By Purushottam P. Khatri
Kathmandu, Aug. 3: Experts who made an aerial on-site observation of the floods and landslides in Melamchi and Helambu areas of Sindhupalchowk district on Sunday have suggested relocating communities in lower costal area, pointed out risk in those areas for the next two months.
The National Disaster Risk and Reduction Management Authority (NDRRMA) Sunday afternoon conducted an aerial inspection of the Helambu and Melamchi areas of Sindhupalchowk after sudden flash floods Saturday night washed away 17 houses and a bridge at Chanaute.
Hydrological, geological and landslide hazard experts have informed that locations like Panchpokhari, Thangpal, Helambu and Melamchi are still at high risk of natural disaster at any time for the next two months.
A team of NDRRMA, including local people's representatives and experts, had inspected the source of Melamchi River in course of the observation.
Anil Pokhrel, CEO of the NDRRMA, said that there is a huge volume of debris deposited in the source of the River, where two other rivers Yangri and Larke also converge with the main river.
"After the return, we have tested soil samples of the source of Melamchi River," said Pokhrel. The test showed that the debris flowing in the river contains large amount of limestone that has been making the topography extremely fragile, Pokhrel said. When rainfall occurs, that limestone turns into mud and starts flowing along the river and when there is no rainfall, it turns into solid form of limestone, he said.
Shiva Kumar Banskota, a geologist at the Department of Mines and Geology, said that the lower part of the river could be washed away and may face another disaster in the next two months as a large quantity of mud and debris has been deposited near the source of the river which seems like a big playground filled with limestone mud and other stuff, Banskota said.
He further said, "Similar and even more dangerous flood may occur again in Melamchi."
The NDRRMA had also conducted a drone survey in the upper belt of Melamchi, Yangri and Larke rivers in coordination with international agencies after the floods on June 15, 2021.
"We have never experienced such a large debris flow in the Himalayan range," said Banskota. CEO Pokhrel said, "We have started studying the impact of the floods on Dolalghat and below."
Professor Bishnu Pandey said that there is a lot of erosion in Melamchi and Helambu areas due to narrow course of the river, which can generate more energy and force even when there is little rainfall.
Pandey, who returned from the on-site visit, said, "Landslides which have blocked the regular flow of the river should not be termed as flood because landslides cannot retain the regular flow of water for a long time, and as a regular process this has been happening repeatedly in Melamchi."
Professor at Pulchowk Engineering Campus Dr. Basanta Adhikari said that debris which had been deposited for a long time has just become 'reactivated'.
Dr. Adhikari said, "Debris might have been mixed up in different parts of the river and this lot of energy carrying debris flowing with water has been ravaging the lower coastal human settlement areas like in Chanaute market."

Requires detailed study
Experts have suggested a detailed study of the area. Deputy Secretary and Hydrologist Rajendra Sharma said that a ground like a small airport has been formed near the source of the river and huge quantity of debris has been flowing with the river. Such artificially formed ground of debris must be studied and researched properly, he said.
Stating that muddy water along with debris has been flowing in the area every 10 to 15 days, Sharma said, "It is necessary to conduct a detailed study of the location. It is also necessary to do a study on relocating the settlements from there immediately."