1. A Comparison of Channel Pattern of the Historic and Proposed (Restored) Clark Fork River
Karen Williams, PhD student
College of Natural Resources
Utah State University, Logan, Utah

2. Geomorphic effects of dams
Closure of Milltown dam (1906)
Downstream effects
Acute decrease in sediment supply
Channel erosion/incision
Upstream effects
Sediment transport interrupted
Aggradation
Decrease channel slope
Channel narrowing
Removal of dam will re-start the geomorphic processes
For more information,

3. Post-dam Removal: Process-based Restoration Framework
Rivers adjust shape to the supplied water and sediment load
Water and sediment load create channel pattern and geometry
A process-based approach ensures the designed channel can route water/sediment load without major morphologic adjustments
Restoration of form, rather than process, makes it difficult to sustain dynamic and self-maintaining geomorphic processes
Clearly channel restoration is in order in the area where the reservoir currently exists, but how far upstream does the channel need to be reconstructed. First rule is if not broken, don’t fix it. What evidence do we need to decide if it’s broken? One arguable criteria is Chronic and pervasive sedimentation or erosion; clear sign that the channel is unable to route its water and sediment load w/o major upsets or changes to morphology. State criteria (4) is based in part upon presence of terraces, extent of inundation at large flood events

4. Channel Pattern Channel configuration seen in plan (aerial) view
Pattern is quantified by sinuosity
channel length/valley length, or
valley slope/channel slope
Sinuous pattern: >1.05
Straight pattern:
Channel pattern reflects how the channel adjusts in a horizontal plane
Schumm identified 14 channel patterns including transitional patterns; the criteria for this classification is the load carried by the channel (bedload, suspended load, mixed) Channels respond and adjust to changes in water or sediment load in 3 dimensions (horizontal plane x and y width, and vertical z bed elevation)
Graphic by Railsback, Univ. GA.

5. What creates channel pattern?
Pattern originally considered to be a function of slope and bankfull discharge (Leopold and Wolman, 1957)
Now recognized to also be a function of:
sediment load
sediment size
width/depth ratio
stream power
There are many empirical equations relating these variables, these are just a couple

6. Historic Channel Patterns of Clark Fork River
General Land Office Survey by John McIntyre, Survey Date: 1884
USGS Topo, SurveyDate:1900

7. Recent Channel Patterns of Clark Fork River
In the 1930’s photo, the river channel upstream of the dam appears braided. It’s hard to tell if the bars and islands are permanent/vegetated or bare unstable features. But this extensive display of braiding indicates high sediment loads and perhaps low streampower. The 1995 aerial photo shows a single thread channel immediately upstream of the dam, in the area inundated or influenced by backwater effects of the dam. Upstream of the backwatered area, the channel has irregular meanders, and the light spots adjacent to the wetted channel are indicative of depositional features such as bars. You can see remnants of some formerly occupied channels, which indicates the dynamic nature of the channel. It appears to have migrated back and forth across its FP.
1930’s
1995

8. Clark Fork River channel pattern 1995

9. 1900 and 1995
channel patterns

10. Clark Fork River Channel Patterns: 1995 and 2002
Flood of record (18 yrs of record) at Turah in 1996 (12,400 cfs) Q15-Q20
2002
1995

11. Channel Pattern of Proposed Restored Clark Fork River
Single-thread
Regular (repeating) and symmetric pattern
Sine-generated curve:
Introduced by Leopold and Langbein (1962) as a means to describe symmetrical meander paths
Highly sinuous
this is a broad scale plan to provide
restoration concepts, draft plan views and elevation information
Graphics courtesy of Matt Kondolf, UC Berkeley

12. (from dam to 2.75 mi. upstream)
Differences between the historic channel pattern and the proposed channel pattern
Characteristic
Historic Pattern
Proposed Pattern
Sinuosity
1.10
(from dam to 2.75 mi. upstream)
Symmetry
Weakly expressed
High
Regularity
Number of channels
2 or more 1

13. What classification best fits the current Clark Fork River?
Clark Fork River ~ 1 mi. upstream of Turah bridge
Proposed Clark Fork River Design
Graphs from Knighton, 1998

14. How was the CFR channel pattern designed?
4.2 PLAN FORM GEOMETRY
“Plan view geometry and characteristics are also a function of the bankfull discharge and the bankfull design width. The most probable channel patterns for the project area reaches were determined from empirical models developed by Leopold et al (1964), Williams (1986), Rosgen(1996), and WCI’s reference reach database.”
No longer valid so don’t worry about the numbers, focus on design approach and how to evaluate that

15. How can you design channel pattern for restoration? (Part 1)
Typical paradigms include use of empirical meander planform equations and reference reaches
Use of empirical planform equations is tricky
“The equations are empirical in nature, and not applicable outside of the magnitude and physiographic ranges of the data used to calibrate the equations” (Rinaldi and Johnson, 1999)
Example, L = 10.9 x W (Leopold, 1960)
The graphs show data points nicely clustered about this line because the plot is log-log.

16. Example of Regular Meander Patterns used in Restoration Projects
Uvas Creek, Gilroy, CA
Graphics courtesy of Matt Kondolf, UC Berkeley

17. CFR Design Approach
“Reach characterization is core to this methodology and in its rudimentary form, categorizes streams into one of eight primary stream types
The reference reach should… serve as a model for the design channel.
The final restoration design developed with NCDP seeks to mimic a stream in dynamic equilibrium with its watershed, and provides a diverse and complex channel capable of conveying flows, transporting sediment, and integrates essential habitat features related to native fish recovery goals.”

18. How can you design channel pattern for restoration? (Part 2)
“Mistakes are made when an apparently stable reach is used as a template for the restored channel or when general empirical relations between channel geometry and flow frequency are used as the basis for design…Although the general empirical relations for river channel geometry are real…they provide an inappropriate basis for river restoration. The wrong questions are being asked.
A more useful paradigm is that rivers adjust to the water and sediment supplied to them…This approach leads immediately to the cause of channel response: changes in water and sediment supply.
When the design goals are…based upon general physical principles (rather than referenced to a variously and empirically defined equilibrium state), physical, ecological, and management objectives can be considered consistently”
Wilcock, P., Friction between science and practice: the case of river restoration. American Geophysical Union, EOS, vol. 78, no. 40.

19. Process-based Framework: Design channel slope to accommodate the sediment load
Erosion
Aggradation
Use basic principles of flow hydraulics: continuity, flow resistance, momentum, sed trans (MPM),
Graph made using Wilcock spreadsheet

20. Use design channel slope to get sinuosity
Sinuosity = valley slope/channel slope
For channel slope = ,
sinuosity = 1.11

21. Product of Process-based Design: Provo River, Heber City, UT
Q ~ 2000 cfs
Through the use of process-based design you can come up with river designs and construction that look and function like a natural river system

22. Questions?