Uttarkashi flash flood satellite image analysis confirms cloudburst

Suhora Technologies has released satellite-based analysis confirming that the recent flash floods in Dharali village, Uttarkashi, were triggered by a cloudburst, not a glacial lake burst. This analysis was conducted following heavy damage to homes, public infrastructure, and roads in the region.

The incident occurred after intense rainfall in the upper catchment of the Kheerganga River. While initial media reports and expert opinions suggested a glacial burst, Suhora Technologies used Synthetic Aperture Radar (SAR) and high-resolution optical imagery to determine otherwise.

The analysis was carried out using SAR imagery acquired at 23:01 on 5 August through Suhora’s geospatial platform SPADE. The company also cross-checked data from the National Remote Sensing Centre (NRSC) and its own glacial lake inventory. The results ruled out the presence of glacial lakes upstream of Dharali, dismissing the possibility of a glacial lake outburst flood.

Impact on Infrastructure and Connectivity

According to Suhora’s findings, around 16 hectares of area have been affected. Nearly 148 buildings, including housing units and schools, have sustained damage. One bridge and approximately 0.95 kilometres of road infrastructure were also impacted. Portions of National Highway 34, which leads to Gangotri, were temporarily blocked. Power and communication services were disrupted in multiple areas. Several families were displaced, and reports of missing persons and livestock loss are under investigation.

As rescue and disaster-management operations entered the third day on 7 August, the Army reported that 70 people had been rescued, while over 50 remain missing. On 6 August, approximately 190 individuals were evacuated from the flood-affected region.

These disruptions have affected both local residents and public service continuity, raising questions about emergency preparedness and response coordination. The disruption of power and communications also delayed early assessments and response efforts in the initial hours following the disaster.

Investigation and Use of Satellite Monitoring

The Ministry of Home Affairs (MHA) on Wednesday asked the Indian Space Research Organisation (ISRO) to investigate the incident further. While Suhora’s data attributes the cause to a cloudburst, the Indian Meteorological Department (IMD) has stated that its records do not meet the technical threshold for a cloudburst, which is defined as rainfall of over 100 mm within an hour over a 10 square kilometre area. IMD officials cited the limited number of rain-gauge stations in the region as a potential limitation in the data collected.

The Wednesday meeting, convened by the MHA, brought together representatives from ISRO, IMD, the National Disaster Management Authority (NDMA), and scientists from IIT Roorkee to identify the primary cause. Officials suggested that satellite data might reveal hyperlocal weather patterns not captured by ground observatories.

Suhora’s deployment of near-real-time satellite imaging and cross-verification demonstrates the role of space-based observation in environmental risk assessment. The ability to detect infrastructure damage, track debris paths, and confirm the absence of glacial activity shows how remote sensing can support rapid response and long-term planning in hazard-prone regions.

Understanding SAR and Its Role in Disaster Tracking

Synthetic Aperture Radar or SAR is a radar that captures high-resolution images of the Earth’s surface using microwave signals. Unlike optical sensors, SAR can penetrate cloud cover and operate in both day and night conditions, making it particularly valuable during natural disasters where visibility is low or weather conditions are unstable. Mounted on satellites or aircraft, SAR systems send out radio waves that bounce off the ground and return to the sensor, enabling detailed imaging of terrain, structures, and water flow patterns.

During flood events like the one in Uttarkashi, SAR is used to map inundation zones, assess infrastructure damage, and monitor changes in land cover over time. It helps identify blocked routes, damaged roads, submerged buildings, and shifts in river paths. In this case, Suhora Technologies used SAR to acquire images of the affected area on 5 August, enabling early detection of damage and verification of the absence of glacial lake activity. By comparing SAR data with archived imagery, analysts can also track the extent of water spread and prioritise rescue and relief operations accordingly.

Krishanu Acharya, CEO of Suhora Technologies, said the incident signals the need for data-driven risk assessment in mountainous terrain. He added that satellite analytics could support planning and preparedness strategies across government agencies and communities.

The investigation remains open as multiple agencies continue to analyse the hydrometeorological triggers. Final confirmation on the cause will follow a detailed report by ISRO and the MHA.