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The Evolution of a Tie Channel. Joel C. Rowland & William E. Dietrich University California - Berkeley. Source: Google Earth. Goal of Study. Develop a conceptual model for the development of a self-formed leveed channel created by a sediment-laden current entering still water. Tie channel.

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the evolution of a tie channel
The Evolution of a Tie Channel

Joel C. Rowland & William E. Dietrich

University California - Berkeley

Source: Google Earth

goal of study
Goal of Study
  • Develop a conceptual model for the development of a self-formed leveed channel created by a sediment-laden current entering still water
what is a tie channel
Tie channel

250 m

Fly River , Papua New Guinea

What is a Tie Channel?
  • Self-formed leveed channel
  • Connect rivers to lakes
  • Jet entering still water
  • Bi-directional flow
  • Stable
slide5
Raccourci Old River Tie Channel
    • 65 km upstream Baton Rouge, LA
    • Formed in 1851

2 km

slide6
Why Raccourci Old River ?
  • Largest known tie channel
  • Largely unaltered channel in naturally functioning floodplain
  • Unprecedented documentation of channel development
  • Data sources:
  • Historical records
  • Hydrographic surveys (> 1880s)
  • Aerial photographs (> 1940s)
  • Satellite imagery
  • ALSM data (Lidar)
  • Long-term records for Miss River
  • Field data
slide7
Talk Outline
  • Channel Characteristics
    • Morphology
    • Sedimentology
  • Conceptual Model
    • Levee growth
    • Channel widening
slide9
Mississippi River

Oxbow lake margin

1 km

Long profile of channel levees and width

slide11
Channel and levee growth
  • Vertically accretes
  • Channel widens
  • Levee flanks broaden
slide12
Levees composed of sub-horizontal alternating layers
  • Sand deposition: U* > Ws in channel, U* < Ws over levees
  • Mud and organic deposition: U* < Ws everywhere
slide13
TC Levee Coarse

TC Levee Fine

TC Bed

Miss Susp Sed

Miss Bed

Incoming load sorted by tie channel processes

clay

silt

sand

slide15
150 m

Jet Sedimentation

  • Large “quasi-2D” turbulent structures
  • Scale with jet width
  • Sweep across newly forming channel advecting sediment to margins
slide16
150 m

Localized shear along inundated levee crests

?

slide17
Lake level > levee crest
  • Unpaired levee crests heights
  • Super-elevated bends
  • Asymmetric levee x-sections

Large-scale advective transfer of sediments

Lake level < levee crest

slide18
Local advective transfer of sediments: Splays
  • Locally erode crests
  • Deposit on flanks

Concepts Watershed, 2005

slide20
Conclusions
  • Channel selectively sorts and deposits incoming sediment
  • Majority of levee sedimentation occurs during submerged/inundated conditions
  • Splays redistributes sediments and broaden levees
  • Channel width controlled by mass failures which are linked to levee height
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