Government holds urgent meeting to tackle floods in the East and Central regions as a large rain mass approaches from 23-26 September

The National Water Resources Office, or ONWR, has issued a warning urging relevant agencies to prepare for a new spell of heavy rain between 22 and 26 September 2026, after a strong low-pressure cell off the central coast of Vietnam was found to be moving in over Thailand along the monsoon trough. At the same time, the southwest monsoon will strengthen, bringing heavy to very heavy rain in some areas, especially the lower North, the lower Northeast, the Central region, the East, and the upper South. ONWR identified areas at risk of waterlogging, flash floods, forest runoff, and mudslides, covering many provinces such as Mae Hong Son, Tak, Phitsanulok, Uthai Thani, Si Sa Ket, Lop Buri, Saraburi, Pathum Thani, Nonthaburi, Bangkok, Samut Prakan, Kanchanaburi, Ratchaburi, Nakhon Nayok, Prachin Buri, Sa Kaeo, Chon Buri, Chanthaburi, Trat, Ranong, Songkhla, and Narathiwat. It also called for close monitoring of sudden rises in water levels and overtopping of riverbanks along major rivers and their tributaries, such as the Moei River, the Yuam River, the Mae Sariang stream, the Wang Thong River, the Phachi River, the Nakhon Nayok River, the Prachin Buri River, Khlong Phra Thueng, Khlong Phra Prong, the Chanthaburi River, Khlong Kapoe, the Sai Buri River, and the Kolok River. For the area downstream of Chao Phraya Dam, inflows through the dam are expected to reach 1,500 cubic metres per second, pushing water levels up by about 0.75 to 1.25 metres from current levels, affecting low-lying areas outside the flood barriers in Chai Nat, Sing Buri, Ang Thong, Phra Nakhon Si Ayutthaya, and Pathum Thani provinces. ONWR asked relevant agencies to continuously monitor weather and water conditions, especially in areas with more than 90 millimetres of accumulated rainfall within a 24-hour period, to inspect and repair riverside embankments, clear waterway obstructions, and manage water in reservoirs and drainage dams in a coordinated way from upstream to downstream. It also urged them to prepare flood response plans, personnel, and machinery, and to issue advance public warnings so that residents can evacuate in time.

The Department of Disaster Prevention and Mitigation, acting as the central disaster prevention and mitigation command, has coordinated with 10 central provinces, namely Uthai Thani, Chai Nat, Sing Buri, Ang Thong, Suphan Buri, Phra Nakhon Si Ayutthaya, Lop Buri, Pathum Thani, Nonthaburi and Samut Prakan, as well as Bangkok, to closely monitor the water situation in the Chao Phraya River, especially low-lying areas outside the flood barriers in Phra Nakhon Si Ayutthaya province. This follows the Royal Irrigation Department's forecast that on 27 September 2026, at station C.2 in Mueang Nakhon Sawan district, Nakhon Sawan province, the flow rate will be approximately 1,100 to 1,250 cubic metres per second, with an additional estimated 50 to 100 cubic metres per second from tributaries, putting the volume of water above the Chao Phraya Dam at between 1,150 and 1,350 cubic metres per second, with 400 to 450 cubic metres per second being taken into the irrigation system on both banks. Mr Teerapat Katchamat, Director-General of the Department of Disaster Prevention and Mitigation, said it is necessary to release water through the downstream side of the Chao Phraya Dam at a rate of between 700 and 1,000 cubic metres per second, which will raise water levels by about 0.60 to 1.50 metres above the current level in low-lying areas outside the flood barriers, namely Sena, Phak Hai, Bang Ban, Phra Nakhon Si Ayutthaya, Bang Pa-in and Bang Sai districts of Phra Nakhon Si Ayutthaya province. Community areas inside the flood barriers will not be affected. The central disaster prevention and mitigation command has asked the provinces to coordinate with local authorities and relevant agencies to inspect flood barrier lines, prepare disaster-response machinery and personnel to monitor the situation and provide assistance to the public around the clock, and to publicise warnings to private operators doing business along the Chao Phraya River, such as riverbank protection dam construction and restaurants, as well as to people living along both banks of the Chao Phraya River and the Noi River, urging them to follow the situation and move their belongings to higher ground away from the water's path.