In this method, the main emphasis is placed on backwater effects. Traditionally, during the design of hydraulic structures, the effects on river flooding are mostly evaluated by the one-dimensional (1D) method which is based on the law of conservation of energy. Therefore, 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. In addition, the presence of such structures will affect the flooding of the river channel. For the design of such hydraulic structures, flooding is treated as one of the most important factors. 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. Furthermore, with the climate change (such as global warming) in recent years, it has been found that extreme rainfalls occur more intensely and therefore result in more serious floods. 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. The findings of this study are helpful for the evaluation of flood risks of the river. Areas with the potential for scour and deposition of the river bed are also pointed out. The flow velocity fields under both floods are changed obviously after local reconstruction in the Ba River. However, the maximum water level rises are limited, and the levees in this river channel are safe enough. 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. 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 numerical model is validated by comparison with the results of a physical model of 1 : 120 scale. The finite volume method and an unstructured triangular mesh are used to solve the governing equations numerically. 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. 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.

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.

Mike 21 flood