Grantee Research Project Results
1999 Progress Report: Formation and Propagation of Large-scale Sediment Waves in Periodically Disturbed Mountain Watersheds
EPA Grant Number: R824779Title: Formation and Propagation of Large-scale Sediment Waves in Periodically Disturbed Mountain Watersheds
Investigators: Parker, Gary
Institution: University of Minnesota , St. Anthony Falls Laboratory
EPA Project Officer: Packard, Benjamin H
Project Period: January 1, 1996 through December 1, 1998
Project Period Covered by this Report: January 1, 1998 through December 1, 1999
Project Amount: $280,000
RFA: Water and Watersheds (1995) RFA Text | Recipients Lists
Research Category: Watersheds , Water
Objective:
Human-induced disturbances in mountain watersheds, such as mining or timber harvesting, combined with hydrologic conditions appropriate for the release of large amounts of sediment often lead to the formation and propagation of large-scale pulses of sediment in rivers. Such pulses typically enter mountain rivers as landslides or debris flow deposits. These massive inputs of excess sediment can lead to temporary or long-term deleterious effects on the morphology and ecosystem of the river.
Sediment pulses are natural phenomena, the frequency of which can be greatly increased by anthropogenic effects. One goal of the research was to determine how rivers "digest" this excess sediment. A commonly-advanced hypothesis is that these pulses form downstream-migrating waves that can damage river morphology and habitat far downstream of the point where the pulse initially entered the river. Another hypothesis is that the sediment pulses decay by dispersion with less massive downstream effects. The research was directed toward delineating the dominant mechanism for pulse evolution.
Another goal of the research was the development of a predictive numerical model for pulse evolution that could be applied at field scale. The predictive model was developed with the aid of theory, experiments, and field data. A final goal was to cast the predictive model in a form so that it could be implemented by land-use managers to determine the short- and long-term effects of large sediment inputs to mountain rivers.
Progress Summary:
The main goal of the research was achieved in the course of the project. In particular, it was demonstrated definitively that in relatively steep mountain streams covered with alluvium sediment pulses typically decay by dispersion, displaying little tendency for downstream translation. The result was confirmed by means of theory, numerical modeling, experimentation, and an analysis of field data from a landslide into the Navarro River, California. The most important parameter governing the relative roles of translation and dispersion in pulse evolution is the flood Froude number. If this number is high (but below unity), translation tends to be minimum and dispersion dominates. At very low Froude numbers translation becomes more important. In practical terms, this implies that sediment pulses in typical high-slope mountain gravel-bed rivers tend to disperse in place, whereas in low-slope plains sand-bed streams, both dispersion and translation play an important role.
The research included theoretical, numerical, experimental, and field elements, each of which contributed to the understanding of the phenomenon of sediment pulses. Specific project results are enumerated below.
1. It was verified that in steep, gravel-bed mountain streams sediment pulses
are "digested," mostly by dispersion in place rather than translation.
Translation of thin sand or gravel sheets with thickness of one or two grain
sizes can occur once the pulse has dispersed to a very thin layer.
2. In
low-slope sand-bed streams such pulses also disperse, but in addition can show a
significant element of translation before decaying.
3. A numerical model
designed for field application was developed to predict the deformation of
sediment pulses in mountain streams. The model will be made available for
general use in the near future.
4. Experiments on dam and debris jam removal
in steep mountain streams indicate that the resulting sediment pulse disperses
rather quickly. This suggests that the "blow and go" removal technique may be appropriate in at least some cases.
Future Activities:
This is the final year of the grant.
Journal Articles on this Report : 4 Displayed | Download in RIS Format
Other project views: | All 6 publications | 4 publications in selected types | All 4 journal articles |
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Type | Citation | ||
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Cui Y, Parker G, Lisle TE, Gott J, Hansler-Ball ME, Pizzuto JE, Allmendinger NE, Reed JM. Sediment pulses in mountain rivers: 1. Experiments. Water Resources Research 2003;39(9):1239. |
R824779 (1999) R824779 (Final) |
Exit Exit |
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Cui Y, Parker G, Pizzuto J, Lisle TE. Sediment pulses in mountain rivers: 2. Comparison between experiments and numerical predictions. Water Resources Research 2003;39(9):1240. |
R824779 (1999) R824779 (Final) |
Exit Exit |
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Cui Y, Parker G. Numerical model of sediment pulses and sediment-supply disturbances in mountain rivers. Journal of Hydraulic Engineering-ASCE 2005;131(8):646-656. |
R824779 (1999) R824779 (Final) |
Exit Exit |
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Cui Y, Parker G. Sediment transport following dam or debris jam removal. Journal of Hydraulic Engineering. |
R824779 (1999) |
not available |
Supplemental Keywords:
water, watersheds, land, soil, sediments, ecosystem, terrestrial, environmental assets, engineering, hydrology, geology, pacific northwest., RFA, Scientific Discipline, Water, Ecosystem Protection/Environmental Exposure & Risk, Hydrology, Ecology, Water & Watershed, Ecosystem/Assessment/Indicators, Ecosystem Protection, Ecological Effects - Environmental Exposure & Risk, Geology, Watersheds, Ecological Indicators, ecological effects, ecological exposure, sediment wave, anthropogenic processes, fate and transport, timber harvesting, debris flows, large scale sediment waves, sediment transport, aquatic ecosystems, mountain watersheds, formation and propagation, riparian habitat, land useRelevant Websites:
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.