Accuracy of Estimated Flood Discharge Hydrograph in Steep River by 2-D Numerical Simulation

Abstract

Floods accompanied by bed elevation change were observed in a steep reach of the Minochi River in 2009 and 2010. The flood discharge hydrograph in 2009 is estimated by three methods, namely the conventional float measurement, Large-scale PIV method and 2-D unsteady flow simulation. The 2-D flow simulation considers vegetation toppling during flood and bed elevation change due to bed load transport. In the numerical simulation, water level hydrographs observed at various points are used for boundary conditions at upstream and downstream ends and the evaluation of the vegetation drag parameter. The flood discharges obtained by three methods are compared to find that the 2-D unsteady flow model yields good agreement with the discharge by Large-scale PIV method. The selection method of the location of suitable upstream boundary in a step reach is also discussed