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<br />5 <br /> <br />2600 discharge measurements that have been made at this site since 1909. <br />We supplemented this detailed temporal analysis of a single cross section with <br />air photo analys,isof an adjacent 26.4-km reach, stratigraphic analysis of bank x <br />deposits, channel cross-section measurements of scour and fill during flood <br />passage, and measurement of velocity and suspended sediment distribution at <br />flood stage. The purposes of this thesis are to describe the history of channel <br />change of the Green River in the study area, to relate that history to climatic <br />change, saltcedar (T~marix sp.) invasion, and dam construction, and to <br />describ~ the process of channel narrowing by vertical accretion. <br /> <br />ChannelFonn <br /> <br /> <br />Classic studies conclude that channel geometry in a river system is <br /> <br /> <br />largely controlled by the magnitude and duration of flood events (Wolman and <br /> <br /> <br />Leopold, 1957; Wolman and Miller, 1960). Andrews (1980) introduced the term <br /> <br /> <br />"effective discharge" which is the increment of discharge that transports the <br /> <br /> <br />most sediment, when averaged over a period of years. He also showed that <br /> <br /> <br />channels narrow in association with decreased magnitude of the effective <br /> <br /> <br />discharge. Other studies have shown that channel form changes in response to <br /> <br /> <br />factors either directly or indirectly associated with the magnitude and duration <br /> <br /> <br />of flow. These factors include; large magnitude floods (Schumm and Lichty, <br /> <br /> <br />1963; Burkham,1972; Osterkamp and Costa, 1987; Pizzuto, 1994; Gomez et aI., <br /> <br /> <br />1995; Friedman et aI., 1996), damming and diversion (Williams, 1978; Williams <br />