Abstract

Abstract. Floods caused by levee breaching pose disastrous risks to the lower reaches and the flood flow zones of rivers. Thus, a comprehensive assessment of flow and sediment transport during floods must be performed to mitigate flood disasters. Given that the flow state becomes relatively more complex and the range of the submerged area becomes more extensive after a levee breach, this paper established a flow and sediment model by using two-dimensional shallow water equations (SWEs) to explore the breach development process and the flow and sediment transport in a curved bed after a levee breach due to overtopping. A three-element weighted essentially non-oscillatory Roe scheme was adopted for the discretization of SWEs. In addition, a non-equilibrium total-load sediment transport model was established to simulate the scour depth development process of the breach. A stable equilibrium of the breach was established based on flow shear force and soil shear strength. The lateral widening of the breach was simulated by the scouring-collapse lateral widening mode. These simulations, together with the levee breach experiment conducted in the laboratory, demonstrate the validity of the flow and sediment transport process established in this paper. The effects of water head in and out of the watercourse, the flow rate, the levee sediment grading, and other variables during levee breaching were also analyzed. The mathematical model calculation provided a number of physical quantities, such as flow rate and flow state at the breach, that are difficult to measure by using the current laboratory facilities. The results of this research provide fundamental data for developing measures that can reduce casualties and asset loss due to floods caused by levee breaching.

Highlights

  • Floods caused by levee breaching due to overtopping can cause major disasters

  • The aim of this study is to test the applicability of this approach for simulation of levee breach processes, and this was done by establishing a non-equilibrium total-load sediment transport model and the scouring-collapse mode of breach lateral widening based on the high-precision numerical format in calculating the flow from levee breaching to simulate the scour depth and lateral widening of breach development

  • The flow rate through the breach reached a stable both sides of the watercourse after levee breaching by an- value as well

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Summary

Introduction

Floods caused by levee breaching due to overtopping can cause major disasters. Many scholars have indicated the importance of studying this area. A considerable number of fruitful studies have been conducted (Morris, 2009). Risk assessment is a crucial premise for the mitigation of flood disasters. The flood development process, which is crucial to flood from levee breaching, must first be understood before flood risk assessment can be conducted (Apel et al, 2006). The use of mathematical models to calculate flood from levee breaching is currently a focus of several studies (Wu and Wang, 2007, Wu et al, 2012; Yu et al, 2009; Savant 5 et al, 2010; Liu and Wu, 2011; Chen, 2013)

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