Dutch flood defence plan for Ho Chi Minh City

Dutch flood defence plan for Ho Chi Minh City

Dutch water experts have presented a smarter and cheaper flood defence plan for Ho Chi Minh City, Vietnam. Engineering firm Royal HaskoningDHV and research institute Deltares have revealed details of the Flood and Inundation Management Project , a plan that combines a small ring-dike around the city centre and floodable outlying areas.

Ho Chi Minh City is confronted with floods every year during the rainy season. Causes of the flooding are complex and include flood tide, heavy rainfall, high discharges of upstream rivers, insufficient capacity of the drainage system, low ground elevations of the city and land subsidence, spatial planning, policies and regulations, lack of public awareness and participation.

Local authorities originally proposed building a 172-kilometre ring-dike with twelve flood gates. Although the Dutch companies’ alternative plan is considerably less expensive, it also provides an adequate response to the heavy rainfall in the region.

Controlled flooding
The concept is that the city itself will be protected by dikes but controlled flooding will be permitted in outlying areas. This multilayered protection approach is also applied in the Netherlands under the national Room for the River programme. In the first instance, a small ring-dike will be constructed around the city centre to provide adequate flood defences until 2025. It will then be possible to extend and raise this barrier if sea levels continue to rise.

Royal HaskoningDHV and Deltares have used computer simulations to forecast the likely rise in the sea level caused by climate change. Three scenarios could then be produced: for 2025 (which assumes a 17-centimetre rise), 2050 (25 centimetres) and 2100 (75 centimetres). The prognoses formed the basis of the proposal for a flood defence system which is both smaller and less expensive than that envisaged by the Vietnamese authorities. If the actual rise in the sea level is faster or slower than projected, the Dutch plan can be adapted accordingly.

Sources:
Dutch Water Sector website: www.dutchwatersector.com
Royal HaskoningDHV press release: www.royalhaskoningdhv.com
Deltares press release: www.deltares.com

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