Author(s): W. H. Graf; L. Suszka
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Abstract: Experimental data are reported for unsteady channel flow and its effect on sediment transport. 15 hydrographs (see Fig. 3) - consisting of different base flows, ▲, and wave characteristics, △h/△T, - were investigated (for definition, see Fig. 8), together with the instantaneously measured sediment dis-charge, Q_s, (t), and the calculated sediment discharge, Q_so (t), by assuming the flow depth as an equivalent steady one (for examples, see Fig. 4). Further, let v_8。and v_so be the sediment volume after passage of the entire hydrograph, obtained with eq. (8). The data are presented in dimensionless form on Fig. 6 according to equation (9). The trend is evident: an increase in (△h/△T) /u_* values - for a given base flow this implies a steeper hydrograph - has as consequence an in crease in (V_s - v_so. ) /V_so value. However, no matter how steep the hydrograph, as long as there exists unsteady flow, the (true) sediment volume, v_s。, is always larger than the one calculated for an equivalent steady flow, V_so; or V_s > V_so. With two real cases - one during the flushing of a power station and one during a flash flood in a creek - ve show (see Tab. 1) the importance of ourf indings.
Year: 1985