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

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.

[1]  W. R. Meehan,et al.  Forest Management and Anadromous Fish Habitat Productivity , 1981 .

[2]  P. Bartlein,et al.  A 9000-year fire history from the Oregon Coast Range, based on a high-resolution charcoal study , 1998 .

[3]  John E. Costa,et al.  Debris Flows/Avalanches: Process, Recognition, and Mitigation , 1987 .

[4]  C. E. Van Wagner,et al.  Age-class distribution and the forest fire cycle , 1978 .

[5]  E. Foufoula‐Georgiou,et al.  Channel network source representation using digital elevation models , 1993 .

[6]  K. Whipple.  Predicting debris-flow runout and deposition on fans: the importance of the flow hydrograph , 1992 .

[7]  J. Agee.  Fire Ecology of Pacific Northwest Forests , 1993 .

[8]  A. Harvey.  Debris Flows and Fluvial Deposits in Spanish Quaternary Alluvial Fans: Implications for Fan Morphology , 1984 .

[9]  A. Rachocki,et al.  Alluvial fans : a field approach , 1990 .

[10]  W. Dietrich,et al.  The importance of hollows in debris flow studies; Examples from Marin County, California , 1987 .

[11]  Robert L. Edmonds,et al.  Analysis of coniferous forest ecosystems in the Western United States , 1982 .

[12]  M. Mosley.  An Experimental Study of Channel Confluences , 1976, The Journal of Geology.

[13]  L. Benda,et al.  Stochastic forcing of sediment routing and storage in channel networks , 1997 .

[14]  David R. Montgomery,et al.  Forest clearing and regional landsliding , 2000 .

[15]  Garrison Sposito,et al.  Scale Dependence and Scale Invariance in Hydrology , 1998 .

[16]  F. Swanson,et al.  Morphology and processes of valley floors in mountain streams , 2013 .

[17]  R. Naiman,et al.  THE RESIDENCE TIME OF LARGE WOODY DEBRIS IN THE QUEETS RIVER, WASHINGTON, USA , 2001 .

[18]  W. Dietrich,et al.  Sediment budget for a small catchment in mountainous terrain , 1978 .

[19]  John E. Costa,et al.  Physical Geomorphology of Debris Flows , 1984 .

[20]  William C. Orr,et al.  Geology of Oregon , 1976 .

[21]  L. Benda,et al.  Predicting deposition of debris flows in mountain channels , 1990 .

[22]  David R. Montgomery,et al.  Scale Dependence and Scale Invariance in Hydrology: Hillslopes, Channels, and Landscape Scale , 1998 .

[23]  R. Kostaschuk,et al.  Depositional process and alluvial fan‐drainage basin morphometric relationships near banff, Alberta, Canada , 1986 .

[24]  R. Hooke.  Steady-state relationships on arid-region alluvial fans in closed basins , 1968 .

[25]  J. Mount,et al.  Effect of baselevel change on floodplain and fan sediment storage and ephemeral tributary channel morphology, Navarro River, California , 2001 .

[26]  David R. Montgomery,et al.  Regional test of a model for shallow landsliding , 1998 .

[27]  W. Ayrton.  Canadian Society of Petroleum Geologists: GEOLOGIC NOTES , 1977 .

[28]  A. N. Strahler.  Quantitative geomorphology of drainage basin and channel networks , 1964 .

[29]  D. M. Mark,et al.  On size and scale in geomorphology , 1980 .

[30]  David R. Montgomery,et al.  Geomorphic processes and riverine habitat. , 2001 .

[31]  L. Benda,et al.  Stochastic forcing of sediment supply to channel networks from landsliding and debris flow , 1997 .

[32]  W. Bull.  Geomorphology of segmented alluvial fans in western Fresno County, California , 1964 .

[33]  R. Horton.  EROSIONAL DEVELOPMENT OF STREAMS AND THEIR DRAINAGE BASINS; HYDROPHYSICAL APPROACH TO QUANTITATIVE MORPHOLOGY , 1945 .

[34]  C. May.  Spatial and temporal dynamics of sediment and wood in headwater streams in the central Oregon Coast Range , 2001 .

[35]  P. C. Impara.  Spatial and temporal patterns of fire in the forests of the central Oregon Coast Range , 1997 .

[36]  G. Grant,et al.  Sediment and Wood Storage and Dynamics in Small Mountainous Watersheds , 2013 .

[37]  F. Swanson,et al.  Material transfer in a western Oregon forested watershed , 1982 .

[38]  C. May.  DEBRIS FLOWS THROUGH DIFFERENT FOREST AGE CLASSES IN THE CENTRAL OREGON COAST RANGE 1 , 2002 .

[39]  A. Orme.  THE NATURE AND RATE OF ALLUVIAL FAN AGGRADATION IN A HUMID TEMPERATE ENVIRONMENT, NORTHWEST WASHINGTON , 1989 .

[40]  James R. Sedell,et al.  A Disturbance-Based Ecosystem Approach to Maintaining and Restoring Freshwater Habitats of Evolutionarily Significant Units of Anadromous Salmonids in the Pacific Northwest , 1995 .

[41]  Torsten Schaub,et al.  The variability of root cohesion as an influence on shallow landslide susceptibility in the Oregon Coast Range , 2001 .

[42]  R. Ziemer,et al.  Roots and the stability of forested slopes , 1999 .