Southern Vietnam may be in the midst of a historic drought, but a major concern regarding the future of the region, and in particular Ho Chi Minh City (HCMC), is flooding. The annual monsoon rains regularly flood sections of the city and even high tide on the Saigon River can inundate low-lying areas.
While HCMC floods have not yet reached the disaster level of the 2011 Bangkok floods the ingredients are in place for increasingly severe flooding in the coming years.
A major cause of concern is the growing exploitation of HCMC’s groundwater reserves. Data from the Saigon Water Supply Company (Sawaco) shows that the city uses about 2.2 billion litres (581.2 million US gallons) of water every day. Of this amount 1.65 billion litres (435,883 million US gallons) or about 75 per cent is produced by surface water treatment plants drawing from the Saigon and Dong Nai Rivers, while the rest comes from roughly 300,000 tube wells, which take water directly from the ground.
HCMC Sinking on Weight of Development
Removing water from the ground causes land to settle, and parts of HCMC are sinking at an alarming rate.
The local Department of Natural Resources and Environment (NRSE) estimates that 20 areas of the city are sinking at an average of 15mm (half an inch) per year while 40 other areas sank 5-10mm last year. The total affected area currently covers more than 7,200 hectares (17,792 acres).
These figures may seem small, but they add up over time and HCMC is a low-lying city as is with about 63 per cent of the city less than 1.5 meters (4.92 ft) above sea level and some as low as 0.6 to 0.9 meters (1.97 – 2.95 ft).
Another aspect of this problem is the rapid expansion of the city, both horizontally and vertically. Suburbs are branching into areas that used to be swamps or mangrove forests, while the construction of high rises requires the excavation of huge amounts of soil and water.
The development of the long-planned, oft-delayed HCMC metro system (See: Hanoi & HCMC Metros Struggling to Get on Track) will contribute to this issue as well once engineers begin tunneling underneath the city to install train lines. The concrete used in these projects prevents rainwater from making its way back into the soil. As a result, groundwater isn’t replaced, while whatever falls from the sky pools on the street and quickly causes flooding.
Reservoirs & Pumps to Combat HCMC Floods
|HCMC floods: An annual occurrence that city planners have yet to achieve little success in alleviating. Video uploaded to YouTube by Zui Zui|
Authorities recognise that HCMC has a water problem, but little has been done to effectively combat the issue. One proposed plan that could help was announced last year. Over the next five years the city hopes to build three reservoirs to store rainwater at a cost of US$42.3 million. A 95 hectare reservoir will be constructed in the outlying district of Thu Duc, while two smaller ones will be built in the city proper.
Officials claim that these reservoirs will help reduce HCMC floods by 30 per cent, an ambitious goal, but such a project is a step in the right direction.
In another move in the same vein, last month the city anti-flooding agency requested permission to purchase 63 mobile pumps for US$62.5 million. These pumps would be deployed on 30 of the most flood-prone streets as needed and can clear 20,000 to 60,000 litres (5,283 to 15,850 US gallons) of water per minute.
This idea looks good on paper, but it has a serious flaw: the water would be pumped into the nearest canal or sewer, but these systems often flood as well. The crux of the problem is that there is simply nowhere for water to go, no matter where it is pumped. This quandary will continue to present major challenges for HCMC moving forward.
Vietnam’s economy is booming, and the city is growing rapidly as a result. Former swamps like the Thu Thiem Peninsula in District 2 are being drained and paved over to create huge new developments, displacing even more water.
Driving during a monsoon downpour can be a frightening proposition, as streets quickly turn into rivers; rivers which seem to be getting deeper every year. Although HCMC has earmarked US$6.85 billion for anti-flooding projects over the next five years, its efforts to date have little to show for it with HCMC floods a worsening annual event.
All city leaders have to do to get a sense of what could be in store if unchecked development continues to run roughshod over the physics of water is look at what happened in Bangkok five years ago. The damage from such a flood would cost far more than the planned spending.
- The Challenges of Water Governance in Ho Chi Minh City (Integrated Environmental Assessment and Management)
- Ho Chi Minh City sinks by up to 28 mm in 2015 (Thanh Nien News)
- Polluted rivers, dwindling groundwater threaten Vietnam city supply (Thanh Nien News)
- Ho Chi Minh City proposes buying $62.5mn worth of trucks to clear flooded streets (Tuoi Tre News)
- HCMC plans 3 reservoirs to reduce flooding (Thanh Nien News)
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