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<br />11
<br />
<br />backwaters which was expected because of the braided nature of Island Park.
<br />However, the average bank backwater was substantially larger than the
<br />average channel backwater. Backwater number per mile ranged from 5.6 at
<br />2,423 ft3/s to 9.8 at 1,381 ft3/s, which was the most for any site.
<br />Backwater area per mile ranged from 1,379 m2 at 5,260 ft3/s to 3,886 m2 at
<br />1,101 ft3/s, which was second only to the Ouray site. The average size of
<br />all backwaters usually increased at lower flows, and was maximized at
<br />1,101 ft3/s (426 m2) (table 5).
<br />
<br />Jensen
<br />
<br />The areas of interpreted classes at each flow for Jensen are presented in
<br />table 6. An inverse relationship between flow and backwater area occurred
<br />at the Jensen site similar to that at the Island Park site (table 7). The
<br />largest increases in backwater area occurred between 2,423 and 1~773 ft3/s
<br />where backwater area increased 49 percent from 7,328 to 10,944 m and
<br />between 1,430 and 1,381 ft3/s where area increased 37 percent from 15,014 to
<br />20,569 m2. Total backwater area was maximized at 1,381 ft3/s (20,569 m2).
<br />
<br />Total number of backwaters was qreatest at 1,687 ft3Ls (table 7).
<br />Backwaters were generally more prevalent-at the lower flows and were least
<br />abundant at 5,260 and 2,423 ft3/s. The >20-m2<200-m2 size class contained
<br />the most backwaters for both bank and channel classes. The largest
<br />backwaters (>1,000 m2) generally increased in number at lower flows.
<br />Numbers of bank backwaters were consistently greater than channel backwaters
<br />for all size classes, and the average size of bank backwaters was much
<br />greater than that of channel backwaters. Total backwaters per mile ranged
<br />from 4.6 at 5,260 ft3/s to 8.4 at 1,687 ft3/s, sli~htly less than at Island
<br />Park. Backwater area per mile ranged from 1,118 m at 5,260 ft3/s to
<br />2~981 m2 at 1,381 ft3/s. The average size of all backwaters ranged from 183
<br />m at 2,423 ft3/s to 447 m2 at 1,381 ft3/s (table 7). Isolated pool area
<br />increased as flow decreased with the exception of the 1,430 ft3/s flow.
<br />Isolated ~ool ar~ was maximized at 1,101 ft3/s and was lowest at
<br />5,260 ft3/S.
<br />
<br />Ouray
<br />
<br />The ~ of interpreted classes for each flow at Ouray are presented in
<br />table 8. The relationship between flow and backwater area was not as
<br />consistent at the Ouray site as it was at Island Park and Jensen. There was
<br />a lafge !7eadY increase in backwater area from 5,260 ft3/s (18,789 m2) to
<br />(J,68 ft_ $)(52,608 m2), however decreases in area occurred between
<br />1,687 ft /s and 1,430 ft3/s, and between 1,430 and 1,381 ft3/s (table 9).
<br />
<br />Total backwat~rs were maximized at ([;381 ft3/S) (74) and were also high at
<br />1,687 and 1,430 ft3/s (Table 9). With the exception of 5,260 ft3/s, there
<br />were more bank backwaters than channel backwaters at each flow. The >20-
<br />m2<200-m2 size class again contained the most backwaters, both bank and
<br />channel. However, the Ouray site had a disproportionately hi~h number of
<br />very large backwaters (>1,000 m2) at all flows except 5,260 ft Is. The
<br />large Ouray backwaters may account for the different relationship between
<br />flow and backwater area than that observed at Island Park and Jensen.
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