A Numerical Study of Hydrodynamic Processes and Flood Mitigation in a Large River-lake System
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A Numerical Study of Hydrodynamic Processes and Flood Mitigation in a Large River-lake System Hongwu Tang 1 & Hao Cao 2 & Saiyu Yuan 1 & Yang Xiao 1 & Chenyu Jiang 2 & Carlo Gualtieri 3 Received: 2 March 2020 / Accepted: 21 July 2020/ # Springer Nature B.V. 2020
Abstract
Floods out of all other water problems cause very large damages in China. Previous flood management plans mainly focused on a single river by controlling its water level and conveyance capacity, while research on mitigation solutions to flooding issues in riverlake systems is scarce. This study considers the Huai River - Lake Hongze system, which is one of the largest river-lake systems in China. Very large damages associated with small floods are frequently observed in this river-lake system, although a series of flood management measures have been implemented in the Huai River Basin since the middle of the last century. An unstructured-grid finite-volume numerical model was applied to simulate hydrodynamic processes in this system, which is characterized by discrepant spatial scales between these two types of water bodies. It is found that the lake affects the upstream river flooding, but lowering the lake level would have limited effects that would be rapidly impaired by the sharp meander bend connecting the river and the lake. The artificial cutoff of this intensively-embanked bend has great potential in reducing the river stage and flood damages, as the construction of a diversion channel would shorten the flow path and increase the hydraulic gradient. This study extends the current knowledge about the hydrodynamics of river-lake systems and is beneficial to flood mitigation strategies for similar systems. Keywords Hydrodynamics . Flooding . River-lake interactions . Huai River . Lake Hongze . FVCOM
* Saiyu Yuan [email protected]
1
State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China
2
College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China
3
Department of Civil, Architectural and Environmental Engineering (DICEA), University of Naples Federico II, Naples 80125, Italy
H. Tang et al.
1 Introduction Floods, more than other water problems, cause the most damage and have taken a severe toll on reduction in crop yield, heavy casualties, and huge economic losses in China (Zhao et al. 2014). According to the Bulletin of Flood and Drought Disasters in China (Ministry of Water Resources of the People’s Republic of China 2019), annual direct monetary loss caused by floods from 1990 to 2018 was 150.90 billion RMB on average (about 21.35 billion US dollars). Conventional measures for flood management include (1) structural types of reservoirs on the upper reach, retention areas, dams and sluices, flood bypasses, dykes, and dredging (Hudson et al. 2008; Zhang et al. 2010; Zhang and Song 2014; Wan et al. 2018); and (2) non-structural types of flood forecasting by hydro-meteorological modeling or machine learning, and flood monitoring by re
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