Bangkok has long been known as one of the world's fastest sinking cities, a city that will one day be underwater. Whether this prediction will come to fruition in the next few hundred years remains to be seen.
But one thing is for sure: the city has a long history of flooding and hasn't done enough to prevent its recurrence. The Big Mango's vulnerability to flooding stems from a complex mix of geographical, environmental, and human-induced factors.
Given the recent high tides that caused the Chao Phraya, Tha Chin, and Mae Klong rivers to overflow, I thought I'd take a closer look at the problem, its contributing factors, and the implications of Bangkok's flood-prone future.
My Personal Experience
In 2011, Bangkok experienced severe flooding, and as a resident of Huay Kwang at the time, I witnessed firsthand the impact on daily life. As water levels rose, streets quickly became impassable, reaching knee-high depths in some areas and confining residents to their homes.
The atmosphere shifted dramatically, marked by an unusual sense of urgency among Bangkok’s typically resilient residents. People flooded local stores to buy essentials, and shelves in my neighborhood 7-11 were quickly emptied.
Perhaps the most surreal sight was on Ratchada Road, where boats replaced the usual flow of cars and motorcycles, ferrying stranded residents through submerged streets. The rapid transition from bustling streets to makeshift canals underscored the vulnerability of a city with limited flood defenses.
Though the water receded within days, this event was a sobering reminder of the precariousness of life in a flood-prone urban area.
I have also experienced flooding in Chiang Mai and on Koh Samui, but nothing as movie-like as 2011.
Geographical and Environmental Factors
Low-Lying Topography
Bangkok is located in a low-lying delta region, with an average elevation of just 1.5 meters (5 feet) above sea level.
A low-lying delta region is an area of land that is formed at the mouth of a river, where the river meets a body of water such as an ocean, sea, or lake. This region is typically characterized by its flat and low elevation, often just a few meters above sea level.
The land in a delta is made up of sediment that the river has deposited over time as it slows down and spreads out before entering the larger body of water. Because of its low elevation, a delta region is especially prone to flooding, especially during heavy rains or high tides. Additionally, these areas may be susceptible to rising sea levels, which can further increase the risk of flooding and erosion.
The Chao Phraya River, which flows through the city and drains into the Gulf of Thailand, swells significantly during the monsoon season (May to October). Heavy rains, particularly in recent years, push river levels dangerously close to overflow, often resulting in widespread flooding. The low-lying nature of Bangkok exacerbates this risk.
Land Subsidence and Rising Sea Levels
Bangkok is subsiding at an estimated rate of 1-2 centimeters annually, largely due to excessive groundwater extraction, compounded by soil compression and urban infrastructure weight.
Research shows that have shown that certain areas of the city have reported subsidence rates as high as 5 cm per year. This makes Bangkok one of the world’s fastest-sinking cities.
That being said, subsidence in some areas has been considerably reduced. In 2003, subsidence rates ranging between 2 and 5 cm/year were measured in Samut Prakan and Samut Sakhon. However, more than 35 cm of cumulative subsidence was recorded in Samut Sakhon between 1996 and 2003 (1).
Several mitigation policies were implemented to reduce these escalating rates, such as the enforcement of the Groundwater Act B.E. 2520 (1977), which restricts groundwater use and exploration within critical groundwater zones.
Unfortunately, rising sea levels are adding to this challenge of keeping the city safe. the Intergovernmental Panel on Climate Change (IPCC) has projected a potential sea-level rise of up to 1 meter by 2100. With current trends, parts of Bangkok could experience chronic flooding or even permanent submersion by the end of the century (2).
Increased Rainfall
It is said that climate change has intensified the monsoon season in Southeast Asia, including Bangkok, by increasing the frequency and severity of rainfall. As global temperatures rise, warmer air holds more moisture, leading to heavier and more frequent downpours.
I know that many people are skeptical about climate change and the causes of irregular weather patterns. But one truth that is undeniable is that Bangkok is at risk of flooding and needs to develop better management strategies to secure a sustainable future.
Over the past two decades, the Thai Meteorological Department has reported that rainfall during the monsoon months has increased by 20-30%, placing additional pressure on the region’s drainage systems. These systems, which were already outdated, struggle to cope with the intensified rainfall, resulting in more frequent flooding in urban areas (3).
In addition to heavier rainfall, climate change has altered monsoon wind patterns, making storms stronger and less predictable. This unpredictability, combined with the increased volume of rain, exacerbates flooding risks, particularly in cities like Bangkok, where rapid urbanization has reduced natural water absorption and worsened drainage issues.
The combination of climate change, aging infrastructure, and urban development creates a perfect storm for more frequent and severe flooding events in the future.
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Human-Induced Factors Contributing to Flooding
Urban Development and Limited Drainage Capacity
Bangkok’s rapid urban expansion has greatly affected its flood resilience. Over recent decades, Bangkok has paved over its wetlands and green spaces, reducing natural water-absorption capacity and increasing “surface runoff,” where rainwater flows over streets and paved areas instead of soaking into the ground.
The World Bank has published reports indicating that Bangkok’s urbanization has significantly heightened its flood risk due to reduced green spaces and increased impermeable surfaces (4).
Aging and Inadequate Drainage Systems
The city’s drainage system, originally developed in the early 20th century, was not designed for the demands of today’s population and urban density. Despite incremental updates, the system remains insufficient to handle Bangkok’s current rainfall volume.
Official reports from the Bangkok Metropolitan Administration (BMA) highlight these shortfalls, noting that the network frequently reaches capacity during heavy downpours, resulting in localized and citywide flooding .
Impact of Canal (Khlong) Loss on Flood Management
Historically, Bangkok was known as the “Venice of the East,” with an extensive network of canals, or “khlongs,” that once served as natural drainage systems for the city. However, rapid urban development has led to the filling or restriction of many of these waterways, greatly diminishing their ability to manage floodwaters.
Restoration efforts have started to reopen certain canals, but these initiatives face logistical and financial challenges. Additionally, canals often become clogged with litter and sewage, further reducing their effectiveness in flood prevention and creating sanitation concerns in flood-prone neighborhoods.
Risks and Considerations for Long-Term Residents and Investors
Bangkok remains an attractive destination for expatriates and investors, but the threat of flooding cannot be ignored. For those planning to relocate or invest in the city, carefully evaluating property location, elevation, and flood preparedness can mitigate risks.
Property Investment Risks
- Property Damage: Properties, especially those in districts prone to flooding like Bang Khen, Don Mueang, and Bang Kapi, are at high risk of water damage. Prospective investors should carefully review historical flood data and consult developers about flood-resistant construction measures.
- Insurance and Maintenance Costs: Insurance premiums for properties in high-risk areas have risen. Some flood-prone properties may even struggle to secure coverage. Maintenance costs also increase with frequent flood repairs .
- Resale Value: Flood risks can reduce property value, as prospective buyers often hesitate to invest in flood-affected or subsiding areas .
Business Implications
- Operational Disruptions: Flooding disrupts transportation and critical infrastructure, affecting supply chains, employee commutes, and customer access. Businesses, particularly those relying on logistics, may face higher operating costs during flood season.
- Damage to Facilities and Stock: Flooding can damage office spaces, equipment, and inventory, resulting in unanticipated expenses for repairs or replacements. Companies should assess flood insurance coverage and consider strategic locations less vulnerable to water damage .
Risks to Personal Safety
Bangkok’s floods are generally more disruptive than dangerous. However, severe storms and floods pose health risks, including waterborne diseases. In 2011, Thailand experienced its worst flood in decades, impacting more than 13 million people and resulting in nearly 700 fatalities, with significant impacts in Bangkok (5).
What is Being Done to Mitigate Flood Risks?
Government Initiatives & Infrastructure Projects
In the past two decades the Thai authorities have been working on several flood-control initiatives to protect Bangkok, though a comprehensive solution may still be years away.
Flood Control Center
The Bangkok Flood Control Center operates around the clock to monitor and manage flood conditions in real time. Using an extensive network of sensors and predictive modeling, the center can quickly assess water levels, forecast areas at risk, and issue timely alerts. This advanced monitoring system allows for faster emergency response and helps authorities coordinate preventative measures like opening floodgates and deploying pumps to critical areas. Additionally, it provides data that informs long-term flood management policies.
Barriers and Drainage Tunnels
Bangkok has made significant investments in flood barriers along the Chao Phraya River and in constructing large-scale underground drainage tunnels. These barriers, often reinforced with steel and concrete, protect against river overflow during heavy rains and high tides.
The underground tunnels, such as the Phra Khanong and Rama IX drainage tunnels, channel floodwaters away from inner-city areas and store excess water in large holding tanks until it can be safely discharged. These structures have proven effective in preventing many of Bangkok’s low-lying neighborhoods from flooding.
Canal Restoration Projects
In recent years, the government has initiated projects to restore and reopen some of its canals, recognizing their critical role in flood mitigation. Restoring these waterways improves drainage capacity and helps prevent water stagnation. However, these projects have faced obstacles, including budget constraints, the need to relocate informal housing settlements, and pollution control issues, which complicate efforts to fully utilize the canals for flood management.
One notable project is the Klong Chong Nonsi Canal Park, an initiative aimed at revitalizing one of Bangkok’s oldest canals by turning it into a green public space that also improves the city's flood resilience. The project reimagines the canal with tree-lined walkways, bike paths, and community areas, creating an inviting park that stretches over several kilometers. In addition to its aesthetic and recreational benefits, the redesigned canal enhances drainage and stormwater management, helping to reduce flooding risks in nearby neighborhoods.
International Programs
Thailand is a member of the 100 Resilient Cities Program (100RC), initiated by The Rockefeller Foundation. This international initiative launched in 2013 to help cities around the world build resilience against a range of social, economic, and environmental challenges. Bangkok joined the program as one of the original 100 cities and committed to addressing key issues such as flooding, extreme weather, and rising sea levels.
As part of the 100RC, Bangkok has taken steps to enhance flood prevention and urban resilience, which includes investing in infrastructure to manage floods, conserving green spaces to absorb water, and restoring canals to improve drainage.
Through the program, Bangkok has collaborated with experts and other cities facing similar challenges, exchanging knowledge to improve early warning systems, develop better urban planning to reduce surface runoff, and build retention areas to temporarily store excess rainwater during monsoons (6).
Private Sector and Community-Based Actions
In response to Bangkok’s chronic flooding issues, real estate developers have increasingly integrated flood-resilient designs into their projects.
Newer developments often feature elevated structures, where building foundations are raised to minimize the risk of water damage. This elevation keeps key areas like parking garages, lobbies, and other essential infrastructure above potential flood levels. Many properties are also incorporating flood barriers – reinforced walls, embankments, and water-resistant materials – to prevent floodwaters from reaching the interiors of buildings.
Alongside these private efforts, some communities have established their own flood-preparedness plans. These plans involve a combination of communal action and infrastructure enhancements designed to protect neighborhoods from the worst effects of seasonal monsoon flooding.
Community-led initiatives may include sandbagging efforts, setting up pumps to divert excess water, and creating neighborhood flood watch groups. Local groups also work to keep drainage systems clear of debris, helping to prevent water from accumulating in low-lying areas.
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Article References:
1. Ahmed, S., Hiraga, Y., & Kazama, S. (2024). Land subsidence in Bangkok vicinity: Causes and long-term trend analysis using InSAR and machine learning. Retrieved from https://www.sciencedirect.com/science/article/pii/S0048969724044334
2. Various Authors. (2022). Sea Level Rise and Implications for Low-Lying Islands, Coasts, and Communities. Retrieved from https://www.ipcc.ch/srocc/chapter/chapter-4-sea-level-rise-and-implications-for-low-lying-islands-coasts-and-communities/
3. Climatic Research Unit (CRU) of the University of East Anglia. (2020). Climate Change Knowledge Portal. Retrieved from https://climateknowledgeportal.worldbank.org/country/thailand/climate-data-historical
4. The World Bank. (2010). Climate Risks and Adaptation in Asian Coastal Megacities. Retrieved from https://documents1.worldbank.org/curated/zh/866821468339644916/pdf/571100WP0REPLA1egacities01019110web.pdf
5. Poapongsakorn, N., & Meethom, P. (2013). Impact of the 2011 Floods, and Flood Management in Thailand. Thailand Development Research Institute. Retrieved from https://www.eria.org/ERIA-DP-2013-34.pdf
6. Laeni, N., van den Brink, M., & Arts, J. (2019). Is Bangkok becoming more resilient to flooding? A framing analysis of Bangkok's flood resilience policy combining insights from both insiders and outsiders. Retrieved from https://www.sciencedirect.com/science/article/abs/pii/S0264275118306620