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<br />17 <br /> <br />There have been three periods in the evolution of the channel at the <br /> <br /> <br />cableway (Fig. 10a). Channel narrowing occurred at the bankfull level between <br /> <br /> <br />1930 and 1938 and again after 1959. Between these periods, channel width <br /> <br /> <br />did not change. The channel is continuing to narrow, and has not completely <br /> <br /> <br />adjusted to the present-day hydrologic regime. <br /> <br /> <br />Channel cross sections were plotted from the discharge measurements <br /> <br /> <br />to detennine the location of. the b~nk accretion that has caused channel <br /> <br /> <br />narrowing at the present cableway (Fig. 11). The left bank has been very <br /> <br /> <br />stable at this site, but approximately 12 m of sediment has accreted on the right <br /> <br /> <br />bank. Rapid accretion rates occurred between 1957 and 1962.. <br /> <br />Hydraulic Geometry <br /> <br /> <br />Hydraulic geometrY relations were calculated for the present cableway <br /> <br /> <br />cross section for the time periods 1930 to 1938 (narrowing), 1939 to 1957 <br /> <br /> <br />(stable), and 1963 to 1993 (narrowing), using discharge measurement data. <br /> <br /> <br />The relationships are shown in Figure 12. The figure shows a shift in the width- . <br /> <br /> <br />to-discharge relation. Changes in mean depth and mean velocity are less <br /> <br /> <br />apparent due to the smaller scale of the change when compared to the width <br /> <br /> <br />data. These plots show that the channel width has decreased over the entire <br /> <br /> <br />range of discharges. <br />