Nepal floods show us risks of unravelling Himalayan region

A Tibetan border crossing on a sunny day, an imposing building with people going about their business. Suddenly, crows start to fly away, people begin to run, and in seconds, waves, black and furious, come from either side and over the building, pincering the crowd. The camera relentlessly shoots as wave after wave of rock and water crash over the border post and tour buses until the screen turns black. Downstream, a Himalayan town’s multi-storey, multi-colour buildings stand perilously close to the water. Within seconds, the river rises, crashing against them, then washes away a bridge as though it were a twig.The current explanation has it that an enormous chunk of rock-and-ice fell over a kilometre into the Lhende Khola river system, in Nepal’s Rasuwa district on the Tibet border, causing a flood downstream that killed hundreds.This is not a one-off tragedy. Fourteen months ago, a supraglacial lake on the Purepu glacier rapidly drained, sending another flood down this valley. In 2024, there was flooding across the Himalaya; 2023 brought the Teesta disaster when South Lhonak Lake burst, as well as flooding in Himachal and Uttarakhand that July; and in 2021, Chamoli.It’s a pattern. They share a downstream lived reality: water smashing through concrete and steel, destroying lives and livelihoods. Upstream, however, the disasters begin differently. This week’s flood began with a rock-and-ice avalanche; Uttarakhand was a combination of flooding and unwise building; while Teesta was a glacial lake outburst. A satellite image shows hundreds of glacial lakes glowing like blue streetlights across the high Himalaya. Many form as glaciers recede, exposing hollows that fill with meltwater and rain. What holds the water back is often an ice dam or a moraine, the loose rubble a glacier dumped at its edge. But ice dams can thin, moraines can shift, and an avalanche can plunge into the lake. Then a reservoir built slowly empties in minutes.Rock-and-ice avalanches follow a different route. High in the Himalaya, permafrost — rock and soil that stays frozen year-round — acts like cement, holding otherwise unstable rock together. As the permafrost unfreezes, rock shelves loosen up; meanwhile, glaciers thin and shift on steep slopes. Eventually a section of rock, with a glacier on top, gives way. What arrives downstream is a debris-filled flood.Extreme rainfall, glaciers losing ice, and frozen ground losing its grip — these are the fingerprints of global warming. A new global database of glacier failures records over 100 break-offs in the 2010s, up from 54 in the 1970s, though some of this rise is down to better detection. A separate study showed the number of glacial lakes in the Nepal Himalaya rose from 606 in 1977 to 1,541 by 2017.Not every lake or glacier is a ticking bomb, nor does warming directly ‘cause’ every collapse. Think of it instead like diabetes in an ageing body: the immediate illnesses differ, while the underlying condition makes all of them likelier.Ice is also storage. In a subcontinent where rain falls in a few months but is used all year, that matters. Himalayan snow and ice release stored water gradually, sustaining dry season flows in the river systems below. What fell this week was a tiny fragment of that reserve, released in minutes. Rebuilding that ice, if it happens at all, takes a long time. That’s what climate change does. It releases reserves. We don’t want it now, but physics doesn’t care. The harder question is what happens when those reserves are seriously depleted.Return to the videos, and to what the water took. Nepal needs jobs. Tourism and hydropower matter, economically and geopolitically. The argument is not ‘do not build’. Across Teesta and the last two floods here, nearly 3.8 GW of hydropower capacity has been damaged or knocked offline. That’s not development; it’s bad business. But as one senior official told me, there is more than one way to build a road. This means that, as we create infrastructure and jobs in the region, we do it keeping warming front and centre in our plans.As for tourism: a few decades ago, pilgrims to Manasarovar set their affairs in order and bid farewell before leaving. That ritual, in a modern context, was an acknowledgement of risk. The risk remains even as we have hidden it behind travel agents and AC coaches. The older pilgrim adjusted himself to the mountain: route, pace, sometimes turning back. Today, we ask the mountain to accommodate our schedule. It will not. The answer is not ‘no tourism’, but more sustainable tourism.These waters descend through the Trishuli and the Narayani/Gandak to the Ganga. Our stories paint the Ganga descending with unbearable force, intent on sweeping everything away. It needs Lord Shiva to catch her in his matted tresses, so that she enters the world in streams. Today, as ice melts and rocks come apart, those locks appear to be loosening. We must reckon with that.