Teaching Geomorphology in the Field Channel Classification Karen

Channel Classification Field Lab Goals n Exposure n Familiarity with two prominent channel classification

Channel Classification Methods n Rosgen (1994) n form-based n embraced by federal and state

Measurements for classification n Bankfull width n Bankfull depth n WS slope n Sinuosity

Measurements for Rosgen classification n Entrenchment ratio: ratio of the floodprone width to bankfull

Montgomery & Buffington Classification n Cascade n Step pool Montgomery and Buffington, 1997 n

Montgomery & Buffington Classification Montgomery and Buffington, 1997

Real World E. g. : Reference/Impacted XS Surveys • Impacted Reaches – Plane Bed

n NA indicates cross section did not conform to the Rosgen classification system, likely

Annotated photos and map courtesy of Matt Kondolf

References n n Montgomery, D. and Buffington, J. , 1997. Channel-reach morphology in mountain

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Teaching Geomorphology in the Field Channel Classification Karen Williams, PE Montana State University

Channel Classification Field Lab Goals n Exposure n Familiarity with two prominent channel classification methods n Skill n Ability to perform the field measurements needed to classify channels n Concept n Understand usage and limitations of channel classification

Channel Classification

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

Measurements for classification n Bankfull width n Bankfull depth n WS slope n Sinuosity http: //www. stream. fs. fed. us/publications/videos. html

Rosgen classification

Planform

Measurements for Rosgen classification n Entrenchment ratio: ratio of the floodprone width to bankfull width 5 -3 =2 2 x 2 =4 5 -4 =1 3 5

Montgomery & Buffington Classification n Cascade n Step pool Montgomery and Buffington, 1997 n Plane bed n Pool riffle n Dune ripple

Montgomery & Buffington Classification Montgomery and Buffington, 1997

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

n 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. 184 -192.

Annotated photos and map courtesy of Matt Kondolf

References n n Montgomery, D. and Buffington, J. , 1997. Channel-reach morphology in mountain drainage basins. Geological Society of America Bulletin 109 (5), 596 -611. Rosgen, D. , 1994. A classification of natural rivers. Catena 22, 169 -199.