Nepal’s devastating floods: Why India is watching closely?

New Delhi: At least 105 Indians are among nearly 400 people reported missing after a massive flash flood swept through Nepal’s Rasuwa district along the border with Tibet on Wednesday.

The disaster has killed at least 95 people, damaged settlements and severely disrupted Nepal’s hydropower infrastructure. The scale of the disaster has also raised concerns in neighbouring India, particularly in Bihar, as floodwaters moved through the Trishuli river basin, which feeds into the Gandak river system.

But what caused the sudden flooding, why was its impact so severe, and why are downstream areas in India watching the situation closely?

The flash flood surged through the Bhote Koshi river at around 9 a.m., affecting Rasuwa and Dhading districts along the Tibet border as well as Nuwakot district, southwest of Kathmandu. According to the Nepal Tourism Board, 384 travellers, including 291 foreigners and 93 Nepali nationals, have gone missing in the Rasuwa floods. Among them are 133 Indian tourists and 37 Non-Resident Indians. Others include nationals from the United States, Malaysia, the United Kingdom, South Africa, Australia and the Netherlands.

The flood swept through settlements along the river and damaged roads, communications and other infrastructure. Chameli Gurung, deputy chair of Uttargaya Rural Municipality, told The Kathmandu Post that around a dozen settlements, including Syaphrubesi, Betrawati, Mailung, Salletar, Shantibazar, Pairebesi, Khalti Basti, Sole, Trishuli and Battar, were affected.

China's official Xinhua news agency reported that a mudslide on the Nepali side also hit the Gyirong port, disrupting road, communication and power links in the Shigatse region near the Nepal border. Nepal's hydropower infrastructure has taken a major hit because many projects are located along steep, narrow river valleys where access to fast-flowing water is essential for power generation.

The Independent Power Producers' Association Nepal said eight operational hydropower projects with a combined capacity of 354 MW, along with five projects under construction, were damaged in Rasuwa and Nuwakot.

Among the major operational projects affected were the 111-MW Rasuwagadhi Hydropower Project, 78-MW Sanjen Khola Hydropower Project and 60-MW Upper Trishuli 3A project. Nepal's Energy Ministry said around 430 MW of electricity supply was affected, equivalent to more than 12 per cent of the country's total hydropower capacity of about 3.2 GW.

Why is Nepal particularly vulnerable?

Initial reports suggest that an earthquake may have triggered an avalanche, which subsequently contributed to the severe flooding, according to Nepal's Foreign Minister Shisir Khanal, as cited by Reuters.

However, the exact sequence and scale of the event will require further assessment. This distinction is important because flash floods in mountainous regions can be triggered by several interconnected events including intense rainfall, landslides, avalanches, glacial lake outbursts and earthquakes.

Nepal's geography makes it especially susceptible to sudden flooding and landslides. The country lies in the young and geologically active Himalayas. Its steep terrain funnels water rapidly into narrow valleys and fast-flowing rivers. During the monsoon, intense rainfall can turn relatively small streams into destructive torrents within a short period.

The risk is further complicated by changes taking place in the Himalayan environment. Retreating Himalayan glaciers are leaving behind expanding glacial lakes, many of which are held back by unstable natural barriers made of ice, rock and sediment.

If a landslide, avalanche, earthquake or sudden surge of water destabilises such a barrier, enormous volumes of water can be released downstream in a very short period. That can produce a glacial lake outburst flood (GLOF) or compound flooding, where multiple hazards combine to amplify the damage.

Climate change does not necessarily explain every individual flood, but scientists have warned that warming temperatures are altering the Himalayan cryosphere and increasing the risks associated with unstable glaciers, glacial lakes and extreme rainfall.

Natural hazards become more destructive when people and infrastructure occupy vulnerable areas. Studies on flooding in the Kathmandu Valley have pointed to rapid urbanisation, deforestation, construction near rivers and floodplains, and inadequate drainage as factors that can increase flood exposure.

One assessment found that built-up areas in the Kathmandu Valley increased sharply between 1990 and 2020, while forest cover declined over the same broad period. Other research has identified obstructed or poorly maintained drainage channels, river encroachment, inappropriate land use, unmanaged sand mining and upstream deforestation as factors that can worsen flooding.

In a mountainous country with complex rainfall patterns, these human pressures can leave less room for floodwaters to spread safely.

Why is India watching the situation?

The Nepal floods have implications beyond Nepal because several rivers originating in or flowing through Nepal eventually enter India.

The Trishuli river basin feeds into the Gandak river system, which flows into Bihar. As water levels rose following the flash flood, authorities in Bihar moved to strengthen preparedness. The Bihar government said all 36 gates at the Valmikinagar barrage had been opened as a precaution as water levels rose.

A technical team led by a superintending engineer was also sent to the barrage to monitor the situation.

Chief Minister Samrat Choudhary separately reviewed the situation with senior officials from the state government, including the Chief Secretary, Disaster Management Department and Water Resources Department.