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<br />P tAtS e <br />break <br /> <br />There are two approaches to determining the discharges necessary to maintain the <br /> <br />channel's diversity. One approach is to directly measure habitat movement and <br /> <br />reworking" by measuring sediment transport and bed sco~and fill in those parts of the <br /> <br />channel that ar~~fi6tr~atitat. A second approach is to determine those discharges at <br /> <br />which habitat maintenance is known to occur, on average,"~ typical alluvial streams. We <br /> <br />pursued both approaches in this study. <br /> <br />The most widely accepted surrogates for establishing ~ischarges necessary to <br /> <br />transport significant amounts of sediment andjhereb))maintain the channel are the <br /> <br />concepts ofiM-bankfull and effective discharge6 Frequently.!ccurring floods of <br /> <br />moderate magnitude transport the greatest amount of sediment and are believed to <br /> <br />accomplish the greatest amount of geomorphic work in alluvial rivers (Wolman and <br /> <br />MillerA 960). While extremely high discharges can carry huge amounts of sediment, <br /> <br />large floods are rare, and the majority of sediment is typically transported by more <br /> <br /> <br />frequently occurring moderate floods. The discharge ~. accomplishes the most <br /> <br />geomorphic work is known as the effective discharge. Andrews and Nankervis (1995) <br /> <br />calculated effective dischargtfiin 17 gravel-bedded streams, and found that effective <br /> <br />discharg~typically fell in the range of 0.8 and 1.6 times the bankfull discharge. Andrews <br />',(\+erva-\ <br />(1980) found that the range of effective discharges had a recurrencel\of between 1.2 and <br /> <br />~(.s <br />3.3 in the Yampa River basin. The bankfull flood, because of this association with <br /> <br />effective discharge, is often used as an indicator of the moderate flood)which typically <br /> <br />creates the form of the channel (Andrews and Nankervis0995). <br /> <br />Background -- Geomorphic Research about the White River and Its relationship to the <br /> <br />3 <br />