9390

• UCREFRP Catalog Number: 9390
• Author: Webb, R. H., T. S. Melis and R. A. Valdez.
• Title: Observations of Environmental Change in Grand Canyon, Arizona.
• USFW Year: 2002.
• USFW - Doc Type: 02-4080,
• Copyright Material: NO

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Figure 2. Badger Creek Rapid (mile 8.0).

A. August 1964. In this view of Badger Creek Rapid from the left canyon rim, low water in the Colorado River
reveals many of the rocks that constrict the river. The sand bar on river right has significant sand and a few
scattered, non-native tamarisk trees (Tad Nichols, no number, courtesy of the photographer).

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flows is generally greater than 80 percent. Debris flows
occur infrequently; only 60 percent of the tributaries in
Grand Canyon have produced debris flows in the last
century (Griffiths and others, 1996). Because they
transport large boulders, debris flows leave spectacular
evidence of their occurrence, and most observers of
these floods left a written record or had a vivid memory
of the event. In contrast, streamflow floods have a
sediment concentration of less than about 40 percent
and occur more often. Some observers (e.g., Reilly)
could distinguish the two types of floods.
The Old Timers remember few new debris-flow
deposits, and only a few debris flows are recorded in
diaries. We showed the Old Timers the 1994, Jackass
Creek (mile 7.9-L) debris-flow deposits at Badger
Creek Rapid (mile 8.0), and discussed this geomorphic
process with them extensively (Fig. 2). We then asked
them if they had seen any similar deposits along the
river during their river experiences. Rigg remembered
when the debris fan of Boucher Creek (mile 96.7-L)

changed radically in 1951 or 1952. When he first saw
it, mud was still oozing out from between the boulders.
Using Robert Brewster Stanton's photographs from
1890, we had identified the Boucher Creek debris flow
as one of the largest in the last century in Grand
Canyon but had not known the exact year it occurred
(Melis, 1997; Webb, 1996).
The highest frequency of debris flows in Grand
Canyon occurs at Lava Falls Rapid (mile 179) from
Prospect Canyon (mile 179.4-L; Webb and others,
1999b). In 1954, Georgie White arrived at Lava Falls
on July 24, and saw Prospect Creek (mile 179.4-L)
running at "full force." Large boulders were entering
the river in a manner White likened to a "big black lava
flow." White's observations are only the second
eyewitness account of a Grand Canyon debris flow,
after Robert Brewster Stanton's account of a debris
flow in South Canyon (mile 31.6-R; Smith and
Crampton, 1987). Jones remembered that the debris fan
of Prospect Canyon (mile 179.4-L) was paved with fine

SPECIFIC CHANGES OBSERVED IN GRAND CANYON 9