Damage at Khao Chuk Dam prompts urgent evacuation in Rayong as Prasae Reservoir exceeds maximum level

Authorities in Rayong province, eastern Thailand, ordered residents of at-risk areas to evacuate urgently on Monday, September 28, 2026. The order followed reports of damage at Khlong Ra-ok Reservoir, also known as Khao Chuk Dam, in Klaeng district. A separate warning was issued the same day over critically high water levels at Prasae Reservoir. Both warnings came during widespread flooding across the province after several days of heavy rain.

Khao Chuk Dam

The Thung Khwai Kin Subdistrict Administrative Organisation (SAO) warned that part of the dam's spillway structure had been damaged, raising concern about a possible breach and rapid flooding downstream. China Daily reported that cracks were also found in the reservoir wall, in addition to damage around the spillway.

Residents in affected areas were told to leave within one hour and to move their valuables to higher ground. According to China Daily, the evacuation covered residents of Thung Khwai Kin and Nam Pen, with possible downstream impacts in Kong Din and Khlong Pun. Three temporary evacuation sites were designated at Wat Chumnum Sung, Chamnan Samakkhi Witthaya School and Wat Noen Sombun.

Local authorities said the reservoir held about 23.5 million cubic meters, about 117% of its capacity, and water was still spilling over the structure. The outlet gates were fully opened to release water and reduce pressure on the reservoir.

Prasae Reservoir

The Prasae Operation and Maintenance Project, under Regional Irrigation Office 9 of the Royal Irrigation Department, issued its eighth water situation warning for Prasae Reservoir. The project reported the following conditions:

• The water level had reached 36.62 m above mean sea level, higher than the stated maximum of 36.57 m.
• Storage stood at 331 million cubic meters, reported as 112.6% of normal storage capacity. This is above the stated maximum storage volume of 322 million cubic meters.

Officials said they lowered the folding weir gates to protect the structural integrity of the dam. This lets more water pass downstream and reduces pressure on the reservoir. The gates will be raised again once water levels fall sufficiently and conditions allow.

Officials estimated that up to 279.65 cubic meters per second could flow through the spillway into downstream areas, equal to about 24.16 million cubic meters per day. Downstream residents were advised to monitor conditions and move belongings to higher ground.

Residents living near Prasae Reservoir told the media that this flooding is the worst they have seen in 60 years. They said the water rose too quickly for them to move their belongings to safety.

Other structures affected

In Thap Ma subdistrict, Mueang Rayong district, floodwater damaged a perimeter wall around Modern City Village on September 28. CCTV footage shared on social media by a resident shows floodwater rushing into the village after the wall failed. According to the resident, the wall had previously protected the community from flooding but could not withstand the strong currents. He said the entire community was inundated within about 20 minutes, with water reaching around knee height on the ground floor of his home.

In Pluak Daeng district, residents were urged to monitor the situation closely after Dok Rai Reservoir reportedly held more water than its capacity. Drainage operations were carried out in response.

Extent of flooding

The National Water Command Centre reported that Rayong recorded the highest rainfall in the country, at 289 mm.

As of 18:00 on September 27, the Rayong Provincial Disaster Prevention and Mitigation Command reported flooding at 10 locations across the districts of Klaeng, Mueang Rayong, Wang Chan and Ban Khai. Water depths were reported at between about 30 cm and 80 cm, and the most affected area had about 1,500 households impacted. No injuries or deaths had been reported at that time.

In Ban Khai, the Khlong Yai canal overflowed into several communities, particularly around the district office and market. Officials later declared Klaeng, Mueang Rayong, Khao Chamao and Wang Chan as disaster zones.