7387

• UCREFRP Catalog Number: 7387
• Author: U.S. Bureau of Reclamation.
• Title: Glen Canyon Environmental Studies Executive Summaries of Technical Reports.
• USFW Year: 1988.
• USFW - Doc Type: \
• Copyright Material: NO

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Figure 1. Map of the Colorado River through Grand
Canyon National Park with location of the study sites.

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15-40 percent compared with 40-80 percent for hypercon-
centrated flow and 80-100 percent for streamflows
(Beverage and Culbertson 1964). Debris-flow deposits
were identified in tributary canyons on the basis of
poor sorting of particle sizes, lack of sedimentary
structures, and matrix support of cobbles and boulders.

During this study, debris-flow deposits were observed
in 36 tributaries of the Colorado River. Of these, 21
showed evidence of recent activity. On the basis of
previous reports of debris flows, we selected three of
these tributaries for more detailed study: Lava-Chuar
Creek drainage at River Mile (RM) 65.5, Monument Creek
drainage at RM 93.5, and Crystal Creek drainage at RM
98.2. The fieldwork for this project was completed in
March and April 1986.

The frequency of past debris flows was determined from
analysis of preserved stratigraphy in the tributaries.
Sediments from discrete debris flows were traced
longitudinally using their characteristic color,
lithology, and particle sizes. Radiocarbon dating,