1. Iowa’s River Restoration Toolbox Level 1 / Base Training
Module # 13 Understanding the Key Instability Drivers to Inform Design/Decision Matrix
Iowa’s River Restoration Toolbox Level 1 / Base Training

2. Key Design Parameters

3. Key Drivers Floodplain Access Bank Height Ratio Entrenchment
Bankfull Properties
Area
Discharge
Width
Depth
Channel Evolution Stage
Dominant BEHI
Buffer Width

4. Bank Height Ratio (BHR)
BHR= LBH/Dbkf
Lowest Bank Height (LBH)
Bankfull Depth (Dbkf)

5. Geomorphic Floodplain
Entrenched Channel
Bankfull Depth
Geomorphic Floodplain
Bankfull Width

6. Bankfull Geometry

7. Channel Evolution Models
Simon’s Modification of Schumm’s Model

8. Shear Stresses in Streams
Discharge Return Interval
Shear Stress
Natural Stream
Channelized Stream
2-Year Storm
100-Year Storm
D100 D2
Channelized Stream
100-Year Storm
D100
2-Year Storm D2
Natural Stream

9. BEHI Study Bank Height Bankfull Height Root Depth Bank Angle
Surface Protection
Bank Material Adjustment
Stratification Adjustment
Bank Length
Reach Length

10. Heading for Text Over a Photo
Riparian Buffer

11. Additional Key Drivers
Pattern/Geometry
Radius of Curvature
Meander Width Ratio
Pool to Pool Spacing
Width to Depth Ratio
Channel Length
Channel Slope
Stream Type
Presence of Headcuts/Bed Stability
Geomorphic Region/Geology
Sediment Supply/Bed Materials
Constraints

12. Pattern/Geometry Wbkf = Bankfull Width Lm = Meander Wavelength
Wblt = Belt Width
Am = Amplitude
Lm = Meander Wavelength
Rc = Radius of Curvature

13. Channel Slope

14. BKF Width / Mean BKF Depth
Stream Type
Classification A B C E DA D F G
Entrenchment ratio*
<1.4
>2.2
>4.0
n/a
FP width / BKF Width
BKF Width / Mean BKF Depth
W / D ratio*
<12
>12
<40
>40
Typical sinuosity
1 -1.2
>1.2
>1.5
Not predictive
Well-defined
point bars
Veg. islands
Heavy veg.
Both banks erode in wide dirt canyon
Confined, u-shaped valley
Often bedrock / log controlled
Visual Cues
Gully in soft materials
Sed. islands
Typical slope
<.02
<.005
<.04
Typical stability
Usually Stable
Likely Unstable
Classifications from Rosgen, 1996

15. Headcuts/Bed Stability
Caused by Excess Shear Stress
Often Triggered by Downstream Straightening of Channel
Will Propagate Upstream
Increases Channel Entrenchment

16. Sediment Supply/Bed Materials

17. Constraints

18. Key Design Parameters

19. Functional Status

20. The Assessment Process
8. Submit final analysis for review
7. Perform analysis of appropriate practices/techniques
6. Receive adjusted recommendations based on design intent
5. Update Key Drivers for design based on step 4
4. Make initial decisions that will affect the project design
3. Receive initial assessment based on site conditions
2. Fill out data collection Excel workbook
1. Assess project site conditions

21. Purpose of Decision Matrix
Documentation of intuitive knowledge used in stream restoration design
Establish logic used to determine appropriate practices & techniques
Note that there are multiple “right answers”

22. Channel Evolution Models
Simon’s Modification of Schumm’s Model

23. Decision Matrix – Channel Evolution

24. Bank Height Ratio (BHR)
BHR= LBH/Dbkf
Lowest Bank Height (LBH)
Bankfull Depth (Dbkf)

25. Decision Matrix – Bank Height Ratio

26. Decision Matrix - Slope

27. Decision Matrix – Bankfull Width

28. Design Assessment Tab

29. Technique Ranking

30. Iowa’s River Restoration Toolbox Level 1 / Base Training
Module # 13 Understanding the Key Instability Drivers to Inform Design/Decision Matrix
Iowa’s River Restoration Toolbox Level 1 / Base Training