Flood Mitigation Using an Innovative Flood Control Scheme in a Large Lake: Dongting Lake, China

Abstract

A large lake plays an important role in mitigating flood disasters in its nearby regions during the flooding period; however, the effect is limited, because most of its storage capacity becomes dead storage prior to the arrival of the flood wave. In the current study, an innovative flood control scheme (IFCS) is applied to Dongting Lake (the second largest freshwater lake in China) to alleviate flood disasters. MIKE 21 FM was used to examine its feasibility to mitigate flood disasters. One of the largest floods in the 20th century, the 1998-type flood, was modelled and the maximum water levels with/without IFCS were compared. The result shows that the effective flood control storage could be at least doubled when compared with the natural condition once IFCS was applied. The peak flood level in the Dongting Lake could be lowered by at least 0.32 m at the Chenglingji station in the same flood passage of Dongting Lake. The case study reveals that, after applying IFCS, the hydraulic gates play a very important role in floodwater regulation and further study should be conducted to find the optimized operation for each gate in the flood control scheme system.

Hydrological Drought in Dongting Lake Area (China) after the Running of Three Gorges Dam and a Possible Solution

“…A previously calibrated 2D depth-averaged hydrodynamic model (Mike 21 FM) was used in this study since it could simulate the hydrodynamic process well in Dongting Lake [21]. The model covers the whole area of Dongting Lake, "three channels", "four rivers" and a part of the middle reach of Yangtze River.…”

“…The upstream boundary conditions were specified as the daily inflow records of Yangtze River (i.e., Zhicheng station) and the four rivers (Xiangtan station, Taojiang station, Taoyuan station and Jinshi station). The downstream boundary condition used the rating curve observed at Luoshan station on Yangtze River [21]. The wetting and drying process function [27] was used as the water surface varies significantly in the lake area [28].…”

“…Previously calibrated parameters such as Manning roughness number (from 32 m 1/3 /s to 60 m 1/3 /s) of the lake and the minimum time step (i.e., 2s) were used in the current module. More details of the model could be found in the previous study [21], thus a brief description of the model is given here. The 2D hydrodynamic model was validated using the measured water level at the stations in the lake (i.e., Nanzui, Yintan, Lujiao and Chenglji stations, see Figure 2) during the dry season of 2006.…”

“…Therefore, to solve its water shortage problem, one has to convert its floodwater into water resources in the dry period. Yang et al [20] and Liu et al [21] proposed an innovative flood control scheme (IFCS) as shown in Figure 1. Together with the existing dike surrounding the lake, they suggest building an inner dike with several gates to form an inner lake for mitigation of flood disaster in wet seasons.…”

“…During the flood period, the peak floodwater could be diverted into the inner lake for storage by opening the gates, thus the inner lake functions as a giant flood-detention pond. More details could be found in the previous study [21]. The stored water will be released when the gates are open to regulate the outflow in the dry seasons.…”