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Spatial and temporal patterns of debris flow deposition in the Oregon Coast Range, USA

Journal of Geomorphology

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Abstract

Patterns of debris-flow occurrence were investigated in 125 headwater basins in the Oregon Coast Range. Time since the previous debris-flows was established using dendrochronology, and recurrence interval estimates ranged from 98 to 357 years. Tributary basins with larger drainage areas had a greater abundance of potential landslide source areas and a greater frequency of scouring events compared to smaller basins. The flux rate of material delivered to the confluence with a larger river influenced the development of small-scale debris-flow fans. Fans at the mouths of tributary basins with smaller drainage areas had a higher likelihood of being eroded by the mainstem river in the interval between debris-flows, compared to bigger basins that had larger, more persistent fans. Valley floor width of the receiving channel also influenced fan development because it limited the space available to accommodate fan formation. Of 63 recent debris-flows, 52% delivered sediment and wood directly to the mainstem river, 30% were deposited on an existing fan before reaching the mainstem, and 18% were deposited within the confines of the tributary valley before reaching the confluence. Spatial variation in the location of past and present depositional surfaces indicated that sequential debris-flow deposits did not consistently form in the same place. Instead of being spatially deterministic, results of this study suggest that temporally variable and stochastic factors may be important for predicting the runout length of debris-flows.

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Additional publication details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Spatial and temporal patterns of debris flow deposition in the Oregon Coast Range, USA
Series title:
Journal of Geomorphology
Volume:
57
Issue:
3-4
Year Published:
2004
Language:
English
Contributing office(s):
Northern Rocky Mountain Science Center
Description:
15 p.
First page:
135
Last page:
149
Country:
United States
State:
Oregon
Other Geospatial:
Coast Range
Online Only (Y/N):
N
Additional Online Files (Y/N):
N