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Last modified
1/26/2010 3:16:33 PM
Creation date
10/12/2006 4:48:50 AM
Metadata
Fields
Template:
Water Supply Protection
File Number
8220.101.10
Description
Colorado River-Water Projects-Glen Canyon Dam/Lake Powel-Glen Canyon Adaptive Management
Basin
Colorado Mainstem
Water Division
5
Date
1/1/2002
Author
Webb-Melis-Valdez
Title
Observation of Environmental Change in Grand Canyon Arizona
Water Supply Pro - Doc Type
Report/Study
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<br />'1~'9 <br /> <br />Table 3. List of known driftwood fires in Grand Canyon, 1937-1964. <br /> <br />Relative Size <br /> <br /> Year Date Diarist Location <br /> 1455 Jul 5 P.T. Reilly Spfln!!, Canynn <br /> 1955 J"I 13 F. Wright Hance Ibrid <br /> lY56 lUll 19 P.T Reilly 24 1/2-J\.file k::Jpid <br /> IY56 JUIl 20 P,T. Reilly Pre"idt"111 Hanling Rapid <br /> 19.5f1 lUll 30 P.T. Reilly Fern Glen C<lnyon <br />I 11,156 J"I 13 F. Wrighl Hanct' Rapid <br /> <br />Largl' <br />Signal tire <br />Unknown <br /> <br />Unknown <br /> <br />Largt" <br />Signal fire <br /> <br />, <br /> <br />were. The Old Timers remarked on the severe beach <br />erosion in the reach downstream from Nankoweap <br />Rapid (river mile 53-54) and at the mouth of the Little <br />Colorado River (mile 61.5-L). Elves Chasm (mile <br />116.5-L). Slone Creek (mile 131.9-R). Tapeats Creek <br />(mile 133.8-R: Fig. 3). Deer Creek Falls (mile 136.I-R: <br />Fig. 4), and the mouth of Kanab Creek (mile 143.5-R). <br />Comments about beach erosion decreased <br />downstream of Havasu Creek (mile 156.9-L). which <br />mayor may not be significant. They either continued to <br />see eroded bars and felt it not wor1h additional <br />comment, or the bars may not have been as eroded as <br />upstream, as reported in Sehmidt and others (] 995). <br />and Webb (1996). Although the Old Timers noted the <br />increase in riparian vegetation, none of lhem ::lSSOCialed <br />this increase with a lack of campsites. Most of their <br />comments came at heavily used sites. not generic s:lnd <br />bars. In no case did the Old Timers specifically <br />contradict our interprelations of historic photographs. <br />Both Reilly and Beer lamented the loss of <br />camping beaches during trips they made in the 1980s. <br />During a 1984 trip. Reilly observed erosion of sand <br />bars at Tuckup Canyon (mile 164.5-R). National <br />Canyon (mile I 66.4-Ll. and Fern Glen (mile 168.0-R). <br />Beer. in particular. remembers the sound of sand bars <br />calving off into the river as he swam by in April 1955. <br />Rigg noted that several sand bars he had camped on <br />were now either reduced or eliminated. Nichols <br />commented on the reductions in sand bars at the mouth <br />of the Little Colorado River (mile 61-L). Elves Chasm <br />(mile 116.5-L). and Deer Creek Falls (mile 136.2-R). <br />Cross II pointed out a large reduction in the sand bar at <br />the mouth of Stone Creek as an example of extreme <br />erosion. <br />Reilly observed the relation between sand-bar <br />erosion. tributary flows. and pre-dam river flows. He <br />observed bank calving during a 3-4 foot rise in the river <br />in 1956 that resulted from storm runoff. At Tapeats <br />Creek (mile 133.8-R) in 1962. Reilly watched as the <br /> <br />,: <br /> <br />river eroded the sand bar below the rapid. He saw large <br />channels cut Ihrough sand bars during storm runoff in <br />1953. These incidents were mentioned primarily <br />because Reilly considered sand bar erosion a hazard to <br />sleeping boatmen. not because he was concerned that <br />sand bars were diminishing. <br />Cross II. who ran the river frequently in the years <br />after closure of Glen Canyon Dam. described the slow. <br />progressive loss of sand bars in Marble Canyon <br />through the 1960s. He believed that wind erosion and <br />human impacts. not large clear-water releases slIch as <br />the 1965 high flows. were the dominant reasons for <br />sand bar erosion from 1963. through about the mid- <br />1970s. He used tile separation bar at Soap Creek Rapid <br />(mile 11.3) as an example of a campsile that. from his <br />memory. just gradually blew away. <br />Rigg thought that the sand-bar erosion <br />downstream from Nankoweap Creek \Vas probably the <br />greatest of any place in Grand Canyon. What formerly <br />\Vas a sand-lined channel is now a reach lined with <br />gravel bars. We had previously recognized the extent <br />of sand-bar erosion in this reach (Webb. 1996). <br /> <br />Channel Bars <br /> <br />The Old Timers were impressed with cllanges in <br />three debris-bar-controlled rapids. The Rock Garden at <br />Crystal Rapid (mile 98.4) formed as a consequence of <br />the 1966 debris flow and subsequent reworking by the <br />Colorado River. No pre-dam river runners (or their <br />photographs) noted the presence of a debris bar below <br />Crystal Rapid before 1966. Shoemaker. Rigg. and <br />Nichols felt that the debris bars at the mouth of the <br />Little Colorado River. and Vaseys Paradise (mile 31.8- <br />R) had aggraded significantly. although they admitted <br />that the perceived changes could. at least partly be <br />attributed to diffaences in water level. Pre-dam river <br />runners. particularly Reilly. ran left of the island at the <br /> <br />SPECIFIC CHANGES OBSERVED IN GRAND CANYON 17 <br />
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