Geoscience Reference
In-Depth Information
bed geometry was the natural river. The time series of flow and sediment input at the
inflow section was basically taken the same as in the experiment, but it was somewhat
smoothed by averaging over certain periods. In addition, the experimental water depth
at the downstream boundary (dam) was prescribed.
Fig. 7.7 shows the calculated surface velocities at the beginning and after 76 years of
dam operation. At the beginning, when the natural bed still existed, the flow occupied
the entire calculation domain and obviously was faster in the narrower upstream reach,
and had a lower velocity and a more complex pattern in the vicinity of the dam where
the cross-section was considerably wider. After 76 years, much sediment has deposited
on the sides, and the river flows only in a fairly narrow channel similar to its behavior
before the dam was erected. The changes in the bed and hence the flow in several
selected cross-sections can be seen from Fig. 7.8 where the bed profiles are given for
the year zero and for the 54th year, showing clearly the rise of bed elevation due to
sediment deposition over the years. The figure compares the calculated bed profiles and
Figure 7.8
Simulated and measured surface velocity and bed profiles upstream of TGP dam
(Fang and Rodi, 2000).
