Evaluating an adaptation: rice-sediment trade-offs in the Vietnamese Mekong Delta

Abstract

The exceptional vulnerability of river deltas to climate change and development pressures means there is an urgent need to implement systemic adaptation actions. One of the most important cases is the Vietnamese Mekong Delta (VMD). This thesis performs a novel application of a system dynamics methodology to evaluate the VMD’s dyke network as a hard adaptation to changes in the region’s hydrological conditions. In doing so it makes a methodological and case study contribution to an emerging research body on the evaluation of adaptation action. Policy analysis and stakeholder consultation are first performed to elucidate the drivers behind the policy to heighten the VMD’s dyke network. A farmer survey is then executed within the rice-growing community in order to quantify the socioeconomic impacts of the adaptation. Finally, a system dynamics model is built to explore the dynamics controlling the impacts of the adaptation and the efficacy of alternative policies for the local agricultural system. A key original theme running through this thesis is its consideration of the socioeconomic role of fluvial sediment in the system.

The principle finding, on which both the model and survey agree, is that the switch to high dyke compartments in the VMD(the adaptation) is exacerbating the divide between land-rich and land-poor farmers through the promotion of triple-cropping and sediment exclusion. Factors including the loss of free sediment-bound nutrients for fertilisation, and increasing fertilisation demands, reduce the resilience of poorer farmers to increasing and unpredictable fertiliser prices. The policy currently recommended by the provincial governments to encourage sediment accretion and mitigate the rate of relative sea-level rise is to advocate triennial inundation of paddies. The data presented herein suggest such a policy is sub-optimal,further increasing the risk of debt for smaller-scale farming operations. The testing of various different success criteria weightings did, however, suggest that the less rigid policy of allowing sporadic floodplain inundation and sediment deposition during intense flooding events is preferable to most stakeholder groups.

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Identifiers

ORCID for Stephen Darby: orcid.org/0000-0001-8778-4394

ORCID for Emma Tompkins: orcid.org/0000-0002-4825-9797

ORCID for Marije Schaafsma: orcid.org/0000-0003-0878-069X

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