CHARACTERISTICS OF LEVEE BREACH AND INUNDATION INFLUENCED BY VARIATIONS OF RIVER DISCHARGE

Abstract

 The overflow breaches in historical flood events have been investigated using a process-based model (Delft3D) in order to understand levee breach and inundation characteristics related to variations in river flood magnitudes. The model consists of shallow water equations coupled with secondary flow, grain-size distribution of riverbed and levee materials, and erosion of steep banks adjacent to wet cells. The model validation is carried out against a 200-meter wide breach of the levee along the Kinugawa River (Japan) in September 2015. The model is appropriate for the estimation of final breach width, morphological changes in flood plain, inundation depth, and flow velocity. Numerical experiments on levee breach and inundation by using river discharges different from the historical flood event show that the variations in flood peak discharge and flood duration have a significant influence on breach widening and deepening.