Accounting for BOUlders in Landslide-flood Disaster Evaluation and Resilience (BOULDER)

Institute

  • University of East Anglia

Background

Landslides and floods are globally occurring natural hazards that pose a significant threat to human life and sustainable development. The most severe losses due to landslides occur in the less economically developed countries of Asia and South America, particularly in those with mountainous topography, earthquakes and monsoonal climates. Landslides and rockfalls in these regions often detach fractured bedrock and deliver large boulders downslope that block roads, destroy buildings and kill people. On entering the river channel network, boulders may be bulldozed by large floods and block hydropower infrastructure, jeopardising electricity supply and the economy. Thus, boulders may cause a cascade of hazards.

Aims

This project addresses specific landslide and flood risk-management problems brought to our attention by stakeholders impacted by boulders in the Upper Bhote Koshi catchment in Nepal, one of the most landslide- and flood-prone countries in the world. This project also addresses a lack of data and scientific understanding of boulder production on hillslopes (e.g. by landslides) and boulder transport in floods.

The boulder hazard map and boulder tracking system developed in this research will help make the Bhote Koshi Power Company and the wider hydropower industry more resilient to landslide and flood hazards. The research will also benefit organisations managing transport infrastructure and communities living on steep, landslide-prone hillslopes in the Bhote Koshi.

We will hold two project workshops bringing together project partners and relevant stakeholders from industry, local communities and government institutions with the help of Practical Action Consulting Nepal to research boulder hazard perception and enhance uptake of this research into risk-management practice at local and national governance level, ultimately to aid development in Nepal and South Asia.

Approach

  • Map boulders and investigate the controls on boulder production on hillslopes by landslides and rockfalls
  • Develop a new real-time GPS boulder tracking system with which to improve understanding of boulder movement in floods and monitor hazardous boulders
  • Engage with stakeholders to incorporate findings into disaster management plans and ultimately to increase resilience to landslide and flood hazards

Project site

The project will focus on the Upper Bhote Koshi (UBK) catchment to the north east of Kathmandu, Nepal, and has been designed with specific end users in mind in the UBK that are dealing with boulder hazards related to landslides and floods. This area is particularly vulnerable to boulder hazards as it is the main road link between Nepal and China and contains several major hydroelectric power plants including the Upper Bhote Koshi Hydroelectric Power plant (UBKHEP). The catchment encapsulates the multitude of natural hazards faced by Nepal.

In 2015, the catchment was shaken by the Gorkha earthquake, generating some of the highest densities of landsliding anywhere in Nepal. In July 2016, a complex monsoon flash flood entrained extremely large boulders (>8 m), some of which became jammed in the sluice gates of the UBKHEP, culminating in more than $110 million damage to the power station. The power station remains closed, resulting in lost revenue and compromising Nepal's energy supply. As the power company rebuilds and a further hydroelectric power station is built just downstream, it will be vital to properly account for future boulder hazards in landslide and floods.