Nepal flood waters enter Ganga, Bangladesh on alert

Bangla Press Desk: The death toll in Nepal's Rasua district, bordering Tibet, has exceeded 579. Nearly 2,000 are missing.
This mountain slope, created by a glacier landslide and blocking the flow of the river, is flowing down into the Ganges basin in India through the Bhotekoshi, Trishuli and Narayani rivers. From there, its impact may also reach Bangladesh along with the flow of the Ganges.
However, as the floodwaters spread over a long distance on the plains, Bangladeshi geologists and water experts believe that the risk of direct major disasters from this flood water in Nepal is low. According to them, although there is no immediate major risk, it is important to closely monitor the situation of upstream rains and rising river water. In a report, the Daily Star said that the flash flood occurred in Nepal's Rasua district on August 26. Initial analysis suggests that an avalanche of ice and rocks in the high Himalayas blocked the flow of the Lend River. Later, the barrier was broken and mud, rocks and huge water came down at a great speed. At an observation post on the Trishuli River, the water level rose by about 9 meters in just 30 minutes.
This surge caused widespread destruction in the Narayani River basin from Bhotekoshi to Trishuli within a few hours. Bridges, roads, settlements and various infrastructure were washed away. The river's automatic observation posts were also destroyed in many places before sending signals.
Geologists say that such a flash flood is called a glacial lake outburst flood or gulf. The landslide of a glacier, the blockage of the river flow by ice and rocks, and then the huge amount of water breaking through that barrier, creates a terrible flood in a short time.
It is believed that such a process has worked in this flood in Rasuwa too.
Bangladesh has a direct geographical and hydrological connection with the river system of Nepal. The water will fall into the Narayani-Gandak river system through Bhotekoshi and Trishuli. Later, the Gandak will mix with the Ganges through Bihar, India. The water can enter Bangladesh through the Ganges via Farakka.
However, experts do not see any immediate threat of major flooding for Bangladesh. Professor Dr. Mushfiqus Salehin of BUET's Institute of Water and Flood Management said that the water coming down from Nepal will travel a long way and spread across the plains. As a result, its intensity should decrease significantly by the time it reaches Bangladesh.
He said that there are several glacial lakes in the relevant areas of Nepal. It is important to monitor these lakes regularly. Bangladesh will also have to closely monitor the flood and river water level data from India.
Md. Azahar Hossain, a researcher at the Bangladesh Geological Survey, also does not expect major damage directly. According to him, the speed of the water will decrease significantly while traveling about 450 to 500 kilometers from the source to Bangladesh. However, if there is heavy rainfall upstream in the next few days, a second round of flooding may occur.

For this reason, he suggested regular monitoring of rainfall and river water data from the Ganges basin in Bihar and Uttar Pradesh, India. The researcher also said that the water level of transboundary rivers including Farakka Barrage and Teesta Barrage will be monitored till the first week of September.
A joint study by ICIMOD and UNDP has identified 47 vulnerable lakes in the Himalayan region of Tibet, Nepal and India. According to experts, it is important to further strengthen information exchange and integrated early warning systems between Nepal, India and Bangladesh to deal with such transboundary disasters, as climate change increases the risk of glaciers and glacial lakes.
Although the immediate threat of major danger from this flood for Bangladesh is low, the incident has once again brought to the fore the long-term risks of Himalayan-dependent river basins. Therefore, experts now consider it most important to get accurate and rapid information about the situation upstream before the flood waters reach Bangladesh.
BP/TD