|
|
Hydrologic and Geomorphologic Assessment of
Debris Flow Events for Mount Hood Highway
Amit Armstrong, Ph.D., P.E.
Mark C. Browning, Ph.D., P.E.
Marc A. Veneroso, P.E.
David C. Lofgren, P.E.
PowerPoint Version (12 mb)
|
Slide 2
Study Objectives
- Conduct a Critical Assessment of the Existing Location of Mount Hood Highway
- Address Issues Related to Debris Flow Events
- Suggest Alternatives to Reduce Maintenance and Reconstruction Cost
- Improve Safety in Highway Corridor
|
|
Slide 3
Regional Map
|
|
Slide 4
Study Area Map
|
|
Slide 5
Mount Hood
|
|
Slide 6
Glaciers of Mount Hood
|
|
Slide 7
Recent Debris Flow Events
|
|
Slide 8
Number of Major Mt. Hood Debris Flows per Year, 1975-2001
|
|
Slide 9
Number of Major Mt. Hood Debris Flows per Month, 1975-2001
|
|
Slide 10
Ideal Conditions for Frequent Debris Flows on Mount Hood
- Steep Slopes
- Confined Channels
- Abundant Loose Soil and Rock
- Occasionally Abundant Water
|
|
Slide 11
Water Sources for Mount Hood Debris Flows
- Glacier Meltwater
- Summer/Fall Thunderstorms
- Rain-on-snow Events
- Combination of Above
|
|
Slide 12
Retreat of Elliot Glacier
1740-2000
|
|
Slide 13
Newton Clark Glacier-1901
|
|
Slide 14
Newton Clark Glacier-2000
|
|
Slide 15
Newton Glacier Oct 2000 Landslide
|
|
Slide 16
Recent Landslide
|
|
Slide 17
Pacific Decadal Oscillation Theory
|
|
Slide 18
Pacific Decadal Oscillation Theory
- Proposed by George Taylor, State of Oregon
- Pacific Northwest experiences ~20 year long wet/dry weather patterns
- 1975 - 1995 was a "dry" period (a time of accelerated glacial retreat)
- Now into a "wet" period (a time for glacial streams to mobilize newly-exposed loose glacial material)
|
|
Slide 19
First Bridge at the Existing White River Crossing (1925 - 1954)
|
|
Slide 20
White River Bridge-Before
|
|
Slide 21
White River Bridge-After
|
|
Slide 22
White River Bridge-After
|
|
Slide 23
White River Snow Park-After
|
|
Slide 24
White River Snow Park-After
|
|
Slide 25
White River Bridge D/S-After
|
|
Slide 26
White River Options
- Raise Road Grade and Build a Longer Bridge
- Build a Tunnel at Existing Location
- Build an Encased Highway at Existing Location
- Reconstruct Roadway U/S of Existing Location
- Reconstruct Roadway D/S of Existing Location
- Reconstruct Roadway Further D/S Across a Narrow Channel
- Construct Bypass for Highway 35
- Preventative Maintenance
|
|
Slide 27
Pollalie Creek-Before
(After Restoration)
|
|
Slide 28
Pollalie Creek Oct 1997-After
|
|
Slide 29
Pollalie Creek Oct 1997-After
|
|
Slide 30
Pollalie Creek Options
- Construct a Sabo Dam
- Construct a 30-M Clear Span Bridge
- Construct a 90-M Clear Span Bridge
- Realign and Reconstruct Roadway (Two Different Options)
- Construct Bypass for Highway 35
- Preventative Maintenance
|
|
Slide 31
Newton Creek-Before
|
|
Slide 32
Newton Creek-After
|
|
Slide 33
Decision Matrix
- Enhance & Protect Wild & Scenic White River
- Enhance the Natural Floodplain
- Minimize Impact to Visual Resources
- Minimize Impacts to Terrestrial Habitat
- Reduce Maintenance & Emergency Repair
- Improve Safety
- Optimize Life-Cycle Cost
- Maintain Travel Time
|
|
Slides 33-34
Conclusions
- Conventional Hydrologic Methods to Estimate Magnitude and Frequency of Peak Flow are not Applicable for Upper Reaches of Steep Mountainous Streams.
- Peak Flows Associated with Debris Flows are Significantly Higher than Typical Rain-on-Snow Events.
- Strong Need for Devising Methods that can Estimate Magnitude and Frequency of Peak Flow for Debris Flow Events.
- Stream Morphologies were Significantly Altered by Debris Flow Events (Formation of New Stream Channels)
- Numerical Models are Needed for Quantitative Assessment of Morphologic Changes in Stream Valleys
|
|
Slide 32
Ongoing & Future Work
- Collection of Historic Data from all Previous Events
- Estimate Travel Time of Debris Flow
- Devise Methods to Estimate Magnitude and Frequency of Peak Flow
- Install Real-Time Debris Flow Monitoring Systems
|
|
Slide 37
Cooperating Agencies
- United States Forest Service
- United States Geological Survey
- Oregon Department of Transportation
|
PowerPoint files can be viewed with the PowerPoint Viewer
|
|
