Seite - 486 - in Book of Full Papers - Symposium Hydro Engineering

the amount of sediment supply was determined by considering the trapped sediment by the dam. 4.3 NUMERICAL RESULTS Fig. 4 shows the planimetric changes of the bed for Run-2. In the immediate downstream of the dam, the flow focused on the left bank where the bed elevation decreased. The area corresponded to No. 1 where the sediment placed in the dam downstream. The sediment transported to the river downstream. However, as the flow was dispersed in the straight reach, the bed elevation increased. The bed elevation decreased at No. 2. While the bed elevation decreased in the outer part of the curved region downstream, the elevation increased in the inner part of the meandering reach. Fig. 5 shows the cross-sectional changes at 400 m and 600 m downstream for Run-2. At 400 m downstream, the bed elevation decreased over time. About 10 hours later, the bed elevation decreased at the center of the river and in the right bank (Fig. 5(a)). The bed decreased initially at the center of the channel, and then the bed scoured in the right bank also as the flow focused on the outer part of the curved region (Fig. 5). The sediment was deposited at the center of the river at 600 m. Fig. 6 and 7 show the comparison results of the bed changes between Run- 1 and Run-2. At No. 1 and No. 2, the bed elevation changed over time, and the change was greater in Run-2 than in Run-1. In other words, the change in the bed elevation was greater at a higher discharge. The numerical results showed that the Fig. 4 Planimatric changes for Run-2 486