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Hydraulics Engineering

 

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

US Map with Oregon Highlighted.  The study area is outlined in red.


Slide 4

Study Area Map

Map of study area


Slide 5

Mount Hood

Photo of Mt. Hood


Slide 6

Glaciers of Mount Hood

Map showing location of glaciers on Mt. Hood


Slide 7

Recent Debris Flow Events

Topo sheet showing locaction of recent debris flow events


Slide 8

Number of Major Mt. Hood Debris Flows per Year, 1975-2001

View Chart


Slide 9

Number of Major Mt. Hood Debris Flows per Month, 1975-2001

View Chart


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

Photo showing limits of glacier for 1740, 1840, 1900, 1946


Slide 13

Newton Clark Glacier-1901

photo of Newton Clark Glacier in 1901


Slide 14

Newton Clark Glacier-2000

photo of Newton Clark Glacier in 2000


Slide 15

Newton Glacier Oct 2000 Landslide

View Photo


Slide 16

Recent Landslide

Photo showing crest of lateral moraine, debris-covered stagnat ice of Eliot Glacier, scoured channel, and recent landslide areas.


Slide 17

Pacific Decadal Oscillation Theory

View Chart


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)

Drawing of First Bridge at the Existing White River Crossing


Slide 20

White River Bridge-Before

Photo of White River bridge before debris flow


Slide 21

White River Bridge-After

Photo showing White River bridge after debris flow.  Debris has filled the space between the piers


Slide 22

White River Bridge-After

Photo of White River bridge after debris flow showing damage to the bridge.


Slide 23

White River Snow Park-After

Photo showing debris flow at White River Snow Park


Slide 24

White River Snow Park-After

Photo showing debris flow at White River Snow Park


Slide 25

White River Bridge D/S-After

Photo showing debris flow at White River Bridge


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)

Photo showing Pollalie Creek after restoration


Slide 28

Pollalie Creek Oct 1997-After

Photo showing Pollalie Creek after debris slide


Slide 29

Pollalie Creek Oct 1997-After

Photo showing Pollalie Creek after debris slide


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

Photo showing Newton Creek before debris flow


Slide 32

Newton Creek-After

photo showing Newton Creek after debris flow


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

Slide 38

Questions?

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Updated: 04/07/2011
 

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