The cascading 5-acre garden and retaining ponds absorb up to 3 million gallons of water to protect against flooding in the concrete jungle of Bangkok.
Bangkok is one of the world’s several “sinking cities,” built on a flooding river delta near a rising sea.
The rainy season was a blessing, not a curse, for the rice-paddying villagers of times past. But as the city’s soil becomes more and more sealed off by concrete, floods have become more and more severe.
To combat this problem, landscape architect Kotchakorn Voraakhom designed a rooftop garden at Thammasat University that mimics Thailand’s iconic terraced hillsides of rice to slowdown storm-water runoff and keep it out of the streets.
The water that’s not absorbed by the cascading levels of garden beds is held in four retaining ponds at the bottom and saved for a not-so-rainy day.
Solar power pumps the water back up to the top of the hill during dry spells and powers the building.
Air conditioning costs are greatly improved as the garden insulates the building from the sun’s rays. The ponds are positioned in front of the entrances to the university, where the breeze coming off of them also provides a cooling effect.
In addition to rice, the garden includes 50 species of vegetables, herbs and fruits. It also attracts pollinating insects and birds, increasing biodiversity.
The garden yields 20 tons of organic food per year (and it’s less than 3 years old). That’s enough to provide 80,000 meals to the students and faculty in the cafeteria.
Food waste is composted and used to fertilize the garden.
The 237,000-square-foot roof-top structure is designed in the shape of an H, for “humanity.”
The soil and ponds together are capable of holding up to 3 million gallons of water, slowing down runoff and reducing flooding in the surrounded areas by 20 percent, Voraakhom says.
Staff hired by the university tend the crops and offer workshops on permaculture as part of the university’s sustainability curriculum.
“Students and community members are invited to participate in seasonal seeding, harvesting, too,” Voraakhom says.