# Rosgen Stream Classification

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{{short description|Method for classifying rivets}}

The '''Rosgen Stream Classification''' is a system for [river](/source/river)s and in which [morphology](/source/River_morphology) arrangements of [stream](/source/stream) characteristics are organized into relatively homogeneous stream types.<ref name=":0">Rosgen, David L. 1994. “A Classification of Natural Rivers.” ''CATENA'' 22 (3): 169–99. {{doi|10.1016/0341-8162(94)90001-9}}.</ref> The Rosgen Classification System was developed by David L. Rosgen in 1994's "A Classification of Natural Rivers". This is a widely used method for classifying streams and rivers based on common patterns of channel morphology.<ref>EPA, 2018. “Fundamentals of Rosgen Stream Classification System | Watershed Academy Web | US EPA.” n.d. Accessed May 6, 2018. [https://web.archive.org/web/20170527185555/https://cfpub.epa.gov/watertrain/moduleFrame.cfm?parent_object_id=1189] .</ref> The specific objectives of this stream classification system are as follows: 1) predict a rivers behavior from its appearance; 2) develop specific [hydrologic](/source/hydrologic) and sediment relationships for a given stream type and its state; 3) provide mechanisms to extrapolate site-specific data to stream reaches having similar characteristics; and 4) provide a consistent frame of reference for communicating stream morphology and condition among a variety of disciplines and interested parties.<ref name=":0" /> These objectives are met through Rosgen's four hierarchical levels (I-IV) of river morphology.

== Hierarchy of the Rosgen Stream Classification ==
=== Level I: Geomorphic Characterization ===
Level I categorize stream types into letters A - G based on their [geomorphic](/source/geomorphic) characteristics that result from the integration of basin relief, land form, and valley morphology.<ref name=":1">Rosgen, David L. and H.L. Silvey 1996. “Applied River Morphology” Second Edition. ''Wildland Hydrology''. Pagosa Springs, CO.</ref> This is a general way in which the morphology of a stream can be described. Many of the Level I criteria can be determined through [topographic](/source/topographic) and landform maps, aerial imagery, and geospatial data.<ref name=":1" />

=== Level II: Morphological Description ===
Level II characterizes stream type by using numbers 1 - 6, in addition to letters A - G, to include the assessments of the channel cross-section, longitudinal profile, and plan-form pattern.<ref name=":0" /> Cross-section measurements include a streams entrenchment ratio, width/depth ratio, and dominant substrate. The longitudinal and plan-form measurements consist of [slope](/source/slope), stream bed features, [sinuosity](/source/sinuosity), and [meander](/source/meander) width ratio. Level II is a quantitative morphological assessment of the stream reach which provides greater detail from data collected in the field for the implementation into land management decisions.<ref name=":1" />

=== Level III: Assessment of Stream Condition and Departure from its Potential ===
Level III describes the existing condition of a stream as it relates to its stability, response potential, and function.<ref name=":1" /> This level includes additional measurements such as, sediment supply, channel stability, and flow regime which further describe the condition or “state” of the stream.<ref name=":1" />

=== Level IV: Field Data Verification ===
Level IV verifies the process relationships inferred from the previous three levels of classification.<ref name=":1" /> The objective of this level is to determine empirical relationships for use in prediction (e.g. to develop [Manning's n](/source/Manning's_n) values from measured [velocity](/source/velocity))<ref name=":1" />

== Applications ==
The Rosgen Stream Classification is probably best applied as a communication tool to describe channel form.<ref name=":2">Simon A., Doyle M., Kondolf M., Shields F.D., Rhoads B., and McPhillips M. 2007. “Critical Evaluation of How the Rosgen Classification and Associated ‘Natural Channel Design’ Methods Fail to Integrate and Quantify Fluvial Processes and Channel Response1.” ''JAWRA Journal of the American Water Resources Association'' 43 (5): 1117–31. {{doi|10.1111/j.1752-1688.2007.00091.x}}.</ref> Other uses for the Rosgen Stream Classification include fish habitat indices, surveys of [riparian](/source/Riparian_zone) communities, [stream restoration](/source/stream_restoration) and mitigation, engineering, evaluating livestock grazing related to stream type, and the use of sediment and hydraulic data by stream type.

== Limitations ==
Problems with the use of the Rosgen Stream Classification are encountered with identifying [bankfull](/source/Bankfull_discharge) dimensions, particularly in [incising](/source/River_incision) channels and with the mixing of bed and bank sediment into a single population.<ref name=":2" /> Its use for engineering design and restoration may be flawed by ignoring some processes governed by [force](/source/force) and resistance, and the imbalance between [sediment](/source/Sediment_transport) supply and transporting power in unstable systems<ref name=":2" />

Limitations for Level II classification involve time dependence, uncertain applicability across physical environments, difficulty in identification of a true equilibrium condition, and uncertain process significance of classification criteria.<ref name=":3">Juracek Kyle E., and Fitzpatrick Faith A. 2007. “Limitations and Implications of Stream Classification.” ''JAWRA Journal of the American Water Resources Association'' 39 (3): 659–70. {{doi|10.1111/j.1752-1688.2003.tb03683.x}}.</ref> Implications of using the Rosgen Stream Classification, include: (1) acceptance of the limitations, (2) acceptance of the risk of classifying streams incorrectly, and (3) classification results may be used inappropriately<ref name=":3" />

== References ==
{{reflist}}

Category:Geographic classifications
Category:Geological processes
Category:Planetary science
Category:Water streams

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Adapted from the Wikipedia article [Rosgen Stream Classification](https://en.wikipedia.org/wiki/Rosgen_Stream_Classification) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Rosgen_Stream_Classification?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.