Move to fend off future floods
Project to safeguard Bangkok in pipeline
The Thai and Japanese governments are moving forward with the 3rd Outer Ring Road Diversion Channel megaproject to serve as the primary countermeasure to protect Thailand’s economic powerhouse Bangkok from future flooding.
The Japan International Cooperation Agency (Jica) has been conducting a study on flood management plans for the Chao Phraya River Basin, in collaboration with the Royal Irrigation Department (RID) and the Department of Highways (DOH), to develop a basic plan for the implementation of the 3rd Outer Ring Road and the Diversion Channel.
The construction of the 110km diversion channel running in parallel with the planned 3rd Outer Ring Road, diverting water from the area south of the Chao Phraya River dam, will help to mitigate damage from flooding in the Chao Phraya River basin.
The construction will span from Ayutthaya province to the Gulf of Thailand with a designed flow rate of 500m³/sec, protecting the key economic areas of the metropolitan region and surrounding industrial estates in a cost-effective manner.
“The 2011 floods caused considerable damage to Thailand, and largely damaged the heart of its economy,” said Somkiat Prajamwong, secretary-general of the Office of the National Water Resources.
“The enactment of Section 44 on the Water Resources Act handed us the responsibility to create a database of the country’s water flows, and find out ways to strengthen water resources management, finalise the master plan for countermeasures and calculate the project’s required budget,” Mr Somkiat added.
“The construction of the diversion channel is facing several obstacles, with environmental impact assessments [EIA] yet to be concluded.”
Mr Somkiat said Bangkok can currently discharge 2,800m³/sec, which is considered relatively safe in the majority of cases.
He added the major flood in 2011 was a rare case in which the water discharge even exceeded 3,000m³/sec, so the diversion channel would provide a greater safeguard if such events were to re-occur.
The five-year construction work on the channel will cost the government around 166 billion baht, he said.
The other option that the Thai government has is to develop the East Diversion Channel with the 270km Ayutthaya Bypass, which would cost approximately 293 billion baht and take 15 years to build, he said.
“The Outer Ring Road Diversion Channel should be selected as the top priority project as it has a higher cost-benefit ratio than the East Diversion Channel and requires less construction time,” said Toshiro Suzuki, senior director of Disaster Risk Reduction Group of the Global Environment Department of Jica.
“If the 2011 flood were to occur in a condition where the Ayutthaya Bypass was constructed before the Outer Ring Road Diversion Channel, flood discharge in the Chao Phraya River around Bangkok will increase, making it even more dangerous than the actual situation in 2011,” Mr Suzuki added.
“Dike heightening downstream of the Chao Phraya River and Outer Ring Road Diversion Channel should be prepared before the Ayutthaya Bypass as well, in order to ensure containment when discharges reach its maximum output,” said Mr Suzuki.
Jica has been providing assistance in flood management to the government since the 2011 flood.