Hydrol. Earth Syst. Sci., 21, 3991–4010, 2017 https://doi.org/10.5194/hess-21-3991-2017 © Author(s) 2017. This work is distributed under the Creative Commons Attribution 3.0 License. Has dyke development in the Vietnamese Mekong Delta shifted flood hazard downstream? Nguyen Van Khanh Triet1,4, Nguyen Viet Dung1,4, Hideto Fujii2, Matti Kummu3, Bruno Merz1, and Heiko Apel1 1GFZ German Research Centre for Geosciences, Section 5.4 Hydrology, 14473, Potsdam, Germany 2Faculty of Agriculture, Yamagata University, 1-23 Wakaba-machi, Tsuruoka, Yamagata 997-8555, Japan 3WDRG Water & Development Research Group, Aalto University, Helsinki, Finland 4SIWRR Southern Institute of Water Resources Research, Ho Chi Minh City, Vietnam Correspondence to: Nguyen Van Khanh Triet (
[email protected]) Received: 4 March 2017 – Discussion started: 6 April 2017 Revised: 26 June 2017 – Accepted: 5 July 2017 – Published: 7 August 2017 Abstract. In the Vietnamese part of the Mekong Delta of 19–32 cm. However, the relative contributions of the three (VMD) the areas with three rice crops per year have been drivers of change vary in space across the delta. In summary, expanded rapidly during the last 15 years. Paddy-rice culti- our study confirms the claims that the high-dyke develop- vation during the flood season has been made possible by im- ment has raised the flood hazard downstream. However, it plementing high-dyke flood defenses and flood control struc- is not the only and not the most important driver of the ob- tures. However, there are widespread claims that the high- served changes. It has to be noted that changes in tidal levels dyke system has increased water levels in downstream areas.