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<br />Output Description.-Output of the model include initial bed-material <br />compositions, time and spatial variations of the water-surface profile, <br />channel width, flow depth, flood discharge, velocity, energy gradient, <br />roughness coefficient, median sediment size, and bed-material load. In <br />addition, cross-sectional profiles are printed at different time intervals. <br /> <br />CASE HISTORY OF RIVER CHANNEL CHANGES <br /> <br />The San Dieguito River at Rancho Santa Fe, California, went through <br />significant changes in a two-mile reach (see Fig. 1) during recent floods. <br />Measurements of river channel changes and flood hydrographs were made <br />by the County of San Diego (7,16), providing a valuable set of field data <br />for river studies. <br />Physical Conditions.-The study reach is about four miles from the <br />ocean and about five miles below Lake Hodges Dam. The channel has <br />a wide and flat natural configuration; the natural slope and bed-material <br />size decrease significantly in the downstream direction. Bed material of <br />the study reach varies from coarse sand (d", = 0.85 nun) at the upstream <br />end to fine sand (d", = 0.24 nun) downstream. <br />The natural channel configuration was distorted prior to recent flood <br />events by man's activities including sand mining and construction of the <br />VUl de Santa Fe Road and bridge as shown in Fig. 1. As a result of sand <br />mining, several large borrow pits with a depth as great as 25 ft were <br />created. The natural wide channel was encroached upon by the road <br />embankment on each side of the bridge (Section 51). While the river <br />channel has an erodible bed and banks, the banks, however, are con- <br />strained by the hills at the south bank of Section 51 and along the north <br /> <br /> <br />--<'-J) I <br />L <br /> <br />FIG. 1.-Topographles and Cross Section Locations <br />162 <br /> <br />11 <br />