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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 22, issue 3
Hydrol. Earth Syst. Sci., 22, 1875-1896, 2018
https://doi.org/10.5194/hess-22-1875-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.
Hydrol. Earth Syst. Sci., 22, 1875-1896, 2018
https://doi.org/10.5194/hess-22-1875-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 16 Mar 2018

Research article | 16 Mar 2018

Assessing impacts of dike construction on the flood dynamics of the Mekong Delta

Dung Duc Tran1,5, Gerardo van Halsema1, Petra J. G. J. Hellegers1, Long Phi Hoang2, Tho Quang Tran3, Matti Kummu4, and Fulco Ludwig2 Dung Duc Tran et al.
  • 1Water Resources Management group, Wageningen University, P.O. Box 47, 6700 AA Wageningen, the Netherlands
  • 2Water Systems and Global Change group, Wageningen University, P.O. Box 47, 6700 AA Wageningen, the Netherlands
  • 3Southern Institute for Water Resources Planning, 271 An Duong Vuong Street, District 5, Ho Chi Minh City, Vietnam
  • 4Water & Development Research Group, Aalto University, P.O. Box 15200, Aalto, Finland
  • 5Centre of Water Management and Climate Change, Vietnam National University Ho Chi Minh City, Ho Chi Minh City, Vietnam

Abstract. Recent flood dynamics of the Mekong Delta have raised concerns about an increased flood risk downstream in the Vietnamese Mekong Delta. Accelerated high dike building on the floodplains of the upper delta to allow triple cropping of rice has been linked to higher river water levels in the downstream city of Can Tho. This paper assesses the hydraulic impacts of upstream dike construction on the flood hazard downstream in the Vietnamese Mekong Delta. We combined the existing one-dimensional (1-D) Mekong Delta hydrodynamic model with a quasi-two-dimensional (2-D) approach. First we calibrated and validated the model using flood data from 2011 and 2013. We then applied the model to explore the downstream water dynamics under various scenarios of high dike construction in An Giang Province and the Long Xuyen Quadrangle. Calculations of water balances allowed us to trace the propagation and distribution of flood volumes over the delta under the different scenarios. Model results indicate that extensive construction of high dikes on the upstream floodplains has had limited effect on peak river water levels downstream in Can Tho. Instead, the model shows that the impacts of dike construction, in terms of peak river water levels, are concentrated and amplified in the upstream reaches of the delta. According to our water balance analysis, river water levels in Can Tho have remained relatively stable, as greater volumes of floodwater have been diverted away from the Long Xuyen Quadrangle than the retention volume lost due to dike construction. Our findings expand on previous work on the impacts of water control infrastructure on flood risk and floodwater regimes across the delta.

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We modeled hydrological changes under impacts of large-scale dike constructions for intensive rice production in the floodplain of the Vietnamese Mekong Delta. Four scenarios show a significant increase in peak water levels in the upstream rivers, but very few water level changes are found downstream. Water balance calculations show where the floodwater goes under four dike construction scenarios. Its impacts on the tidal areas need to be clarified in the future with a 3-D hydraulic model.
We modeled hydrological changes under impacts of large-scale dike constructions for intensive...
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