How Did The Nepal-Tibet Floods Become This Deadly?
It’s been almost two weeks since Harichandra Khadka’s family last heard from him.
As an operator for a hydropower project, he would often spend days away from his family, staying and working at the camp at Felung near the Trishuli River, between Timure and Syabrubesi in Rasuwa.
The last time his youngest son, Anish Khadka, 24, heard from him was during the early hours of August 26th. Since then, Khadka’s phone has been turned off. Shortly after, his family learnt of the glacier that crashed into the Lāṅṭāṇ National Park, in Rasuwa district, triggering widespread floods across parts of Nepal and Tibet.
“We [have] looked everywhere from hospitals in Kathmandu to Chitwan to see if Baba is there. We don’t know his whereabouts,” Anish told The Xylom.
From social media to reaching out to the local rescue teams and the federal government, the family is using all means necessary to locate the Khadka. Anish is fervently hoping that the army troops, armed police force, and police personnel deployed for search and rescue in Rasuwa and neighbouring districts will be able to find his father.
“We haven’t heard from anyone who used to work in the camp, " said Anish.
45-year-old Harichandra is one of over 5,000 people still missing in the deadly floods. As per the Ministry of Home Affairs' latest bulletin, the death toll has risen to 1,377 while 13,656 people have been rescued.
Scientists are still assessing the incident to trace how the disaster unfolded, and most importantly, how it swiftly turned destructive.
What Triggered The Disaster
So far, scientists have pieced together that a glacier broke off and crashed into the valley floor at the Langtang Lirung mountain, near the border with China.
At the U.S. Geological Survey (USGS), Benjamin Mirus’s team is monitoring the floods, looking for clues that will tell them more about it. “We know it was triggered by a rock avalanche that entrained rock, sediment, ice, and water to become a rapidly moving debris flow with devastating impact on the communities downstream,” the research geologist said in an email. The debris and associated floods travelled nearly 100 kilometers (62.1 miles), which affected downstream communities along the Lende Khola and Trishuli Khola rivers.
According to the USGS, the slope failure involving a glacier generated energy equivalent to a 5.2‑magnitude earthquake. A second seismic event was recorded approximately three hours later, generating energy equivalent to a 4.2‑magnitude earthquake,” the USGS reported.
Initially, it was believed that the flash flood was caused by an earthquake that triggered a glacial lake outburst or collapse.
Glacial rock and meltwater moved with debris and rubble, merging with rivers in the downstream valley. The river, filled with rocks and debris, surged downstream, swallowing settlements and taking lives in its path. It impacted settlements along the Lenden River, Trishuli, and Bhotekoshi river basins, including the Rasuwagadhi border post between Nepal and China.
Mirus uses the example of washing machines. In volume, the ice and rocks were equivalent to 100 million washing machines — enough to wrap two to three times around the globe.
“Now imagine those being dropped from a mountaintop into a valley... the crashing sound and vibrations make a seismic signal with energy equivalent to an earthquake,” he added.
Experts in the Hindu Kush Himalaya (HKH) region, which stretches 3,500 kilometers (2,174 miles) across eight countries from Afghanistan to Myanmar, including Nepal, say it resembles a version of the 2021 Chamoli flood in India.
“It looks similar to Chamoli, in that too rock and ice mass fell and melted, but the scale is very large here,” said Dr. Bashata Raj Adhikari, director of the Center for Disaster Studies under the Institute of Engineering at Tribhuvan University.
Based on the analysis so far, the assumption is that the debris and floodwater moved at about 180 kilometers per hour (112 miles per hour), he added.
“What remains unclear is exactly why it was triggered and how fast it moved. It is also unclear how often these types of magnitude events have happened in the past, which makes it difficult to attribute a trend or definitive cause,” Mirus added.
But the region is not new to disasters, from glacial lake outbursts (GLOF) and earthquakes to landslides and flooding.
Last July, GLOFs in Tibet caused flooding in Rasuwagadhi. A report published by the International Centre for Integrated Mountain Development (ICIMOD) in March found that HKH glaciers are melting faster than before, with ice‑loss rates doubling since the year 2000. This is forming new lakes while expanding the existing ones.
Scientists analyzed satellite images from the region to observe changes in the glaciers before the floods. The analysis of 20 satellite images taken between January 8th and August 19th identified that the internal part of the glacier, the site of the rock avalanche, had experienced faster movement, by up to one centimeter (0.39 inches) per month.
“Those faster rates coincide with what is suggested to be the site of glacial collapse that led to the flood disaster,” said Manoochehr Shirzaei, associate professor of Geophysics and Remote Sensing at Virginia Tech.
Early Warning Systems Could Have Made A Difference
At their home in Anbu Khaireni, about 250 kilometers (155 miles) southwest of where the flood tore through the district, Anish and his brother constantly hear how big this disaster was. Those who survived recount how, within moments, everything disappeared.
The sons still don’t know what they are waiting for or where their father is.
The rising death toll and ongoing search and rescue efforts in the geographically challenging terrain add to the fear faced by the kin of the missing people. Anish worries constantly about whether his father paid heed to the flood warning and managed to escape.
Ahead of a disaster, early warning systems that offer timely and actionable warnings can avert the magnitude of the tragedy and potentially save lives. These tools, which can range from ground-based sensors, satellites, and weather stations to advanced forecasting models that disseminate accurate and actionable warnings of oncoming hazards, are considered one of the most cost‑effective responses to adapting to climate change.
But from the rock avalanche to the first warning text, there was a 38‑minute gap, according to a report by the Kathmandu Post.
A rapid assessment report pointed out that no operational early warning system was set up in this area for glacier‑related hazards. The report further pointed out that given the rapid speed of the initial avalanche, warning time from conventional in‑channel systems would likely have been insufficient for successful evacuation at the Nepal–China border checkpoint at Rasuwagadhi.
Anil Pokhrel, former chief executive of the National Disaster Risk Reduction & Management Authority (NDRRMA), attests to this. “We need permanent channels between countries, including China, to share disaster risk information. But we don’t have it yet,” he added. He said that sharing information on changes in the mountains year-round, rather than only before and after disasters, would be more effective.
In Europe, member countries follow uniform information formatting rules to share data and predict potential avalanches through the European Avalanche Warning Service. The U.S. and Canada maintain daily direct communication to share fire situation reports and weather information to mitigate wildfire-related disasters. Under the Canada-U.S. Reciprocal Forest Fire Fighting Arrangement (CANUS), the two countries have standard operating protocols to work on transboundary effects of forest fires.
But in Nepal, the latest disaster revealed the reality of the existing early warning mechanism, its effectiveness, and the need for a permanent channel for transnational risk assessment and information sharing.
“This has to be the subject of policy decisions. Policy should not be only about economics,” said Shirzaei. “It’s about the exchange of knowledge, sharing science, and understanding knowledge. Those have to be part of the policy decision.”
In 2019, when Chinese president Xi Jinping visited Nepal, officials from the two countries signed a memorandum of understanding that included provisions for information sharing, risk assessment, and rapid response after disasters. But Pokhrel said it never materialized.
While families wait for their loved ones, China is facing accusations of a lack of transparency in hydrological and meteorological data and of not providing adequate disaster‑related information.
But Nepal’s government officials and Chinese officials in Kathmandu rejected these accusations, saying they are sharing information and are in constant conversation.
“Nepal and China have maintained regular coordination and exchange of information. This information‑sharing mechanism is part of the ongoing cooperation between the two countries and has continued in the context of the recent disaster,” the Public Diplomacy Division of Nepal’s Ministry of Foreign Affairs responded to The Xylom in an email.
Given the criticism, the Chinese embassy in Kathmandu issued two statements rejecting the claims since the flood. “Chinese expert teams have always made every effort, within the limits of existing technologies, to conduct monitoring, assessment, and analysis, and have shared important information with the Nepali side in a timely manner,” the statement reads.
This flood serves as a wake‑up call for the HKH region.
“We have to establish a regional information center for the HKH region to mitigate loss and work in collaboration,” says Adhikari. Nepal has recently sought climate compensation from the world’s largest emitters of carbon dioxide, China, the U.S., and India.
While countries exchange jabs at the global level, the Khadka family waits anxiously by the phone. “When night falls, your heart starts to get scared. Everyone is scared now,” Anish said.
