How Bangkok is turning to nature to help fight floods

“I remember when I was a young child in Bangkok, we used to sail our boat on the clean floodwater,” says landscape architect Kotchakorn Voraakhom. “Flooding was fun.”

But when a tropical storm hit the city of Bangkok in 2011, her opinion of floods changed forever. Residents had to flee their homes and more than 800 people in Thailand lost their lives. “Floods were no longer fun, it moved to fear,” Voraakhom says.

Not only has rainfall increased in Voraakhom’s lifetime, but so has the sea level. The densely populated capital is also sinking by up to 2 centimeters (0.8 inches) each year. According to the World Bank, 40% of Bangkok could be flooded by 2030.

Now Bangkok is turning to nature to help fight the floods. Voraakhom is among a group of landscape architects helping to launch urban forests throughout the city, which not only create more inviting spaces for its inhabitants but are filled with innovations to help tackle floods.

A city forest larger than New York City’s Central Park is slated to open in the capital as early as this December. The site of a former racetrack, it will become named His Majesty King Bhumibol Adulyadej the Great Memorial Park. The new park will be filled with 4,500 trees and a floodplain where rainwater will be purified with vegetation.

This joins Benjakitti Forest Park, where a former tobacco factory has been turned into a new $20 million city forest. The park, which was fully opened in June 2024 after a soft launch in 2022, acts as a sponge during the monsoon season, and another urban forest in Bangkok has been tilted by 3 degrees so when the monsoons hit it fills like a pond.

The city has one of the lowest ratios of green spaces in Southeast Asia. The aim is to build 500 parks by 2026.

The rapid growth of Bangkok in the 1980s saw a capital that was once surrounded by orchards and rice fields turn into an urban metropolis. The Chao Praya River, one of the largest in Thailand, cuts through the capital, and from it have sprung a network of rivers and canals in the city, which now battle monsoon rains, wastewater and rising tides.

As the city grew, the once porous landscape changed to fit the needs of a modern nation. Skyscrapers replaced stilt houses, and some of the canals were filled in to create roads.

“The increase in impervious surfaces like roads and housing, coupled with policies that focus solely on draining water into pipes, canals and rivers, has been a significant cause of the severe flooding in Bangkok,” says Pakkasem Tongchai, water and wetlands officer for IUCN Thailand.

The change in river habitat and water quality also affected marine life such as the critically endangered giant Siamese carp (Catlocarpio siamensis).

Yet nature is now helping to provide the solution. The picturesque new memorial park contains an inbuilt floodplain, a weir that slows down the flow of water, and turbines to clean the water. The floodplain is inspired by the late king’s concept of kaem ling, or monkey cheeks, where stormwater is stored in water tanks for later use. The urban forest, which is surrounded by three canals, will also filter any water overflow from the canals with a nature-based water filtration system.

“City parks that are designed with features such as ponds, storm drainage basins, rain gardens, or other elements can potentially contribute to slowing down runoff and retaining water within the park itself,” Tongchai says.

Throughout the city, blue-green architecture is now showing how nature can help fight floods. The grounds of a former tobacco factory are now the 41-hectare (102-acre) Benjakitti Forest Park. This urban wetland has been designed not only to regulate stormwater, but clean contaminated water and provide habitat for wildlife. Native vegetation such as the rain tree (Samanea saman), bo tree (Ficus religiosa) and khee lek (senna siamen) were planted within the grounds that are designed to retain 87 million liters (23 million gallons) of water.

Award-winning landscape architect Kongjian Yu, founder of Beijing-based firm Turenscape, has turned an impermeable concrete ground into a porous landscape by creating giant ponds dotted with islets. Polluted water from a neighboring canal is pumped into the park and run through the filtration system of native plants before flowing out into the wetland. Bioswales, in the form of flower beds, have been carved into the center of former haulage roads to help make them more permeable.

Yu says that persuading people to tear up concrete barriers and use plants for flood protection isn’t an easy task. “Cities in monsoon regions cannot adapt to climate change because we are copying Western-developed models, such as concrete, pipe systems and [manicured] gardens,” Yu says. “Those models are based on a mild climate. We need [to] find a new model which is more climate-resilient, environmentally friendly. It needs to be a sponge-like system.”

Today, tens of thousands of visitors stroll along the boardwalks and wind their way up the skywalk that zigzags through the tree canopy. More than 90 species of birds, including egrets, bitterns and storks, have been seen at the park. “The birds will now disperse the native seeds and the forest will flourish on its own,” Yu says.

Voraakhom says the key is not how you can rid the city of water, but how you can live with water: “Bangkok used to be a big swamp, a big delta city. I think the capacity of capturing the water [has] been destroyed.”

Voraakhom’s company, Landprocess, is behind the innovative Chulalongkorn University Centenary Park, built at an incline so that stormwater can flow down its sloping lawns and gather in the built-in retention pond at the bottom. A hidden reservoir under the park means it can now hold nearly 4 million litres of water.

While vegetation is used to clean the water, visitors can also ride stationary water bikes to help aerate the retention ponds. Voraakhom says a park can have more than greenery — it can also have layers of practicality.

Wijitbusaba Marome, director of the Urban Futures & Policy research unit at Thammasat University in Bangkok, says that while extreme rainfall will be challenging to a park, a localised system of containing water is the way forward. “We have strategies to divert water away from the city, but there is still a large volume of water that has to pass through Bangkok because of its topography. When you talk about a new town or development, you should talk about an area for water, because otherwise you have to keep following the problems.”

This article was first published on Mongabay.