BMA blames Bangkok flooding on low-lying terrain, heavy rain and rubbish-clogged drains

Bangkok’s drainage authority has explained that the capital’s repeated flooding during heavy rain is caused by a combination of its low-lying geography, rainfall exceeding system capacity and rubbish clogging key drainage points, as officials work around the clock to keep water moving.

The Bangkok Metropolitan Administration’s Drainage and Sewerage Department said on Wednesday (June 3) that the issue known to residents as “water waiting to be drained” is the result of both natural and man-made factors.

The department said Bangkok’s geography makes it particularly vulnerable to standing floodwater, while discarded rubbish often blocks drainage grates, sluice gates and other water channels, reducing the efficiency of the city’s flood response system.

Bangkok’s low-lying terrain makes drainage difficult

The department said Bangkok’s physical landscape is one of the main reasons the city is prone to flooding.

The capital sits on low-lying flat land and is often compared to a basin, making natural drainage difficult, especially during periods of intense rainfall.

Because of this, Bangkok relies heavily on pumping stations and large drainage tunnels to divert rainwater into the Chao Phraya River.

However, when rainfall exceeds the system’s capacity, or when drainage points are blocked, water can accumulate on roads and in low-lying areas before it can be pumped away.

Rubbish worsens flooding by blocking key drainage points

The department said rubbish remains one of the biggest and most difficult obstacles to effective drainage.

Items such as plastic bags, food waste, old mattresses and tyres are often dumped in public areas. During heavy rain, they can be swept into drainage grates and sluice gates.

Once these drainage points are blocked, the system has to work harder, while water flow slows down immediately. This causes floodwater to build up on road surfaces, affecting motorists, commuters and residents.

The department said the problem is not caused by rainfall alone, but also by everyday behaviour that creates blockages across the city’s drainage network.

BMA says officials are on standby 24 hours a day

The Drainage and Sewerage Department said its Water Control System Office has stepped up measures to reduce flood risks and respond faster when heavy rain hits.

Officials are stationed at pumping stations around the clock to monitor rainfall, canal levels and flood conditions in real time.

The BMA is also upgrading pumping stations to improve capacity, increasing the frequency of rubbish removal from drainage grates and lowering water levels in major canals to prepare for new rainfall.

The department said these measures are aimed at keeping drainage routes open and ensuring rainwater can be moved out of flood-prone areas as quickly as possible.

Public cooperation seen as key to long-term solution

The department said technology and infrastructure alone cannot solve Bangkok’s flooding problem if rubbish continues to block drainage channels.

It urged residents not to dump rubbish in public areas, rivers, canals or waterways, saying clean drainage routes would help water flow more quickly and reduce the risk of prolonged flooding.

The department said small acts of littering can create large-scale problems for the city, especially during the rainy season.

It added that public cooperation is essential if Bangkok is to manage heavy rainfall more effectively and reduce disruption for residents.