Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Sediment reservoirs at mountain stream confluences; dynamics and effects of tributaries dominated by debris-flow and fluvial processes

Stephen T. Lancaster, Emily F. Underwood and W. Terry Frueh
Sediment reservoirs at mountain stream confluences; dynamics and effects of tributaries dominated by debris-flow and fluvial processes
Geological Society of America Bulletin (November 2010) 122 (11-12): 1775-1786

Abstract

Radiocarbon age estimates (N=68) from bank, terrace riser, and in-channel materials sampled from random locations near two channel confluences, a debris-flow-dominated tributary to Cedar Creek, and a fluvially dominated tributary to Golden Ridge Creek in the Oregon Coast Range, are proxies for sediment transit times through tributary and mainstem sediment reservoirs separated from one another by incised bedrock risers. Geomorphic, volumetric, stratigraphic, and sedimentologic data aided reservoir characterizations. Inferred transit-time distributions for tributary deposits are right-skewed and heavy-tailed, indicating preferential evacuation of younger deposits. The debris-flow fan is much larger than fluvial terraces on the other tributary, but mean transit times (+ or -sigma ) in both reservoirs are similar: 1370+ or -2240 yr and 1660+ or -2130 yr for fan and terrace deposits, respectively. Whereas tributary deposits are much larger than mainstem deposits at both sites, mainstem deposits adjacent to the fan have a relatively short mean transit time of 442+ or -491 yr, but mean transit time in mainstem deposits adjacent to the fluvial terrace is much greater: 3870+ or -6720 yr. Reservoir flux estimates indicate that most (>60%) of the debris-flow fan tributary's sediment yield enters fan storage, but only a small part (3%) of the fluvial tributary's yield enters storage at the confluence. Debris flows from the debris-flow fan tributary apparently promote both greater storage of mainstem sediments and more rapid unbiased evacuation of mainstem deposits, whereas old mainstem deposits adjacent to the fluvial tributary have a much greater probability of preservation.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 122
Serial Issue: 11-12
Title: Sediment reservoirs at mountain stream confluences; dynamics and effects of tributaries dominated by debris-flow and fluvial processes
Affiliation: Oregon State University, Department of Geosciences, Corvallis, OR, United States
Pages: 1775-1786
Published: 201011
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 56
Accession Number: 2010-098060
Categories: HydrogeologyGeomorphology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2010215
Illustration Description: illus. incl. 1 table, sketch maps
N43°42'00" - N43°42'00", W123°49'60" - W123°49'60"
N43°53'60" - N43°53'60", W123°54'00" - W123°54'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201051
Close Modal

or Create an Account

Close Modal
Close Modal