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Rosgen Classification Method

Last Updated: January 25, 2012

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The Rosgen method is a more detailed way to classify streams than the Strahler method. It is often used by state and federal agencies. It is also known as the channel shape method. This approach categorizes streams into types A-G on the basis of

  • Slope
  • Sinuosity
  • Ratio of the stream’s width to depth
  • Degree of entrenchment
  • Soil particle size (texture) of the streambanks and channel bottom.

In addition to the letter (A-G) it is given for classification, the stream/river can also be followed by numbers 1-6 which relates to the stream bed material type. They are classified as follow:
1 – Bedrock
2 – Boulders
3 – Cobble
4 – Gravel
5 – Sand
6 - Silt-Clay

The Rosgen Method is useful because it can provide hints about what type of management activities may be best suited for a given stream.

Summary of the Rosgen Stream Types, reprinted from Rosgen (1994)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


The basic tenant of the Rosgen classification approach is as follows:

Natural stream stability is achieved by allowing the river to develop a stable dimension, pattern, and profile such that, over time, channel features are maintained and the stream system neither aggrades nor degrades. For a stream to be stable, it must be able to consistently transport its sediment load, both in size and type, associated with local deposition and scour. Channel instability occurs when the scouring process leads to degradation, or excessive sediment deposition results in aggradation. (From Rosgen, 1994)

 

Further information is provided on the following Rosgen Stream Types:

Rosgen Type Aa+ Streams
Rosgen Type A Streams
Rosgen Type B Streams
Rosgen Type C Streams
Rosgen Type D Streams
Rosgen Type DA Streams
Rosgen Type E Streams
Rosgen Type F Streams
Rosgen Type G Streams


References:

Montana Stream Management Guide for Landowners, Managers, and Stream Users. 1998. Montana Dept. of Environmental Quality. 34 pp.

Rosgen, D. L. (1994). A classification of natural rivers. Catena, 22, 169-199.

Rosgen, D.L. and H.L. Silvey. 1996. Applied River Morphology. Wildland Hydrology Books, Fort Collins, CO.

Surber, Gene and Bob Ehrhart. 1998. Stream and Riparian Area Management. Montana State University Cooperative Extension Service.

United States Environmental Protection Agency. 2008. Fundamentals of the Rosgen Stream Classification System. USDA EPA Watershed Academy. http://www.epa.gov/watertrain/stream_class/index.htm Accessed on 17 May 2010.

Ward, A., J. L. D’Ambrosio, and D. Mecklenburg. 2008. Stream Classification. The Ohio State University Extension. Agriculture and Natural Resources Fact Sheet AEX-445-01.

Image Information:

Reprinted from: Rosgen, Dave. 1996. Applied River Morphology. Page 5-5, image 5-2, with permission granted from Darcie Frantila, Wildland Hydrology, 11210 North County Road 19, Fort Collins, CO 80524. http://wildlandhydrology.com

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