Floodway construction worth 120 billion baht and covering 375,000 rai is expected to be finished 21/2 years from now.
The government project is intended to be a permanent solution to flooding in the Chao Phraya River plain.
It is part of a long-term, 350-billion-baht management initiative from the Strategic Committee for Water Resources Management.
Supoj Towijakchaikul, acting secretary-general of the Office of the National Water and Flood Management Policy, said the floodway proposal is the best alternative.
The money will cover construction of a two-kilometre-wide road that will double as a dyke, extending 300 km from Nakhon Sawan province to the Gulf of Thailand.
Water will be allowed to cover the road to a depth of 1.5 metres, while flow is projected at 2,000 cubic metres a second.
The plan includes two floodways. A 322-km eastern floodway will extend from the Pasak River to the Chao Phraya, while a 314-km western construction will go from the Tha Chin River to the Chao Phraya.
The western floodway will be easier to build due to the fewer number of communities and general construction along the path.
“I feel both floodways are crucial components of a permanent solution to the flooding. If there’s a problem with one, then the other can be used. Construction may be more difficult in the future due to growing communities and more construction,” said Mr Supoj.
He said the government also plans to build infrastructure to facilitate current residents and attract new communities.
An irrigation system is also in the pipeline to allow farmers to grow two or three rice crops a year instead of just one.
“The government has designated 350,000 rai of choice locations. That and the planned infrastructure improvements should attract residents,” said Mr Supoj.
He said flooding along the project area is expected for one or two months each year, so the government will also have to pay compensation for damage to crops and homes.
Residents can of course move to new areas, but for those willing to stay, the government will provide support by building them new homes of an environmentally suitable design.
The government expects to obtain funding for the project from domestic financial institutions.
It will accept proposals from local consultants and foreign government agencies in another three months, with the screening process completed by the end of September.
The US, Hungary, the Netherlands, South Korea, Japan, Italy, China and Israel have expressed interest in participating.
