A day after flash floods caused by heavy rains Sunday swept away a man in Da Lat, an hour’s downpour Monday saw water rise roof-high in many places.
Experts said the Central Highlands town did not flood so easily until even a couple of years ago, when it saw greenhouses mushroom, reducing the area of land for rain to percolate.
Most roads in downtown Da Lat were flooded that afternoon as water rose in lakes and streams, and drained very slowly.
Some men had to remove steel sheets from the roof of a house to save a woman and her son stuck inside a flooded house.
People living along Cam Ly, a major, 60-kilometer-long stream in Da Lat, said their houses flood whenever it rains for more than half an hour.
Tran Quoc Nhan, a local, told Tuoi Tre newspaper that his family has to be ready to flee to higher ground whenever it rains more than half an hour.
“Because the water would then flood our house. How much depends on how long it rains.”
His house was flooded eight times in the past two years, he said.
Hoang Thi Hong, a local farmer, said her vegetable garden has been flooded every time it rained in the last two months.
“When the water recedes, there is mud and trash all over the place. The vegetables would die after a couple days.”
The experts said heavy rains are one reason for the flooding, but not the main reason because the rainfall on Monday measured only 70.5 mm and the city used to absorb rainfall of up to 100 mm.
They said the main reason is the large number of greenhouses now.
Nguyen Huu Tranh, a researcher, said too many greenhouses have reduced the area of open land for rainwater to percolate.
A farmer clears mud from his greenhouse after heavy rains caused flooding in Da Lat June 1, 2015. Photo credit: Tuoi Tre
Nguyen Minh Son, director of the Da Lat drainage management center, expressed a similar view.
“In the past we had forests, vacant lands and lots of vegetation and so had room for the rain to go down,” he said.
“But now everywhere there are houses and greenhouses. Rain water pours into streams and lakes, and there is flooding when they can no longer take the water.”
Figures from the Lam Dong Province agriculture department showed that greenhouses cover 1,320 hectares or 8 percent of Da Lat’s flower and vegetable gardens.
Most of the greenhouses are along Cam Ly stream.
Lam Ngoc Tuan, a senior environment lecturer at Da Lat University, said farmers are not using greenhouses effectively.
Greenhouses are used in Scandinavian countries mostly to provide heat for plants in freezing conditions, but in Da Lat, they are used to protect the plants from rains, he said.
Flooding is not the only problem, he said, pointing out that groundwater levels have been falling since rainwater does not percolate through the soil.
Da Lat greenhouses should use a removable plastic roof with a layer of netting below that would let rainwater pass through gently, protecting the plants, he said.
He also suggested building small ponds near large greenhouses to hold rainwater.