Bengaluru: On the afternoon of August 5, a flash flood flattened around 20 hectares of the village of Dharali in Uttarakhand’s Uttarkashi district.It all happened in a matter of seconds: a dark grey angry river of mud came cascading down a narrow river valley. Cries rose in the background as hapless tourists filming the disaster on their phones from a hill nearby watched in shock. As the flood left behind sections of villages buried deep in sediment and debris, rescue workers are still struggling to even unearth the dead.The state government has still not released official figures of the number of people who died in the disaster. And six days after the disaster, rescue operations are still underway. Locals said that at least 200 people were still missing as of August 8, according to Reuters. A week after the floods, on August 11, the government issued its first official note and said that 43 were still missing.Before than, on August 9, Uttarakhand chief minister Pushkar Singh Dhami announced an immediate assistance of Rs 5 lakh each to the next-of-kin of people who have been killed in the floods, and for those who lost their homes.Nearly a week later, authorities are still clueless about what caused the devastating flash flood. It is “very unfortunate” that in this age of technology, there were no Early Warning Systems in place that could have helped evacuate people from harm’s way – despite a history of landslides, flash floods and changing rainfall patterns in the state – geologists told The Wire. Apart from this lack of preparedness, rampant construction in floodplains is also making people more vulnerable to such disasters, the scientists warned.n this screengrab from a video posted by @uttarakhandcops via X on Aug. 10, 2025, fire and rescue personnel remove debris at the disaster-hit Dharali area, in the aftermath of the recent flash floods, in Uttarkashi district, Uttarakhand. Photo: X/@uttarakhandcops via PTI Photo.Cause still uncertainThe cause of the floods that swept away parts of the villages of Dharali and Harsil in Uttarkashi district is still up in the air. And officials’ takes are contradictory.Though the Uttarakhand State Disaster Management Authority and several news reports such as this one cited a cloudburst as the cause, many scientists have since pointed out that meteorological data did not back a cloudburst in the area. Cloudbursts are a period of intense rainfall during a relatively short span of time.Per one report, the India Meteorological Department (IMD) recorded only 8-10 millimetres of rainfall in the area on August 4-5. This is nowhere close to the 100 mm threshold typically associated with a cloudburst.“I agree that it was not a cloudburst because the rainfall data on that day was very low,” said Y. P. Sundriyal, Adjunct Faculty-Geology at Doon University, Uttarakhand.However, the gradient of the stream (the Kheer Ganga joins the Bhagirathi river near Dharali) is very high and it is fed by the glaciers, Sundriyal pointed out. And Dharali is less than 15 kilometres from the Gangotri glacier as the crow flies. So a rock-ice avalanche could have triggered the flash flood too, Sundriyal said.Scientists and glaciologist at the Wadia Institute of Himalayan Geology, D.P. Dobhal, also concurred.“Rainfall can increase snow and ice melt on glaciers, and this could have temporarily accumulated in an area upstream,” Dobhal said.Even a small avalanche then could have triggered the water, already at high pressure, to flow down the steep slope of the Bhagirathi valley — turning into a flash flood at Dharali, he added. Reports from the ground suggest that the sediment and debris is at least 30-40 metres thick, he said.On August 7, the Department of Space’s Indian Space Research Organisation (ISRO) said that “intense rainfall” triggered the “catastrophic flash flood” that swept through these villages. The ISRO’s statement also included satellite imagery of the affected areas both before and after the floods.“The event highlights increasing vulnerability of Himalayan settlements to disasters. Scientific analysis is being carried out to ascertain the cause of the triggering event,” the statement read.Satellite Insights Aiding Rescue & Relief OpsISRO/NRSC used Cartosat-2S data to assess the devastating Aug 5 flash flood in Dharali & Harsil, Uttarakhand.High-res imagery reveals submerged buildings, debris spread (~20ha), & altered river paths, vital for rescue teams on… pic.twitter.com/ZK0u50NnYF— ISRO (@isro) August 7, 2025The satellite imagery showed that a “number of buildings appear to be submerged with mud/debris” in Dharali village. The statement also said that there were signs of partial or complete destruction and disappearance of several buildings in the flood-affected zone, “likely submerged or swept away by the intense mud flow and debris”.It also noted a “fan-shaped deposit” of sediment and debris at Dharali village, at the confluence of the Kheer Gad and Bhagirathi River. This sediment and debris deposit was spread across around 20 hectares, it noted.It is going to be a week since the disaster struck, but authorities still do not have any idea about what caused the flash flood, Sundriyal told The Wire. “No planning authority or government is in a position to say why this happened.”The ‘why’ matters because only then can scientists and authorities implement appropriate actions to deal with future disasters, including setting up efficient early warning systems so that people can be moved out of harm’s way in time.Though scientists have access to CARTOSAT satellite imagery which can give high resolution imagery of between 2.5 meters to even 1 meter, these did not work due to dense cloud cover, clarified Dobhal.“But we have to know what caused the flash flood,” he said.Where were the Early Warning Systems?One factor that aggravated the losses to human life at Dharali was the stark absence of any early warning system at all, Sundriyal remarked. The Uttarakhand government says it has Doppler radars, but where were they, the geologist asked.Efficient early warning systems are among the many immediate actions that scientists worldwide recommend countries invest in as increased global warming and climate change make extreme events far more intense and frequent than before. These include equipment such as Doppler radars, which can monitor weather conditions far more precisely than other radar systems, and across a larger area — within a radius of 100 kilometres.Uttarakhand, in fact, has three Doppler radars in total: one each at Lansdowne in Pauri Garhwal, Mukteshwar in Nainital and Surkanda in Tehri Garhwal. However, none of these are in the higher reaches of the Himalaya near where Dharali is located (less than 15 km from the Gangotri glacier). On August 8, Hindustan Times quoted home secretary Shailesh Bagauli as saying that he had requested the National Disaster Management Authority to set up three more Doppler radars in the higher elevations of the state.“The IMD has said that Uttarakhand does not have an Early Warning System [EWS] which can warn of high rainfall at more than 4,500 m. This is very unfortunate, we have so much technology but no EWS,” Sundriyal said.Though the Uttarakhand government says they have a specialised disaster management system, this will kick in only after a disaster happens, he added.“When scientists say the truth, the government thinks we are opposing them. We are not opposing anybody. We are simply saying that if you have installed that equipment, you can at least warn people…otherwise what is the point of early warning?”Search and rescue operation underway at flood-ravaged Dharali, in Uttarkashi, Saturday, Aug. 9, 2025. Photo: PTI.Encroachment on riverbanksThe village of Dharali is situated over a “paleo flash flood”, Dobhal told The Wire. This means that it already stands on loose alluvial deposits — making it very vulnerable. To make things worse, new construction and habitations had come up on the river bank and in the way of the river, he added.“They say that a river never forgets its old path, and this is what happened in the case of Dharali,” Dobhal told The Wire.Sundriyal too quoted similar phrases.“It is a natural phenomenon, a river always occupies its course. It will not encroach on a human settlement unless the settlement is constructed on the river [bed],” he said.Moreover, most Himalayan roads and highways are along the rivers and in valleys, and run on the banks of the river. In the rainy season the rivers are in full flow, and will occupy these areas. The government should ban this, or implement strong rules that ensure that people do not occupy such unsafe areas, Sundriyal said.“Planners should know the fragility of the Himalayas, they need to understand that climate-wise and tectonicity-wise this area is highly sensitive.”But neither Sundriyal nor Dobhal hold much hope. Both independently cited the example of Kedarnath and the devastating flash floods that ripped through the town in 2013. More than 6,000 people died in the floods, which were caused by the bursting of a glacial lake.“Even after 2013, areas where infrastructure damage has happened, buildings have come up in the same place…Many of the private constructions are by politically connected people who have money,” Sundriyal said.Post the 2013 Kedarnath floods, scientists including Dobhal prepared and submitted several reports recommending that the area not be disturbed for at least 5-10 years so that the ground stabilises.“Nobody cared,” Dobhal said. “The big boulders brought down by the flash flood have now been used for construction in that very area.”This is not just the story of Dharali but of every Himalayan town and village, Dobhal said. Many villages are situated on weak foundations and sediment mounds such as Joshimath.“We are overburdening the ground with unplanned development and construction,” Dobhal added. “We must understand the Himalaya.”