No rain, but massive deluge: What really triggered Nepal`s sudden, destructive flash floods? EXPLAINED

There has been an unexpected flash flood in Nepal, resulting in extensive damage in Rasuwa, Nuwakot, Dhading, and Chitwan. Several bridges were destroyed, and there was damage to power infrastructure facilities. With the flooding waters flowing further south along the Narayani-Gandak river basin, Bihar and Uttar Pradesh governments maintain high alert status.

The disaster originated from the upper regions of Lhende river near the border with Tibet, striking the Rasuwa district before flowing further downstream. Efforts are underway to ascertain how much water gathered in the region so quickly despite a lack of heavy rainfall.

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The following three hypotheses have been put forward as explanations for the unusual flooding event. Meteorologists, disaster management officials, and open source intelligence (OSINT) analysts are working to verify them.

Debris dam bursting: The prevailing hypothesis states that there was a major avalanche of snow, rocks, and mountain debris blocking the river flow, thus forming a temporary natural dam. When the water pressure built up beyond the capacity of this blockage, it failed and unleashed the massive amount of water downriver.

Earthquakes and landslides: The initial reports suggested that the event might be connected to earthquakes in the vicinity of the border with Tibet. However, new data provided by USGS shows that the ground vibration was caused by the massive landslide.

Glacial Lake Outburst Flood (GLOF): According to senior meteorologist of Nepal, Min Kumar Aryal, Rasuwa experienced less than 7 millimeters of rain in the last 24 hours. This means that it is very likely that the cause of the disaster was a high mountain glacial lake bursting its banks.

This is due to the fact that the Trishuli River flows into the Kali Gandaki River at Devghat and forms the Narayani River, which enters India as the Gandak River at Valmikinagar.

Six districts in Bihar: Central Water Commission has identified six districts in the danger zone, namely, West Champaran, East Champaran, Gopalganj, Saran, Muzaffarpur, and Vaishali. NDRF and SDRF units are currently positioned in Betiah, Gopalganj, and Muzaffarpur.

Uttar Pradesh border: Officials in the Maharajganj and Kushinagar districts also activated the emergency plan due to increasing water levels.

While other separate rivers, like Kosi, Bagmati, and Ghaghra, are not affected, Gandak route requires constant surveillance due to the surge traveling towards the Ganges at Hajipur.

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