With its basement car parks filling up with storm water this week, Ho Chi Minh City in Vietnam has unveiled plans to spend $4.4bn (97 trillion dong) on flood control measures over the next five years.
Vulnerable to rising tides of the South China Sea, and flooding from the Saigon River, the city will erect extensive tidal defences, upgrade its narrow drains and build sewage treatment plants, according to reports.
It faces a job finding money for the projects, however. Local and national government cash and international development aid have been lined up for around 40% of the necessary capital, but the remainder will have to be raised in taxes and solicited from the private sector.
A top priority is a massive new sewage pipe, slated for completion in 2020.
Over 3m in diameter, and budgeted at $500m, the pipe will run 8km between the southern section of the Saigon River and the Nhieu Loc-Thi Nghe sewage works.
It will prevent household sewage being dumped into the Saigon River, said local media.
A $450m tide control project will involve building flood defences along a 7.8km section of the Saigon River, and building channels to drain floodwater away. Two pumping stations, whose capacities are 12 and 24 cubic metres per second, are set to be constructed in areas vulnerable to rising tides.
These measures will complement a $58m scheme to build three reservoirs, announced last year. The excavations, which are being carried out with help from the Dutch government, will be 125m long, 32m wide and 2.5m deep, will each be able to contain 10,000 cubic metres of water.
10 minute floods
The urgency of the measures has been underlined in the past week, as continual downpours have flooded 21 parking basements across the city. According to Tuoi Tre News, the vehicles in one underground motorbike park were submerged 10 minutes after the storm broke on Monday.
As a first step, the city may raise the rate it charges for municipal services such as drainage and wastewater treatment.
Up until now the city has relied on makeshift measures, such as local pumps and sandbags. In March, the city announced a controversial decision to buy 63 mobile water pumping vehicles, each costing around $1m.
Among the critics is Pham Xuan Mai, an engineer at the Ho Chi Minh University of Technology. "I must say that it is not feasible to fight against flooding with mobile pump machines in HCM City," Pham told Vietnam.net.
He added that the underlying problem was that the city’s drainage pipes were too narrow. "This is the mistake made by designers who could not estimate their real drainage capacity," he said.
To deal with the kind of surface runoff caused by tropical storms, Pham said the city needed drains that could accommodate 30 cubic metres of water a second.
Image: Everyday life in HCM City (YouTube Creative Commons)
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Maybe they could go for a network of storm water surface tunnels to safely dispose of any flood problem! However many other countries, including my own, experience rising sea levels creeping up below us and not enough rain to fill our upland dams so we have to do build secure dikes to keep out the water and then draw off the sea water and convert it into potable drinking water via increasing our power supply to apply reverse osmosis to desalinate the sea water!