1. Teaching Geomorphology in the Field
Channel Classification
Karen Williams, PE
Montana State University
I teach fluvial geomorph and surface water resources for jrs, srs and grad students

2. Channel Classification Field Lab Goals
Exposure
Familiarity with two prominent channel classification methods
Skill
Ability to perform the field measurements needed to classify channels
Concept
Understand usage and limitations of channel classification
Add mention of straight, braided, anabranching as common basis for beginning?

3. Channel Classification

4. Channel Classification Methods
Rosgen (1994)
form-based
embraced by federal and state agencies
limitation: commonly used to “predict a river’s behavior from its appearance” (Rosgen, 1994)
Montgomery and Buffington (1997)
process-based
widely used in PNW
limitation: most applicable in mountain settings
Spelled out “federal”. Limitation (singular)?

5. Measurements for classification
Bankfull width
Bankfull depth
WS slope
Sinuosity
I understand that it is clipped and pasted, but the text is too fine!

6. Rosgen classification

7. Planform

8. Measurements for Rosgen classification
Entrenchment ratio: ratio of the flood-prone width to bankfull width
5-3 =2
2 x 2 =4
5-4 =1 3 5
Cleaned, cropped, and slightly zoomed image. Animate lines/steps to emphasize? Seems like you could use a Rosgen summary section here with perhaps four photos of streams of various classifications, or perhaps some caveats (e.g. identification of bankfull stage).

9. Montgomery & Buffington Classification
Cascade
Step pool
Plane bed
Pool riffle
Dune ripple
Make into two slides with text or add a textbox and animate insertion of profile and plan view.
Montgomery and Buffington,
1997

10. Montgomery & Buffington Classification
Coupling reach-level channel processes with the spatial arrangement of reach morphologies, their links to hillslope processes, and external forcing by confinement, riparian vegetation, and woody debris defines a process-based framework within which to assess channel condition and response potential in
mountain drainage basins. Steep alluvial channels (cascade and step pool) have high ratios of transport capacity to sediment supply and are resilient to changes in discharge and sediment supply, whereas low-gradient alluvial channels (pool riffle and dune ripple) have lower transport capacity to supply ratios and thus exhibit significant and prolonged response to changes in sediment supply and discharge. General differences in the ratio of
transport capacity to supply between channel types allow aggregation of reaches into source, transport, and response segments, the spatial
distribution of which provides a watershed-level conceptual model linking reach morphology and channel processes.
Montgomery and Buffington,
1997

11. Real World E.g.: Reference/Impacted XS Surveys
Impacted Reaches – Plane Bed
transporting (not sorting or storing) all spawning gravel
Reference Reaches – Pool Riffle
sorting and storing spawning gravel
Goal of channel design and structures is to shift the channel into the sediment transport capacity limited regime
Pictures?

12. NA indicates cross section did not conform to the Rosgen classification system, likely due to the geomorphic modifications caused by historic land use
“classification and description are usually insufficient bases for extrapolation and thus for prediction.”
Leopold, Luna B., and Langbein, W.B., 1963,
Association and Determinacy in Geomorphology, in
The Fabric of Geology, Geological Society of America, p

13. Annotated photos and map courtesy of Matt Kondolf

14. References
Montgomery, D. and Buffington, J., Channel-reach morphology in mountain drainage basins. Geological Society of America Bulletin 109 (5),
Rosgen, D., A classification of natural rivers. Catena 22,