Seminar Sum-Up: Hutton Club 02/11/18

There was a clear motivation behind the seminar I attended by Stephen Darby of the University of Southampton that focused on the Mekong Delta in Southern Vietnam (Fig 1). The area is being affected by climate change at a rapid rate, with predicted temperature increase of 1.5⁰C resulting in a 1.5-3m sea level rise, areas of low lying land such as the Mekong Delta are at a huge risk of submergence. Sedimentation is the only process that can offset this sea level increase and therefore the reason Stephen started his research journey.






Figure 1: Map of the Mekong Delta





Unfortunately, there are two main reasons there is now a limited supply of sediment to the Mekong delta preventing this offset. Firstly, after fieldwork the team realised a huge amount of discharge and sediment arriving in the delta was related to when tropical cyclones were occurring. Using numerical modelling they were able to quantify that the cyclone attributed rainfall caused more impact than the mean amount of rainfall, so the cyclone related rainfall is very hydrologically important and would also bring the highest fluxes of sediment. However, recently the tracks of these tropical cyclones have been migrating north and therefore less intense events and less sediment is reaching the delta. Secondly, from 2005 onwards there has been a dramatic increase in the amount of dams built or being built upstream of the delta. The effect of these dams has nearly completely cut off the natural sediment supply to the delta. Both these factors have made it much harder for sedimentation to offset sea level rise. Stephen then addressed the question of WHY – why do we care if the Mekong Delta is submerged?

This is the part of the seminar I found especially interesting especially considering so much scientific research fails to include the social implications of their work and how the people where they are studying are just as important as the science. 20 million people live on the Mekong Delta and the area is hugely important for rice production partly due to the high productivity of the land as sediment provides natural fertiliser. As the world population continues to increase it is important to maintain rice production considering it currently provides 1/5th of the world's calorie supply.

To combine sediment supply and management of the agricultural land Stephen and others developed four farming policies to run in a complex socio-economic model (Fig 2) that includes declining sediment supply. They concluded not one scenario will completely satisfy the government and the local farmers however the outcomes can provide decision makers with better information on how to tackle the issues of declining sediment and rice production that includes the economy and the environment.
Figure 2: Loop diagram showing the connections modelled and boundaries of the model (Chapman and Darby, 2016).

The policy that they deemed the most successful was the ‘1 year in 3’ where one year in three when the area is going to have the largest flood no farming is carried out, to flood the area and put as much natural fertiliser back into the system as possible.

In conclusion, the Mekong Delta is an area unfortunately like many others that faces future difficulties due to sea level rise and this is exacerbated by natural and man-made sediment decline. Leading to a higher flood risk, land loss and threat to livelihood. However, research that Stephen Darby is actively working on provides simple changes to rice farming that may help the area build resilience and keep productivity and rice outputs high in the face of adversity. 


I really enjoyed this seminar, I thought it was engaging, informative but also super understanding. The introduction of the socio-economic impacts were very interesting and what captivated my attention the most.


- Meg

Chapman, A. and Darby, S., 2016. Evaluating sustainable adaptation strategies for vulnerable mega-deltas using system dynamics modelling: Rice agriculture in the Mekong Delta's An Giang Province, Vietnam. Science of the Total Environment, 559, pp.326-338.

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