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Differentiation of debris-flow and flash-flood deposits: implications for paleoflood investigations

By:
,
Edited by:
Shen Hsieh WenSu S.T.Wen Feng

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Abstract

Debris flows and flash floods are common geomorphic processes in the Colorado Rocky Mountain Front Range and foothills. Usually, debris flows and flash floods are associated with excess summer rainfall or snowmelt, in areas were unconsolidated surficial deposits are relatively thick and slopes are steep. In the Front Range and foothills, flash flooding is limited to areas below about 2300m whereas, debris flow activity is common throughout the foothill and alpine zones and is not necessarily elevation limited. Because flash floods and debris flows transport large quantities of bouldery sediment, the resulting deposits appear somewhat similar even though such deposits were produced by different processes. Discharge estimates based on debris-flow deposits interpreted as flash-flood deposits have large errors because techniques for discharge retrodiction were developed for water floods with negligible sediment concentrations. Criteria for differentiating between debris-flow and flash-flood deposits are most useful for deposits that are fresh and well-exposed. However, with the passage of time, both debris-flow and flash-flood deposits become modified by the combined effects of weathering, colluviation, changes in surface morphology, and in some instances removal of interstitial sediment. As a result, some of the physical characteristics of the deposits become more alike. Criteria especially applicable to older deposits are needed. We differentiate flash-flood from debris-flow and other deposits using clast fabric measurements and other morphologic and sedimentologic techniques (e.g., deposit morphology, clast lithology, particle size and shape, geomorphic setting).

Additional Publication Details

Publication type:
Conference Paper
Publication Subtype:
Conference Paper
Title:
Differentiation of debris-flow and flash-flood deposits: implications for paleoflood investigations
ISBN:
0872629201
Issue:
pt 2
Year Published:
1993
Language:
English
Publisher:
Publ by ASCE
Publisher location:
New York, NY, United States
First page:
1900
Last page:
1901
Number of Pages:
2
Conference Title:
Proceedings of the National Conference on Hydraulic Engineering
Conference Location:
San Francisco, CA, USA
Conference Date:
25 July 1993 through 30 July 1993