Vietnam metro to tackle floods with ponds, lakes

Thanh Nien News

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Children walk on flooded Calmette Street in downtown Ho Chi Minh City. The city is considering a plan to build underground water tanks and dig lakes to store rainwater in a controversial effort to tackle inundation. Photo: Diep Duc Minh
Thien, a resident of the Le Thanh Apartments in Ho Chi Minh City, said the streets surrounding his home flood whenever there is rain or high tides, and the inundations have become more serious over the years since he settled there in 2011.
“I have to hang my shoes on the motorbike and wade through the floods when going to work. The situation is no better when I come back in the afternoon.”
“Sometimes I fell in the water. But I feel more pity for the children wading in the water following their parents on the way to school. Some children fell and their clothes and books all got wet,” he said.
In an effort to tackle the worsening inundation caused by urbanization and rising sea levels, city authorities are considering a controversial plan to dig ponds, small lakes and underground water tanks around the city to drain water.
At a recent conference, city mayor Le Hoang Quan warned about worsening flooding in the city due to the impacts of climate change, saying the city can only mitigate damages.
“The Mekong Delta will suffer the most when up to 30 percent of the area is affected by rising sea levels in 2050. HCMC is no exception and nearly 700 square kilometers (270 square miles) will be affected.”
He said city dwellers will have to “live with floods because it will be impossible to totally solve inundation.”
A 2013 study by the National University Ho Chi Minh City's Geoinformatics Center also found that parts of the southeastern region and the Mekong Delta are sinking, with HCMC suffering the most.
Researchers found the city has been sinking since 1996, with the speed increasing gradually since 2004. Many sections of the city are sinking by up to 20 millimeters (0.8 inch) a year.
According to the city Department of Natural Resources and Environment, many neighborhoods will sink a further 12-20 centimeters by 2020.
Besides geological factors, the surface is sinking also due to urbanization and dwindling groundwater, according to the agency.
Slow to react
In 2009, the central government approved a plan to drain water in HCMC but little work has been done so far.
According to HCMC People’s Committee, the plan was not carried out fully because it is a major project while the city has been unable to disburse money for it due to economic difficulties.
Due to the slow process, the plan’s cost has increased from VND11 trillion to VND57.8 trillion.
By late last year, only 31 of 149 km of dikes along the Saigon River have been built and only one of nine large sewer valves envisioned has come into operation.
With the rainy season coming next month, HCMC authorities need to rush to prevent inundation that will hit an apex when the rainy season meets with high tides.
Last week, the HCMC People’s Committee instructed all districts to facilitate projects to construct and upgraded dike systems and sewer valves and dredge drainage canals.
Early last month, city authorities asked the Ministry of Planning and Investment to categorize a VND16 trillion (US$759 million) project to tackle inundation in HCMC as one that can use the World Bank official development assistance.
The project, expected to be implemented from 2015-2020, includes training the staff and solving inundation along the Tham Luong and Ben Cat canals and in the city center.
From 2011-2013, the city spent more than VND8 trillion ($379 million) in battling inundation.
City ponds
According to Do Tan Long, head of the drainage management branch at the HCMC Center for Flood Control Program, relevant agencies have agreed with the center’s plan to build ponds and underground water tanks.
The plan will be submitted to the HCMC People’s Committee for approval in May, he said.
“This is an open plan that does not have a fixed number of ponds and tanks. Maybe dozens or hundreds of them based on the amount of rain water that the current sewer system cannot drain in a short time.”
Long said the ponds and tanks can be built in parks or empty spaces near apartments in the city center, where land is very expensive.
“Meanwhile, we can dig small lakes in the outskirts like in Binh Chanh, Thu Duc and District 12 which can become part of eco-tourism areas,” he said.
The draft plan aims to temporarily store rainwater as dozens of canals in the city have been filled by urbanization.
According to the Center for Flood Control Program, 47 canals with a total area of 16.4 hectares (40.5 acres) have disappeared over the past decade.
The water storage capacity of the city’s lakes and ponds grew ten times smaller from 2002-2009 and continuing urbanization in outlaying districts are creating new inundated areas, the center said.
If the plan is approved, a large underground tank of 4,000 square meters will be built at Tan Binh District’s Bau Cat Park as a first step.
Besides small underground tanks in the city center, there will be 30 small lakes in the city’s outskirt. The plan aims to reduce 30 percent of inundation citywide.
Controversies
Ho Long Phi, director of the HCMC Center for Water Management and Climate Change, said the plan is a good solution for flooding in the city.
“The plan aims to drain rainwater naturally and correct the previous mistake of installing sewers to replace canals,” he said.
However, he said it will be a difficult plan because it may affect many residents’ land.
“Governmental offices should be a good example by setting aside their land for the plan,” he said.
Meanwhile, Pham Sanh, an urban development expert at the HCMC University of Transport, is suspicious about the effectiveness of the plan.
“There is not enough land in the city center for ponds while digging lakes in the outskirts will not be effective in reducing inundation in the city center.”
He said the city should install larger sewers to facilitate rainwater drainage.
“Besides, cement sidewalks should be replaced with materials that can absorb water and more trees should be planted for faster water draining.”

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