Numerical appraisal of the relationship between a lake’s shrinkage and flooding in Dongting Lake area (China)

Author(s): Yizhuang Liu
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Institution or organization of origin: a School of Hydraulic Engineering, Changsha University of Science & Technology
Country: China


Floods are the most common and devastating natural disasters, which are becoming more severe and more frequent due to climate change, improper river regulation, urbanization and sedimentation alike. Generally, it is widely believed that a large plain lake can mitigate the flood disasters in a certain extent, which is supported by the fact that higher floodwater level at the same flood discharge can be observed when a lake loses partially or completely its storage capacity. This has also occurred in the Dongting Lake, the second largest lake in China currently, but it was the largest one in China about 50 years ago before shrinkage which is result from the land reclamation and the siltation. However, in the literature, there are few quantitative analyses of the relationship between Dongting Lake’s shrinkage and floodwater level. This paper aims to answer it using an open source software ANUGA. Different shrinking scenarios were modelled for comparison under the same flood event. The results show that the highest floodwater level increases by 2.8 m, 2.5 m and 1.02 m in west, south and east Dongting Lake if the lake area decreases to 860 km2. The peak discharge increases by around 13% (i.e., 6025 m3/s) and the peak flow occurs 21 hours earlier at its outlet or Chenglingji station due to a reduction of lake area from 4350 to 860 km2. For the hydrograph, the rising and falling limbs appear steeply due to the less storage capacity of floodwater after the lake shrinkage, which should

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