City Hall has warned communities along the Chao Phraya River to brace for flooding from Friday until Tuesday while nine provinces in the Central Plains Region have also been alerted after the Pasak Jolasid Dam sped up water discharges.
Bangkok governor Aswin Kwanmuang said the Meteorological Department has forecast that a monsoon trough would move across the lower Central Region and the upper South, causing heavy rain.
As a result, rain-triggered run-offs from the Chao Phraya River Basin will flow into the Chao Phraya Dam in Chai Nat, Pol Gen Aswin said.
Water is expected to flow into the dam at a rate of 3,200 cubic metres per second, he said, adding the Royal Irrigation Department has been asked to manage the water and divert it into irrigation canals.
This will help reduce the water volume to 2,700 cubic metres per second, the governor said.
He also said more run-off is flowing into the Pasak Jolasid Dam in Lop Buri so dam officials had to speed up water discharges at a rate of 900-1,200 cubic metres per second, resulting in water passing through the gauging station in Ayutthaya's Bang Sai district at a rate of 3,000-3,200 cubic metres per second.
As a result, water levels downstream of the Pasak Jolasid Dam will increase to between 1.20-2.40 metres and water levels downstream of the Rama VI Dam in Ayutthaya's Tha Ruea district will surge to between 2.30-2.89 metres from today until Tuesday, Pol Gen Aswin said.
"City Hall is monitoring the situation, particularly in low-lying areas along the Chao Phraya River in Bangkok,'' he said.
"We are also checking the strength of embankments which are 78.93 kilometres long on both sides of the river. Sandbags have been piled up in areas without permanent flood levees. All 97 water pumping stations along the Chao Phraya have also been checked for readiness,'' Pol Gen Aswin said.
He alerted Bangkok communities living along the Chao Phraya River, Klong Bangkok Noi, and Klong Mahasawat to prepare for flooding in the coming days.
There are a total of 239 households in 11 communities located outside the embankments in Bang Sue, Dusit, Phra Nakhon, Samphanthawong, Bang Kho Laem, Yannawa, Klong Toey, Bangkok Noi, and Klong San districts, he said.
They have been advised to move their belongings to higher ground to avoid damage caused by surging water levels, Pol Gen Aswin said.
Samroeng Saenphuwong, secretary to the National Water Command, warned people in nine provinces in the Central Plains to prepare for flooding as the Pasak Jolasid Dam speeds up water discharges.
The areas expected to be affected are riverside communities in Chai Nat, Sing Buri, Ang Thong, Lop Buri, Ayutthaya, Saraburi, Pathum Thani, Nonthaburi, and Bangkok.
Prime Minister Prayut Chan-o-cha on Thursday said the flood situation in several areas was still manageable partly because the provinces had followed the government's flood management plans.
According to one estimate, if no more storms set in, the flooding is expected to recede in 10-15 days.
Flooding has affected more than 200,000 households in 31 provinces over the past week and persists in 18 provinces to the north of Bangkok.
Flooding triggered by days of rain brought by Tropical Storm Dianmu ravaged 31 provinces in the North, Northeast and Central Plains.
A total of 6,335 villages in 190 districts were left awash by floods that affected 227,470 households, the Department of Disaster Prevention and Mitigation said on Thursday.