Ajay Kumar and Arindam Roy, Senior Geologists, M-IV, NR GSI Dehr
UK_CHA_MDR_ 063
Retaining wall at the outer end of the road, breast wall with lined toe drain, spot bolting and layer of shotcrete with wiremesh.
Heavy rainfall facilitated planar and wedge failure in the rock which had inherent joints and shear planes.