Rasuwa: The Department of Hydrology and Meteorology has said that it has started a study to confirm the causes behind the massive floods that occurred in the Bhotekoshi river in Rasuwa district on Tuesday morning. Chief of the Department’s Flood Forecasting Division, Binod Parajuli, stated that satellite images are being analyzed to ascertain potential causes of the flood and its impacts on the riverbanks.
According to National News Agency Nepal, Parajuli mentioned that there are several glacial lakes in the Bhotekoshi water reservoir in China’s Tibet area. Initial observations and details from hydrology and meteorology centers suggest that heavy rain could not be considered a cause of the massive flood. Data from the Kyanzing meteorology center near China and another in Dhunche indicated sporadic rainfall. Additionally, the weather radar in Palpa showed no rainfall in the bordering area of Nepal and China in Rasuwa district.
The satellite-based rainfall forecasting guidance system of the World Meteorology Organization also reported no heavy rain at the Bhotekoshi water reservoir site in the past 24 hours, indicating that rain was not the cause of the flood. A flash flood entered the Bhotekoshi river from Tibet at 3:00 am, raising the water level at Timure of Rasuwa by 3.5 meters.
According to Parajuli, the riverbank areas in Rasuwa and Trishuli experienced severe impacts, with effects ranging from medium to normal from Nuwakot to Benighat area in Dhading. He has urged caution as the flood in the river is receding.
Meanwhile, the International Centre for Integrated Mountain Development (ICIMOD) stated that it is too early to determine the exact cause of the flood event in Rasuwa, emphasizing that extreme rainfall was not the cause. A comprehensive investigation is required, but clear satellite imagery is needed once the monsoon cloud cover clears.
A multidisciplinary team consisting of geologists, glaciologists, hydro-meteorologists, and remote sensing analysts should jointly undertake a study to determine the actual cause of the flood, the ICIMOD stated. While a Glacial Lake Outburst Flood (GLOF) or a Landslide Lake Outburst Flood (LLOF) is suspected, there is no conclusive evidence yet. The ICIMOD’s 2021 inventory shows one glacial lake upstream of the Trishuli river in Tibet Autonomous Region of China categorized as high risk, requiring close monitoring. Cloud cover has hampered optical satellite analysis, necessitating cloud-free, high-resolution satellite imagery to verify if any of these lakes have breached or if any sudden change in lake volume has occurred.