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| Titel |
Impacts of dyke development in flood prone areas in the Vietnamese Mekong Delta to downstream flood hazard |
| VerfasserIn |
Van Khanh Triet Nguyen, Viet Dung Nguyen, Hideto Fujii, Matti Kummu, Bruno Merz, Heiko Apel |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127855
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| Publikation (Nr.) |
 EGU/EGU2016-7776.pdf |
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| Zusammenfassung |
| The Vietnamese Mekong Delta (VMD) plays an important role in food security and
socio-economic development of the country. Being a low-lying coastal region, the VMD is
particularly susceptible to both riverine and tidal floods, which provide, on (the) one hand, the
basis for the rich agricultural production and the livelihood of the people, but on the other
hand pose a considerable hazard depending on the severity of the floods. But despite
of potentially hazardous flood, the area remain active as a rice granary due to its
nutrient-rich soils and sediment input, and dense waterways, canals and the long standing
experience of the population living with floods. In response to both farmers’ requests
and governmental plans, the construction of flood protection infrastructure in the
delta progressed rapidly in the last twenty years, notably at areas prone to deep
flooding, i.e. the Plain of Reeds (PoR) and Long Xuyen Quadrangle (LXQ). Triple rice
cropping becomes possible in farmlands enclosed by “full-dykes”, i.e. dykes strong
and high enough to prevent flooding of the flood plains for most of the floods. In
these protected flood plains rice can be grown even during the peak flood period
(September to November). However, little is known about the possibly (and already
alleged) negative impacts of this fully flood protection measure to downstream
areas.
This study aims at quantifying how the flood regime in the lower part of the VMD (e.g.
Can Tho, My Thuan, …) has been changed in the last 2 recent “big flood” events of 2000 and
2011 due to the construction of the full-dyke system in the upper part. First, an evaluation of
35 years of daily water level data was performed in order to detect trends at key gauging
stations: Kratie: upper boundary of the Delta, Tan Chau and Chau Doc: areas with
full-dyke construction, Can Tho and My Thuan: downstream. Results from the
Mann-Kendall (MK) test show a decreasing trend of the annual maximum water
level at 3 stations Kratie, Tan Chau and Chau Doc. The MK test statistic results (Z)
for these stations are -0.23, -1.39 and -0.84 respectively. In contrary, significant
increasing trend (at α = 1%) of annual flood peak at Can Tho and My Thuan is
calculated, with the Z value are 5.20 and 4.28. A Monte Carlo experiment by adding
assumed observation errors of 5%, 10% and 15% results in similar trend for these
stations.
After the trend analysis, a set of scenarios are generated based on various hydrological
boundaries, infrastructure developments and climate change scenarios. The scenarios are
simulated with the quasi-2D hydrodynamic model for the Mekong Delta (Dung, 2011; Manh,
2014) in order to separate and quantify the impacts of flood protection measures to the
flood regime in the lower part of the delta in a spatially explicit manner, with a
special focus on the urban and economic centers Can Tho and My Thuan. Based on
these scenarios the change in flood hazard caused by the infrastructure development
that has to be expected is described and possible mitigation actions are proposed. |
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