Rosgen Classification Table and Continuum Concept
Rosgen (1994) classification integrates the qualitative and quantitative FGM work of Leopold, Wolman, Miller, Schumm and others into a systematic procedure for taxonomically naming Valleys, river pattern, profile, dimension, and substrate. Much of the classification was developed on US rivers, with many original applications in the central and western states. Today, many federal and state environmental management agencies, as well as private consulting firms, use the classification as part of a standard lexicon to describe Streams.
Classification in this system uses letters and numbers to describe the FGM pattern, profile, dimension and substrate of a river Reach. It is not typical that an entire river fits within one classification. In general, letters A and B describe steeper sloped headwater Streams, letter G incised gully like channels, letter F relatively wide and shallow channels, letter E highly sinuous vegetation lined channels, letter C Meandering channels, and letter D and DA braided channels. Further, numbers denote the size of predominant substrate in the Reach. Number 1 is associated with bedrock, 2 with boulders, 3 with cobble, 4 with gravel, 5 with sand, and 6 with silt and clay.
Classification of rivers with the Rosgen system subscribes to the continuum concept, which acknowledges that many rivers will not fit neatly into a single class. As such, some Stream types are shown to have two letters, and others might be denoted with two numbers, the first indicating the origin, the second the tendency. Navigation through this table to classify a Stream Reach requires multiple FGM measurements, including channel widths for entrenchment, channel depth for width to depth ratio, channel Meander and Valley length for Sinuosity, and bed material.
Image courtesy of Rosgen