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<br />11 <br /> <br />the present floodplain. At still lower elevations, a willow-covered inset bench <br /> <br />also is visible in many locations. <br /> <br />The bed, material in the study reach is gravel and cobbles, mantled by <br /> <br /> <br />sand or silt. Channel width is variable through the reach but exceeds 100 m at <br /> <br />most locations. Slope varies from .0001 to .001 m1m through the reach but is <br /> <br />generally between .0003 and .0005 m1m. Several semipermanent island <br /> <br />complexes are found within the study reach, and secondary channels separate <br /> <br />these islands from nearby floodplains and terraces. A few small rapids and <br /> <br />riffles are found in the reach, primarily where debris from dry washes enters the <br /> <br />channel. Two debris flows constrict the river into a rapid in the upstream <br /> <br />portion of the study reach. <br /> <br />METHODS <br /> <br />Analysis of USGS Discharge <br />Measurement Records <br /> <br />Over 2600 discharge measurements of the Green River were made at or <br /> <br />near Green River, Utah, between 1909 and 1993 by the U.S. Geological <br /> <br />Survey. Discharge measurements prior to 1909 are not available. Between <br /> <br />1912 and 1930 the measurements were made at a ferry and cableway located <br /> <br />approximately 9 km downstream from the present cableway (see Fig. 1). This <br /> <br />site was reoccupied and surveyed in 1997. After 1930, most measurements <br /> <br />were made at the present cableway, and these measurements provide an <br />