Seite - 485 - in Book of Full Papers - Symposium Hydro Engineering

Fig. 3 Location map of study area is about 1 km downstream from the Yeongju Dam (Fig. 3). At No. 1, the bed slope was 0.0026 and the channel width was 86.5 m. At No. 2, the bed slope was 0.0012 and the width was 112.3 m. The channel is significantly changed at a bankfull discharge where the water overflows the lower channel and starts to fill the flood plain. Therefore, for the sediment supply to the dam downstream, a bankfull discharge of 9.00 m3/s, calculated using HEC-RAS, was applied to the study reach. In addition, the effect of sediment supply was analyzed at the discharge of 15.13 m3/s, considering the discharge from the dam. 4.2 COMPUTATIONAL CONDITIONS A two-dimensional numerical model, Nays2DH, was employed to simulate the effect of the sediment supply to the dam downstream. Table 1 shows the hydraulic conditions for the numerical simulation. The length of the river was 10 km, and the bed slope was 0.001. The mean diameter of the sediment was 4.61 mm. The Manning's n value was set to 0.031. The time step for the numerical calculation was 0.01 seconds. Considering the geographic effects of the relatively steep slope and the serpentine flow, the grid size was set to 0.2 m in the flow direction and 0.1 m in the transverse direction. To investigate the channel changes, Table 1 Parameters for numerical simulation Case Discharge (m3/s) Sediment inflow condition Remarks Run-1 9.00 Trap efficiency : 98.7% Bankfull discharge Run-2 15.13 Trap efficiency : 98.7% Water supply 485