The Rosgen Stream Classification is a system for

river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

s and in which

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

arrangements of

stream A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a strea ...

characteristics are organized into relatively homogeneous stream types.Rosgen, David L. 1994. “A Classification of Natural Rivers.” ''CATENA'' 22 (3): 169–99. . 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.EPA, 2018. “Fundamentals of Rosgen Stream Classification System , Watershed Academy Web , US EPA.” n.d. Accessed May 6, 2018. https://cfpub.epa.gov/watertrain/moduleFrame.cfm?parent_object_id=1189 . The specific objectives of this stream classification system are as follows: 1) predict a rivers behavior from its appearance; 2) develop specific

hydrologic Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and drainage basin sustainability. A practitioner of hydrology is called a hydro ...

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. 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 Geomorphology () is the scientific study of the origin and evolution of topography, topographic and bathymetry, bathymetric features generated by physical, chemical or biological processes operating at or near Earth#Surface, Earth's surface. Ge ...

characteristics that result from the integration of basin relief, land form, and valley morphology.Rosgen, David L. and H.L. Silvey 1996. “Applied River Morphology” Second Edition. ''Wildland Hydrology''. Pagosa Springs, CO. 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 Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the landforms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary scienc ...

and landform maps, aerial imagery, and geospatial data.

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. Cross-section measurements include a streams entrenchment ratio, width/depth ratio, and dominant substrate. The longitudinal and plan-form measurements consist of

slope In mathematics, the slope or gradient of a Line (mathematics), line is a number that describes the direction (geometry), direction of the line on a plane (geometry), plane. Often denoted by the letter ''m'', slope is calculated as the ratio of t ...

, stream bed features,

sinuosity Sinuosity, sinuosity index, or sinuosity coefficient of a continuously differentiable curve having at least one inflection point is the ratio of the curvilinear length (along the curve) and the Euclidean distance ( straight line) between th ...

, and

meander A meander is one of a series of regular sinuous curves in the Channel (geography), channel of a river or other watercourse. It is produced as a watercourse erosion, erodes the sediments of an outer, concave bank (cut bank, cut bank or river cl ...

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.

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. This level includes additional measurements such as, sediment supply, channel stability, and flow regime which further describe the condition or “state” of the stream.

Level IV: Field Data Verification

Level IV verifies the process relationships inferred from the previous three levels of classification. The objective of this level is to determine empirical relationships for use in prediction (e.g. to develop Manning's n values from measured

velocity Velocity is a measurement of speed in a certain direction of motion. It is a fundamental concept in kinematics, the branch of classical mechanics that describes the motion of physical objects. Velocity is a vector (geometry), vector Physical q ...

)

Applications

The Rosgen Stream Classification is probably best applied as a communication tool to describe channel form.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. . Other uses for the Rosgen Stream Classification include fish habitat indices, surveys of

riparian A riparian zone or riparian area is the interface between land and a river or stream. In some regions, the terms riparian woodland, riparian forest, riparian buffer zone, riparian corridor, and riparian strip are used to characterize a ripar ...

communities,

stream restoration Stream restoration or river restoration, also sometimes referred to as river reclamation, is work conducted to improve the environmental health of a river or stream, in support of biodiversity, recreation, flood management and/or landscape develop ...

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 dimensions, particularly in incising channels and with the mixing of bed and bank sediment into a single population. Its use for engineering design and restoration may be flawed by ignoring some processes governed by

force In physics, a force is an influence that can cause an Physical object, object to change its velocity unless counterbalanced by other forces. In mechanics, force makes ideas like 'pushing' or 'pulling' mathematically precise. Because the Magnitu ...

and resistance, and the imbalance between

sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

supply and transporting power in unstable systems 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.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. . 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

References

{{reflist Geographic classifications Geological processes Planetary science Water streams