Rayong flood alert widens as Khao Chuk Dam and Prasae Reservoir raise concerns

Authorities in Rayong have ordered residents in at-risk areas to evacuate urgently after damage was reported at the spillway of Khlong Ra-ok Reservoir, also known as Khao Chuk Dam, while a separate warning has been issued over critically high water at Prasae Reservoir.

The Thung Khwai Kin Subdistrict Administrative Organisation (SAO) in Klaeng district warned on Monday (September 28, 2026) that part of the Khao Chuk Dam spillway structure had been damaged, raising fears of a possible breach and rapid downstream flooding.

Residents in affected areas were told to evacuate within one hour.

Three evacuation points were designated: Wat Chumnum Sung, Chamnan Samakkhi Witthaya School and Wat Noen Sombun.

The warning came as widespread flooding continued across Rayong following days of heavy rain.

Prasae Reservoir reaches critical level

Separately, the Prasae Operation and Maintenance Project under Regional Irrigation Office 9 of the Royal Irrigation Department issued its eighth water situation warning, reporting critically high levels at Prasae Reservoir.

The reservoir level had risen to 36.62 metres above mean sea level, exceeding the stated maximum level of 36.57 metres.

Water storage stood at 331 million cubic metres, reported as 112.6% of normal storage capacity and above the reservoir’s stated maximum storage volume of 322 million cubic metres.

To protect the structural integrity of the dam, officials said they had to lower the folding weir gates to allow more water to pass downstream and reduce pressure on the reservoir.

The gates will be raised again when water levels fall sufficiently and conditions allow, the project said.

Officials estimated that up to 279.65 cubic metres of water per second, equivalent to about 24.16 million cubic metres per day, could flow through the spillway into downstream areas.

Residents were urged to monitor conditions closely, prepare for rising water levels and move belongings and valuables to higher ground or other safe locations.

Authorities also advised the public to continue following official announcements as the situation develops.

Flooding affects four Rayong districts

The Rayong Provincial Disaster Prevention and Mitigation Command, under Governor Traiphop Wongtrairat, reported at 6pm on Sunday (September 27) that flooding had affected 10 locations across four districts — Klaeng, Mueang Rayong, Wang Chan and Ban Khai.

No injuries or deaths had been reported at that time.

In Klaeng district, the situation had yet to ease:

• Ban Na subdistrict, villages 1–11: about 60 households affected, with water around 80 centimetres deep.
• Thung Khwai Kin subdistrict, villages 2–11: about 300 households affected, with water around 80cm deep.
• Thang Kwian subdistrict and Klaeng municipality, covering 16 communities: about 250 households affected, with water around 50cm deep.

In Mueang Rayong district, flooding was also continuing:

• Choeng Noen, villages 1–7: about 1,500 households affected, with water around 30cm deep.
• Kachet, villages 1–10: about 250 households affected, with water around 40cm deep.
• Samnak Thong, villages 1–5: about 150 households affected, with water around 40cm deep.
• Taphong, villages 1–16: about 50 households affected, with water around 30cm deep.

In Ban Khai district, around 100 households in Chak Bok subdistrict, villages 1–10, were affected by water approximately 40cm deep.

Ban Khai communities hit by overflowing canal

At about 9pm on September 27, Ban Khai district chief Wichit Phaplongam inspected flooding in Ban Khai municipality after water levels continued to rise.

Water from Khlong Yai had overflowed into several communities and homes, particularly around the Ban Khai District Office and Ban Khai market.

Officials were continuing to monitor water levels and the spread of flooding while coordinating assistance for affected residents.

People in flood-hit areas were advised to follow official announcements closely, particularly changes in water levels and the direction of floodwater.

Traffic disruption reported towards Rayong

At 7.40am on September 28, heavy traffic was reported on the motorway from Chonburi towards Rayong around Bang Phra in Si Racha, with long queues of vehicles. Motorists were advised to drive cautiously.

Thap Ma Municipality in Rayong also reported that the Thap Ma–Khao Bot road was impassable, advising motorists to avoid the route and use alternatives.

The emergency warnings come as authorities monitor both local flooding and reservoir conditions across Rayong, with residents in downstream and low-lying communities urged to remain ready to evacuate if further warnings are issued.