Scientists have urged local authorities of Mekong Delta provinces to adjust development plans so as to choose the right treatment and avoid serious consequences in the future.
They pointed out serious landslides in the delta were caused by sand overexploitation, too many houses on riverbanks as well as deep holes in rivers.
Flood in Mekong Delta.
The problem lies in the lost volume of sand which cannot be offset by the new sediment, said expert Duong Van Ni from the Can Tho University.
A large amount of sand has been lost mostly because of hydropower dams in the upper course, which prevent sand from going downstream.
Over-exploitation of sand is also a reason. However, the biggest reason is the treatment of the rivers and the sea, Mr Ni pointed out.
The alluvium reaching the delta can be divided into two groups: coarse sediment (sand, gravel, grit), and fine silt. There are natural deep holes In the riverbed, some of which have existed for 1,000 years.
Water from the upper course flows strongly towards the delta every June and July. It brings materials in the deep holes in the upper course to holes in the lower course.
Nearly 500 such deep holes in the river sections are found from the northern part of Laos to Vietnam. This means that sand needs hundreds of years to reach the delta.
While the volume of coarse sediment is on a sharp decrease because of the hydropower dams and sand overexploitation, fine sediment cannot enter fields because of embankment. So it has been drifting into the deep sea. The coastline then suffers from serious landslides.
He explained: “The coast is just like armor that protects the delta body. As the armor is torn, the delta's body will become vulnerable. We have misunderstandings about the ecosystem, and we engage in wrong behaviors. We then blame everything on severe nature. ”
Local authorities have to spend a lot of money to build dykes and saltwater prevention works. However, this only ‘gives a false sense of security’, according to Mr Ni.
