Floods: Thailand faces a risk of economic collapse

Without urgent investments to address flooding, Thailand could suffer major damage and a lasting economic crisis.

Thailand is facing extreme rainfall and rapid water rise, revealing serious flaws in its water management system.

Chawalit Chantararat, a hydraulic resources engineer and member of the board of directors of TEAM Consulting Engineering and Management PCL (TEAM Group), is one of Thailand's leading experts in water management.

He has warned against the critical shortcomings of the country's flood response system.

He highlighted the lack of a legally binding national master plan for water management and the obsolescence of infrastructure, which can no longer withstand current extreme weather conditions.

He urged the government to invest urgently and proactively in large-scale strategic projects, such as “monkey-cheek” type “sea water retention reservoirs”.

Without these measures, future economic losses could reach tens of billions of baht.

The “new era” of disasters in Thailand is exceeding limits

Chawalit noted that Thailand is now facing a permanent climate change, with a clear turning point from 2021.

The old assumption that disasters are temporary is no longer valid, he said.

Shift to high-intensity rainfall

In recent years, there has been a significant shift to high-intensity rainfall, commonly referred to as “torrential downpours”, which has put unprecedented pressure on urban drainage systems.

Localized extreme downpours

Instead of spreading over large areas, storms now dump significant volumes of water on small, concentrated areas.

For example, Phuket recorded 350 mm of rainfall in just eight hours, while San Pa Tong district in Chiang Mai recorded 300 mm in a short time.

These volumes far exceed the nominal capacity of most urban drainage systems.

Longer duration of disasters

Beyond their intensity, the duration of extreme events has also increased significantly.

Recent floods in the south of the country, in Phatthalung, Songkhla, Yala and Pattani, were accompanied by heavy continuous rainfall for 5 to 7 days, unlike past storms which generally subsided after about three days.

The accumulation of rainfall over longer periods led to catastrophic damage that is difficult to quantify.

Case study: a complex and serious crisis related to flooding in the south

Recent floods in southern Thailand were caused by the convergence of three major climatic factors, which intensified the monsoon well beyond normal levels:

Cold air mass from China

A cold air wave moved south, forcing the monsoon trough to move down and settle over the south of the country.

Influence of a nearby low-pressure system

A low-pressure cell forming near Kota Bharu, Malaysia, strengthened the monsoon winds and prevented them from leaving the region.

La Niña phenomenon

La Niña amplified the northeast monsoon, drawing large amounts of moisture from the Gulf of Thailand. This resulted in extreme rainfall of 200 to 400 mm per day in several provinces.

Assessment of Thailand's state of preparedness: persistent weaknesses highlighted

Despite efforts to improve water management, Thailand remains faced with systemic weaknesses that limit its ability to cope with increasingly severe disasters.

Political problem: a water master plan without legal authority

The National Office of Water Resources (ONWR) was established to integrate water-related agencies, which is a step in the right direction.

However, its key instrument, the "national water master plan", lacks enforceability and does not have the same authority as urban zoning laws.

Impact on urban development

In practice, building permits and urban planning continue to follow urban zoning rather than hydraulic zoning.

As a result:

• Water flow areas and natural retention zones (monkey cheeks) are often ignored.
• Developments often encroach on designated flood evacuation routes, including areas initially demarcated under the direction of His Majesty King Rama IX.
• Urban expansion increasingly hinders natural drainage, reducing the landscape's ability to absorb or redirect floodwaters.

Obsolete infrastructure and chronic "bottlenecks"

Existing drainage infrastructure in Thailand was designed for past weather conditions and can no longer cope with today's intense rainfall.

Undersized culverts under roads and railways have become major bottlenecks, preventing water from flowing quickly enough and causing severe flooding.

Urgent need to increase capacity

Studies have identified 52 locations along the southern railway line where water crossing structures need to be expanded.

At several locations, the number of culverts needs to be increased from four to six, or even eight, depending on local hydrological conditions.

Major drainage canals also require immediate action.

In Hat Yai, the Khlong R.1 canal, one of the city's main drainage arteries, urgently needs to be dredged downstream to restore flow capacity to Songkhla Lake.

Strategic Proposals: Proactive Investments for Long-Term Survival

To address long-term threats, particularly sea-level rise, bold strategic decisions will be needed, adopting a 25-year vision.

Adapting to a predicted 75 cm sea-level rise

What no longer works: raising barriers along 3,000 km of coastline

The old idea of continuously raising dikes along the Chao Phraya River and coastline, over 3,000 kilometers, has been rejected.

Studies show that this would take more than 22 years and cause serious ecological damage to coastal ecosystems.

A new strategic proposal: "retention basins in the form of monkey cheeks at the river mouths"

The TEAM group proposes building large offshore water retention basins near the river mouths.

These would have two functions:

• to serve as giant reservoirs shaped like monkey cheeks to temporarily store floodwaters, and
• to serve as barriers against high tides to protect inland areas from rising waters.

This concept is considered to have a significantly lower environmental impact and offers a much more effective solution than fighting rising water levels solely on land.

Consequences of inaction: saltwater intrusion threatens Thailand's agricultural economy

Without decisive and timely intervention, saltwater intrusion will penetrate deeper inland, causing serious damage to valuable agricultural areas and major economic corridors.

Several river basins are expected to face increasing impacts:

• Chao Phraya River: the border between Ayutthaya and Ang Thong is highly threatened, and vast agricultural and economic areas are at risk of significant losses.
• Tha Chin River (Suphan Buri): saltwater intrusion could destroy key crops such as pomelo, coconut, and other high-value products.
• Bang Pakong River (from Bang Khla to Prachin Buri): threats to freshwater ecosystems and vast agricultural areas.
• Mae Klong River (Ban Pong, Ratchaburi) – impacts are expected even with the support of the Tha Muang dam.

Policy recommendations for long-term sustainability

Thailand is facing challenges that can no longer be managed with traditional reactive measures.

It is essential to move to urgent and proactive actions.

Economic Justification

Investing in preparedness offers far greater economic value than absorbing repeated losses.

The tens of billions of baht in damages caused by a single flood in Hat Yai could have funded long-term infrastructure improvements capable of preventing future crises.

Lessons learned from the Netherlands

Even one of the world's most experienced countries in water management needed 22 years to complete its large-scale flood protection systems.

Thailand must therefore make strategic decisions now and start construction work immediately to meet the challenges expected over the next 25 years.

Five policy measures that Thailand must take now

1. Elevate the “national water master plan” to the rank of applicable law

The master plan must be given legal authority equivalent to urban zoning laws in order to put an end to developments that hinder the natural flow of water.

2. Strict application of existing zoning laws

Local authorities must ensure that designated natural retention areas and flood evacuation routes are protected against encroachment.

3. Urgent allocation of funds to modernize infrastructure

Implement a systematic national plan for dredging, expanding and maintaining failing drainage structures across the country.

4. Engage in large-scale strategic projects

Thailand must promptly select and launch major long-term solutions, such as offshore monkey-cheek water retention basins.

5. Design future infrastructure to cope with extreme rainfall

All new constructions must be designed for larger capacities to withstand rainfall volumes at least twice as high as the old design standard, reflecting current high-intensity and long-duration storms.

Source: The Nation Thailand