Nepal Flood Death Toll Crosses 1,000 With Nearly 4,000 Still Missing in Natural Disasters

Nepal's death toll from devastating floods triggered by a glacial collapse on the border with Tibet has crossed 1,000, with at least 1,114 people killed across both countries and nearly 4,000 still missing amid natural disasters. [2]

Death Toll Surpasses 1,000 in Natural Disasters

The death toll in Nepal from devastating floods on the border with Tibet has crossed 1,000. [1] At least 1,114 people have died in both countries, the vast majority in Nepal, and nearly 4,000 are still missing. [2] The glacial flood sent a gigantic wall of mud, water and rock through mountain valleys, knocking out at least four gauging stations and delaying public alerts by more than 40 minutes. [2] Last week's flood struck a border crossing at 8.32am, but a public alert was not issued until 9.13am. [2] The immediate danger from two barrier lakes near the border formed after the glacial collapse has passed after they drained. [2]

Nepal to Rebuild Border Warning System

Nepal plans to rebuild an early-warning system for landslides on part of its border with China, installing seismic sensors, cameras and a satellite link. [2] The equipment is being set up at Timure, a border settlement in Nepal's Rasuwa district on the same river corridor along the border with China where a collapsing glacier sent a gigantic wall of mud, water and rock hurtling through mountain valleys. [2] Central to the plan is a satellite system known as Very Small Aperture Terminal (VSAT), meant to keep monitoring posts connected even when mobile networks go down, so they can spot fresh hazards and issue warnings quickly. [2] Such a blackout occurred when last week's flood knocked out at least four gauging stations near the border. [2] Officials have already surveyed the area by helicopter to assess their placement. [2] An early-warning system for any landslide-triggered events would give authorities only a few minutes to alert downstream communities of another flood, a brief window that could still prove critical. [2]

Transboundary Rivers Link Nepal and India

Nepal has more than 6,000 rivers and streams, most draining south into India and the Ganges. [1] Three major systems dominate: the Kosi in the east, the Gandaki (Gandak in India) in the centre and the Karnali (Ghaghara in India) in the west, with the Mahakali (Sharda) along the western border. [1] A dozen smaller rivers rising in the Siwaliks and Chure including the Bagmati, Kamala, Rapti and Babai are less famous but can produce faster, more unpredictable floods because their catchments are small and steep. [1] Seven to nine major rivers flow from Nepal into the Indian plains, and they are responsible for flooding in India, according to Manish Shrestha, a hydrologist at the International Centre for Integrated Mountain Development (ICIMOD). [1] India's Central Water Commission identifies the Kosi, Gandak, Bagmati and Ghaghara as some of the main transboundary rivers. [1]

Indian States at Highest Risk

Bihar is by far the most exposed Indian state, with roughly three-quarters of north Bihar officially classified as flood-prone. [1] Almost all the major rivers that flood the state originate in Nepal, with the Kosi the most notorious, followed by the Gandak, Bagmati and Kamala. [1] Eastern Uttar Pradesh is vulnerable to the Ghaghara, Rapti and Gandak rivers. [1] Districts like Gorakhpur, Bahraich, Lakhimpur Kheri and Shravasti are regularly affected. [1] Uttarakhand state shares the Mahakali-Sharda rivers. [1] North Bengal receives the Mechi and Mahananda. [1] Bihar bears the greatest burden, but Uttar Pradesh is a significant and often overlooked part of the risk. [1]

What Determines Flood Impact in India

Think of it as a three-part chain, say hydrologists. [1] First, the rain: where it falls and how heavily. [1] Flood peaks reaching India are often generated not in the high Himalayas but lower down, in the Siwaliks, Chure and Terai, where intense monsoon rain can fall on steep, small catchments. [1] Second, the river. [1] Nepal's rivers cross a sharp break in slope at the mountain front, drop their sediment, and spread across the plains as braided, shifting channels. [1] Third, when the water meets India. [1] How bad the flooding becomes depends on what the water encounters the volume of rain on the Indian side, how full the Ganges is, embankments and barrages, and blocked drainage from roads, railways and settlements on the floodplain. [1] The 2008 Kosi disaster shows why: the river was carrying far less water than the embankment was designed to handle. [1] Nearly 400 people died in Bihar after the Kosi breached an embankment in Nepal. [1] The catastrophe was caused by the embankment failing, not by an exceptional flood. [1] The embankments constructed in the 1950s and 1960s had not been properly maintained. [1] They had become eroded and eventually developed a weak point. [1] The river breached its embankment through these vulnerable points and entered parts of India that had not seen flooding for perhaps 100 years. [1] The failure was structural, not hydrological. [1]

Gaps in Warning and Data Sharing

For ordinary monsoon floods, India may have roughly 12 hours to two days of warning, depending on how quickly the water travels downstream. [1] Water can take about a day to reach the Bihar plains from the Nepal mountain front along the Kosi and Gandak, and somewhat longer along the Ghaghara. [1] Flash floods from the Chure rivers can arrive within hours. [1] A landslide-dam burst or debris flow can be even faster in the current floods, the peak surge from Rasuwa reached Triveni, near the Indian border, in about seven-and-a-half hours. [1] India and Nepal do share real-time rainfall and river-level data from a network of stations. [1] Nepal's Department of Hydrology and Meteorology feeds rainfall and river levels to India's Central Water Commission, which uses them for flood forecasts. [1] But important gaps remain. [1] They include too few real-time monitoring stations in the fastest-flowing Chure catchments. [1] There's also no single shared forecasting model between the two countries; and limited routine sharing on embankment conditions, river-channel changes and sediment. [1] For these transboundary rivers, cooperation on information sharing and early-warning systems is extremely important. [1] We need rapid continuous monitoring of glacial lakes, their outflows and how they are changing over time. [1] Nepal had pressed China for more detailed, real-time sharing of data on glacier movements and water levels in the months before the disaster, and Nepali officials now plan to deepen their cooperation. [2]

What to watch next: The landscape is adjusting after the mega event, so it could trigger a few more landslides, and cameras, sensors and the VSAT will be installed at a single site by Nepal's National Disaster Risk Reduction and Management Authority with more to follow. [2]