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<br /> 100 <br /> 50 <br />::t . <br /> e <br />I- - 100 .. <br />0 . ... <br />. e <br /> I/. ~ <br />~ <br /> 50 <br /> 10 <br /> <br />. <br /> <br />e <br /> <br />~ j <br /> <br />, I <br />t.: I <br /> <br />I <br />!' <br />I <br />I <br />! <br />I, <br />,: i <br />:i I <br />-(i,:'! <br />~ ; <br />I: <br />, ! <br /> <br />1500 <br /> <br />W. L. GRAF <br /> <br />LENGTH <br /> <br />Figure 12. Allometric relationship between lengths and widths of islands and bars. See <br />Tabid. <br /> <br />~: e <br />-~i' , <br />':1 <br /> <br /> <br />j i, <br />ril;: <br />~~;- 1 <br /> <br />Ii; <br />II <br />h <br />11'_ <br />Ill! <br />;l[ <br />J\ <br /> <br /> <br />Met r e . <br /> <br />10 <br /> <br />50 <br /> <br />100 <br /> <br />500 1000 <br /> <br />Almost all of the particles were derived <br />from local sandstones of the Navajo, <br />Kayenta, and Wingate Formations. <br />The 70 yr of recorded discharge data for <br />the lower Green River indicate that there <br />was a steady decline in discharge prior to <br />1934 (Fig. 13), which may have resulted in <br />the formation of new depositional featureSi <br />When high discharges occurred in th~ <br />1950s, these new forms were not rf:' <br />mobilized because of the anchoring effeC1'f <br />of invading tamarisk. Future changes are <br />unlikely unless' stream discharges are <br />dramatically altered by climatic change, a su <br />catastrophic flood, or human intervention. ',Ut <br />Photographic evidence, map analysis, co <br />and field surveys provide data that shoW St; <br />that tamarisk was introduced into the Co~ <br />orado River system from the southwestern RJ <br />part of the basin and spread throughout the <br />drainage system at a rate of 20 kmlyr (12 <br />mityr), and that the fluvial geomorphic sys- <br />terns in canyons with gentle gradients re- <br />sponded to the tamarisk invasion by de- <br /> <br /> <br />[\rei, <br />bar <br />1'55' <br />,dir <br />~: <br />!; <br />lAC <br />! <br />~ <br />~ <br />(thl <br />fin <br />.Re <br />th, <br /> <br />;se; <br /> <br />Al <br /> <br />B~ <br /> <br />Bt <br /> <br /> <br />-~, ; 7 <br />I"r <br />:;.,;'f <br /> <br />Figure 13. Annual discharge of Green River at upstream end of study area. Gage data from Green River (town), Utah, pub1i~hed' <br />U.S. Geological Survey Water-Supply Papers. Gage not operated 1900-1904. Mean annual discharge for 70 yr of record is 6,349 <br />· if::! <br /> <br />500 <br /> <br /> <br /> <br />50 <br /> <br />100 <br /> <br />500 1000 <br /> <br />15000 10,000 <br /> <br />Flit <br /> <br />12000 <br /> <br /> <br />100 <br /> <br />~ <br />II) <br />"" 8000 <br />2 <br />w <br />(!) <br />IX: <br /><t <br />1: <br />U 6000 <br />rJ) <br />0 <br />...J <br /><t <br />=> <br />Z 4000 <br />Z <br /><t <br /> <br />2000 <br /> <br />o <br />1890 <br /> <br />1900 <br /> <br />1910 <br /> <br />1920 <br />