STUDY ON BED VARIATIONS AND FLOODING FLOWS OF THE JULY 2012 FLOODS IN THE KAGETSU RIVER

Abstract

Successive large scale floods which exceeded the designed discharge occurred in the Kagetsu River in July 3 and 14, 2012. The floods caused serious damages such as levee breaches and flood inundations. In this paper, we analyzed both flood behavior in the river and inundations by numerical analysis of quasi-three dimensional flows and bed variations. Causes of levee breaches were investigated by velocity distributions and bed variations during the floods. Numerical simulation showed that the river-crossing structure (Yuta Bridge) caused severe overflows by the drift-woods accumulation and large inundation over dense housing areas.