Numerical Simulation of Effects of River Reconstruction on Flooding: A Case Study of the Ba River, China

Haixiao Jing,Xinhong Wang,Mingyang Yang,Zongxiao Zhang,Yongbiao Lang,Yanhu Mu

doi:10.1155/2021/5538059

Abstract

The local reconstruction of river channels may pose obstacles of flood flow, local eddy currents, or high flow velocity which pose potential threats to human life and infrastructures nearby. In the design of such projects, the effects of local reconstruction of the river channel on flooding are often evaluated by the one-dimensional method, which is based on the formula of one-dimensional nonuniform flow. In this study, a two-dimensional hydrodynamic model based on shallow water equations is employed to investigate the impacts of river reconstruction on flooding in the Ba River, China. The finite volume method and an unstructured triangular mesh are used to solve the governing equations numerically. The numerical model is validated by comparison with the results of a physical model of 1 : 120 scale. The backwater effects and impacts of flood flow fields under two flood frequencies are analyzed by comparing the numerical results before and after local reconstruction. The results show that the backwater length under both 10-year and 100-year floods can be reached up to the upstream boundary of the computational domain. However, the maximum water level rises are limited, and the levees in this river channel are safe enough. The flow velocity fields under both floods are changed obviously after local reconstruction in the Ba River. Areas with the potential for scour and deposition of the river bed are also pointed out. The findings of this study are helpful for the evaluation of flood risks of the river.

Highlights

River flooding, which is commonly caused by sudden and intense rainfalls or storms in the river’s watershed, can cause loss of human lives and serious damage to infrastructures and properties along the river
Backwater effects caused by an obstruction in rivers are a common phenomenon which increase flood risk by raising the water level upstream
In order to evaluate the effects of local reconstruction on the flooding of the Ba River in China, a two-dimensional hydrodynamic model was developed, in which the TVD

Summary

Introduction

River flooding, which is commonly caused by sudden and intense rainfalls or storms in the river’s watershed, can cause loss of human lives and serious damage to infrastructures and properties along the river. With the climate change (such as global warming) in recent years, it has been found that extreme rainfalls occur more intensely and result in more serious floods [1, 2]. For river channels through urban areas, hydraulic structures such as weirs and artificial islands are often designed to raise the water level upstream where wetlands or parks are built to improve the scenery nearby. For the design of such hydraulic structures, flooding is treated as one of the most important factors. The presence of such structures will affect the flooding of the river channel. Proper evaluation of the impact of river reconstruction on river floods is of great help for the design of river projects and flood risk management of the river channel

Methods

Results

Conclusion