On the morning of August 26, at 8:40, the automatic gauge on the Bhote Kosi river at Nepal’s border with China recorded a water level of 1.62 meters, a low and decreasing measurement. This was the last reading from that station before a surge of water from the Lhende Khola obliterated the equipment. When the floodwaters struck Devghat later in the afternoon, the river reached a peak of 6.57 meters, which is below the warning threshold of 7.3 meters established by the Department of Hydrology and Meteorology.
Three monitoring stations ceased operations before hitting their warning limits. At Syaphrubesi, situated 15 kilometers downstream from the border, the gauge became nonfunctional at 3.8 meters; Betrawati’s gauge became inactive at 3.55 meters. The warning thresholds were set at 6 meters at Rasuwagadhi, 5.5 meters at Syaphrubesi on the Bhote Kosi, and 4.1 meters at Betrawati on the Trishuli.
The river peaked at Devghat at 4 pm on the Narayani River, which is 168 kilometers away from the Tibet-Nepal border. The Flood Forecasting Division noted a peak flow of 5,850 cubic meters per second, signifying a flood occurrence expected every two to three years.
The gauges were primarily designed for monitoring monsoon rains, elevating river levels to seasonal highs. Nonetheless, this flood was triggered by an avalanche, entering a gorge as debris and losing elevation as it moved. The gauges were not equipped to handle the swift increase in water level, which was substantial even though it was not exceptionally high upon reaching Devghat.
Belbase proposes a second catalyst for the unusual swift increases in river levels, which might have initiated earlier alerts at Malekhu and Devghat. On the day of the flood, alerts were issued based on forecasts a day earlier, and warnings were active for districts in danger. However, according to Belbase, there was a lack of a true emergency alert that bears immediate accountability.
The Flood Forecasting Division became aware of the flood through phone calls at 9 am. By 9:15 am, they set off high alerts for the Trishuli corridor, dispatching over 600,000 text messages warning of the impending flood. Warnings reached Devghat ahead of the floodwaters, emphasizing the limitations of in-channel systems in such circumstances.
The figures regarding fatalities and missing persons during the flood remain variable. Initial reports confirmed 469 deaths, with later updates significantly raising that total. The final count indicated more than 1,100 dead and thousands missing, with many believed to be trapped. While data and measurements fluctuate, the focus remains on enhancing the warning system to possibly save more lives in the future. The incident underscored that despite the current system indicating escalating threats upstream, it failed to issue warnings based on quick water level increases, highlighting the need for enhancement.