Interview: Neera Shrestha Pradhan
We need a reliable cross-border information-sharing mechanism in place
Neera Shrestha Pradhan, Water and Disaster Risk Reduction (Water and DRR) Lead at the International Centre for Integrated Mountain Development (ICIMOD), speaks to Prothom Alo's Partha Shankar Saha about the recent devastating flash flood in Nepal. She says that when a glacier snout breaks off, it can release not only water but also a thick and fast-moving mixture of ice, sediment and debris, which can be far more destructive than a conventional flood.
From a water systems perspective, how does a glacier snout breakoff of this scale affect downstream rivers and communities? Can the sudden release of ice, water, sediment and debris significantly amplify the volume and destructive power of a flash flood?
Neera Shrestha Pradhan: The glacier snout breakoff of this scale will not only increase the volume of water but brings the mix of ice, water and debris that moves downstream of the river channel as a thick, fast and heavy slurry. This will be far more destructive than just flood water damaging whatever comes within its pathway. More importantly, for the communities downstream, it will be a sudden impact without any pre-information. That means they will not be prepared for this unforeseen disaster.
What makes the Himalayan river system particularly vulnerable to this type of sudden glacier-related disaster? Are there specific river basins in Nepal where a similar event could cause much greater damage?
If you look at the topography and elevation of Nepal - Himalayas (3000–8848m), Mid-hills (1000–3000m), Mahabharat range (1500–2700m), Chure hills (600–1500m), and Terai (60–300m). This means, Nepal's rivers drop steeply from very high, cold, glaciated terrain into narrow valleys where communities live and infrastructures are built along this way. ICIMOD (2021) report shows that there are 26 GLOF events recorded in Nepal since 1977, and 11 of these have had transboundary impacts between China and Nepal. There are 47 potentially dangerous glacial lakes, out of which 25 lies in China, 21 in Nepal, and 1 in India, covering the Koshi, Gandaki, and Karnali river basins across Nepal. These are potential to future hazards.
How much of the current risk comes from changes in the glaciers themselves, and how much comes from increasing settlements, roads, hydropower projects and other infrastructure along vulnerable river valleys?
This needs a detailed research and is context dependent.
In your view, are existing flood forecasting and river-monitoring systems in Nepal capable of detecting a sudden glacier-related flood early enough to warn downstream communities? If not, what are the biggest gaps?
Neera Shrestha Pradhan: Nepal has made progress on rainfall-triggered flood forecasting. There are hydro-met stations installed along the main rivers but they are not sufficient to detect a sudden glacier-related flood. For this, we need real-time monitoring stations in remote high-altitudes and sensors to detect ice-mass movement. Also, we need a reliable cross-border data/information sharing mechanism in place.
Could real-time monitoring of glacier fronts, high-altitude lakes, river discharge and weather conditions help provide an early warning for events like this? What technologies or monitoring systems should Nepal prioritise?
Real-time monitoring of glaciers and river discharge will certain help in providing early warning in these types of events. Satellite based monitoring of glaciers and lake, automatic sensors for river-discharge and turbidity, and seismic sensors to detect landslide and ice collapse from an earthquake might be useful for the monitoring. Besides that, ICIMOD’s experience on community-based flood early warning systems, which is simple, low-cost water-level sensors that alert villages by mobile phone or WhatsApp has also helped communities to get more time for preparedness. Combination of these technologies will help Nepal to provide early warning to save lives and livelihoods of the downstream communities.
The recent disaster also affected areas across the Nepal-China border. From a water-management perspective, what kind of cooperation between Nepal, China, Bhutan and India is needed to monitor and respond to such transboundary hazards?
In my opinion, we might not need the exact river flow “data”, which might be difficult. If we can share the “information” about the water level rising in upstream, then the downstream communities can use to it prepare themselves, which will save lives and livelihoods.