Coastal and flood risk management in South East Asia - Part 2 Vietnam
A collection of interesting, different or strange approaches to manage coastal and flood risks that I stumbled across during a trip though South East Asia.
Flood risk in Vietnam
Over the last week I have travelled from Hanoi in north Vietnam, to the Mekong Delta in the south. Whilst visiting a south-east Asian country in the rainy season (which runs from July to October) has its drawbacks, it does mean I get to see plenty of water. Vietnam is a country with known flood problems: due to either flash flooding and landslides, flooding from some of the world’s largest rivers, and storm surges from typhoons. Looking forward, a 1m sea-level rise is expected to put more than 14 million additional residents in the Mekong Delta at risk, and submerge half of the region’s agricultural land. Scary.
A reliance on structural flood measures In Hanoi I hunted out the some of the earliest known flood defences. The Hanoi levee bank (or dyke) system is mentioned in the early 11th century, with some archaeological evidence suggesting they were constructed as far back as the second century*. They now extend over 3000km and are impressive tall - see the photo below I took whilst standing on three story tall, earth levee bank, that is just metres away from an urban area.
Above: A part of a thousand year old levee bank system in Hanoi
The Mekong Delta I travelled south past Ho Chi Minh City to the seaward end of the mighty Mekong River. I was able to get a lift along one of the northernmost tributaries, near Mỹ Tho, Tien Giang province. These tributaries are awesomely named the “Nine Dragons of the Mekong Delta”, and have been the setting for human settlements as far back as the 4th century BC. Being historic trade routes there are thousands of houses located directly on the river banks. For these communities, located along the lowest areas of the Delta, there is the risk of both river flooding and storm surges, with the annual flooding some of the most frequent in any other country of the Mekong River Basin.
Above: Development along the banks of the river
I have found references to several flood mitigation strategies, but, given the vast area of the delta these will always have limited effect. Other approaches, such as through house raising and flood proofing have merit*, although rebuilding houses when people’s only source of income, rice crops, is also lost in a flood is thought to be almost impossible. (*see the bottom of this blog for references to an interesting study by the UNDP)
Above: Waterside houses in Tien Giang province
An early warning system for Vietnam In addition to structural flood risk mitigation strategies, other options include the development of an early warning system, which I am pleased to say is going ahead. Flood warning systems are one of the most cost-effective means to mitigate extreme weather events – with earlier warnings of events able to provide greater preparedness for residents and trigger evacuations if needed.
The JBA Group are currently developing the core forecasting engine of the National Fluvial and Coastal Flood Forecasting System for Vietnam. This will be used by the National Centre for Hydro-Meteorological Forecasting to turn five-day forecasts of rainfall and coastal systems into the likely impacts that will be experienced on the ground: through either river flooding or storm surges. This project is being funded by the World Bank, and we are working with Kisters (https://www.kisters.de/en/) and our local partner Harmony EV. Keep your eyes peeled for more information!
*Information on the Hanoi levee banks
*UNDP project investigating house raising: http://www.vn.undp.org/content/vietnam/en/home/operations/projects/closed-projects/environment_climate/Flood-Proofing-of-Poor-Coasta-and-Inland-Households-in-the-Mekong-River.html