Production services provided by:

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Branch of Publishing Services

Copies available from:

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Printed Materials Distribution Service, BC-652

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Fax: 303-236-0845

E-mail: blm_ncs_pmds@blm.gov

BLM/ST/ST-05/002+1737
by

Karl Gebhardt, P.E. Ervin Cowley

Hydrologist/Environmental Engineer Natural Resource Specialist

Bureau of Land Management Bureau of Land Management

Boise, Idaho Boise, Idaho

Don Prichard Mike Stevenson

Fishery Biologist/Riparian Coordinator Hydrologist

Bureau of Land Management Bureau of Land Management

Denver, Colorado Coeur d’Alene, Idaho
Suggested citations:

Gebhardt, K., D. Prichard, E. Crowley, and M. Stevenson. 2005. Riparian area management: 

Riparian and wetland classification review and application. Technical Reference 1737-21. 

U.S. Department of the Interior, Bureau of Land Management, Denver, CO. 

BLM/ST/ST-05/002+1737. 26 pp.

U.S. Department of the Interior. 2005. Riparian area management: Riparian and wetland 

classification review and application. Technical Reference 1737-21. Bureau of Land Management, 

Denver, CO. BLM/ST/ST-05/002+1737. 26 pp.
RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

TECHNICAL REFERENCE 1737-21 iii

Acknowledgements

The authors wish to thank Steve Leonard 

and George Staidle, who authored Technical 

Reference 1737-5, Riparian and Wetland 

Classification Review, which provided the basis 

for this document. We also thank those who 

reviewed and commented on Technical Reference 

1737-5: Paul Hansen, Bill Platts, Bud Kovalchik, 

Bob Wagner, Jim Fogg, Dan Muller, Mark 

Vinson, Allen Cooperrider, Ray Boyd, Allan 

Strobel, and Al Amen. In addition, we thank 

Tim Burton for his review of this document.

RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

TECHNICAL REFERENCE 1737-21 v

Table of Contents

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

II. Purpose of Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

III. Applying Classification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Define Your Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

 Land Use Planning and Environmental Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

 Proper Functioning Condition Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

 Resource Restoration, Habitat Creation, and Wetland Mitigation. . . . . . . . . . . . . . . . . . . 6

Develop a Data Warehouse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Develop an Understanding of Process Commensurate with Your Purpose . . . . . . . . . . . . . . . . 7

Maintain Data Integrity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

IV. Classification Systems and Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Regional Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

 Major Land Resource Areas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

 Ecoregions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Geomorphic Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

 Brinson’s Hydrogeomorphic Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

 Rosgen’s Classification of Natural Rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

 Montgomery and Buffington’s Stream Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

 Other Geomorphic Classification Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Vegetation Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

 Wetland Classification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

 Successional Classification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

 Standard Ecological Site Description Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Habitat Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

V. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

References Cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

TECHNICAL REFERENCE 1737-21 1

I. Introduction

Since the release of Technical Reference (TR) 

1737-5, Riparian and Wetland Classification 

Review, in 1990, the use of classification in 

riparian and wetland disciplines has been refined. 

Some of the previously described classification 

techniques have become increasingly popular, 

and new systems have emerged to fill the gaps 

identified by land managers, wetland regulators, 

and wetland scientists. While TR 1737-5 

focused on vegetation classification methods, this 

Technical Reference presents a general discussion 

of several areas of classification related to 

riparian and wetland management and provides 

guidance on applying classification to solve land 

management problems.

There are a number of statements, questions, 

and theories that provide a context for using 

classification. Understanding these items is 

essential to the successful application of any 

classification system:

• Classification should permit comparison and 

reproducibility, provide an estimate of potential 

success or failure, and improve communication.

• “...many salmon restoration projects fail 

because they rely on ‘off-the-shelf’ concepts 

and designs rather than developing site-specific 

understanding...” (Kondolf et al. 2003).

• Are we repeating the application of failed 

techniques because we are too lazy to monitor 

their effectiveness?

• “While both physical and biological criteria 

have been used to classify lotic system, successful 

integration of these related aspects into a single, 

process-based framework that encompasses a range 

of spatio-temporal scales remains a considerable 

challenge” (Thomson et al. 2004).

• “Classifying riparian vegetation therefore requires 

a full understanding of species distribution 

and succession, in relation to environmental 

parameters and disturbance factors over a large 

area” (Muller 1997).

• “Watershed and ecoregion frameworks are 

complementary. Watersheds provide the 

framework for determining the land/water 

associations, and ecoregions provide the 

framework for extrapolating and reporting this 

information” (Omernik 2003).

• As with any procedure, misapplication is 

likely to occur if the users rely solely on the 

classification tool or its products and not on the 

underlying science behind the classification. Users 

must always place the science in front of the 

classification and not the other way around.

• Riparian and wetland systems are dynamic. 

Mapping and classification often produce only a 

snapshot that does not represent the dynamics of 

the system.

• Conducting riparian and wetland projects 

without examining site history and process is 

irresponsible.

• Do we want the right answer or the easy answer?

RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

TECHNICAL REFERENCE 1737-21 3

II. Purpose of Classification

Classification is defined as a systematic 

arrangement of items into groups or categories 

according to established criteria. The purpose of 

classification for land management applications 

often has to do with providing a reasonably easy 

way to talk about management areas, establish 

priorities for decisionmaking, determine costeffective strategies for dealing with resource 

restoration, or simply provide a basis to 

summarize inventory data into meaningful 

groups. Kondolf (1995) states that “classification 

allows scientists to stratify an otherwise confusing 

universe into sets of similar objects, conduct 

careful study on representative objects, and 

apply results to other members of that class.” 

Classification should permit comparison and 

reproducibility, provide an estimate of potential 

success or failure, and improve communication.

In TR 1737-5, a number of vegetation 

classification systems were described so that 

practitioners could choose those that 

appeared most applicable to their needs. In 

the 15 years since the release of TR 1737-5, 

riparian and wetland classification requirements 

have expanded to encompass a variety of needs, 

and a number of applications have emerged 

that can benefit from classification strategies. 

Those applications most important to specialists 

in the Bureau of Land Management (BLM) 

include: environmental analysis, proper 

functioning condition (PFC) analysis, resource 

restoration, habitat creation, and wetland 

mitigation. Generally these applications require 

either a stratification of data for management 

presentation and discussion purposes or a 

stratification of data with cause and effect 

analysis. In recent years, cause and effect analysis 

has become the principal reason for beginning a 

classification effort.

RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

TECHNICAL REFERENCE 1737-21 5

III. Applying Classification

Technical Reference 1737-5 presented a number 

of vegetation classification systems and clearly 

stated that:

“It is the policy of the Bureau of Land Management 

(BLM) to apply the Standard Ecological Site 

Description procedure patterned after the Soil 

Conservation Service (SCS) Range Site procedure and 

expanded by the BLM (USDA-SCS 1976, USDIBLM 1990) to grazable woodland, native pasture, 

and riparian sites. However, other classification 

and description procedures exist and often must be 

used to make use of all available information or to 

coordinate between other agencies and institutions 

during riparian and wetland inventory.”

In the current century, specialists need to move 

towards an even better understanding of the 

systems they are attempting to manage. Many of 

the vegetation classification systems previously 

reviewed embraced the ecological concepts of 

vegetation succession, and some recognized 

the need to incorporate the hydrogeomorphic 

(and other) processes that influence often rapid 

and severe changes to vegetation communities 

(Youngblood et al. 1985, Kovalchik 1987, Hansen 

et al. 1988, Hansen 1989, Szaro 1989, Kovalchik 

and Chitwood 1990, and Hansen et al. 1995).

Gurnell et al. (1994) compiled stream 

classification methodologies from literature over 

the last century and grouped them in terms of 

spatial units from small to large:

• Habitat units—relatively small

• Sections—several hundred meters in length

• Zones—a bit larger, where a river would be 

described in terms of 3 or 4 zones

• Regions—watersheds and subwatersheds

• River—the whole river system

• Ecoregion—implying more than one river 

system

• Hierarchical—representing systems that have a 

nested range of units

The “early period,” from 1890 through 1969, 

had 34 classification methodologies identified in 

the open literature, and the “late period,” from 

1970 through 1989, had 30. River and section 

classification systems accounted for 74 percent 

in the early period and 17 percent in the late 

period, while the hierarchical methods totaled 

3 percent in the early period and 33 percent 

in the late periods. Heritage et al. (2001) state, 

“The majority of the hierarchies are structured 

from the catchment scale downward on the basis 

that it is the catchment variables that control 

the dynamics and, hence, the morphology of the 

river (Van Deusen 1954).” They also point out 

that the top-down hierarchy employed by many 

classifications, which assumes that the watershed 

system above a subsystem forms the environment 

of the subsystem, may not be applicable in all 

situations and cites Mosely (1987) as suggesting 

it may be more useful to classify rivers by their 

components, resulting in a bottom-up hierarchy. 

Thomson et al. (2004) state “While both physical 

and biological criteria have been used to classify 

lotic systems, successful integration of these 

related aspects into a single, process-based 

framework that encompasses a range of spatiotemporal scales remains a considerable challenge.”

What we can conclude from the discussion above 

is that no single classification approach may be 

the best in every situation. We can, however, 

make some educated guesses at which system or 

combination of systems may prove most useful 

in a particular setting. Chances are there is a 

classification procedure or approach that will fit 

your needs. In all likelihood, a combination of 

elements from several systems may be needed to 

develop the appropriate tool. Existing data or 

a previously completed classification often will 

require only minor changes or interpretation to 

make the information as useful as possible. The 

following steps are suggested to help you decide 

on an approach to use for riparian-wetland 

classification:

• Define your purpose

• Develop a data warehouse

• Develop an understanding of process 

commensurate with your purpose

• Maintain data integrity
RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

6 TECHNICAL REFERENCE 1737-21

Define Your Purpose

Classification should be a tool that helps you 

get something done. Classification should 

not be done for the purpose of classification; 

it should be based on need. In defining your 

purpose for classification, you should write a 

purpose statement that describes exactly what 

the classification is to provide. It should list 

management requirements, assumptions, output 

formats, and goals. 

Land Use Planning and Environmental 

Analysis

Environmental analysis comes from a number 

of requirements rooted in the National 

Environmental Policy Act. Analysis can range 

from project- and site-specific applications, such 

as environmental assessments (EAs), to broader 

and programmatic applications, such as resource 

management plans, to holistic and cumulative 

applications, such as a watershed analysis. 

Classification, if well designed, can provide a 

powerful tool for presenting, describing, and 

predicting the consequences of management 

actions.

Environmental analysis requires specialists to 

describe the riparian and wetland resource as 

well as to provide some level of prediction of 

the potential effect of management decisions. 

Often, the analysis will serve as the basis for more 

detailed analyses because of specific actions. The 

importance of structuring the initial classification 

effort to accommodate future requirements 

cannot be overemphasized. Classification that 

simply presents mapping units without some 

framework for anticipating future management 

actions may not be very useful.

Proper Functioning Condition Analysis

The BLM has used the PFC analysis since 1993 

to provide a barometer of sorts in evaluating the 

agency’s efforts to improve riparian habitat. The 

PFC analysis involves a qualitative assessment 

designed to evaluate riparian ecologic and 

hydrogeomorphic function. It is conducted by a 

team of specialists who assess 17 items based on 

a site’s perceived potential. Ward et al. (2003) 

recommended the use of habitat classification 

and geomorphic classification in combination 

with PFC to provide the most information about 

riparian area and stream health.

Resource Restoration, Habitat Creation, 

and Wetland Mitigation

In recent years, the number of projects related 

to resource restoration, habitat creation, and 

wetland mitigation has increased. Classification 

can provide a useful tool for analyzing conditions 

and determining restoration, creation, and 

mitigation goals, priorities, strategies, and design 

(Sather-Blair et al. 1983, Frissell et al. 1986, 

Lanka et al. 1987, Delong and Brusven 1991, 

Moore et al. 1991, Olson and Harris 1997, 

Harris and Olson 1997, Suzuki and McComb 

1998, Wissmar and Beschta 1998, Quinn et al. 

2001, and Montgomery 2004). Montgomery 

(2004), citing Kondolf et al. (2003), suggests 

that many salmon restoration projects fail 

because they rely on “off-the-shelf” concepts 

and designs rather than developing site-specific 

understanding. He goes on to suggest that 

salmon recovery efforts, to be successful, need 

to be rooted in understanding hydrogeomorphic 

processes and historical changes to rivers and 

streams. Kondolf (1995) recognized that stream 

channel classification is commonly carried 

out by those who are not geomorphologists 

and who may not fully understand its use. 

Kondolf et al. (2003) present a discussion on 

the uses and limitations of such classification 

tools and document the popularity among land 

managers of the system developed by Rosgen 

(1985, 1994). Kondolf (1985) warns, “Despite 

their real value, classification schemes can be 

seductive, especially for non-geomorphologists 

(who are unlikely to appreciate the nature of 

geomorphological processes), who may feel that 

the channel is completely described once it has 

been ‘classified.’” Kondolf (1985) also provides 

an example in which a designer filled a natural 

pool because it did not fit with the designated 

stream classification, even though the project 

was to increase pools in the reach. Fortunately, 

the trend of classification has been towards 

developing a better understanding of process. 

Muller (1997) states, “Classifying riparian 

vegetation therefore requires a full understanding 

of species distribution and succession, in relation 

to environmental parameters and disturbance 

factors over a large area.”
RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

TECHNICAL REFERENCE 1737-21 7

Develop a Data Warehouse

Data warehouse is a term that refers to all of 

the available data, generally digital, that may 

be applicable to a project. A typical data set 

includes historical aerial photographs, oblique 

photographs, past inventories, maps, and studies. 

The data may also be useful in determining 

temporal and spatial changes, cause and effect 

relationships, and limiting factors.

Riparian inventories have been conducted 

throughout the West and may be applicable to 

your need. Look for previous applications of 

classification in your region and consider using 

them or their components for your classification 

project. However, be aware that past classification 

efforts may not be designed to accommodate 

your purpose.

Develop an Understanding of 

Process Commensurate with 

Your Purpose

Dominant processes, limiting factors, causative 

and disturbance factors, spatial and temporal 

factors, and reference areas are all important in 

understanding how riparian-wetland systems 

function. A classification that is based on a 

solid understanding of process can be used to 

extrapolate cause and effect relationships between 

similar classification units. A classification 

that is not based on process will have limited 

value for extrapolation and can lead to serious 

judgment errors when used beyond its design. 

If the purpose of the classification is simply to 

provide a visual representation of some riparianwetland characteristic, that fact should be clearly 

noted in the classification. Classification efforts, 

particularly those from a decade or more ago, 

often were used to display meaningful groupings 

of a resource inventory and nothing more.

In our experience, the most common 

misapplication of classification information 

comes from using a dated classification that 

represents a “snapshot” of resource information 

where some aspect of the riparian-wetland 

system has changed. One example is the 

National Wetland Inventory (NWI). That 

inventory uses the U.S. Fish and Wildlife Service 

(USFWS) classification technique developed 

by Cowardin et al. (1979), which describes 

the dominant vegetation, and to some degree, 

expected hydrologic conditions at the time of the 

inventory. It is an extremely useful technique, 

but it is not designed nor intended to go much 

beyond description unless coupled with more 

process-based analyses. Using NWI information 

for restoration planning, impact analysis, 

reference area selection, and other similar 

applications may be inappropriate, especially 

where hydrologic or morphologic conditions are 

complex or variable.

Maintain Data Integrity

Data integrity remains a serious concern when 

using classification techniques. The actual 

resource data upon which a classification is based 

should always be protected and documented. A 

classification and its data should be permanently 

joined. Also, a classification technique should 

help portray the data it is based on and guard 

against the “point and classify” approach. The 

“point and classify” approach occurs when 

an area becomes classified without using 

data. Sometimes data becomes secondary 

to classification and users assume that site 

characteristics of a classified area reflect actual 

data, which may not be the case. An example 

of this would be using the Rosgen classification 

descriptors to describe a riparian-wetland system 

without actually going through the steps that the 

classification procedure demands.

RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

TECHNICAL REFERENCE 1737-21 9

IV. Classification Systems and 

Approaches

This section provides summaries and potential 

applications for selected classification systems 

that are useful to riparian and wetland 

practitioners. They are listed in general 

hierarchical order: regional systems, geomorphic 

systems, vegetation systems, and habitat 

systems. As with any procedure, misapplication 

is likely to occur if the users rely solely on the 

classification tool or its products and not on 

the underlying science behind the classification. 

Users must always place the science in front of 

the classification and not the other way around.

Regional Systems

Regional systems are representations of large 

spatial areas having similar characteristics of 

broad variables such as climate, geology, soil, 

vegetation, elevation, or a combination of these 

variables. Three major regional systems are in 

wide use: the Natural Resources Conservation 

Service (NRCS) major land resource area, which 

is defined in the National Soil Survey Handbook

(USDA-NRCS 2003), the U.S. Environmental 

Protection Agency (EPA) ecoregion mapping 

effort featuring four nested levels of resolution, 

and the well-known Bailey ecoregion system 

used by the U.S. Forest Service (USFS) and 

other groups. These systems are shown in 

Figure 1a-c.

The usefulness of regional classifications will tie 

directly to the intended use of the classification 

Figure 1a. The major land resource area system is used by the Natural Resources Conservation Service.
RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

10 TECHNICAL REFERENCE 1737-21

Figure 1b. The ecoregion system used by the Environmental Protection Agency has four levels of resolution.

Figure 1c. The Forest Service uses the Bailey (1995) ecoregion system.
RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

TECHNICAL REFERENCE 1737-21 11

project you are embarking on. At a minimum, 

regional classifications should be examined to:

1. Determine what regional systems are available 

and used in the project area.

2. Initially identify variability at the regional 

level within a watershed, which should help to 

identify important processes.

3. Locate other areas having similar regional 

classification attributes that can be used 

for finding potential reference sites and 

comparable projects and in extrapolating 

results (Omernik 1995).

Brewer (1999) listed the following factors that 

guided the development of the EPA ecoregion 

system:

1. Holistic, broad-based regional analysis and 

assessment of resource management.

2. Inventory and assessment of environmental 

resources.

3. Establishment of resource management goals.

4. Wetland classification and management.

5. Development of biological criteria for water 

quality standards.

6. Refinement of chemical water quality 

standards.

The above lists should provide suitable ideas for 

incorporating regional-level classification into 

more site-specific endeavors.

Major Land Resource Areas

“Major land resource areas (MLRA) are based 

upon aggregations of geographically associated 

land resource units and identify nearly 

homogeneous areas of land use, elevation, 

topography, climate, water resources, potential 

natural vegetation, and soils. Major land 

resource area boundaries reflect an appropriate 

generalization of land resource unit boundaries 

(as derived from state soil geographic database 

map unit boundaries). The approximate 

minimum size of a major land resource area 

that may be delineated is 580,644 hectares, or 

1,434,803 acres. This minimum delineation is 

represented at the official major land resource area 

map scale of 1:7,500,000 by an area approximately 

1 cm by 1 cm (0.4 inch by 0.4 inch). Minimum 

linear delineations are at least 0.3 cm 

(0.1 inch) in width and 2.5 cm (1 inch) in 

length. The Pacific and Caribbean Islands, 

which have land areas less than 580,644 hectares 

(1,434,803 acres) in size, are excluded from 

the minimum delineation rule. Large existing 

major land resource areas may be subdivided 

to create more homogeneous areas as needed, 

provided that cartographic criteria regarding 

minimum delineations are met. The descriptions 

of the map units on major land resource area 

maps emphasize land use and water resource 

management. Generally, a major land resource 

area occupies one continuous delineation; 

but it may occupy several separate ones. 

Major land resource areas are most useful for 

statewide agricultural planning and have value 

for interstate, regional, and national planning” 

(USDA-NRCS 2003).

Additional information can be found at 

http://www.nrcs.usda.gov/technical/land/mlra.

Ecoregions

“The ecoregion concept, introduced by 

Crowley (1967), is based on the notion that 

such homogeneous ecosystem regions exist in 

nature and can be delineated and classified. This 

concept is not new, but is merely a new name for 

old ideas developed in scientific and geographic 

theory. The ecoregion concept, or theory, is used 

to create classifications and frameworks that 

depict ecoregions” (Brewer 1999). Omernik and 

Bailey (1997) state, “In broad terms, ecological 

regions, at any scale, can be defined as areas with 

relative homogeneity in ecosystems.”

Additional information can be found at 

http://www.epa.gov/wed/pages/ecoregions.htm.

“Ecoregions denote areas of general similarity in 

ecosystems and in the type, quality, and quantity 

of environmental resources. They are designed 

to serve as a spatial framework for the research, 

assessment, management, and monitoring of 

ecosystems and ecosystem components. By 

recognizing the spatial differences in the capacities 

and potentials of ecosystems, ecoregions stratify 

the environment by its probable response to 

disturbance. These general purpose regions 

are critical for structuring and implementing 

ecosystem management strategies across federal 

agencies, state agencies, and nongovernment 

organizations that are responsible for different 
RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

12 TECHNICAL REFERENCE 1737-21

types of resources within the same geographical 

areas” (Omernik and Bailey 1997).

EPA Ecoregions

Omernik (1995) states “Hence, the difference 

between this approach to defining ecoregions 

and most preceding methods is that it is based 

on the hypothesis that ecological regions gain 

their identity through spatial differences in a 

combination of landscape characteristics. The 

factors that are more or less important vary 

from one place to another at all scales.” Omernik 

(1995) provides the basis of the EPA methodology 

that is leading a nationwide effort to provide 

ecoregion classification at a relatively more 

detailed, larger scale (level IV), which is available 

in nearly all of the United States through the 

cooperation of many federal agencies, including 

the NRCS and USFS (Figure 2). The assimilation 

Figure 2. This map of Wyoming illustrates the level IV application of the Environmental Protection 

Agency’s ecoregion system.
RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

TECHNICAL REFERENCE 1737-21 13

of NRCS and USFS regional classifications and 

state and federal watershed delineation efforts 

is a credit to those professionals who can see 

the value of cooperation over competition. 

The EPA method, while being relatively 

qualitative, involves local resource experts 

along with national experts to provide utility 

and consistency. The qualitative method allows 

the developers to include features within an 

ecoregion boundary that might be overlooked 

in a single-featured classification. At its core, 

the EPA system’s purpose is to provide useful 

information for managers of water quality and 

aquatic habitat. As such, the EPA system should 

provide an excellent information source for 

riparian and wetland classification efforts.

U.S. Forest Service Ecoregion

The USFS ecoregion effort applies Bailey (1995) 

and provides an excellent source for classification 

at the regional level. The following excerpt from 

Brewer (1999) provides an outstanding review of 

ecoregion history:

“Robert G. Bailey recognized the need 

for a comprehensive system for classifying 

ecosystems to aid regional and national 

long-range land management and planning. 

In 1976, Bailey, working for the United 

States Forest Service, published a map titled 

‘Ecoregions of the United States,’ (Bailey, 

1978). This map was published for the Interior 

Department’s Fish and Wildlife Service to aid 

in the National Wetlands Inventory. In 1978, 

he published a supplement that contained 

detailed descriptions of the various ecoregions 

depicted on the original map.

Bailey’s methodology closely paralleled 

the work of Crowley. He defined ecoregions 

as geographical zones that represented 

geographical groups or associations of similarly 

functioning ecosystems (Bailey, 1983). By 

analyzing environmental factors that acted as 

selective forces for the creation of ecosystems, 

Bailey constructed a 1:7,500,000-scale map 

of the United States’ ecoregions. A detailed 

explanation of the delineation methods was 

published in 1983.

Ecoregions, according to Bailey, divided 

the landscape into variously sized ecosystem 

units that had significance for development of 

resources and conservation of the environment. 

Landscape analysis helped identify ecoregions 

which were defined as broad areas where one 

would expect to find similar vegetation and soil 

associations (Bailey, 1983).

Bailey proposed two important management 

functions that could be derived from an 

ecoregion classification. The map suggested 

the areal extent of productivity relationships 

derived from experiments and allowed users to 

apply individual experience. Ecoregion maps 

also provided a geographical framework that 

would allow recognition and prediction of 

similar responses from correspondingly defined 

sites (Bailey, 1983).

Climate, in Bailey’s delineation methodology, 

became the most important reflection of 

zonality. Second was surface configuration, or 

land surface form. Vegetation regions based 

on Dasman (1969)1 and Küchler (1973) 

represented the next level of subdivision. 

Bailey established a hierarchical order based 

on sub-continental domains that were defined 

by broad climatic similarities. The fairly 

heterogeneous domains could be divided 

into divisions, which correspond to definite 

vegetational classifications such as prairies or 

forests. Zonal soils were given consideration 

at this level. The next class was the province 

level, based on climax plant formations. Soil 

zones also were important for province level 

delineation. The base level of classification 

was the section level, based almost entirely on 

Küchler’s potential natural vegetation regions 

(Bailey, 1983).”

Additional information can be found at 

http://www.fs.fed.us/institute/ecolink.html.

Geomorphic Systems

Riparian and wetland work often involves 

describing and analyzing stream systems, 

including the channel, banks, floodplain, 

terraces, surface and subsurface water, and 

associated habitats. Several geomorphic 

systems are now commonly used to classify 

stream systems. Their basic methodologies and 

applications are described on the following pages.

1 Complete reference information was not provided in Brewer (1999).
RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

14 TECHNICAL REFERENCE 1737-21

Brinson’s Hydrogeomorphic 

Classification

The hydrogeomorphic (HGM) classification 

system (Brinson 1993) has been used extensively 

to better understand and evaluate wetland 

ecosystems. The HGM procedure emphasizes 

geomorphic and hydrologic controls, which are 

most important in defining many riparian and 

wetland systems. The procedure was designed 

to be simple to enable fast learning and flexible 

to allow for revision and correction. Its major 

purpose is to assess ecosystem function in 

pre- and postproject situations. HGM can be 

extremely useful in planning, analysis, and 

design, as it embraces the concepts of process 

(function) and reference areas, as well as 

potential. The procedure is now recommended 

for developing compensatory mitigation plans 

(U.S. Army Corps of Engineers 2002), and 

its expedited development was directed by 

the White House Office on Environmental 

Policy in 1993 (Clairain 2002). A vast amount 

of support literature is available including: a 

functional assessment of the Upper Yellowstone 

River (Hauer et al. 2001), functional guidance 

(Smith et al. 1995, Brinson et al. 1995, Wakely 

and Smith 2001, Smith and Wakely 2001, and 

Clairain 2002), a tidal application (Shafer and 

Yozzo1998), reference area guidance (Smith 

2001), prairie pothole guidance (Hauer et al. 

2002a), Rocky Mountain riverine floodplains 

guidance (Hauer et al. 2002b), wetland 

hydrology guidance (Cole and Wardrop 1997), 

and impact and mitigation assessments (Hauer 

and Smith 1998). In addition, the procedure 

has been evaluated using two support teams on 

44 riverine sites demonstrating a high degree 

of agreement for most variables and Functional 

Capacity Index scores (Whigham et al. 1999) 

and the procedure also supports statistical 

treatment of the scoring within functional 

category (Pohll et al. 2000).

The HGM procedure uses three components: 

landscape (geomorphic setting), water source 

and transport, and hydrodynamics. Geomorphic 

setting is the wetland’s landscape position 

and is related to how that topographic setting 

processes water (transport and storage). Examples 

of geomorphic settings include: areas with no 

inlet or outlet, streamside zones (riparian), and 

shorelines that are associated with depressional, 

riverine, and fringe wetland classes, respectively. 

Seven hydrogeomorphic wetland classes currently 

exist: riverine, depression, slope, organic soil flat, 

mineral soil flat, estuarine fringe, and lacustrine 

fringe. The water source for the wetland is 

generally described as precipitation, groundwater, 

or surface or near-surface inflow, depending 

on its importance to the functionality of the 

wetland. Precipitation would be identified as 

dominant for bog type wetlands existing in a 

wet climate, which rarely results in unsaturated 

conditions. Distinguishing whether a wetland 

system is from a groundwater or surface water 

source is more difficult in many cases, but the 

fundamental determination would be how 

surface water contributes to the functionality 

of the wetland. Hydrodynamics refers to the 

frequency, magnitude, and duration of vertical 

fluctuations (groundwater and precipitation 

water sources), unidirectional fluctuations as 

influenced by surface riverine flooding, and 

bidirectional fluctuations as seen in wave action 

and tides in the tidal classes. The following 

assumptions are inherent in the HGM procedure 

(Rheinhardt et al. 1997):

1. Ecological processes (functions) in relatively 

unaltered wetlands occur at levels that are 

sustainable and predictable for any given 

HGM wetland type (barring severe natural 

perturbations).

2. Ecological processes are so similar in form 

and magnitude within any narrowly defined 

regional subclass that they shape biotic and 

abiotic components in ways characteristic for 

the subclass.

3. Some of these biotic and abiotic parameters 

can be measured in the field using standard 

and relatively rapid techniques.

4. Variables derived from field measurement can 

be combined to coarsely model functions of 

the subclass.

One of the most useful parts of the HGM 

procedure is the requirement to link fundamental 

wetland properties with ecological significance, 

which results in the identification of wetland 

function (process). A first step in identifying 

function is to define reference wetlands, which 

provide the standard for comparison in the 

HGM procedure (Clairain 2002). Reference 
RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

TECHNICAL REFERENCE 1737-21 15

subclass wetlands are assumed to be fully 

functional and are rated as “1.” Other wetlands 

that are less than fully functional and share the 

same subclass are rated between “0” and “1.” The 

HGM procedure for riverine systems uses 

15 functions distributed among 4 functional 

areas (Brinson et al. 1995):

Hydrologic

Dynamic Surface Water Storage

Long-Term Surface Water Storage

Energy Dissipation

Subsurface Storage of Water

Moderation of Groundwater Flow or Discharge

Biogeochemical

Nutrient Cycling

Removal of Imported Elements and Compounds

Retention of Particulates

Organic Carbon Export

Plant Habitat

Maintain Characteristic Plant Communities

Maintain Characteristic Detrital Biomass

Animal Habitat

Maintain Spatial Structure of Habitat

Maintain Interspersion and Connectivity

Maintain Distribution and Abundance of 

Invertebrates

Maintain Distribution and Abundance of 

Vertebrates

The procedure calls for an application team 

(A-team) to evaluate functions by further 

defining them with functional variables, which 

are the physical process components that 

enable the function to work. For example, 

under the “Dynamic Surface Water Storage” 

function, there are variables such as: frequency 

of overbank flow, average depth of inundation, 

microtopographic complexity, and plant roughness, 

which represent the components important to 

distributing water over the floodplain. Hauer et 

al. (2002a) defined a surface water function on 

the Upper Yellowstone River as “Surface WaterGroundwater Storage and Flux” with variables 

of frequency of surface flooding, frequency of 

subsurface flooding, macrotopographic complexity, 

and geomorphic modification.

Hauer et al. (2002a) provides an example of the 

range of functional descriptions for the variable 

geomorphic modification:

Description Score

No geomorphic modifications (e.g., 

dikes, levees, riprap, bridge approaches, 

roadbeds, etc.) made to contemporary 

(Holocene) floodplain surface.

1.0

Few changes to the floodplain surface 

with little impact on flooding. Changes 

restricted to < 1m in elevation and only 

for farm roads or bridges with culverts 

maintained. Geomorphic modifications 

do, however, result in minor change in 

cut-and-fill alluviation.

0.75

Modification to the floodplain surface <1 

m in elevation. Riverbank with control 

structures (e.g., riprap) <10% of river 

length along LAA [landscape assessment 

area]. Geomorphic modifications result 

in measurable change in cut-and-fill 

alluviation.

0.5

Multiple geomorphic modifications to the 

floodplain surface to control flood energy, 

often with bank control structures, but 

still permitting flow access via culverts to 

backwater and side channels. Geomorphic 

modifications result in significant 

reduction in cut-and-fill alluviation.

0.25

Complete geomorphic modification along 

the river channel of the floodplain surface 

to control flood energy. Bank control 

structures in the form of dikes and riprap 

in a continuous structure or constructed 

to prevent channel avulsion, but still 

permitting flow access via culverts to 

backwater and side channels. Geomorphic 

modifications result in termination of cutand-fill alluviation.

0.1

Complete geomorphic modification along 

the river channel of the floodplain surface 

to control flood energy. Bank control 

structures in the form of dikes and riprap 

in a continuous structure preventing 

channel avulsion and also preventing flow 

access via culverts to backwater and side 

channels

0
RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

16 TECHNICAL REFERENCE 1737-21

These types of descriptions provide excellent 

documentation that is useful in analyzing 

impacts, developing design goals for restoration 

activities, and establishing action levels for 

monitoring plans.

The HGM procedure results in the 

development of regional standards for wetland 

functions, particularly in assessing mitigation, 

enhancement, and creation of wetland in a 

regulatory setting, which was a primary purpose 

for its development. The full application and 

accounting of wetland functions can be arduous 

to those developing the standards (akin to the 

habitat evaluation procedure), but can be well 

worth the investment in providing a rapid 

comparison technique that is process based and 

well-documented. The HGM procedural concept 

also can be used in a less intensive manner to 

fit many BLM needs, such as in environmental 

analysis and planning, ecosystem analysis, and 

watershed analysis, and as a companion in 

conducting the proper functioning condition 

assessments. The thought process used in the 

HGM procedure serves as a technical framework 

that can lead to process-based analysis.

The HGM procedure does not determine 

value, is not intended for comparing different 

subclasses, and is not intended for analyzing 

cumulative impacts (Clairain 2002). Value is 

defined as “the rules that determine what people 

consider important” (Brinson 1993). In the 

process of identifying wetland and riparian units, 

their functional importance may provide an 

opportunity to assign or describe their value as it 

relates to the ecosystem. Certainly determining 

their monetary value is another exercise. Hauer 

et al. (2001) demonstrated the use of the HGM 

procedure in a cumulative impact analysis of the 

Upper Yellowstone River. Using HGM and other 

impact assessment procedures, they produced a 

suitable impact analysis for the wetland ecosystem.

As with any procedure, misapplication is likely to 

occur if the users rely solely on the classification 

tool or its products, such as on HGM models, 

and not on the underlying science behind the 

classification. Users must always place the science 

in front of the classification and not the other 

way around.

Rosgen’s Classification of Natural Rivers

Rosgen’s (1994, 1996) classification of natural 

rivers is designed to:

• Predict a river’s behavior from its appearance

• Develop specific hydraulic and sediment 

relations for a given morphological channel 

type and state

• Provide a mechanism to extrapolate sitespecific data collected on a given stream reach 

to those of similar character

• Provide a consistent and reproducible frame of 

reference of communication for those working 

with river systems in a variety of professional 

disciplines.

Rosgen (1994) acknowledges the complexity 

of natural rivers and states, “Obviously, a 

classification scheme risks over-simplification 

of a very complex system.” With this in mind, 

Rosgen (1996) suggests that “stream morphology 

displays a continuum of form” and develops a 

stream classification system progressing through 

four hierarchical levels: a broad geomorphic 

assessment (level I); a more detailed description 

based on reference reach information (level II); a 

description of existing condition (level III); and, 

finally, verification where measurements are made 

to determine the strength of process assumptions 

used in the previous levels (level IV).

Level I begins with characterizing the basin’s 

landform and valley types and integrating this 

information with observed stream morphology 

based on form and pattern. A characteristic 

“stream type” is determined from parameters of 

entrenchment, pattern, slope, and channel shape 

to be one of nine types (Aa+, A, B, C, D, DA, 

E, F, and G). The level I classification strives 

to provide a consistent initial framework for 

organizing information and communication. In 

addition, this level helps to develop priorities and 

consider other resource inventories that share the 

stream system.

Level II stream types develop more refinement 

using field measurements to help resolve 

questions regarding sediment supply, sensitivity 

to disturbance, resiliency, channel response, and 

habitat potential. The level II step assumes, as 

does the remainder of the hierarchy, that the 
RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

TECHNICAL REFERENCE 1737-21 17

stream system behaves as a continuum. At the 

level II step, because of its relationship with 

width and channel patterns, bankfull discharge 

becomes the most important characteristic in the 

classification system and is required in estimating 

two of the five level II criteria. The application of 

the level II stream type results in the refinement 

of the level I determination, for example, from a 

“C” type to “C3” and “C4” types. Unfortunately, 

in our experience, many users of the Rosgen 

system stop at the level II step.

The level III step provides some of the most 

useful information about stream behavior and 

management and requires the user to figure 

out what the stream is doing and what it has 

done. Level III involves collecting and analyzing 

data about vegetation, streamflow, stream size 

and order, debris and blockages, depositional 

patterns, meander patterns, streambank erosion 

potential, aggradation or degradation potential, 

channel stability, and altered channel materials 

and dimensions. At this level, the user is asked 

to develop a description of the “full operating 

potential” for a particular reach, along with its 

departure. This step is demanding and requires a 

high degree of experience not generally available 

to those who are not geomorphologists, but it 

can provide valuable information for resource 

management.

Level IV requires a stream inventory to validate 

the predictions made in level III. The inventory 

techniques are selected to compare a reach of 

interest to some reference or baseline. Techniques 

may include such things as vertical stability, 

lateral stability, and bed material. The inherent 

variability among these types of parameters may 

require exceptional sampling design or long 

periods of time for validation.

Some geomorphologists (Juracek and Fitzpatrick 

2003, Kondolf et al. 2003, and Miller and Ritter 

1996) advise caution to those considering using 

the Rosgen system for other than descriptive 

purposes, such as for stream rehabilitation, 

restoration, or creation. Users should be aware of 

the data required by the methodology and avoid 

overextension or misapplication. A number of 

authors have found Rosgen’s system useful for 

descriptive and habitat application purposes (Tsao 

et al. 1996, Savery et al. 2001, FISRWG 1998).

Montgomery and Buffington’s Stream 

Classification

Montgomery and Buffington (1993) proposed a 

classification primarily for streams in the Pacific 

Northwest. The hierarchy of classification is 

based on a range of rivers that are sediment 

limited to transport limited and placed 

into bedrock, alluvial, and colluvial groups, 

respectively. Stream groups include colluvial, 

bedrock, cascade, step-pool, plane-bed, poolriffle, regime, and braided. River characteristics 

such as bed material, pattern, transport/

depositional reach, dominant roughness 

features, dominant sediment sources, dominant 

sediment storage features, slope, confinement, 

and pool spacing are used in the classification. 

The strength of this system is in its simplicity 

and descriptive names. A system of this type 

is conducive to habitat management and 

hierarchical integration with other classifications 

such as habitat types for fish.

Other Geomorphic Classification 

Systems

Many other river and stream classifications are 

available. Kondolf et al. (2003) provides an 

excellent review of river classification, which 

includes the history, application, evolution, and a 

brief description of several dozen systems.

Vegetation Systems

Wetland Classification

Classification of Wetlands and Deepwater 

Habitats of the United States (Cowardin et al. 

1979) is the basis for the USFWS National 

Wetlands Inventory and is a major reference for 

many wetland regulatory guidance documents. 

The classification is designed for new inventories 

of wetlands and deepwater habitats and is 

intended to describe ecological taxa, arrange 

them in a system useful to resource managers, 

furnish units for mapping, and provide 

uniformity of concepts and terms. The principal 

users for this classification system are land 

managers and biologists. The system provides 

hierarchical levels from the broad functional 

level (marine, estuarine, riverine, lacustrine, 

palustrine) to a habitat-level dominance type, 

which is named for the dominant plant or animal 
RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

18 TECHNICAL REFERENCE 1737-21

form of the area. The hierarchical structure is 

provided below:

Classification

Units

Description

System Basic water source/feature 

(marine, estuarine, riverine, etc.).

Subsystem Basic water persistence attributes 

(subtidal, intertidal, lower 

perennial, upper perennial, etc.).

Class Gross substrate/vegetation form 

(rock bottom, aquatic bed, 

emergent wetland, rocky shore, 

forested wetland, etc.).

Subclass Specific substrate/vegetation type 

(bedrock, sand, mud, needleleaved evergreen, broad-leaved 

deciduous, etc.). 

Dominance 

Type

Dominant plant/animal species 

(horsetail, black cottonwood, 

willow, caddisfly, crayfish, etc.).

Modifiers Site-specific attributes of soil, 

regime, water chemistry, and land 

alteration (salinity, pH, flooding 

condition, mineral or organic, 

farmed, diked, etc.).

This system is currently used by many agencies, 

organizations, and individuals for the general 

inventory and classification of habitats. It has 

been used in small and large applications. 

Products from the classification can give 

managers a good overview of the resource. The 

system is easy to apply and particularly useful 

with aerial photos. However, it becomes more 

complex as modifiers, such as specific hydrology 

and water chemistry modifiers, are added to the 

description. The addition of modifiers changes 

this procedure from a wetland and riparian 

vegetation classification procedure to one that 

is more process-based, since determining water 

regime, chemistry, alteration, and certain other 

characteristics requires some thought on how the 

wetland functions. This procedure can be used 

to describe the state of a riparian system, but not 

the cause and effect relationships that would be 

useful in determining potential state changes in a 

riparian system.

The USFWS is open to incorporating more 

detailed modifiers, such as soils information. 

Standard soil taxonomic classification can 

be placed into the procedure at the modifier 

level. The dominance level is fairly standard as 

vegetation descriptions go. Some differences 

between other procedures can be expected in 

the delineation between overstory, dominance 

density, etc. The procedure also appears to fit 

into other vegetation classification schemes, such 

as those used on a regional or provincial level. 

Overall, the procedure recognizes the difference 

between fluvial surfaces and major vegetation 

forms at a level that makes it reasonably easy to 

merge with classification procedures for other 

considerations, such as geology, climate, 

and landforms.

Because of its relative simplicity, the USFWS 

procedure has become an ideal tool for the initial 

inventory of the nation’s wetlands. Most wetlands 

in the United States are currently mapped 

and available in digital format. The procedure 

was not designed to reflect potential natural 

communities or community ecology. However, 

additional classification using some of the 

successional procedures discussed could provide 

such information within the mapping boundaries 

of the existing wetland areas.

Successional Classification

Currently, the most frequently used procedure 

for classifying community ecology follows the 

concepts introduced by Daubenmire (1959). 

Many investigators have used these concepts in 

their work with riparian and wetland environments 

(Youngblood et al. 1985, Kovalchik 1987, 

Hansen et al. 1988, Hansen 1989, Szaro 

1989, and Hansen et al. 1995). These authors 

demonstrate that the concepts of succession used 

in upland environments are equally applicable 

to riparian systems, although riparian sites are 

generally much more dynamic. A review and 

comparison of some of the basic terminology and 

concepts applied in these documents follows:

• Association—In normal usage, an association 

is a climax community type or potential plant 

community. In riparian systems, because 

of their dynamic nature, a true climax 

community may not have an opportunity to 

occur (Youngblood et al. 1985). An association 

for a riparian environment is therefore a 

plant community type representing the latest 
RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

TECHNICAL REFERENCE 1737-21 19

successional stage attainable on a specific 

hydrologically influenced surface (Kovalchik 

1987, Hansen 1989). Hansen (1989) uses the 

term “riparian association,” while Youngblood 

et al. (1985) chose the term “potential 

stable community type” that approaches an 

association.

• Community Type—This is defined as an 

aggregation of all plant communities in some 

procedures or as existing or dominant plant 

communities in others. Community types 

are distinguished by floristic and structural 

similarities in both overstory and undergrowth 

layers. Community types are considered to 

represent seral stages.

• Site Type—This is the area of land occupied 

or potentially occupied by a specific 

association. Site types that are the same would 

have similar environments that could develop 

the same potential plant community. Hansen 

(1989) uses the term “riparian site type” 

when describing a site capable of producing a 

“riparian association.”

Standard Ecological Site Description 

Classification

The NRCS National Range Handbook

(USDA-SCS 1976), as supplemented by the 

BLM National Range Handbook (H-4410-1) 

(USDI-BLM 1990), includes procedures for 

preparing standardized ecological site (range site) 

descriptions. The NRCS handbook provides 

for range site descriptions that include a unique 

name, physiographic features, climatic features, 

vegetation ecology and production, soils, and 

management interpretations (which can be used 

in making management recommendations). 

Early in 1988, BLM determined that the 

standard site description procedures as applied 

to uplands would accommodate land features 

associated with riparian and wetland sites as 

well. The BLM handbook further applies the 

procedure to grazable woodlands, forests, and 

riparian and wetland sites.

The standard ecological site description 

procedure is for all levels of land users and is 

applicable to rangeland, woodland, and native 

pasture. The system is hierarchical, using 

classification units of physiographic regions, 

climatic features, vegetation ecology, soils, 

associated water features, and the primary 

unit, site. An identifier is also used, which is a 

reference to a major land resource area, similar 

to a regional ecological setting. A major purpose 

of the procedure is to define community 

response and the reasons why a particular 

response occurs. The procedure is well suited 

for identifying changes of state and the reasons 

for site progression (aggradation/degradation). 

Use of this procedure is limited by the extent of 

knowledge of similar sites and by the expertise of 

the users. Experienced personnel are required to 

correctly identify site potential. The end product 

of the procedure is a very useful document 

for management. The procedure makes use of 

other nationally or internationally recognized 

procedures, such as those in the National Soil 

Survey Handbook (USDA-NRCS 2003). It is 

conceptually similar to others in recognizing 

a potential or climax plant community and 

successional stages or communities. The 

procedure in the National Range Handbook

(USDA-SCS 1976) is used worldwide to prepare 

site descriptions for rangelands. These procedures 

have been modified, tested, and validated for 

use in preparing site descriptions for riparian 

areas. Procedures for site correlation exist and 

are compatible with the National Soil Survey 

Handbook (USDA-NRCS 2003).

The ease of the application of this procedure 

depends on the ability and experience of the 

users. A team of specialists, consisting of a 

biologist, botanist or ecologist, soil scientist, and 

hydrologist, is required to use these procedures 

on riparian and wetland sites. The procedures 

for mapping, delineating, describing, and 

interpreting sites have been used by several 

agencies for several years. Sufficient training, 

review, and correlation are key to the success of 

the procedure.

Habitat Systems

Habitat level classifications are used to provide 

information for discrete and small features 

within a riparian system at a large scale. These 

classifications are often specialized, looking for 
RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

20 TECHNICAL REFERENCE 1737-21

particular habitat structures and characteristics 

that are important to specific species. Examples 

would include classification for beaver habitat 

(Suzuki and McComb 1998), vegetation used by 

particular songbirds, and fish habitat. Probably 

the best known habitat classification system 

involves the channel geomorphic unit (American 

Fisheries Society 1999), based on Bisson et 

al. (1982) and later refined by Hawkins et al. 

(1993).
RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

TECHNICAL REFERENCE 1737-21 21

V. Conclusion

Riparian-wetland resource data spans a number 

of disciplines, as illustrated in the previous 

descriptions of classification tools. Riparianwetland management has become much more 

complex in recent years, concerned with 

not only vegetation, fisheries, water quality, 

geomorphology, or wildlife but with all of these 

characteristics. The assessment of the riparianwetland resource is typically a team effort now, 

with several disciplines working together to 

design inventories and collect, analyze, interpret, 

and present data to develop a product that is 

most useful for resource management. 

The classification systems presented in this 

document can be combined to produce very 

powerful presentation and assessment products. 

Coupled with advanced inventory design and 

geographic information systems, the appropriate 

classification systems can be integrated to solve 

many problems. Approaches that integrate 

process-based hydrogeomorphological 

classification as a basic structure will benefit from 

an increased ability to extrapolate information 

and make better resource decisions.

Riparian-wetland systems are dynamic, for the 

most part, and therefore require the information 

base used to manage them to be dynamic as well. 

Classification techniques and the data they are 

built upon should be routinely and systematically 

updated to keep pace with changes not only in 

the riparian-wetland systems, but also in our 

understanding of the science pertaining to them.

RIPARIAN AND WETLAND CLASSIFICATION REVIEW AND APPLICATION

TECHNICAL REFERENCE 1737-21 23

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Bailey, R.G. 1978. Description of the ecoregions 

of the United States. USDA Forest Service, 

Intermtn. Reg. Ogden, UT. 76 pp.

Bailey, R.G. 1983. Delineation of ecosystem 

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Bailey, R.G. 1995. Description of the ecoregions 

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