Dikes, Rice and Floods: How Flood-Control Infrastructure Shapes the Vietnamese Mekong Delta
A PhD thesis at Wageningen University by Dung Duc Tran (HAPRI Senior Research Associate) finds higher economic and environmental returns to low-dike farming systems in the long run on the floodplains of the Vietnamese Mekong Delta. The thesis suggests a need for flood-based land and water management strategies and farming systems instead of continued expansion of high-dike infrastructure, while recognizing the advantages that high dikes offer.
Context
Induced by national food security policy, rice production in the upper parts of the Vietnamese Mekong Delta has intensified, changing the floodplains from a seasonal floodplain into a highly intensified rice production area. To enable this, large-scale flood-control infrastructure has been built, particularly low dikes and high dikes, to control the water entering agricultural fields. As a result, the delta has become a primary contributor to Vietnam's food security, and the delta's high production has made Vietnam one of the world's foremost rice exporters.
The thesis also notes the costs of this transformation: it has reduced the flood retention capacity of the delta, degraded land and water quality, and undermined delta ecosystem services. The research had two aims. The first was to identify the impacts of extensive flood-control infrastructure on the flood dynamics of the delta. The second was to explore adaptation options that maximize livelihood sustainability and ecological sustainability on the delta.
Methods
The thesis developed an available 1D-quasi2D hydrodynamic model for the delta system as a whole to simulate flood discharges and river water levels under four dike construction scenarios. From a sustainable livelihood perspective, it then explored alternative farming systems with multi-criteria analysis and cost-benefit analysis at the local scale. This drew on multiple interviews with stakeholders working under different types of dikes and at different locations on the floodplains. Finally, it set out costs and benefits at the delta scale, also considering various future flood-control scenarios.
Key findings
From its hydrodynamic modelling, the thesis concludes that high dikes have reduced the volumes of floodwater reaching the Long Xuyen Quadrangle (LXQ).
In the farm-level cost-benefit analysis, the profits of triple rice farmers diminished over time.
In the multi-criteria ranking by farmers and experts, the preferred systems varied, but there was a clear preference for flood-based (low-dike) farming systems.
Overall, the thesis found higher economic and environmental returns to low-dike farming systems in the long run.
Policy implications
The study suggests a need to develop flood-based land and water management strategies and farming systems, instead of continued expansion of high-dike infrastructure and related farming systems. The study adds that certain advantages of the high-dike systems must be recognized, such as their protection of built up areas and farmers' ready access to the stable market for rice.
Keywords:
Vietnamese Mekong Delta
Dike Construction
Flood Dynamics
Rice Farming
Adaptation
Flood-Based Farming
Link:
Citation:
Tran, D. D. (2018). Agricultural land-use dynamics in the floodplains of the Vietnamese Mekong Delta: hydrodynamic implications on flood regimes and adaptation options. PhD thesis, Wageningen University.
