The government has released a detailed technical report on the floods that occurred in Bhotekoshi, Trishuli and Narayani rivers on 10th Bhadra 2083. The report, prepared by the Department of Hydrology and Water Resources Research, Flood Forecasting Division, under the secretariat of the Water and Energy Commission of the Government of Nepal, covers in detail the impact of the flood from its origin to the lower coastal areas. According to the report, after the 4.4 Richter scale earthquake that occurred at 8:37 am on the 10th of Bhadra, an unimaginable flood entered the Bhotekoshi river from Tibet.
The Flood Forecasting Division received a formal notification of heavy flood entering Bhotekoshi at 9:05 am. As soon as the notification was received, the department started continuous monitoring of the impact on its lower coastal areas, the report states. The flood, which started from Tibet, entered the Trishuli river system through Bhotekoshi and gradually moved towards the lower coastal areas at a rapid pace.
The velocity of the flood was so fast that it completely swept away four important water measuring stations operated under the Hydrology and Water Resources Research Centre, according to a government report. Rasuwa Bhotekosi, Rasuwa Syafruvesi, Nuwakot-Betravati and Dhading Malekhu centers were swept away by floods, so the latest statistics of those places could not be obtained. Especially at 11:43 in the morning, immediately after crossing the danger level in Furke (Malekhu) center, the flood washed away the center and the bridge there.
Analyzing the flood wave travel time mentioned in the report, it appears that the flood reached the low-lying areas very quickly. The flood reached around Galchi of Dhading at 10:28 in the morning and reached around Malekhu Bazar at around 11:50. The flood, which crossed Muglin at 1:00 PM and caused havoc in the upper reaches, reached Narayani-Devghat area of Chitwan at 3:20 PM.
According to the statistics released by the government, the impact of the flood reached its highest point at 4:00 pm in the Trishuli river at Devghat. At that time, the water level at Devghat was measured at 6.57 meters and the flood flow was measured at 5,850 cubic meters per second. During this flood period, the estimated volume of water passing through Devghat is about 57.40 million cubic meters, and out of this, the volume of excess flood water is about 19.96 million cubic meters. After 6:30 pm, the flow in Devghat decreased and returned to the normal level of about 4 meters.
The report shows that early warning systems are widely used by the government to minimize potential damage during disasters. The Flood Forecasting Division sent a total of 679,295 early warning messages (SMS) through Nepal Telecom and Ncell aimed at the citizens of river coastal areas and highways. As the flood progressed, constant messages were sent to the villages around Prithvi Highway, Muglin-Narayanghat road section and Trishuli River to be on high alert and move to safe places.
Although the water level in the low-lying areas has decreased, the risk of disaster has not completely disappeared yet. The division has concluded that there is still a possibility of more water flowing in the upper Bhotekoshi area at any time as it has been informed that the lake formed at the point where the river is blocked towards China has not yet fully opened. Due to this, the Bhotekoshi-Trishuli-Narayani river system is being continuously monitored and the government has advised the residents of the potentially inundated areas to remain in safe places and exercise high vigilance until further notice.
