1. Module # 17 Overview of Geomorphic Channel Design Practice
Iowa’s River Restoration Toolbox Level 1 / Base Training

2. Geomorphic Channel Design
Process by which new or re-constructed stream channels and their associated floodplain riparian systems are designed to be naturally functional, stable, healthy, productive, and sustainable.

3. Soil Bioengineering
The use of living and non-living materials to provide soil reinforcement and prevent erosion

4. Comparison of Geomorphic Channel Design and Soil Bioengineering
Bankfull Discharge Bankfull Depth
Channel Design
Design of Channel Form Channel Form Not Altered
Stream System and Processes Disturbed Section
Channel Dimensions Critical Vegetation Critical
Design Parameters Vary Typically Constant
In-Stream Construction Streambank Construction
Sediment Transport Slope Stability
Bioengineering

5. Geomorphic Channel Design Components
Analog
Empirical
Analytical

6. Form Vs Process Not Mutually Exclusive Process Drives Form
Must Consider Time Scale as Part of Design Process
Ultimately Must Design and Build a Stream Form
Can Create Backlash Towards the Profession

7. National Engineering Handbook
Primary Reference
Stream
Restoration
Design
National Engineering Handbook
Part 654
Released, August 2007 (vs )
Chapter 11: Geomorphic Approach for Natural Channel Design
USDA NRCS, Stream Restoration Design Handbook, 2007.
U.S. Department of Agriculture
Natural Resources Conservation Service

8. Phases of Geomorphic Channel Design (NCD Approach)
Define Restoration Objectives
Develop Regional & Localized Specific Geomorphic and Hydraulic Data
Conduct Watershed/River Assessment
Assess Potential for Passive Restoration (i.e. Land Use Changes)
Initiate Geomorphic Channel Design w/ Analytical Testing of Hydraulics & Sediment Transport
Design Stabilization/Enhancement Measures
Implement Proposed Design
Design & Implement Monitoring & Maintenance Plan

9. Define Restoration Objectives
Flooding Issues
Streambank Stability
Reduction in Sediment Supply
Improved Fish Habitat & Biological Diversity
Self Maintenance /Natural System
Aesthetics
Mitigation Needs

10. Develop Regional & Localized Specific Geomorphic and Hydraulic Data
Identify Valley Type & Stream Type
Obtain Reference Reach Data for Intended Stream Type
Compare Impacted Reach and Reference Reach Data to Regional Curves
Convert Reference Reach Data to Dimensionless Ratios
Calculate Bankfull Discharge & Velocity

11. Locating Reference Reaches
Same Stream as Impacted Reach
Same General Watershed
Review Gazetteer Maps for Similar Pattern Streams as Intended Design
Be Prepared to Drive to Numerous Sites
Reference Reaches are Typically not Found at Bridges and Culverts!!
Look upstream and downstream of impacted reach for possible references. Look at best “spots” of degraded reach to evaluate natural tendencies of the reach and have some ballpark for where you should be landing your design.

12. Reference Reach Criteria
Stable Reference Stream in Same Hydro-Physiographic Region
Same Stream Type as Intended Design
Stable for Two Meander Wavelengths (20 Bankfull Widths)
Best if Similar Valley Slope and Sediment Regime as Impacted/Design Reach
Coastal Plains or Piedmont, etc.
Design valley slope and width may be different than overall valley.

13. Dimensionless Ratios
Key Element in the Geomorphic Approach to Natural Channel Design
Used to “Size” a Reference Stream to a Designed Stream
Requires Numerous Geomorphic Measurements
Make “Dimensionless” Geomorphic Measurements by Dividing by a Bankfull Parameter
In Order to Capture Stream’s Natural Variability, Need a Range of Dimensionless Ratios
Used to Design Pool/Riffle/Glide/Run Habitat
Obtain all ratios on reference reach
Obtain only some of the “useful” ratios on degraded reach if you don’t need them for comparison or to show divergence.

14. Dimensionless Ratios
Wbkf = 20
Lm = 200 Feet

15. Dimensionless Ratios
Lm/Wbkf = 200/20=10
Wbkf = 20
Lm = 200 Feet

16. Dimensionless Ratios Reference Reach Designed Reach Wbkf = 10
Lm = 100 Feet
Wbkf = 20
Lm = 200 Feet

17. Primary Dimensionless Ratios – Cross Sectional Dimensions
Pool, Run, or Glide
Feature Area/Riffle Bankfull Area
Max. Feature Depth/Mean Riffle Bankfull Depth
Mean Feature Depth/Mean Riffle Bankfull Depth
Feature Width/Riffle Bankfull Width

18. Primary Dimensionless Ratios – Pattern
Meander Wavelength (Lm)/Riffle Bankfull Width (Wbkf)
Radius of Curvature (Rc)/Riffle Bankfull Width (Wbkf)
Beltwidth (Wblt)/Riffle Bankfull Width (Wbkf) = MWR
MWR = Meander Width Ratio

19. Primary Dimensionless Ratios – Profile
Slope
Riffle Slope/Bankfull Slope
Pool Slope/Bankfull Slope
Run Slope/Bankfull Slope
Glide Slope/Bankfull Slope
Pool Spacing
Pool to Pool Spacing/Riffle Bankfull Width
Pool Length/Riffle Bankfull Width
Maximum Depths
Max. Riffle Depth/Mean Riffle Bankfull Depth
Max. Pool Depth/Mean Riffle Bankfull Depth
Max. Run Depth/Mean Riffle Bankfull Depth
Max. Glide Depth/Mean Riffle Bankfull Depth

20. Geomorphic Data Collection
Site Review/Toothpick Survey
Cross Sections
Longitudinal Profiles
Pebble Counts/Sediment Samples
Stream Assessments

21. Profile Analysis Bankfull Slope
Facet Slopes – Always Measure Water Surface
Pool to Pool Spacing
Pool Lengths
Facet Maximum Depths – Channel Bottom to Bankfull Elevation
Low Bank Height or Valley Bottom

22. Cross Sections Bankfull Call/Elevation Inner Berm Features
Floodprone Width
Bankfull Area
Bankfull Width and Depth

23. Pebble Counts & Bar Samples
3. Obtain Sieve Analysis
at the location of the
largest particle on
lower 1/3 of
point bar or other
depositional feature
1. Obtain a 100-particle pebble
count on 10 transects from
bankfull to bankfull throughout
the reach (Classification)
2. Obtain a 100-particle pebble count
in the riffle bed (Sediment Transport)

24. Design Reach Data Collection
Dependant Upon Purpose of Project
Impacted Reach (Minimum Data per Stream Type)
Planform Measurements
Riffle Cross Section
Reach Average Pebble Count
Riffle Bed Material Pebble Count
Bar Sample Sieve Analysis
Longitudinal Profile
If you are looking at a long tributary that changes from 5% slope at the top down to 1% slope at the bottom, you will need data for more than one reach.

25. Reference Reach Data Collection
Planform Measurements
Facet Cross Sections (Riffle, Run, Pool & Glide)
Longitudinal Profile through 2 Meander Wavelengths (Minimum) or 20 to 30 Bankfull Widths
Reach Average Pebble Count
Riffle Bed Material Pebble Count
Bar Sample Sieve Analysis
Pfankuch Channel Stability Assessment
Site Controls (Bedrock, Wood)
Multiple Cross sections preferred
Understand what type of material is moving through the site and what type of material is armoring
Are site controls holding the stream in place (such as large bolders) or is the stress very low…

26. Compare Impacted & Reference Reach Data to Regional Curves
Make Comparison to Help Validate Data
Need to Use Regional Curves from Same Hydro-physiographic Area
If No Curves Exist Consider Developing Smaller Scale, Site Specific Curves A B 1 10
100
0.1
1.0
10.0
Drainage Area (square miles)
Bankfull Width (feet)
Field Measurement
Eastern U.S.
Buffalo Run
Ref

27. Calculate Bankfull Velocity & Discharge
Velocity Equations
Manning’s
Chezy
Darcy-Weisbach
Relative Roughness R/D84
Discharge Equation
Q = U*A

28. Sediment Transport Validation
Stop, Store, and/or Transport Sediment Delivered to the System
Procedures for Gravel Systems Typically Based on Sediment Transport Competency and Capacity
Procedures for Sand Systems Typically Based on Sediment Transport Capacity
Define Competency and Capacity

29. Module # 17 Overview of Geomorphic Channel Design Practice
Iowa’s River Restoration Toolbox Level 1 / Base Training