Abstract

The catastrophic debris flow along the Melamchi River in Sindhupalchowk district on June 15, 2021, was a devastating natural disaster that severely impacted the local population and infrastructure. Twenty lives were lost, approximately 600 individuals from 260 households in two municipalities were displaced, and critical infrastructure—including residential and public buildings, roads, bridges, transmission lines, and the much-anticipated Melamchi Water Supply Project (MWSP) headworks—suffered extensive damage.

To assess the extent of this disaster, our research team conducted a field reconnaissance from June 21–22, 2021. This involved geo-referenced imaging, detailed field observations, and collection of soil samples to understand the sediment composition and deposition patterns. Aerial and satellite images were analyzed to compare the extent of the flooding before and during the event. The reconnaissance revealed that debris deposits, up to 10–15 meters thick in places, caused substantial aggradation, buried buildings, and rendered infrastructure unusable. The Melamchi-Helambu Road, connecting key locations, was severely damaged, with numerous sections washed away or turned into floodplains.

The study highlights the region’s vulnerability due to its steep topography, fragile geology influenced by the Main Central Thrust, and residual impacts from the 2015 Gorkha Earthquake. The field reconnaissance provided crucial data for evaluating the impacts, understanding contributing factors such as extreme rainfall and geomorphological conditions, and developing recommendations for disaster preparedness and mitigation.

Our ongoing research aims to inform stakeholders—including decision-makers, engineers, and community leaders—about the mechanisms behind debris flow events, their impacts on infrastructure and communities, and measures for enhancing resilience. The findings underscore the importance of proactive geotechnical studies and interdisciplinary collaboration to safeguard vulnerable regions and improve disaster risk management practices in Nepal.

Status:

Ongoing

Team:

Keshab Sharma, Saroj Karki, Mandip Subedi, Netra Prakash Bhandary, Rajan KC