Forensic review of the Chamoli disaster and implications for the hydropower sector

A devastating debris flow occurred on 7 February 2021 in Chamoli district, Uttarakhand, northern India, resulting in more than 200 dead or missing. It originated as a rock and ice avalanche (sturzstrom). The source area, which has been identified as being around 3.25 km to the north of Nanda Ghunti peak (el. 6309 m), on the northern flank of Ronti Peak (el. 6029 m), has a history of significant rock/ice avalanches and landslides. The debris/mud flow emanating from this event destroyed the 13.2 MW Rishiganga hydro plant and covered the headworks of the 520 MW Tapovan hydro plant with mud. Forensic analysis of the source area has been undertaken to determine how the area has been preconditioned to lead to multiple regular large slope failures. Questions must be asked as to whether, and how, these aspects of the catchment a short distance upstream of the two hydropower schemes were assessed in relation to intended hydropower development.