CATENA
ELSEVIER Catena 22 (1994) 169 199
A classification of natural rivers
David L. Rosgen
Wildland Hydrology, 1 Steven's Lake Road, Pagosa Springs, CO 81147, USA
Abstract
A classification system for natural rivers is presented in which a morphological arrangement
of stream characteristics is organized into relatively homogeneous stream types. This paper
describes morphologically similar stream reaches that are divided into 7 major stream type
categories that differ in entrenchment, gradient, width/depth ratio, and sinuosity in various
landforms. Within each major category are six additional types delineated by dominate channel
materials from bedrock to silt/clay along a continuum of gradient ranges. Recent stream type
data used to further define classification interrelationships were derived from 450 rivers
throughout the U.S, Canada, and New Zealand. Data used in the development of this classi-
fication involved a great diversity of hydro-physiographic/geomorphic provinces from small to
large rivers and in catchments from headwater streams in the mountains to the coastal plains. A
stream hierarchical inventory system is presented which utilizes the stream classification system.
Examples for use of this stream classification system for engineering, fish habitat enhancement,
restoration and water resource management applications are presented. Specific examples of
these applications include hydraulic geometry relations, sediment supply/availability, fish
habitat structure evaluation, flow resistance, critical shear stress estimates, shear stress/velocity
relations, streambank erodibility potential, management interpretations, sequences of morpho-
logical evolution, and river restoration principles.
1. General statement
It has long been a goal o f individuals working with rivers to define and understand
the processes that influence the pattern and character o f river systems. The differences
in river systems, as well as their similarities under diverse settings, pose a real
challenge for study. One axiom associated with rivers is that what initially appears
complex is even m o r e so u p o n further investigation. Underlying these complexities is
an assortment o f interrelated variables that determines the dimension, pattern, and
profile o f the present-day river. The resulting physical appearance and character o f
the river is a p r o d u c t o f adjustment o f its boundaries to the current streamflow and
sediment regime.
0341-8162/94/$07.00 ~, 1994 Elsevier Science B.V. All rights reserved
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170 D.L. Rosgen / Catena 22 (1994) 169 199
River form and fluvial process evolved simultaneously and operate through mutual
adjustments toward self-stabilization. Obviously, a classification scheme risks over-
simplification of a very complex system. While this may appear presumptuous, the
effort to categorize river systems by channel morphology is justified in order to
achieve, to some extent, the following objectives:
1. Predict a river's behavior from its appearance;
2. Develop specific hydraulic and sediment relations for a given morphological
channel type and state;
3. Provide a mechanism to extrapolate site-specific data collected on a given
stream reach to those of similar character;
4. Provide a consistent and reproducible frame of reference of communication
for those working with river systems in a variety of professional disciplines.
2. Stream classification review
A definition of classification was offered by Platts (1980) where "classification in
the strictest sense means ordering or arranging objects into groups or sets on the basis
of their similarities or relationships." The effort to classify streams is not new. Davis
(1899) first divided streams into three classes based on relative stage of adjustment:
youthful, mature, and old age. Additional river classification systems based on qua-
litative and descriptive delineations were subsequently developed by Melton (1936)
and Matthes (1956).
Straight, meandering, and braided patterns were described by Leopold and
Wolman (1957). Lane (1957) developed quantitative slope-discharge relationships
for braided, intermediate, and meandering streams. A classification based on
descriptive and interpretive characteristics was developed by Schumm (1963) where
delineation was partly based on channel stability (stable, eroding, or depositing) and
mode of sediment transport (mixed load, suspended load, and bedload).
A descriptive classification was also developed by Culbertson et al. (1967) that
utilized depositional features, vegetation, braiding patterns, sinuosity, meander
scrolls, bank heights, levee formations, and floodplain types. Thornbury (1969)
developed a system based on valley types. Patterns were described as antecedent,
superposed, consequent, and subsequent. The delineative criteria of these early
classification systems required qualitative geomorphic interpretations creating
delineative inconsistencies. Khan (1971) developed a quantitative classification for
sand-bed streams based on sinuosity, slope, and channel pattern.
To cover a wider range of stream morphologies, a descriptive classification scheme
was developed for and applied on Canadian Rivers by Kellerhals et al. (1972, 1976),
Galay et al. (1973), and Mollard (1973). The work of these Canadian researchers
provides excellent description and interpretation of fluvial features. This scheme has
utility both for aerial photo delineation and for describing gradual transitions
between classical river types, and to date offers the most detailed and complete list
of channel and valley features. The large number of possible interpretative
