Predicting deposition of debris flows in mountain channels

1990 ◽  
Vol 27 (4) ◽  
pp. 409-417 ◽  
Author(s):  
Lee E. Benda ◽  
Terrance W. Cundy
Keyword(s):  
Pacific Northwest ◽  
Debris Flows ◽  
Field Measurements ◽  
Coast Range ◽  
Oregon Coast Range ◽  
Oregon Coast ◽  
Aerial Photos ◽  
The Pacific ◽  
Channel Slope ◽  
Junction Angle

An empirical model for predicting deposition of coarse-textured debris flows in confined mountain channels is developed based on field measurements of 14 debris flows in the Pacific Northwest, U.S.A. The model uses two criteria for deposition: channel slope (less than 3.5°) and tributary junction angle (greater than 70°). The model is tested by predicting travel distances of 15 debris flows in the Oregon Coast Range and six debris flows in the Washington Cascades, U.S.A. The model is further tested on 44 debris flows in two lithological types in the Oregon Coast Range using aerial photos and topographic maps; on these flows only the approximate travel distance is known. The model can be used by resource professionals to identify the potential for impacts from debris flows. Key words: debris flow, deposition, travel, erosion.

Fertile Usnea Longissima in the Oregon Coast Range

2002 ◽  
Vol 34 (1) ◽  
pp. 13-17 ◽  
Author(s):  
D. B. Keon
Keyword(s):  
Pacific Northwest ◽  
Coast Range ◽  
Oregon Coast Range ◽  
Oregon Coast ◽  
History Of ◽  
Usnea Longissima ◽  
Published Account ◽  
The U.S

AbstractApothecia from Usnea longissima thalli collected in the Oregon Coast Range are described. Fertile U. longissima specimens have seldom been observed and rarely documented in the literature. A brief history of accounts in the literature is given, and possible reasons for the infrequent occurrence of apothecia are discussed. This is the first published account of fertile U. longissima specimens in the U.S. Pacific Northwest.

Orographic Modification of Convection and Flow Kinematics by the Oregon Coast Range and Cascades during IMPROVE-2

2008 ◽  
Vol 136 (10) ◽  
pp. 3894-3916 ◽  
Author(s):  
Brian A. Colle ◽  
Yanluan Lin ◽  
Socorro Medina ◽  
Bradley F. Smull
Keyword(s):  
Static Stability ◽  
Convective Cell ◽  
Mountain Range ◽  
Coast Range ◽  
Oregon Coast Range ◽  
Oregon Coast ◽  
Freezing Level ◽  
The Pacific ◽  
Convective Cells ◽  
Precipitation Enhancement

This paper describes the kinematic and precipitation evolution accompanying the passage of a cold baroclinic trough over the Central Oregon Coast Range and Cascades during 4–5 December 2001 of the second Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE-2) field project. In contrast to previously documented IMPROVE-2 cases, the 4–5 December event featured weaker cross-barrier winds (15–20 m s−1), weaker moist static stability (Nm < 0.006 s−1), and convective cells that preferentially intensified over Oregon’s modest coastal mountain range. These cells propagated eastward and became embedded within the larger orographic precipitation shield over the windward slopes of the Cascades. The Weather Research and Forecasting Model (version 2.2) at 1.33-km grid spacing was able to accurately replicate the observed evolution of the precipitation across western Oregon. As a result of the convective cell development, the precipitation enhancement over the Coast Range (500–1000 m MSL) was nearly as large as that over the Cascades (1500–2000 m MSL). Simulations selectively eliminating the elevated coastal range and differential land–sea friction across the Pacific coastline illustrate that both effects were important in triggering convection and in producing the observed coastal precipitation enhancement. A sensitivity run employing a smoothed representation of the Cascades illustrates that narrow ridges located on that barrier’s windward slope had a relatively small (<5%) impact on embedded convection and overall precipitation amounts there. This is attributed to the relatively weak gravity wave motions and low freezing level, which limited precipitation growth by riming.

scholarly journals Rainfall triggers more deep-seated landslides than Cascadia earthquakes in the Oregon Coast Range, USA

2020 ◽  
Vol 6 (38) ◽  
pp. eaba6790
Author(s):  
S. R. LaHusen ◽  
A. R. Duvall ◽  
A. M. Booth ◽  
A. Grant ◽  
B. A. Mishkin ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Pacific Northwest ◽  
Cascadia Subduction Zone ◽  
Mean Annual Precipitation ◽  
Coast Range ◽  
Ground Acceleration ◽  
Oregon Coast Range ◽  
Oregon Coast ◽  
Subduction Zone Earthquakes ◽  
Large Earthquakes

The coastal Pacific Northwest USA hosts thousands of deep-seated landslides. Historic landslides have primarily been triggered by rainfall, but the region is also prone to large earthquakes on the 1100-km-long Cascadia Subduction Zone megathrust. Little is known about the number of landslides triggered by these earthquakes because the last magnitude 9 rupture occurred in 1700 CE. Here, we map 9938 deep-seated bedrock landslides in the Oregon Coast Range and use surface roughness dating to estimate that past earthquakes triggered fewer than half of the landslides in the past 1000 years. We find landslide frequency increases with mean annual precipitation but not with modeled peak ground acceleration or proximity to the megathrust. Our results agree with findings about other recent subduction zone earthquakes where relatively few deep-seated landslides were mapped and suggest that despite proximity to the megathrust, most deep-seated landslides in the Oregon Coast Range were triggered by rainfall.

Regrowth of understory epiphytic bryophytes 10 years after simulated commercial moss harvest

2006 ◽  
Vol 36 (7) ◽  
pp. 1749-1757 ◽  
Author(s):  
JeriLynn E Peck
Keyword(s):  
Species Richness ◽  
Pacific Northwest ◽  
Percent Cover ◽  
Coast Range ◽  
Vegetative Cover ◽  
Oregon Coast Range ◽  
The Pacific ◽  
Nontimber Forest Product ◽  
Term Evaluation

Commercial moss harvest is the predominant disturbance for understory epiphytic bryophyte mats in the Pacific Northwest, yet the rate and dynamics of regrowth of this nontimber forest product are unknown. The first long-term evaluation of cover and species richness regrowth following simulated commercial moss harvest from understory vine maple (Acer circinatum Pursh) shrub stems is reported. Stems harvested of moss on six sites in the Oregon Coast Range in 1994 were examined for species composition and relative abundance of regrowth over the course of a decade. Percent cover increased 5.1%/year, averaging only 51% cover in year 10. Forty percent of the total cover in year 10 was attributable to encroachment from adjacent undisturbed mats and 14% to reestablished litterfall. Shortly after harvest, many taxa established on the newly available habitat, such that species richness surpassed preharvest levels by year 3. In the absence of competitive exclusion even by year 10, species richness continued to exceed preharvest levels by two taxa. Vegetative cover regrowth may require 20 years and volume recovery even longer. Commercial moss harvest should be managed on rotations of several decades, and patchy harvest methods should be encouraged over complete strip harvesting to ensure moss regeneration and promote bryophyte diversity.

Geologic map of the Tillamook Highlands, Northwest Oregon Coast Range

1994 ◽  
Author(s):  
R.E. Wells ◽  
P.D. Snavely ◽  
N.S. MacLeod ◽  
M.M. Kelly ◽  
M.J. Parker
Keyword(s):  
Coast Range ◽  
Oregon Coast Range ◽  
Oregon Coast ◽  
Geologic Map
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