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<br />32 <br /> <br /> <br />002482 <br /> <br />abundant deposits of bare sand and narrow strips of vegetated flood plain and terrace <br />(Figure 19). Older oblique photographs, including some taken as early as 1889 show a <br />similar landscape (Turner and Karpiscak, 1980; Webb, 1996). Most of the large alluvial <br />deposits occurred on the inside of sharp meander bends, or downstream from these bends. <br />Eddy deposits were much less frequent and generally much smaller than the channel- <br />margin deposits. Averaged for all years of mapping, sand within eddy depositional zones <br />comprises about 11 % of the total area of fine-grained alluvium (Table 5). Gravel <br />deposits also occurred, but were less common than sand deposits. In most cases, the <br />gravel bar surfaces had numerous patches of sand and were mapped as mixed sand and <br />gravel. Sand deposits covered approximately 84% of the 122 ha of mapped alluvial <br />deposits; the remaining area was covered by mixed sand and gravel. <br />Although bare alluvial sand deposits were abundant in 1952, terraces covered <br />with vegetation made up a greater percentage of the alluvial valley. Of the 122 ha of <br />mapped alluvial deposits, 66% were terraces and the remainder were low and high <br />elevation active-channel deposits. The 1952 bankfull channel area was calculated as the <br />sum of the active channel deposits and the wetted channel. This area was divided by the <br />length of the mapped area (25211 m), yielding a reach-average estimate for bankfull <br />channel width of 156 m (Table 6). <br />Tables summarizing the area of map units for 1952 and each subsequent year of <br />aerial photography are included in Appendix F. <br /> <br />Glen Canyon in 1984-2000 <br />The character and distribution of alluvial deposits changed dramatically following <br />closure of Glen Canyon Dam. The total area of alluvial deposits increased by about 50% <br />(60 ha) between 1952 and 1984, but the proportion of those deposits composed of sand <br />decreased (Figure 20). The increased abundance of gravel and cobble is most dramatic in <br />the upstream 10 km of the study area where these bars were rare in 1952 and abundant in <br />1984 (Plate 1). The net increase in the area of alluvium, which is mostly gravel, has been <br />accompanied by an increase in the area of dense vegetation on,the remaining fine- <br />sediment deposits, resulting in a reduction ofthe area of bare sand (Figure 20). Although <br />