Mekong Delta - case study
The Mekong Delta is a low-lying region in southern Vietnam. Around half of the Mekong Delta is less than 2 m above sea-level, making it vulnerable to fluvial flooding, storm surges and saline intrusion.
Sea-level rise is a threat to the economy and ecology of the region. The Mekong Delta alone generates over half of Vietnam's total rice production.
Under a 4 °C global average temperature increase the global average sea-level could rise by up to 80 cm by the end of the century.
Taking account of local variations in sea-level and changes in land height, this would translate to a local, relative sea-level rise of 65 cm in the Mekong Delta region;
Such sea-level rises would submerge the lowest parts of the delta with up to 13% (5,100 km2) of the land mass in the area being below sea-level. It would also considerably increase the threat of saline intrusion and storm surge damage to vital rice crops across the whole region.
In Vietnam, the Mekong Delta alone yields 54% of the national rice production with the Red River Delta adding another 17% (data for 2005 from IRRI 2008). Production growth in the Mekong Delta has driven the steadily increasing rice production in Vietnam over the last decades. The Mekong Delta contributes to the vast share of rice exports in Vietnam, which accounts for 4.7 million tons of rice every year, making it the second largest exporter worldwide (IRRI 2008). Any shortfall in rice production in this area because of climate change would not only affect the economy and food security in Vietnam but also have repercussions on the international rice market.
The coastal region is vulnerable to sea-level rise because the land is so low - 20,900 km2 of the Mekong Delta is less than 2 metres in height above sea-level with a storm surge area of 9,800 km2 (Syvitski et al, 2009).
Flooding
In past years, extreme flooding has affected the delta. In 2000, severe weather flooded tens of thousands of hectares of rice paddies, and 800 died in the lower basin, many of them children (MRC, 2001). Throughout the year, the cost of the flooding across the Cai Be district was estimated to be $35 million, most of which was due to agricultural losses (MRC, 2009). In addition to intense rainfall, flooding in deltas can also occur from river overbanking or from storm surges.
Such losses could substantially exacerbate under sea-level rise (SLR). A relative sea-level rise of 65 cm in the Mekong Delta region would submerge the lowest parts of the delta and will increase the risk of flooding from storms moving across the region, threatening the Mekong Delta's population and its economy further.
References
Ericson, J.P., Vorosmarty, C.J., Dingman, S.L., Ward, L.G. and Meybeck, M. 2006: Effective sea-level rise and deltas: Cause of change and human dimension implications. Global and Planetary Change, 50, 63-82.
IRRI (International Rice Research Institute) World rice statistics, 200.
Mekong River Commission (MRC), 2001: Annual report 2000. Mekong River Commission, Phnom Penh, Cambodia.
Mekong River Commission (MRC), 2003: State of the Basin Report 2003. Mekong River Commission, Phnom Penh, Cambodia.
Mekong River Commission (MRC), 2009: Flood Protection Criteria for the Mekong Delta, Vietnam. Mekong River Commission, Phnom Penh, Cambodia.
Ministry of Natural Resources and Environment, 2009: Climate change, sea level rise scenarios for Vietnam.
Syvitski, J.P.M., A.J. Kettner, I. Overeem, E.W.H. Hutton, M.T. Hannon, G.R. Brakenridge, J. Day, C. Vorosmarty, Y. Saito, L. Giosan and R.J. Nicholls, 2009: Sinking deltas due to human activities. Nature Geoscience, 2. 681-686.
Wassman, R., N.X. Hien, C.T. Hoanh, and T.P. Tuong, 2004: Sea level rise affecting the Vietnamese Mekong Delta: Water elevation in the flood season and implications for rice production. Climatic Change, 66. 89-107.
