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Portable Electronic Presentations

A portable electronic presentation is an online \ offline interactive learning resource
representing key scientific talks in an on-demand rich media format.

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The Geomorphic Response of Rivers to Dam Removal

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Dam Removal Presenter: Gordon Grant, USDA Forest Service, Pacific Northwest Research Station
Length: 3 parts, 63 min and 40 s

View: Part 1 | Part 2 | Part 3

       Topics:

       Part 1

  • Big Dams / Little Dams
  • Geomorphic Issues
  • Geomorphic Issues: Upstream
  • Geomorphic Issues: Downstream
  • Coupled upstream downstream problem
  • What do we want to know upstream of a dam removal
  • Controls / Caveats
  • Dam Removal Scenarios
  • Examples of Geomorphic Effects
  • Examples Matrix
  • Let's Explore Maple Gulch: small dam removal
  • Maple Gulch Dam Site - Aug 2002
  • Sep 2002: sediment wedge
  • Nov 2002: Knickpoint
  • Dec 2002: Knickpoint marches backward
  • New Years Eve 2002: sediment deposits left behind
  • May 2003: revegitation
  • Dinner Creek Dam- Aug 1 2003
  • Aug 5 2003: shortly after removal
  • Nov 2003: first storm of year
  • Dec 11 2003: windthrow event
  • Dec 15 2003: largest storm of the year
  • Main point: Knickpoint migration
  • Simple geometrical modelling of migration
  • Reservoir Erosion Due to Knickpoint Retreat
  • Cumulative Sediment Graph Post Dam Removal

       Part 2

  • Erosion Model for Filled Reservoir
  • Upstream Effects: Episodic
  • Upstream Effects: Knickpoint retreat
  • Upstream Effects: Interaction with valley margins
  • Upstream Effects: Channel may or may not find old bed
  • Examples: Partially filled reservoirs
  • Glines Canyon Dam
  • Pictures of the Delta
  • Drawdown Experiment
  • After drawdown: Two main channels
  • Cougar Reservoir Aerial
  • Temperature Control Structure
  • The delta
  • Focus on delta mid-section
  • Aerial of delta
  • Area of focus
  • Shortly after the drawdown, April 5 02
  • Emergence of dominant channel, April 12 02
  • Drawdown proceeded about 100 ft, April 29 02
  • Drawdown continues, May 15 02
  • The following winter, Jan 29 03
  • Jan 30 03: Channel sweeps back
  • Jan 31 03: Channel straightens
  • Feb 15 03
  • Channel and Stratigraphy
  • Focus on this cross section
  • Cougar Delta Stratigraphy
  • Cougar Delta: Drawdown Incision
  • Cougar Delta: Post-Storm Incision
  • Modeling Glines Canyon Dam Removal
  • Model Dam Notches
  • Feeding Sediment In
  • Empty Model
  • Filled model during expirement
  • Video of model during expirement
  • Model: What is left behind after removal
  • Erosion Model for Partially-filled Reservoir
  • Upstream Erosion of Partially-filled Reservoirs
  • Upstream Effects: Rate of dam removal drives rate of delta propogation
  • Upstream Effects: Incision can be limited by armoring
  • Upstream Effects: Complex response
  • Upstream Effects: Interaction with valley walls
  • Time since dam removal
  • What do we want to know downstream of dam removal?
  • Questions to ask
  • Controls and Caveats

       Part 3

  • Downstream Sediment Storage Elements
  • Types of Downstream Channel Response
  • Examples: Small dam downstream
  • Downstream Sediment Delivery
  • Downstream from Maple Gulch Dam: pre-removal
  • Downstream from Maple Gulch Dam: just after removal
  • Downstream from Maple Gulch Dam: incision
  • Cross-sectional representation of downstream deposition
  • Dinner Creek - Pre-removal... looking downstream
  • Dinner Creek: following first storm
  • Examples: Cougar Reservoir Downstream of removal
  • Downstream sediment delivery
  • Longitudinal and Cross-section view
  • The Cougar Reservoir Drawdown: A tale of woe
  • The Cougar Reservoir Drawdown: Immediately following
  • The Cougar Reservoir Drawdown: drawdown continued
  • The Cougar Reservoir Drawdown: beautiful McKenzie into turbid waters
  • Turbidity increased in reservoir during drawdown
  • Did the sediment intrude into the gravels?
  • Relative Abundance of Fines
  • Marmot Dam Sandy River, Oregon
  • Sand and gravel released in blow and go in 2007
  • Where will it end up?
  • Marmot Dam
  • Below Marmot, Above Canyon ~13,000 cfs
  • Channel response depends on channel morphology
  • Steep Narrow Canyon
  • Water Alluvial Channel
  • Broad, unconfined Valley Bottom
  • Predicted Sand Deposition
  • Fine sediment survey in pools
  • Scuba and probing
  • Hydro-dynamic models
  • Dog Pool: Erosivity as a Function of Discharge
  • If you think geomorphic response is complex...
  • Filled vs. partially-filled reservoirs
  • What does it all mean?- O'Connor's Law
  • Grant's Corollary
  • Grant's Lemma
  • We know more than we think
  • Societal enthusiasm for dam removal
  • Need for carefully planned and monitored removals
  • Dam removals are great experiments!
  • Dam Failure
  • Apres Moi Le Deluge