Chadchart warns eastern Bangkok of flood risk until Sept 27

Bangkok Governor Chadchart Sittipunt on Friday (September 25) warned residents in low-lying canal-side communities in eastern Bangkok to move belongings to higher ground and remain alert until September 27, as persistent heavy rain pushed water levels in several canals to critical levels.

The most closely watched areas include Min Buri, Lat Krabang and Sai Mai, where a lingering low-pressure system has brought widespread rain and kept drainage canals close to capacity.

The Bangkok Metropolitan Administration (BMA) has stepped up pumping and drainage operations, with pumps on the Phra Nakhon side running at full capacity of 1,200 cubic metres per second.

Heavy rain puts eastern canals under pressure

Rainfall reached as much as 133 millimetres overnight, followed by another 30mm from the morning into the afternoon across Khlong Sam Wa, Sai Mai, Min Buri and eastern areas extending to Lat Krabang.

Despite the heavy rainfall, Chadchart noted that major roads had seen relatively few problems, with most waterlogging confined to roads along canals and smaller side streets.

Runoff from the eastern districts has flowed into Khlong Saen Saep, Khlong Phra Ong Chao and Khlong Prawet before being directed towards the Phra Khanong sluice gate for discharge.

Chadchart stressed that the immediate priority was to lower canal levels as quickly as possible because the system remained under pressure and further rain was expected.

BMA pushes water towards Chao Phraya

The BMA is using large drainage tunnels, pumping stations, water-propelling units and sluice gates to move water out of the canal network and towards the Chao Phraya River.

One key facility is the Bueng Nong Bon drainage tunnel, which takes water from the Sukhumvit side towards Bang Na and the Bang Ao tunnel pumping station.

The station has six pumps, four of which are operating because inflow is currently about 40 cubic metres per second, below the system's capacity of 60 cubic metres per second.

Water reaches the station from the Bang Na-Sukhumvit 101/1 area via Khlong Nong Bon, Khlong Phet and Khlong Bang Ao before being discharged into the Chao Phraya River over a distance of about one kilometre.

Chadchart described eastern Bangkok as the main area of concern as canal levels remain high. He observed that although the canals were carrying large volumes of water, widespread road flooding had not developed in the inner city, which he attributed to improvements in drainage and pipe-clearing work.

He added that the city should be able to keep up with drainage if the rain eases to light showers. Officials have also been ordered to ensure drainage pipes remain free of blockages.

Canal-side communities told to prepare

More rain in the evening could still bring additional waterlogging, and officials have been deployed to monitor vulnerable locations. Residents were also urged to check travel conditions before setting out.

Chadchart advised canal-side households to remain prepared for heavy rain overnight, although he expected conditions not to become severe.

Areas along the Chao Phraya River in central Bangkok were not currently considered a major concern, but the city would remain on watch until September 27.

In canals where water levels are critical, water-propelling machines are being used to increase the flow while sluice gates are being managed to accelerate drainage.

Chadchart explained that the BMA could not simply push water from Khlong Prawet east towards Paet Riu in Chachoengsao because an irrigation canal lies in the way and such a move could affect farmers. Water management in that area is therefore controlled by the Royal Irrigation Department.

He added that the BMA had coordinated with relevant agencies and the neighbouring provinces of Samut Prakan and Chachoengsao, both of which were also dealing with severe flooding.

Drainage upgrades limit inner-city flooding

Comparing this year's drainage performance with 2025, Chadchart pointed to drainage tunnels already in service, improvements at several pumping stations, better drainage pipes and higher road levels as reasons some locations no longer flood as they once did.

He cited Ramkhamhaeng sois 21 and 24 as examples and noted that drainage infrastructure had improved in several areas, allowing roads to remain clear even when canals were full.

However, more than 200 of over 700 identified flood-risk points still needed improvement, a share Chadchart described as about 20%.

The low-pressure system remains over Bangkok, with its centre tilted towards the eastern side of the capital, unlike a monsoon system that moves through more quickly. It is expected to shift gradually westwards, with conditions likely to ease after September 27 once the system moves away.

Deputy Governor of Bangkok Wisanu Subsompon explained that Khlong Saen Saep and Khlong Prawet are among the city's main drainage canals.

Khlong Prawet receives water from Phra Khanong, Suan Luang, Prawet, Saphan Sung and Lat Krabang and requires accelerated drainage towards the Phra Khanong pumping station.

The Phra Khanong station also receives water from Khlong Saen Saep, while the drainage network is managed in conjunction with Khlong Lat Phrao. Wisanu noted that additional water was continuing to flow into the system.