Kathmandu— A powerful flood that swept through communities along the Bhotekoshi River in Rasuwa district, Nepal on August 26th has claimed at least 57 lives, with search teams continuing to recover bodies as of Friday evening. The disaster impacted multiple downstream districts including Chitwan, Nawalparasi East and West, Gorkha, Dhading, Nuwakot, Tanahun, and Rasuwa, leaving over 1924 people missing. Initial suspicions of a glacial lake outburst flood (GLOF) have been replaced by evidence pointing to an ice avalanche as the primary cause, according to glaciologists.

From GLOF Fears to Glacier Collapse Confirmation

Early reports suggested the flooding was caused by a glacial lake outburst flood along the Nepal-Tibet border, potentially triggered by an avalanche damming the Lhende River. However, analysis of satellite data and ongoing monitoring revealed that a large block of glacier broke away and tumbled into the Lhende River, initiating the devastating event. Dr. Rijan Bhakta Kayastha, Professor of Glaciology at Kathmandu University, explained that the flood was not caused by a lake outburst but rather a “glacier collapse or an ice avalanche.” He confirmed there was no evidence of a large lake forming prior to the disaster, stating, “Satellite images do not show the formation of a large lake.”

The resulting avalanche carried ice, snow, water, rocks, gravel and other debris downhill at high speed. A debris-covered glacier lower down contributed to the volume of water and debris as supraglacial ponds emptied during the event.

Downstream Impact and Ongoing Monitoring

The floodwaters devastated communities along the Bhotekoshi and Trishuli rivers, particularly impacting Timure and Syaphrubesi. As of Friday evening, Chitwan district reported the highest number of recovered bodies with 222, followed by Nawalparasi East (134), Gorkha (47), Dhading (40), Nuwakot (38), Tanahun (31), and Nawalparasi West (28). Rasuwa itself accounted for 13 confirmed deaths. Qianggong Zhang, Head of Climate and Environmental Risks at the International Centre for Integrated Mountain Development (ICIMOD), reported that a dammed lake formed by the August 26th avalanche has begun to outflow.

While the lake currently holds an estimated few million cubic metres of water, Zhang believes gradual outflow is unlikely to cause major flooding comparable to the initial event. However, he cautioned downstream communities and rescue teams to remain cautious near riverbanks. The Department of Hydrology and Meteorology (DHM) is preparing to install CCTV cameras to monitor the area around Rasuwagadhi and Timure.

Secondary Lake Poses Limited Threat

Following the initial flood, a small lake formed as ice, soil, and rocks blocked an area. While this raised concerns about a potential secondary outburst, Dr. Kayastha stated that the pond was small and did not currently pose a serious threat. “At present, it is not alarming,” he said, adding, “But it is still too early to say what could happen later.” Binod Parajuli, chief at the DHM’s Hydrological Forecasting Division, confirmed the lake is overflowing but described the flow as muddy and not dangerous. He clarified that reports of the lake bursting on Friday were incorrect.

Rainfall Forecast and Rescue Operation Concerns

Meteorologist Binu Maharjan from the DHM forecasts moderate rainfall with potential for heavy showers in parts of Madhes Province, Tarai areas of Koshi, Bagmati, Gandaki, Lumbini, and Sudurpaschim provinces. Rasuwa, Nuwakot, Dhading, and surrounding areas are expected to receive mostly moderate rainfall, though isolated heavy downpours are possible. Maharjan indicated that the forecast is not expected to significantly disrupt rescue operations, with heavier rainfall likely concentrated in the afternoon on both Saturday and Sunday.

Search and recovery efforts continue as authorities monitor the outflow from the secondary lake and prepare for potential further rainfall in the affected regions.

(With inputs from RN)

Originally published on abcnews.com.np.