The Disappearing Flood Buffers Around Our Cities
How Water Retention Areas Can Help Protect Cities from Flooding
Some people immediately understand the term “monkey cheek,” while many others are unfamiliar with how the system works.

How the System Works
For a simple illustration, imagine a house, factory, or other property covering one rai of land. It has a secure perimeter fence, a gate that can be opened and closed, and a prepared water pit measuring approximately 2 by 3 metres and 2 metres deep.
Under normal conditions, the pit may be covered with a strong lid so that the surface can be used for parking or another purpose.
When floodwater begins to surge into the area, the property is sealed as much as possible. Sandbags are used to block gaps where water may rise around the building, the pit cover is opened, and a water pump is prepared inside the pit.
In reality, fences and drainage channels cannot block water completely. Water will still seep in and spread across the property, but it will flow toward the pit because the pit is lower than the surrounding ground. The pump then removes the water beyond the fence to protect the property. This protection is effective as long as the floodwater does not rise above the fence, and the method is widely used.The Same Principle at City Scale

The Same Principle at City Scale
The monkey cheek system follows the same concept. The difference is that the small pit is replaced by large water retention areas. These may be natural wetlands or excavated basins built below ground level and distributed around major cities such as Bangkok or Hat Yai.
Because these basins surround the city, they are known as “monkey cheeks.” Together, they may cover hundreds or thousands of rai and are designed to receive and store water until it can be discharged.
During heavy rain or when large volumes of water enter an area, the water is directed into the monkey cheeks for temporary storage. It can then be pumped out as soon as the sea level falls or conditions allow the water to be released.
Academics, government agencies, and local authorities understand this basic principle. Many major cities have previously prepared monkey cheek areas to receive excess water.

Why Major Cities Still Flood
In 2026, however, major cities continue to experience repeated flooding. Does this mean the monkey cheek system no longer works?
The answer is no. The monkey cheek system still works well, and many cities around the world continue to use this concept for water management. The real problem is that monkey cheek areas are gradually disappearing.
The monkey cheek system is a royal initiative of King Rama IX and is widely respected. However, maintaining the system and making it work effectively through infrastructure and urban planning require decisions and management by the government and the political sector. Without such support, the retention areas cannot receive enough water, the system loses efficiency, cities flood, and people’s property is damaged.
Changes to urban plans, encroachment on natural water retention areas, poor maintenance, failure to dredge wetlands and prepare them for use, and cuts to infrastructure maintenance budgets are important reasons why monkey cheek areas become less effective and eventually disappear.

How to Bring the Monkey Cheek System Back
A lasting approach to flood prevention therefore requires the return of the monkey cheek system through three measures:
1. Enforce urban planning laws strictly Conserve natural water retention areas and wetlands that serve as monkey cheeks, and prevent them from being converted into construction sites.
2. Restore and improve existing monkey cheek areas Dredge canals and retention basins so that they have sufficient depth and can hold water at full capacity, and continue maintaining these waterways.
3. Invest in modern monkey cheek innovations Examples include underground water retention systems for cities where available land is limited.

The Decisions Behind Lasting Flood Protection
These three measures are widely understood among people who follow the issue. However, urban planning and government agencies operate under the authority of the political sector. If “old politics” continues to pursue conflicts of interest that benefit its own networks, it will neither understand nor pay attention to the monkey cheek system. Citizens must then bring in “new politics” that is free from conflicts of interest.
Only by bringing the monkey cheek system back can the flooding problem be resolved on a lasting basis.
Written by
Dr. Sitthichai Chawaranggoon
Chief Executive Officer (CEO) – SNP GROUP
Translated by
Parinya Visetpanitkij
Sales & Logistics Supervisor – SNP Logistics