United States
Environmental Protection
i Agency
Streamflow Duration Assessment
Methods for the Arid West and
Western Mountains of the United
States of America
~
October 2024
EPA-843-B2-24002
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Streamflow Duration Assessment Methods for
the Arid West and Western Mountains of the
United States
Version 2.0
October 2024
Prepared by Raphael Mazor1, Amy James2, Ken M. Fritz5, Brian Topping3, Tracie-Lynn Nadeau4 Rachel
Fertik Edgerton3, and Kristina Nicholas6.
1 Southern California Coastal Water Research Project. Costa Mesa, CA
2 Ecosystem Planning and Restoration. Raleigh, NC
3 U.S. Environmental Protection Agency—Office of Wetlands, Oceans, and Watersheds. Washington,
D.C.
4 U.S. Environmental Protection Agency—Region 10. Portland, OR
5 U.S. Environmental Protection Agency—Office of Research and Development. Cincinnati, OH
6 Oak Ridge Institute of Science and Education (ORISE) Fellow at U.S. Environmental Protection
Agency—Office of Wetlands, Oceans, and Watersheds. Washington, D.C.
The following members of the National Steering Committee, and the Regional Steering Committee for
the Arid West and Western Mountains, provided input and technical review:
National
Tunis McElwain
U.S. Army Corps of Engineers
Headquarters, Regulatory Program
Washington, DC
Gabrielle David
U.S. Army Corps of Engineers
Engineer Research and Development Center
Hanover, NH
Matt Wilson
U.S. Army Corps of Engineers
Headquarters, Regulatory Program
Washington, DC
Rose Kwok
U.S. Environmental Protection Agency
Office of Wetlands, Oceans and Watersheds
Washington, DC
Regional
Aaron 0. Allen
U.S. Army Corps of Engineers
Regulatory Division
Los Angeles District
Daniel Delgado
U.S. Army Corps of Engineers
Regulatory Branch
Albuquerque District
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Jeremy Grauf and Michael Happold
and Karen Lawrence
U.S. Army Corps of Engineers
Regulatory Branch
Omaha District
Rachel Harrington
U.S. Environmental Protection Agency
Region 8
Denver, CO
(Dale) Jess Jordan
U.S. Army Corps of Engineers
Regulatory Branch
Seattle District
James Mazza
U.S. Army Corps of Engineers
Regulatory Branch
San Francisco District
Loribeth Tanner
U.S. Environmental Protection Agency
Region 6
Dallas, TX
Joe Morgan
U.S. Environmental Protection Agency
Region 9
San Francisco, CA
James Robb
U.S. Army Corps of Engineers
Regulatory Branch
Sacramento District
Suggested citation:
Mazor, R. James, A., Fritz, K.M., Topping, B., Nadeau, T.-L., Fertik Edgerton, R., and Nicholas, K. 2024.
Streamflow Duration Assessment Methods for the Arid West and Western Mountains of the United
States. Version 2.0. Document No. EPA-843-B-24002.
Photographs courtesy of the U.S. Environmental Protection Agency unless otherwise noted.
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Acknowledgments
We thank Abel Santana, Robert Butler, Duy Nguyen, Kristine Gesulga, Kenneth McCune, Jeff Brown,
Liesl Tiefenthaler, Adriana LeCompte Santiago, and Anne Holt for assistance with data management.
Data collection was conducted by several field crews from PG Environmental, California State
University at Monterey Bay, the Southern California Coastal Water Research Project, and the Arizona
Department of Environmental Quality.
We thank Abe Margo, Abigail Rivera, Addison Ochs, Alec Lambert, Alex Berryman, Alex Swain, Alexus
Cobarrubias, Ali Sutphin, Alyssa Schaer, Andrea Romero, Andrew Caudillo, Bryan Van Orman, Buck
Meyer, Caleb Yakel, Charlie Waddell, Cody Maynard, Connor Quiroz, Ellery Charleton, Elliot Broder,
Emma Debasitis, Emma Haines, Fallon Born, Gretchen Wichman, Hannah Erickson, Hannah Kim, Heidi
Fisher, Jack Poole, Jackson Bates, Jake Okun, James Treacy, Jason Glover, Jeff Weaver, Jess Turner,
Jessica Weidenfeld, Joe Kiel, Joe Klein, John Olson, Jon Carmichael, Kate Forsmark, Katharina
Zimmerman, Katie Irving, Kay Nickel, Kelsey Trammel, Kelsey Trammell, Kort Kirkeby, Kristine Gesulga,
Lexi Yokomizo, Libby Lee, Madison McCartey, Marcus Beck, Margaret O'Brien, Mariah Papc, Mason
London, Matthew Robinson, Megan Annis, Megan Rodenbeck, Michael Beidabach, Mindi Lundberg,
Morgan Proko, Nadia McCoy, Paco Villegas, Page Cirillo, Patricia Spindler, Savannah Pena, Tierney
Latham, and Zak Erickson for assistance with data collection. The California Department of Fish and
Wildlife's Aquatic Bioassessment Lab and Daniel Pickard performed taxonomic analysis on aquatic
invertebrate samples.
Numerous researchers and land managers with local expertise assisted with the selection of sites to
calibrate the method: Julie Kelso, Chad Loflen, Patricia Spindler, Eric Stein, Scott Johnson, Andrew C.
Rehn, Peter R. Ode, Chris Solek, Christopher Tracy and the Deep Canyon Desert Research Center
(doi:10.21973/N3V66D), Stephanie Kampf, Lindsey Reynolds, Kris Barrios, Marcia Radke, Michael
Bogan, William Isham, Jonathan Humphrey, Dale Turner, Kacey Shaughnessy, Bryant Dickens, Nathan
Mack, Boris Poff, Ed Schenk, Andy Brummond, Julie Zimmerman, Sky Lovill, and Eric Hargett.
This work was funded through EPA contracts EP-C-17-001 and 68HERC21D0008 to Ecosystem Planning
and Restoration.
Disclaimers
This document has been reviewed in accordance with U.S. Environmental Protection Agency policy and
approved for publication. Any mention of trade names, manufacturers or products does not imply an
endorsement by the United States Government or the U.S. Environmental Protection Agency. The EPA
and its employees do not endorse any commercial products, services, or enterprises.
The contents of this report are not to be used for advertising, publication, or promotional purposes.
Citation of trade names does not constitute an official endorsement or approval of the use of such
commercial products. All product names and trademarks cited are the property of their respective
owners. The findings of this report are not to be construed as an official Department of the Army or
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the U.S. Environmental Protection Agency position unless so designated by other authorized
documents. Destroy this report when no longer needed. Do not return it to the originator.
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Table of Contents
Section 1: Introduction and Background 1
1.1 TheSDAMsforthe AW and WM 4
1.2 Intended use and limitations 5
1.3 Development of the AW and WM SDAMs 6
Section 2: Overview of the AW and WM SDAMs and the Assessment Process 9
2.1 Considerations for assessing streamflow duration and interpreting indicators 9
2.1.1 Clean Water Act jurisdiction 9
2.1.2 Scales of assessment 9
2.1.3 Spatial variability 9
2.1.4 Temporal variability 10
2.1.5 Ditches and modified natural streams 10
2.1.6 Other disturbances 10
2.1.7 Multi-threaded systems 11
Section 3: Data Collection 12
3.1 Conduct desktop reconnaissance 12
3.2 Prepare sampling gear 13
3.3 Order of operations for completing the AW and WM SDAM field assessments 14
3.4 Timing of sampling 15
3.5 Assessment reach considerations 16
3.5.1 Reach placement 16
3.5.2 Reach length 17
3.5.3 How many assessment reaches are needed? 17
3.6 Photo-documentation 18
3.7 Conducting assessments and completing the field form 18
3.7.1 General reach information 18
3.7.2 Assessment reach sketch 24
3.8 How to measure indicators of streamflow duration 24
3.8.1 Bankfull channel width 25
3.8.2 Aquatic macroinvertebrate indicators 25
3.8.3 Slope 29
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3.8.4 Shading (WM only) 30
3.8.5 Number of hydro phytic plant species 31
3.8.6 Prevalence of rooted upland plants in the streambed (AW and WM) 36
3.8.7 Algal cover (AW only) 38
3.8.8 Differences in vegetation 40
3.8.9 Riffle-pool sequence 42
3.8.10 Particle size or stream substrate sorting (WM only) 44
3.9 Additional notes and photographs 46
Section 4: Data Interpretation and Using the Web Application 47
4.1 Outcomes of SDAM classification 47
4.2 Applications of the SDAMs outside their intended areas 48
4.3 What to do when a more specific classification is needed 48
4.3.1 Review historical aerial imagery 48
4.3.2 Conduct additional assessments at the same reach 50
4.3.3 Conduct assessments at nearby reaches 51
4.3.4 Conduct reach revisits during regionally appropriate wet and dry seasons 51
4.3.5 Collect hydro logic data 51
Section 5: References 52
Appendix A. Glossary of terms 56
Appendix B. Guide to Aquatic Invertebrate Orders and Families in the Western United States 60
Ephemeroptera (mayfly) larvae 60
Plecoptera (stonefly) larvae 65
Trichoptera (caddisfly) larvae and pupae 71
Coleoptera (beetle) larvae and adults 79
Other Insect Orders 83
Other invertebrates 84
Appendix C. Field Forms
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Table of Figures
Figure 1. Examples of western stream reaches in each streamflow duration class 2
Figure 2. Map of flow duration study regions 3
Figure 3. Locations of ephemeral, intermittent, and perennial stream reaches used to develop the AW
and WM SDAMs 6
Figure 4. Bankfull measurement and photopoint locations 19
Figure 5. Measuring bankfull width 20
Figure 6. Examples of difficult conditions that may interfere with the observation or interpretation of
indicators 22
Figure 7. Examples of estimating surface and subsurface flow, and isolated pools 23
Figure 8. Examples of evidence of aquatic macroinvertebrates in dry channels 27
Figure 9. Examples of terrestrial macroinvertebrates you may find in a dry channel 27
Figure 10. Schematic illustration of slope measurement using a clinometer 30
Figure 11. Representation of the mirrored surface of a convex spherical densiometer 31
Figure 12. Local conditions that support growth of hydrophytes 33
Figure 13. Long-lived species only represented by young specimens 33
Figure 14. Water-stressed riparian trees near Oro Grande on the Mojave River 34
Figure 15. Examples of plants determined to be hydrophytes based on context 36
Figure 16. Example of an ephemeral stream with rooted upland vegetation growing in the channel. 37
Figure 17. Visual guides to assist estimates of algal cover on a streambed 38
Figure 18. Examples of low (i.e., <2%; left) and high (i.e., >40%; right) algal cover in flowing (top) and
dry (bottom) reaches 39
Figure 19. Example photos of reaches that attained different scores for the Differences in Vegetation
indicator 42
Figure 20. Examples illustrating scoring levels for the Riffle-Pool Sequence indicator 44
Figure 21. Examples illustrating scoring levels for the Particle Size/Stream Substrate Sorting indicator.
46
Figure 22. Examples of using aerial imagery to support streamflow duration classification 50
Table of Tables
Table 1. Number of reaches in each flow duration class and region used to develop the AW and WM
SDAMs 7
Table 2. Examples of online resources for generating local flora lists 13
Table 3. Perennial indicator families for the AW and WM SDAMs 29
Table 4. Scoring guidance for the Rooted Upland Plants indicator 38
Table 5. Scoring guidance for the Differences in Vegetation indicator 41
Table 6. Scoring guidance for the Riffle-Pool Sequence indicator 43
Table 7. Scoring guidance for Particle Size/Streambed Sorting indicator 45
VII
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Section 1: Introduction and Background
Section 1: Introduction and Background
Streams exhibit a diverse range of hydrologic regimes, and the hydrologic regime strongly influences
the physical, chemical, and biological characteristics of active stream channels and adjacent riparian
areas. Thus, information describing a stream's hydrologic regime is useful to support resource
management and regulatory decisions. One important aspect of the hydrologic regime is streamflow
duration—the length of time that a stream sustains surface flow. However, hydrologic data to
determine flow duration has not been collected for most stream reaches nationwide. Although maps,
hydrologic models, and other data resources exist (e.g., the National Hydrography Dataset, McKay et
al. 2014), these may exclude small headwater streams and unnamed second- or third-order tributaries,
and limitations on accuracy and spatial or temporal resolution may reduce their utility for many
management applications (Hall et al. 1998, Nadeau and Rains 2007, Fritz et al. 2013). Therefore, rapid,
field-based methods are needed to determine flow duration class at the reach scale (defined in Section
2: Overview of the AW and WM SDAMs and the Assessment Process) in the absence of long-term
hydrologic data (Fritz et al. 2020).
These methods are intended to classify stream reaches into one of three streamflow duration classes1:
Ephemeral reaches are channels that flow only in direct response to precipitation. Water typically
flows only during and/or shortly after large precipitation events, the streambed is always above the
water table, and stormwater runoff is the primary water source.
Intermittent reaches are channels that contain sustained flowing water for only part of the year,
typically during the wet season, where the streambed may be below the water table and/or where
the snowmelt from surrounding uplands provides sustained flow. The flow may vary greatly with
stormwater runoff.
Perennial reaches are channels that contain flowing water continuously during a year of normal
rainfall, often with the streambed located below the water table for most of the year. Groundwater
typically supplies the baseflow for perennial reaches, but the baseflow may also be supplemented
by stormwater runoff and/or snowmelt.
Example photographs and hydrographs of stream reaches in each class are shown in Figure 1.
1 The definitions used for development of this manual are consistent with the definitions used to develop the SDAMs for
the Pacific Northwest, the Great Plains, Northeast, and Southeast.
1
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Section 1: Introduction and Background
Perennial stream reach
Shell Creek near Shell, WY
(USGS 06278500)
Intermittent stream reach
Truxton Wash near Valentine, AZ
(USGS 09404343)
400
300-
200-
100-
I'" 'I
Ephemeral stream reach
Calf Creek, CA
(STIC logger)
Figure 1. Examples of western stream reaches in each streamflow duration class. The left and center plots show
hydrographs from USGS stream gages; units are in cubic feet per second. The right plot shows the presence of water
inferred from a Stream Temperature, Intermittency, and Conductivity (STIC) logger, which measures positive raw intensity
values when water is present. In all plots, red dots indicate dry conditions. Image credits: Lex Cobarrubias (left), Matthew
Robinson (center), and Mason London (right).
These classes describe the typical patterns exhibited by a stream reach over multiple years, although
observed patterns in a single year may vary due to extreme and transient climatic events (e.g., severe
droughts). Although flow duration classes are not strictly defined by their sources of flow (e.g., storm
runoff, groundwater, snowmelt), the duration is often related to the relative importance of different
flow sources to stream reaches and the stability of their contributions. Perennial reaches have year-
round surface flow in the absence of drought conditions. Intermittent reaches have one or more
periods of extended surface flow in most years, where the flow is sustained by sources other than
surface runoff in direct response to precipitation, such as groundwater, melting snowpack, irrigation,
reservoir operations, or wastewater discharges. Ephemeral reaches have a surface flow for short
periods and only in direct response to precipitation.
This manual describes the final Streamflow Duration Assessment Methods (SDAMs) intended to
distinguish flow duration classes of stream reaches in the Arid West (AW) and Western Mountains
(WM), These regions are defined by the Arid West and Western Mountains, Valleys and Coast regional
supplements to the U.S. Army Corps of Engineers wetland delineation manual (U.S. Army Corps of
Engineers 2008, 2010), excluding portions of the AW and WM regions that overlap with the states of
Washington, Oregon, and Idaho, which are covered by the SDAM for the Pacific Northwest described in
Nadeau et al. (2015). These regions are largely based on vegetation type and precipitation levels.
2
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Section 1: Introduction and Background
Throughout this manual, the term "The West" refers to the combined AW and WM regions, but not the
Pacific Northwest,
Figure 2. Map of flow duration study regions. 'The West" refers to the combined Arid West and Western Mountain regions,
but not the Pacific Northwest region.
The AW and WM SDAMs are based on biological and geomorphological indicators. Biological
indicators, known to respond to gradients of streamflow duration (Fritz et al. 2020), have notable
advantages for assessing natural resources. The primary advantage of these indicators is the ability to
reflect long-term environmental conditions (e.g., Karr et al, 1986, Rosenberg and Resh 1993) making
them well suited for assessing streamflow duration because some species reflect the aggregate
hydrologic conditions a stream has experienced over multiple years. As a result, relatively rapid field
observations of biological indicators made at a single point in time can provide long-term insights into
streamflow duration and other hydrological characteristics of a stream reach. Geomorphological
indicators can also be rapidly measured and provide information about the hydrologic drivers of
streamflow duration. For example, wide channels in areas with low precipitation are associated with
shorter durations of streamflow; in wetter areas, narrow channels are typically associated with
headwaters where the contributing catchments may be too small to generate long-duration flows.
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Section 1: Introduction and Background
1.1 TheSDAMsfortheAWand WM
This manual describes two methods that use a small number of indicators to predict the streamflow
duration class of wadeable stream reaches in the AW and WM. All indicators are measured during a
single field visit. Beta SDAMs for the two regions were released in 2021 (see Mazor et al. 2021a and
Mazor et al. 2021b). After additional data collection, analysis, and user feedback, these final SDAMs
were developed, reflecting somewhat different
indicators from the beta methods. For more
information on the development of these SDAMs or
SDAMs for other U.S. regions, please refer to the U.S.
Environmental Protection Agency's (EPA) SPAM
website.
The AW and WM SDAMs assign reaches to one of six
possible classifications: ephemeral, intermittent,
perennial, at least intermittent, less than perennial, and
needs more information. An at least intermittent
classification occurs when an intermittent or perennial
classification cannot be made with high confidence, but
an ephemeral classification can be ruled out. A less than
perennial classification is the opposite; an ephemeral or
intermittent classification cannot be made with high
confidence, but a perennial classification can be ruled
out. If no class can be determined with confidence, the
stream is classified as needs more information.
Because the AW and WM SDAMs share many indicators
in common, and because many practitioners work in
both regions, the two methods are presented in a
combined manual. When assessing reaches near the
boundary between regions or in areas more closely matching the characteristics of a different SDAM
region, practitioners are encouraged to measure all indicators required for both methods, although
some indicators may only be used for one method.
The AW and WM methods were developed using a machine learning model known as random forest.
Random forest models are increasingly common in the environmental sciences because of their
superior performance in handling complex relationships among indicators used to predict
classifications (Cutler et al. 2007). In some cases, a random forest model can be simplified into a
decision tree or table (e.g., Nadeau et al. 2015, Mazor et al. 2021c); however, that was not possible for
the AW or WM models. To obtain a flow classification for an individual assessment reach, there is an
open-access, user-friendly web application for entering indicator data and running the region-specific
random forest model. No data entered into the web application are visible to or stored by the EPA or
any other agency.
Indicators of the AW and WM SDAMs
Biological indicators
•
Prevalence of rooted upland
plants in the streambed
•
Differences in vegetation
•
Shading (WM only)
•
Algal cover (AW only)
•
Abundance of Ephemeroptera,
Plecoptera, and Trichoptera
(WM only)
•
Abundance of perennial
indicator taxa
•
Number of hydrophytic plant
species
Geomorphological indicators
•
Bankfull channel width
•
Slope
•
Riffle-pool sequence
•
Particle size or stream
substrate sorting (WM only)
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Section 1: Introduction and Background
1.2 Intended use and limitations
The AW and WM SDAMs are intended to support field classification of streamflow duration at the
reach scale in streams with defined channels (having a bed and banks) in the AW and WM regions. Use
of the SDAMs may inform a range of activities where information on streamflow duration is useful,
including jurisdictional determinations under the Clean Water Act; however, the classification resulting
from use of an SDAM is not in itself a jurisdictional determination. SDAMs are not mandatory for
completing a Clean Water Act jurisdictional determination, nor are they intended to supersede more
direct measures of streamflow duration (e.g., long-term records from stream gages). Other sources of
information, such as aerial imagery, reach photographs, traditional ecological knowledge, and local
expertise, can supplement the SDAMs when classifying streamflow duration (Fritz et al. 2020).
Although the AW and WM SDAMs are intended for use in both natural and altered stream systems,
some alterations may complicate the interpretation of field-measured indicators or potentially lead to
incorrect conclusions. For example, streams managed as flood control channels may undergo frequent
maintenance to remove some or all vegetation in the channel and along the banks of the assessment
reach. Although some biological indicators recover quickly from these disturbances, the results from
assessments conducted shortly after such disturbances may be misleading. In addition, these types of
channels may not display channel features that result from natural geomorphic processes, such as a
typical riffle-pool sequence.
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Section 1: Introduction and Background
1.3 Development of the AW and WM SDAMs
Region Arid West Western Mountains
Figure 3. Locations of ephemeral, intermittent, and perennial stream reaches used to develop the AW and WM SDAMs.
These methods resulted from a multi-year study conducted in 194 locations in the AW region and 201
locations in WM region following the process described in Fritz et al, (2020). Of these, data from 387
sites (or reaches) where flow class could be determined from direct hydrologic data were used to
develop the SDAMs (Figure 3). Streamflow duration class was directly determined from continuous
(hourly interval) data loggers deployed at 209 study reaches during the data collection period.
Streamflow duration classes were determined at an additional 101 study reaches from U.S. Geological
Survey (USGS) gages. Multiple sources of hydrologic data (e.g., non-USGS stream gage data, published
studies, consultation with local experts) were used to classify the remaining reaches (80) for which
data from continuous loggers were not available. Four AW reaches and one WM reach were rejected
from the study because streamflow duration class could not be determined. Data from three reaches
in the AW (one intermittent and two perennial) were also excluded because data collection was
incomplete. Thus, 187 reaches in the AW and 200 in the WM were used to develop the SDAMs;
reaches were distributed across flow duration classes as shown in Table 1.
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Section 1: Introduction and Background
Table 1. Number of reaches in each flow duration class and region used to develop the AW and WM SDAMs.
Flow duration class Arid West Western Mountains
Ephemeral
68
56
Intermittent
71
78
Perennial
48
66
Total 187 200
Development of the SDAMs followed the process steps below (Fritz et al. 2020):
Preparation
• Conducted literature reviews (McCune and Mazor 2019, Mazor and McCune 2021):
o Identified existing SDAMs, focusing on those originating in the AW or WM or developed
using a similar approach (see Nadeau 2015; New Mexico Environmental Department
(NMED) 2020).
o Identified 27 potential field biological, hydrological, and geomorphological characteristics
related to streamflow duration for evaluation in the AW and WM.
• Identified candidate study reaches with known streamflow duration class, representing
diverse environmental settings throughout the region.
Data Collection: Beta Method Development
• Collected field data at 238 study reaches, visited up to 3 times each.
Data Analysis
• Evaluated 95 candidate indicators from the field data and geospatial indicators for their ability
to discriminate among streamflow duration classes. Geospatial indicators included climatic
measures that characterize hydrologic drivers of streamflow duration (e.g., long-term
precipitation and temperature) and are straightforward to calculate.
•Calibrated a classification model using a machine learning algorithm (i.e., random forest).
•Refined and simplified the beta method for rapid and consistent application.
Evaluation / Beta Implementation
• Published a beta method, data analysis report, and data used to develop the method.
•Trained EPA and Corps staff on the beta method.
•Collected public comment and agency experience using the beta method for more than a year.
•Collected additional data at 152 additional study reaches and revisited a subset of the study
reaches from beta method development efforts. Half the study reaches were visited at least 3
times, up to a maximum of 10 visits at a reach. A total of 387 study reaches were used across
the AW and WM.
Re-Analysis and Evaluation
• Evaluated 97 candidate indicators from the field data and geospatial indicators for their ability
to discriminate among streamflow duration classes. Geospatial indicators included climatic
measures that characterize hydrologic drivers of streamflow duration (e.g., long-term
precipitation and temperature) and are straightforward to calculate.
•Calibrated a classification model using a machine learning algorithm (i.e., random forest).
•Refined and simplified the final method for rapid and consistent application in light of the
agency experience and public comments received on the beta method.
Implementation
•Publish User Manual, data analysis report, and data used to develop the method.
•Publish web application and code.
•Publish training materials to support implementation.
•Train EPA and Corps staff on the method and how to train others.
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Section 1: Introduction and Background
Eighty percent of sites in the development data set were used for method calibration, while twenty
percent were withheld to provide an independent test of method performance.2 Based on this
withheld subset, the final methods correctly classified 64% of AW reaches and 69% of WM among
three classes (perennial vs. intermittent vs. ephemeral). Accuracy was much higher for differentiating
ephemeral from at least intermittent reaches (82% for the AW and 84% for the WM), as well as for
differentiating perennial from less than perennial reaches (83% for the AW and 84% for the WM).
Generally, misclassifications between intermittent and perennial reaches were more common than
misclassifications between ephemeral and intermittent reaches. The ability of the AW and WM SDAMs
to discriminate ephemeral more accurately and consistently from at least intermittent reaches is
consistent with previous studies evaluating streamflow duration indicators and assessment methods
(Fritz et al. 2008, 2013, Nadeau et al. 2015, Mazor et al. 2021).
2 Note, Table 1 above includes all sites used in method development, those used to calibrate the model and the subset of
sites withheld for determining accuracy.
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Section 2: Overview of the AW and WM SDAMs and the Assessment Process
Section 2: Overview of the AW and WM SDAMs and the Assessment Process
2.1 Considerations for assessing streamflow duration and interpreting indicators
2.1.1 Clean Water Act jurisdiction
Regulatory agencies evaluate aquatic resources based on current regulations, guidance, and policy. The
AW and WM SDAMs do not incorporate that broad scope of analysis. Rather, the methods provide
information that may support timely jurisdictional decisions because they help determine streamflow
duration as ephemeral, intermittent, or perennial in the absence of hydrologic data.
2.1.2 Scales of assessment
The AW and WM SDAMs apply to an assessment reach, the length of which scales with the mean
bankfull channel width. Regardless of channel width, reaches must be a minimum of 40 m and no
longer than 200 m. The minimum reach-length of 40 m ensures that a sufficient area has been
assessed to evaluate indicators. Quantification and observations of indicators are restricted to the
bankfull channel and within one-half bankfull channel width from the top of each bank. However,
ancillary information from outside the assessment reach (such as surrounding land use) is also
recorded.
2.1.3 Spatial variability
Indicators of streamflow duration (and other biological, hydrologic, and geomorphic characteristics of
streams) vary in their strength of expression within and among reaches in a stream system. The main
natural drivers of spatial variation are generally the physiographic province (e.g., geology and soils) and
climate (e.g., seasonal patterns of precipitation, snowmelt, and evapotranspiration). For example,
certain indicators, such as riparian vegetation, may be more strongly expressed in a floodplain with
deep alluvial soils than they would be in a reach underlain by shallow bedrock, even if both reaches
have a similar duration of flow. Therefore, understanding the sources of spatial variability in
streamflow indicators will help ensure that assessments are conducted within relatively homogenous
reaches.
Common sources of variation within a stream system that may affect the expression of indicators
include:
• Natural longitudinal changes in channel gradient, valley width, and size (e.g., going from a
confined canyon to an alluvial fan, or going from wide to narrow valley).
• Other natural sources of variation, such as bedrock material (limestones, sandstones, shales,
conglomerates, and lignite) or water source (runoff, springs, summer rains, and groundwater).
• Drought or unusually high precipitation.
• Transitions in land use with different water use patterns (e.g., from commercial forest to
pasture, from pasture to cultivated farmland, or cultivated farmland to an urban setting), or
changes in management practices (e.g., intensification of grazing).
• Stream management and manipulation, such as diversions, water importation, dam operations,
and habitat modification (e.g., streambed armoring).
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Section 2: Overview of the AW and WM SDAMs and the Assessment Process
2.1.4 Temporal variability
Temporal variability in indicators may affect streamflow duration assessment in two ways: interannual
(e.g., year-to-year) variability and intra-annual (e.g., seasonal) variability. These methods were
developed to be robust to both types of temporal variability and is intended to classify streams based
on their long-term patterns in either flowing or dry conditions. However, both long-term sources of
temporal variability (such as El Nino-related climatic cycles) and short-term sources (such as scouring
storms before sampling) may influence the ability to measure or interpret indicators at the time of
assessment. Timing of management practices, such as dam operations, channel clearing, or
groundwater pumping, may also affect the flow duration assessment.
Some indicators are highly responsive to temporal variability. For example, the AW is known to
experience high intensity, short-lived flood events. After these scouring events, aquatic
macroinvertebrates may be displaced from a stream reach. In contrast, rooted hydrophytic plants, if
present, will likely remain. Similarly, greater numbers of aquatic macroinvertebrates may be able to
colonize an ephemeral to intermittent reach during wet years, depending on the presence of upstream
or downstream refugia; however, changes in flow regimes may take several years to result in changes
to vegetation in the riparian corridor. For example, willows with well-established root systems are
likely to survive in an intermittent reach experiencing severe drought, even when flow in a single year
is insufficient to support aquatic macroinvertebrates in greater numbers or at all.
2.1.5 Ditches and modified natural streams
Assessment of streamflow duration is sometimes needed in canals, ditches, and modified natural
streams that are primarily used to convey water. These systems tend to have altered flow regimes
compared to natural systems with similar drainage areas (Carlson et al. 2019), and the AW and WM
SDAMs may determine if these flow regimes support indicators consistent with different streamflow
duration classes. Thus, the SDAMs may be applied to these systems when streamflow duration
information is needed.
Geomorphological indicators (specifically, bankfull channel width and riffle-pool sequence) may be
difficult to assess in straightened or heavily modified systems. Indicator measurements should be
based on present-day conditions, not historic conditions. Assessors should note if the channel
geomorphology reflects natural processes or if it reflects the effects of management activities.
2.1.6 Other disturbances
Assessors should be alert for natural or human-induced disturbances that either alter streamflow
duration directly or modify the ability to measure indicators. Streamflow duration can be directly
affected by groundwater withdrawals, flow diversions, urbanization and stormwater management,
septic inflows, agricultural and irrigation practices, effluent dominance, or other activities. In the
method development data set, disturbed reaches were identified as those in urban or agricultural
settings or those with notable impacts from grazing, mining, or other human activities; the two SDAMs
had slightly lower accuracy in assessing disturbed reaches compared to undisturbed reaches for
identification of ephemeral, intermittent and perennial flow, but almost no difference when assessing
ephemeral versus at least intermittent flow.
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Section 2: Overview of the AW and WM SDAMs and the Assessment Process
Streamflow duration indicators can also be affected by disturbances that may not substantially affect
streamflow duration (for instance, grading, grazing, recent fire, riparian vegetation management, and
bank stabilization); in extreme cases, these disturbances may eliminate specific indicators (e.g.,
absence of aquatic macroinvertebrates in channels that have undergone recent grading activity).
Groundwater pumping, impoundments, and diversions can affect both vegetation and
geomorphological indicators (e.g., Friedman et al. 1997). Some long-term alterations or disturbances
(e.g., impoundments) can make streamflow duration class more predictable by reducing year-to-year
variation in flow duration and/or indicators. Discussion of how specific indicators are affected by
disturbance is provided in Section 3: Data Collection. Assessors should describe disturbances in the
"Notes on disturbances or difficult site conditions" section of the field form.
2.1.7 Multi-threaded systems
Assessors should identify the lateral extent of the active channel, based on the outer limits of ordinary
high-water mark (OHWM). and apply the method to that area. That is, do not perform separate
assessments on each of the main and secondary channels within a multi-threaded system. Some
indicators may be more apparent in the main channel versus the secondary channels; note these
differences on the field form. Upland islands within the OHWM should not be included within the
assessment.
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Section 3: Data Collection
Section 3: Data Collection
3.1 Conduct desktop reconnaissance
Before an assessment, desktop reconnaissance helps ensure a successful assessment of a stream.
During desktop reconnaissance, assessors evaluate reach
This stage of the evaluation is crucial for determining reach
access. The reach or project area should be plotted on a
map to determine access routes and whether landowner permissions are required. Safety concerns or
hazards that may affect sampling should be identified, such as road closures, controlled burns, or
hunting seasons. These access constraints are sometimes the most challenging aspect of
environmental field activities, and desktop reconnaissance can reduce these difficulties. Also, assessors
can determine if inaccessible portions of the reach (e.g., those on adjacent private property) have
consistent geomorphology or other attributes, compared with accessible portions.
Desktop reconnaissance can also help identify features that may affect assessment reach placement or
determine the number of assessment reaches required for a project. Look for natural and artificial
features that may affect streamflow duration at the reach—particularly those that may not be evident
during the field visit, or that are on inaccessible land outside the assessment area. These features
include sharp transitions in geomorphology, upstream dams or reservoirs, springs, storm drains and
major tributaries. It may be possible to see bedrock outcrops or other features that modify streamflow
duration in sparsely vegetated areas.
A preliminary assessment of adjacent landuse may be ascertained during desktop reconnaissance. This
preliminary assessment should be verified during the field visit.
Evaluating watershed characteristics during desktop reconnaissance can produce useful information
that will help assessors anticipate field conditions or provide contextual data to help interpret results.
The USGS StreamStats tool, as well as the EPA's WATERS GeoViewer. provide convenient online access
to watershed information for most assessment reaches in the United States, such as drainage area,
soils, land use or impervious cover in the catchment, or modeled bankfull channel dimensions and
discharge.
Assessors should consider consulting local experts and agencies to gain further insights about reach
conditions and request additional available data. For example, state agencies may have records on
water quality sampling indicating times when the reach was sampled and when it was dry. Local
experts may have information about changes in the reach's streamflow.
accessibility and set expectations for conditions that may
affect field sampling. In addition, assessors can begin to
compile additional data that may inform determination of
streamflow duration, such as location of nearby stream
gages.
Desktop Reconnaissance for:
• Access, permissions and permits;
• Reach placement;
• Watershed and site context; and
• Flora and fauna lists.
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Section 3: Data Collection
Local or regional flora lists of species known to grow in the vicinity of an assessment reach may be
available to assist with plant identification and helpful for determining a plant's hydrophytic status.
Nearby public land managers (such as U.S. Forest Service or the National Park Service) should be
consulted to see if they have lists of common riparian plants in the vicinity of the assessment reach.
Several online databases can generate regionally appropriate flora lists and/or assist with identification
(Table 2). Consult the appropriate list for your location (see further discussion under 3.8.5 Number of
hydrophytic plant species.
Table 2. Examples of online resources for generating local flora lists.
| Resource
Geographic coverage |
National Wetlands Plant List
United States and territories
The Biota of North America Program
(BONAP) Vascular Flora Taxonomic
United States and territories
Data Center
USDA Plants Database
United States and territories
Lady Bird Johnson Wildflower Center
Continental U.S. (native species only)
SEINet
Arizona, New Mexico, and Colorado
Calflora
California
Arizona Native Plant Society
Arizona and adjacent desert regions
Rocky Mountain Herbarium
Montana, Wyoming, Colorado, Utah, Arizona, and
New Mexico
California Native Plant Society
California
Desktop reconnaissance also helps determine if permits are required to collect aquatic
macroinvertebrates. Threatened and endangered species may be expected in the area, and stream
assessment activities may require additional permits from appropriate federal, Tribal and state
agencies. Additional information on threatened or endangered species may be found on the U.S. Fish
and Wildlife Service's Environmental Conservation Online System, as well as at state resource agencies
and natural heritage programs.
3.2 Prepare sampling gear
The following gear is suggested for completion of the AW and WM SDAMs.
• This manual and field forms (paper or digital).
• Convex spherical densiometer, prepared as described in 3.8.4 Shading (WM only).
• Clipboard, pencils, permanent markers, field notebook.
• Flagging tape.
• Clinometer or laser range finder with slope and stadia rod.
• Maps and aerial photographs (1:250 scale if possible).
• Global Positioning System (GPS) - used to identify the downstream boundary of the reach
assessed. A smartphone that includes a GPS may be a suitable substitute.
• Tape measures - for measuring bankfull channel width and reach length.
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Section 3: Data Collection
• Kick-net or small net and tray - used to sample aquatic macroinvertebrates.
• Hand lens or field scope - to assist with plant and aquatic macroinvertebrate identification.
• Featherweight forceps and/or dropper for sorting macroinvertebrates
• Digital camera (or smartphone with camera), plus charger. Ideally, use a camera that
automatically records metadata, such as time, date, directionality, and location, as part of the
EXIF data associated with the photograph.
• Shovel, soil auger, rock hammer, hand trowel, pick or other digging tools to facilitate
hydrological observations of subsurface flow.
• Aquatic macroinvertebrate field guides (e.g., A Guide to Common Freshwater Invertebrates of
North America Voshell 2002).
• Vials filled with 70% ethanol and sealable plastic bags for collection of biological specimens,
with sample labels printed on waterproof paper.
• Bags or plant press for collecting plant vouchers.
• Hydrophytic plant identification guides (e.g., Trees and Shrubs of California, Stuart and Sawyer
2001; Western Wetland Flora: An Introduction to the Wetland and Aquatic Plants of the
Western United States, Chadde 2019).
• The U.S. Army Corps of Engineers list of wetland plants for sites to be visited.
• Boots or waders.
• First-aid kit, sunscreen, insect repellant, and appropriate clothing.
Ensure that all equipment is functional before each assessment visit and has been cleaned off-site
between assessment visits to prevent the spread of invasive species. Sampling gear that comes into
contact with the water (such as nets and boots or waders) should be properly decontaminated to
prevent the spread of aquatic invasive species. California's Surface Water Ambient Monitoring Program
provides up-to-date information on gear decontamination methods, such as scrubbing, drying,
freezing, or treating with pesticides and herbicides. Stop Aquatic Hitchhikers, an initiative of Aquatic
Nuisance Species Task Force sponsored by USFWS also provides resources and links.
3.3 Order of operations for completing the AW and WM SDAM field assessments
After completing the in-office activities described above, the following general workflow is
recommended for efficiency in the field:
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Section 3: Data Collection
.f "\
1. Walk Assessment Reach (avoid walking in channel)
•Confirm assessment reach placement in the field (3.5.1).
•Measure the bankfull channel width at 3 locations and calculate average to determine
assessment reach length and identify reach boundaries (3.5.2). Record average bankfull channel
width in Step 2.
•Record coordinates ofdownstream reach boundary from center of channel and photograph
reach.
•Begin to note expression and strength of indicators (except bankfull width and aquatic
macroinvertebrate indicators).
•Take photographs at middle and upstream end of reach.
•Start sketching assessment reach on field form.
2. Record General Reach Information on Field Form (3.7.1)
\
3. Evaluate Indicators (3.8)
•Collect aquatic macroinvertebrates from reach, starting from downstream end.
• Measure slope.
•Sort and identify aquatic macroinvertebrates. If two practitioners are available, one should
proceed with other measurements while the other conducts this step.
• Measure other indicators:
o Measure percent shading at top, middle and bottom of reach.
o Identify hydrophytic vegetation taxa and determine presence/absence of upland plants in the
channel.
o Assess live or dead algal cover on the streambed (AW only).
o Assess the degree to which the riparian corridor has different or more vigorous vegetation
than surrounding uplands.
o Assess the expression and degree of riffle-pool sequence.
o Assess the degree of substrate sorting and/or difference of channel substrate material from
surrounding uplands (WM only).
•Complete sketch of the assessment reach on the field form.
4. Review Field Form for Completeness
5. Enter Data into Web Application (in office)
3.4 Timing of sampling
Ideally, application of the AW and WM SDAMs should occur during the growing season when many
aquatic macroinvertebrates are most active, hydrophytes are readily identifiable, and differences in
vegetation or growth vigor in the riparian corridor are easier to discern. In many parts of the West, the
optimal time of sampling is typically between April and June, when biological indicators are most
readily apparent in less-than-perennial reaches. Assessments may be made during other times of the
year, but there is an increased likelihood of specific indicators being dormant or difficult to observe at
the time of assessment, especially in higher elevations of the WM, where the presence of snow and
channel ice during the colder months may also be a factor. However, most of the indicators included in
the methods persist well beyond a single growing season (e.g., hydrophytic vegetation) or are not
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Section 3: Data Collection
dependent on it (e.g., geomorphological indicators), reducing the sensitivity of the methods to the
timing of sampling.
These protocols may be used in flowing streams as well as in dry or drying streams. However, care
should be taken to avoid sampling during flooding conditions and assessors should wait at least one
week after large storm events that impact vegetation and sediment in the active stream channel
before collecting data to allow aquatic macroinvertebrates and other biological indicators to recover
(Grimm and Fisher 1989; Hax and Golladay 1998; Fritz and Dodds 2004) and water level and clarity to
stabilize and enable clear observation of physical features. In general, aquatic macroinvertebrate
abundance is suppressed during and shortly after major channel-scouring events, potentially leading to
inaccurate assessments. Recent rainfall can interfere with measurements (e.g., by washing away
aquatic macroinvertebrates). Assessors should note recent rainfall events on the field form and
consider the timing of field evaluations to assess each indicator's applicability. Field evaluations should
not be completed within one week of significant rainfall that results in surface runoff. Local weather
data and drought information should be reviewed before assessing a reach or interpreting indicators.
Evaluating antecedent precipitation data from nearby weather stations after each sampling event
helps to determine if storms may have affected data collection and informs interpretation of SDAMs
data. The Antecedent Precipitation Tool (APT; U.S. Army Corps of Engineers 2023) can also be helpful
for evaluating recent precipitation conditions at a site relative to the 30-year average.
3.5 Assessment reach considerations
3.5.1 Reach placement
Stream assessments should begin by walking the channel's length, to the extent feasible, from the
target downstream end to the top of the assessment reach. This initial review of the reach allows the
assessor to examine the channel's overall form, landscape, parent material, and variation within these
attributes as they develop or disappear upstream and downstream. This helps determine whether
adjustments to assessment reach boundaries are needed, or whether multiple assessment reaches are
needed to adequately characterize streamflow duration throughout the project area where
information is needed. Walking alongside, rather than in, the channel is recommended for the initial
review to avoid unnecessary disturbance to the stream. Walking alongside the channel also allows the
assessor to observe the surrounding landscape's characteristics, such as land use and sources of flow
(e.g., stormwater pipes, springs, seeps, and upstream tributaries).
The assessor should document the areas along the stream channel where various sources (e.g.,
stormflow, tributaries, or groundwater) or sinks of water (alluvial fans, abrupt changes in bed slope,
etc.) may cause abrupt changes in flow duration. When practical, assessment reaches should have
relatively uniform channel morphology. When evaluating the reach's homogeneity, focus on
permanent features that control streamflow duration (such as valley gradient and width), rather than
on the presence or absence of surface water. Project areas that include confluences with large
tributaries, significant changes in geologic confinement, or other features that may affect flow duration
may require separate assessments above and below the feature.
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Section 3: Data Collection
For some applications, reach placement is dictated by project requirements. For example, a small
project area may be fully covered by a single assessment reach. In these cases, assessment reaches
may contain diverse segments with different streamflow duration classes (e.g., a primarily perennial
reach with a short intermittent portion where the flow goes subsurface). In these cases, the portions of
the reach with long-duration flows will likely have a greater influence on the outcome than the
portions with short-duration flows, depending on each portion's relative size.
Natural features, such as bedrock outcrops or valley confinements, and non-natural features like
culverts or road crossings may alter hydrologic characteristics in their immediate vicinity. For example,
culverts may create plunge pools, and drainage from roadways is often directed to roadside ditches
that enter the stream near crossings, leading to a potential increase in indicators of long streamflow
duration. Specific applications may require that these areas be included in the assessment, even
though they are atypical of the larger assessment reach. For other applications, the area of influence
may be avoided by moving the reach at least 10 m up- or downstream.
3.5.2 Reach length
An assessment reach should have a length equal to 40 bankfull channel-widths, with a minimum
length of 40 m and a maximum of 200 m. An assessment reach should not be less than 40 m in length
to ensure that sufficient area is assessed to observe and appropriately measure indicators.
Assessments based on reaches shorter than 40 m may not detect all indicators and could provide
inaccurate classifications.
Bankfull channel width is averaged from measurements at three locations: at the bottom of the reach,
15 m upstream, and 30 m upstream from the bottom of the reach, or at three locations that are
representative of the reach as a whole. See 3.7.1 General reach information and 3.8.1 Bankfull channel
width for more guidance on measuring bankfull channel width. Width measurements are made at
bankfull elevation, perpendicular to the thalweg (i.e., the deepest point within the channel that
generally has the greatest portion of flow); how to find bankfull elevation is discussed in 3.7
Conducting assessments and completing the field form. In multi-thread systems, the bankfull width is
measured for the entire active channel, based on the outer limits of the OHWM. Reach length is
measured along the thalweg. If access constraints require a shorter assessment reach than needed, the
actual assessed reach-length should be noted on the field form along with an explanation for why a
shortened reach was necessary.
Note that bankfull channel width is also an indicator of streamflow duration, as described below in
3.8.1 Bankfull channel width.
3.5.3 How many assessment reaches are needed?
The outcome of an assessment applies to the assessed reach and may also apply to adjacent reaches
some distance upstream or downstream if the same conditions are present. The factors affecting
spatial variability of streamflow duration indicators (described above) dictate how far from an
assessment reach a classification applies. More than one assessment may be necessary for a large or
heterogenous project area, and multiple assessments are usually preferable to a single assessment. In
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Section 3: Data Collection
areas that include the confluence of large tributaries, road crossings, or other features that may alter
the hydrology, multiple assessment reaches may be required (e.g., one above and one below the
feature).
3.6 Photo-documentation
Photographs can provide strong evidence to support conclusions resulting from application of the AW
and WM SDAMs, and extensive photo-documentation is recommended. Taking several photos of the
reach condition and any disturbances or modifications relevant to making a final streamflow duration
classification is strongly recommended. Specifically, the following photos should be taken as part of
every assessment:
• A photograph from the top (upstream) end of the reach, looking downstream.
• Two photographs from the middle of the reach, one looking upstream and one looking
downstream.
• A photograph from the bottom (downstream) end of the reach, looking upstream.
Photographs that illustrate the following are also strongly recommended:
• Hydrophytic plant identifications, showing diagnostic features and extent within the reach.
• Extent of rooted upland plants in channel.
• Typical riffle-pool sequence, if present.
• Particle size and/or stream substrate sorting.
• Disturbed or unusual conditions that may affect the measurement or interpretation of
indicators.
3.7 Conducting assessments and completing the field form
3.7.1 General reach information
After walking the reach and determining the appropriate boundaries for the assessment area, record
on the field form the project name, reach code or identifier, waterway name, assessor(s) name(s), and
the date of the assessment visit. These data provide essential context for understanding the
assessment but are not indicators for determining streamflow duration class.
Coordinates
Record the coordinates of the downstream end of the reach from the center of the channel.
Weather conditions
Note current weather conditions (e.g., rain and intensity, sun, clouds, snow). If known, note
precipitation within the previous week on the datasheet, and consider delaying sampling, if possible. If
rescheduling is not possible, note whether the streambed is recently scoured, and if turbidity is likely
to affect the measurement of indicators.
Surrounding land use
A preliminary assessment of surrounding land use should be conducted during desktop reconnaissance
(see 3.1 Conduct desktop reconnaissance). Once at the site, verify whether the preliminary assessment
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Section 3: Data Collection
is correct, making sure to note evidence of human activities that may not be evident in or have
occurred since the aerial imagery.
Indicate the dominant land-use around the reach within a 100-m buffer. Check up to two of the
following:
• Urban/industrial/residential (buildings, pavement, or other anthropogenically hardened
surfaces).
• Agricultural (e.g., farmland, crops, vineyard, pasture).
• Developed open space (e.g., golf course, sports fields).
• Forested.
• Other natural.
• Other (describe).
Bankfull channel width
Measure bankfull channel width values (to nearest 0.1 m) at 0, 15, and 30 m above the downstream
end of the reach or at three locations spread out over approximately one-third of the expected reach
length and record values on the field form (Figure 4 and Figure 5). Note, this approach replicates how
the data used to develop these SDAMs were collected at study reaches across the West. Widths should
be measured perpendicular to the thalweg. In multi-threaded systems, width measurements should
span all channels within the OHWM. Calculate the average width.
Flow
# Photopoint location
Bankfull width measurement
Figure 4. Bankfull measurement and photopoint locations. Bankfull is represented by the yellow area and the
blue line represents the thalweg of the channel. Bankfull width should be measured at three locations that are
representative of the expected reach length.
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Section 3: Data Collection
Figure 5. Measuring bankfull width, image credit: james Treacy
The bankfull width3 is the portion of the channel that contains the bankfull discharge, which is a flow
event that occurs frequently (typically every 1.01 to 5 years; David and Hamill 2024), but that does not
include larger flood events. The bankfuli discharge has an important role in forming the physical
dimensions of the channel. For many stream channels, the bankfull elevation (from where bankfull
width is measured) can be identified in the field by an obvious slope break that differentiates the
channel from a relatively flat floodplain terrace higher than the channel, or a transition from exposed
stream sediments or more water and scour tolerant vegetation (e.g., willows) to terrestrial and
intolerant vegetation (David et al, 2022). In locations without vegetation, moss growth on rocks along
the banks can be an indicator of bankfull height as can breaks in bank slope or changes in substrate
composition.
Certain indicators of bankfull height may be more or less evident in different stream types, so assessors
should evaluate multiple bankfull indicators when measuring bankfull channel width. The bankfull
width should be measured in a straight section of the stream (e.g., riffle, run, or glide if present) that is
representative of the study reach. Pools and bends in the stream or areas where the stream width is
affected by the deposition of rocks, debris, fallen trees, or other unusual constrictions or expansions
should be avoided. In the field, it may often be possible to determine the bankfull channel width using
bankfull indicators on only one bank of the stream. This point can be used as a reference to determine
the bankfull elevation on the opposite bank by creating a level line across the stream from the
identified bankfull elevation perpendicular to the stream flow.
3 Resources for bankfuli identification are found on the SPAM training materials site.
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Section 3: Data Collection
In larger systems (e.g., drainage area > 0.5 square miles), it may be helpful to compare field
measurements to bankfull channel dimensions derived from regional curves relating bankfull
dimensions to watershed characteristics. These models may be derived at large regional scales (e.g.,
StreamStats; U.S. Geological Survey 2024) or a local scale (e.g., Texas: Asquith et al. 2020 Wyoming:
Foster (2012)). Bieger et al. (2015) provide regional curves for several regions of the continental United
States. If observed bankfull dimensions are substantially different from estimated bankfull dimensions
derived from regional curves (e.g., more than twice the maximum or less than half the minimum
estimates), it may be helpful to re-evaluate bankfull indicators that were used to establish bankfull
channel height. Regional curve estimates for bankfull dimensions of small channels (small drainage
areas) may be extrapolated outside the range used to develop relationships so such estimates have
unknown errors (bias) associated with them and should be used with caution if at all.
Note that bankfull channel width is also an indicator of streamflow duration, as described below in
3.8.1 Bankfull channel width-
Describe reach length and boundaries
Record the reach length in meters as described in 3.5.2 Reach length. Record observations about the
reach on the field form, such as changes in land use, disturbances, or natural changes in stream
characteristics that occur immediately up or downstream. If the reach is less than 200 m and shorter
than 40 times the average bankfull channel width, explain why a shorter reach length was appropriate.
For example: "The downstream end is 30 m upstream of a culvert under a road. The upstream end is
close to a conspicuous dead tree just past a large meander, near a fence marking a private property
boundary. The reach length was shortened to 150 m to avoid neighboring private property."
Photo-documentation of reach
Record the photo ID or number, or check the designated part of the field form for required
photographs taken from the bottom (facing upstream), middle (facing upstream and downstream) and
top (facing downstream) of the reach (see Figure 4).
Disturbed or difficult conditions
Note any disturbances or unusual conditions that may create challenges for assessing flow duration.
Common situations include practices that alter hydrologic regimes, such as diversions, culverts,
discharges of effluent or runoff, and drought. Note circumstances that may limit the growth of
hydrophytes and/or affect stream geomorphology, such as channelization, or vegetation removal that
may affect the measurement or interpretation of several indicators Figure 6. Also note if the stream
appears recently restored, for example, stream armoring with large substrate or wood additions and
recently planted vegetation in the riparian zone.
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Section 3: Data Collection
Figure 6. Examples of difficult conditions that may interfere with the observation or interpretation of indicators. Left: As the
Arroyo Trabuco progresses through the city of San Juan Capistrano in California, its banks have been hardened and the
natural riparian vegetation has been removed (although there is still aquatic vegetation apparent in the channel itself). The
removal of in-stream and riparian zone habitat and addition of urban non-point source discharges may also impact the
abundance of aquatic macroinvertebrates and hardened banks may obscure identification of bankfull elevation. Right: An
unnamed creek near Vacaville, California, has been straightened and channelized, affecting naturally occurring stream
pattern (e.g., riffle-pool sequence). Image credits: Raphael Mazor (left) and the California Department of Fish and Wildlife's
Aquatic Bioassessment Lab (right).
Observed hydrology
Surface flow
Visually estimate or use a tape measure to determine the percentage of the reach length that has
flowing surface water or subsurface flow. The reach sketch should indicate where surface flow is
evident and where dry portions occur.
Subsurface flow
If the reach has discontinuous surface flow, investigate the dry portions to see if subsurface flow is
evident. Examine below the streambed by turning over cobbles and digging with a trowel. Resurfacing
flow downstream may be considered evidence of subsurface flow (Figure 7). Other evidence of
subsurface flow includes:
• Flowing surface water disappears into alluvial deposits and reappears downstream. This
scenario is common when a large, recent alluvium deposit created by a downed log or other
grade-control structure creates a sharp transition in the channel gradient or in valley
confinement.
• Water flows out of the streambed (alluvium) and into isolated pools.
• Water flows below the streambed and may be observed by moving streambed rocks or digging
a small hole in the streambed.
• Shallow subsurface water can be heard moving in the channel, particularly in steep channels
with coarse substrates.
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Section 3: Data Collection
Record the percent of the reach length with subsurface and surface flow (combined). That is, the
percent of reach length with subsurface flow should be greater than or equal to the percent of reach
length with surface flow (Figure 7).
The reach sketch should indicate where subsurface flow is evident.
Number of isolated pools
If the reach is dry or has discontinuous surface flow, look for isolated pools within the channel that
provide aquatic habitat, if there is continuous surface flow throughout the reach, enter 0 (zero)
isolated pools. The reach sketch should indicate the location of pools in the channel or on the
floodplain (Figure 7). However, only isolated pools within the channel are counted, including isolated
pools within secondary channels that are part of the active channel and within the OHWM. Pools
connected to flowing surface water and isolated pools on the floodplain do not count. Dry pools (i.e.,
pools that contain no standing water at the time of assessment) do not count.
100% surface flow
100% surface +
subsurface flow
0 isolated pools
B
70% surface flow
70% surface +
subsurface flow
0 isolated pools
r
80% surface flow
100% surface +
subsurface flow
0 isolated pools
/
/
70% surface flow
70% surface +
subsurface flow
1 isolated pool
Figure 7. Examples of estimating surface and subsurface flow, and isolated pools. Orange represents the dry channel and
blue represents surface water in the channels. White represents the floodplain outside the channel. The pool in A does not
count because it is outside the channel, whereas the pools in B and C do not count because they are connected to flowing
surface water, In contrast, the lower pool in D counts because it is isolated from any flowing surface water and is within the
channel.
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Section 3: Data Collection
3.7.2 Assessment reach sketch
Sketch the assessment reach on the field form indicating important features, such as access points,
important geomorphological features, the extent of dry or aquatic habitats, riffles, pools, etc. Note
locations where photographs are taken and where channel measurements are made.
3.8 How to measure indicators of streamflow duration
Eight indicators are required for the AW SDAM, and ten indicators are required for the WM SDAM;
seven indicators are shared by both methods. All required indicators must be measured to obtain a
classification.
Biological indicators
• Prevalence of rooted upland plants in the streambed
• Differences in vegetation
• Shading (WM only)
• Algal cover (AW only)
• Aquatic macroinvertebrate indicators
o Abundance of perennial indicator taxa
o Abundance of Ephemeroptera, Plecoptera, and Trichoptera (WM only)
• Number of hydrophytic plant species
Geomorphological indicators
• Bankfull channel width
• Slope
• Riffle-pool sequence
• Particle size or stream substrate sorting (WM only)
Most indicators are positive indicators of streamflow duration; that is, a greater abundance or score of
these indicators is generally associated with longer duration flows (Dodds et al. 2004, Burk and
Kennedy 2013, Bigelow et al. 2020). For example, hydrophytic riparian corridor vegetation and a
stronger riffle-pool sequence are both associated with perennial reaches. Percent shading is typically
slightly higher at intermittent reaches than at ephemeral or perennial reaches. Slope and bankfull
channel width have a less straightforward relationship with streamflow duration, and these indicators
serve to modify the interpretation of other indicators. Although larger bankfull widths and lower-
gradient slopes are often associated with longer flow duration, large, low-gradient ephemeral reaches
are also common, particularly in the AW. Rooted upland plants are negative indicators of streamflow
duration, as the prevalence of upland plants on the streambed is lower at reaches with greater flow
duration.
These indicators are based on what is observed at the time of assessment, not on what would be
predicted to occur if the channel were wet or in the absence of disturbances or modifications.
Disturbances and modifications (e.g., vegetation management, channel hardening, diversions) should
be described in the "Notes" section of the datasheet and are considered when drawing conclusions.
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Common ways that disturbances can interfere with indicator measurement are described within each
indicator description, where applicable. The indicators are presented in the order they appear on the
field forms, also reflecting the recommended order of operations for efficiency in the field.
3.8.1 Bankfull channel width
Bankfull channel width is generally associated with streamflow duration, as wider channels tend to
reflect longer-lasting flows. However, this pattern is sometimes reversed in more arid regions and in
regions overlying alluvial geology, particularly in the AW. Bankfull channel width is measured (to the
nearest 0.1 m) at three locations during the initial layout of the assessment reach and then averaged,
as described in 3.5 Assessment reach considerations (see Figure 4 and Figure 5). In multi-threaded
channels, the width of the entire active channel is measured, based on the outer limits of the OHWM.
Wohl et al. (2016) describe the active channel as the portion of the valley bottom distinguished by one
or more of the following characteristics:
• Channels defined by erosional and depositional features created by river processes (as opposed
to upland processes, such as sheet flow or debris flow).
• The upper elevation limit at which water is contained within a channel.
• Portions of a channel generally without trunks of mature woody vegetation.
3.8.2 Aquatic macroinvertebrate indicators
The WM SDAM has two indicators based on aquatic macroinvertebrates, and one of these indicators is
also used in the AW SDAM. Both indicators are measured from the same sample collection effort
described below.
Sample Collection Instructions
Aquatic macroinvertebrates are assessed within the defined reach. A kick-net or D-frame net is used to
collect specimens. Assessors begin sampling at the most downstream point in the assessment reach
and proceed to sample in the upstream direction. Where there is rapidly flowing water, the net is
placed perpendicular against the streambed while the substrate is disturbed upstream of the net for a
minimum of one minute. This disturbance will dislodge and suspend aquatic macroinvertebrates such
that they are carried by the stream flow into the net. For slower flowing or standing water areas, jab
the net under banks, overhanging terrestrial and aquatic vegetation, leaf packs, and in log jams or
other woody material to dislodge and capture aquatic macroinvertebrates and the leaves or other light
materials they may be clinging to. Samples should be collected from at least six distinct locations
representing the different habitats occurring in the reach. Without releasing aquatic
macroinvertebrates, strain the net contents to remove fine sediments that would interfere with
observing them. Empty contents of the net into a white tray with fresh stream water for determining
abundance of individuals present.
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Searching is complete when:
• At least six different locations within the reach have been sampled across the range of habitat
types and a minimum of 15 minutes of effort expended (not including specimen identification
time), or
• All available habitat in the assessment reach has been completely searched in less than 15
minutes. A search in dry stream channels with little bed or bank development and low habitat
diversity may be completed in less than 15 minutes.
During the 15-minute sampling period, search the full range of habitats present, including: water under
overhanging banks or roots, in pools and riffles, accumulations of leaf packs, woody debris, and coarse
inorganic particles (i.e., pick up rocks and loose gravel). If a reach contains both dry and wet areas,
focus on searching the wet habitats, as these are the most likely places to encounter aquatic
macroinvertebrates, but do not ignore dry areas.
Dry channels: Focus the search on areas serving as refuge such as any remaining pools or areas of
moist substrate for living aquatic macroinvertebrates and under cobbles and other larger bed materials
for evidence such as caddisfly casings (Figure 8) and snail shells. Exuviae of emergent mayflies or
stoneflies may be observed on dry cobbles or stream-side vegetation (Figure 8). In summary, sampling
methodology consistent with the Xerces Society's recommendations on using aquatic
macroinvertebrates as indicators of streamflow duration (Blackburn and Mazzacano 2012) as
developed for the Pacific Northwest SDAM (Nadeau 2015) is recommended. Take care, especially in dry
channels, to only collect aquatic species and life stages. Field guides (e.g., Voshell 2002) and
identification keys (e.g., Merritt et al. 2019) are recommended for both experienced and novice
practitioners.
When searching dry channels (or dry portions of partially wet channels), be sure to avoid counting
terrestrial macroinvertebrates in the streambed. Figure 9 depicts some taxa (especially snails) that may
be found near stream channels in the West, though this list is certainly not exhaustive. If you are
unsure whether the macroinvertebrates you encounter are aquatic or terrestrial, collecting a voucher
specimen and identifying it in a lab setting or consulting an entomologist is recommended.
Taxonomic identification: Analysis of samples can occur streamside with live specimens. Alternatively,
samples may be preserved in 70% ethanol for off-site analysis and identified with an appropriate guide
(e.g., Merritt et al. 2019) or sent to a professional lab. For SDAM development, all insects and mollusks
were identified to the family level, while other organisms were identified to the order or class level.
However, for the AW and WM SDAMs, family-level identifications are only necessary for four insect
orders: Ephemeroptera, Plecoptera, Trichoptera, and Coleoptera. Non-insects and insects in other
orders are not used as indicators in either SDAM. Appendix B presents more information on family-
level identification for this indicator. Photos (if feasible) should be taken of any taxon in question to
allow further identification to be made off-site, if necessary. If the identification is uncertain, then
describe any distinguishing features that were observed in the notes.
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Figure 8, Examples of evidence of aquatic macroinvertebrates in dry channels. Left: Caddisfly cases may persist under large
cobbles or boulders well after the cessation of flow. Right: Stonefly (Plecoptera) exuvia. Exuviae are left behind when
aquatic nymphs or pupae emerge from the stream and go through a final molt to metamorphose to winged adults. Image
credits: Raphael Mazor.
Figure 9. Examples of terrestrial macroinvertebrates you may find in a dry channel. Left: larva of soldier flies
(Stratiomyidae). Right: garden snail (Cornu aspersum).
3.8.2.1 Abundance of Ephemeroptera, Plecoptera, and Trichoptera (WM only)
This indicator is based on the abundance of aquatic macroinvertebrates in the orders of mayflies,
stoneflies, and caddisflies (i.e., Ephemeroptera, Plecoptera, and Trichoptera, or EPT). EPT are
widespread insects in perennial and intermittent streams but are not typically found in ephemeral
streams. Indicate on the field form how many mayflies, stoneflies, or caddisflies are encountered in the
reach in the macroinvertebrate sample. Living aquatic lifestages (e.g., larvae or pupae) and non-living
material (e.g., caddis cases, shed exuviae) all count towards this indicator. Photos are included in
Appendix B. This indicator counts the number of individuals found, which may come from the same or
different orders, such that no one family counts for more than 11 individuals in the total. For example,
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observing 25 Heptageniidae (flathead mayflies) only counts for 11 individuals in the total number of
individuals of EPT taxa. There is also a box for indicating that no aquatic macroinvertebrates were
observed in the assessment reach.
The abundance of EPT taxa may be recorded in these categories:
• 0 EPT individuals observed
• 1 to 4 EPT individuals observed
• 5 to 9 EPT individuals observed
• 10 to 19 EPT individuals observed
• 20 or more EPT individuals observed
3.8.2.2 Abundance of perennial indicator taxa
This aquatic macroinvertebrate indicator is used in both the AW and WM SDAMs. This indicator is
based on the abundance of aquatic macroinvertebrate families that were identified as perennial
indicator taxa in data from across the western United States. These taxa are more commonly found in
perennial reaches, although they may also occur in intermittent or ephemeral reaches (typically at
lower abundance).
Eleven families were identified as indicators of perennial flows in the West (Table 3). Indicator species
analysis determines if >2 sets of samples (e.g., samples from perennial vs. intermittent vs. ephemeral
reaches) differ in relative abundances and occurrence frequencies of different taxa (DeCaceres and
Legendre 2009). All but one of these families are in the Orders of Ephemeroptera, Plecoptera, and
Trichoptera. Living material (e.g., live larvae or pupae) and non-living material (e.g., caddis cases, shed
exuviae) all count towards this indicator. This indicator counts the number of individuals found, which
may come from the same or different families, such that no one family counts for more than 11
individuals in the total. For example, observing 25 Perlidae (common stoneflies) only counts for 11
individuals in the total number of individuals of perennial indicator taxa. There is also a box for
indicating that no aquatic macroinvertebrates were observed in the assessment reach.
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Table 3. Perennial indicator families for the AW and WM SDAMs.
Order Family
Ephemeroptera (mayflies)
Ephemerellidae (spiny crawler mayflies)
Heptageniidae (flathead mayflies)
Leptohyphidae (little stout crawler mayflies)
Leptophlebiidae (prong-gilled mayflies)
Plecoptera (stoneflies)
Chloroperlidae (green stoneflies)
Perlidae (common stoneflies)
Trichoptera (caddisflies)
Brachycentridae (humpless casemaker caddisflies)
Glossosomatidae (saddle casemaker caddisflies)
Hydropsychidae (common net-spinner caddisflies)
Rhyacophilidae (free-living caddisflies)
Coleoptera (beetles) Elmidae (riffle beetles)
The abundance of perennial indicator taxa may be recorded in these categories:
• No perennial indicator taxa detected
• 1 to 4 perennial indicator individuals
• 5 to 9 perennial indicator individuals
• 10 to 19 perennial indicator individuals
• 20 or more perennial indicator individuals
3.8.3 Slope
Slope has an indirect relationship with streamflow duration and can help modify the interpretation of
other indicators measured as part of the SDAM. Reaches with very high slopes are often ephemeral
headwaters, and lower slopes are typical of perennial mainstem reaches. However, these patterns can
be reversed, particularly in the AW, where headwaters often have longer flow durations than lower
portions of the watershed.
Slope is measured as the percent slope between the upper and lower extent of the assessment reach.
This task requires a two-person team (Figure 10). One person stands at bankfull elevation at the
downstream end of the reach, and a second person stands within eyesight at the opposite end of the
reach, also at bankfull elevation. This measurement requires direct line-of-sight between the lower and
upper ends of the reach. If direct line-of-sight from the bottom to top of the reach is not possible, the
slope of the longest representative portion of the reach should be 'line-of-sight' evaluated. If multiple
slope measurements are needed, the average slope of the assessment reach should be recorded (note,
calculation of the average slope would need to be weighted by the channel distance represented by
each slope measurement). Slope should be recorded to the nearest half-percent. Some low-gradient
streams may have slopes that are indistinguishable from zero using this method.
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Figure 10, Schematic illustration of slope measurement using a clinometer.
3.8.4 Shading (WM only)
Data used to develop the WM SDAM indicated that intermittent reaches tended to have higher levels
of shading than ephemeral or perennial reaches. Ephemeral reaches may have insufficient flow to
support extensive riparian forests that provide shade, whereas some perennial reaches may be too
wide for streamside vegetation to affect sun exposure in the middle of the channel. Although this
pattern was also evident with data collected for the AW SDAM, the best predictive model for the AW
SDAM did not include this indicator.
Using a convex spherical densiometer, stream shading is estimated in terms of the percent cover of
objects (e.g., vegetation, buildings, canyon walls, etc.) that have the potential to block sunlight. The
method used in the WM SDAM uses the Strickler (1959) modification of a densiometer to correct for
over-estimation of stream shading that occurs with unmodified readings. Taping off (Figure 11) the
lower left and right portions of the mirror emphasizes overhead structures over foreground structures
(the main source of bias in stream shading measurements).
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bubWe level
Figure 11. Representation of the mirrored surface of a convex spherical densiometer showing the position for taping the
mirror and the intersection points used for the densiometer reading. The score for the hypothetical condition (b) is 9 out of
17 possible covered intersection points within the "V" formed by the two pieces of tape.
The densiometer is read by counting the number of line intersections on the mirror that are obscured
by overhanging vegetation or other features that prevent sunlight from reaching the stream. If
measurements are being taken when leaves of deciduous woody vegetation are not fully expressed,
count all grid intersections that lie within the branches of the woody vegetation. So rather than looking
at individual tree leaves, look at the "zone of influence" of vegetative cover (Nadeau et al. 2020).
All densiometer readings should be taken at 0.3 m above the water surface (or dry streambed surface)
and with the bubble on the densiometer leveled. The densiometer should be held just far enough from
the squatting observer's body so that his/her forehead is just barely obscured by the intersection of
the two pieces of tape, when the densiometer is oriented so that the "V" of the tape is closest to the
observer's face.
Take and record four readings from the center of each of three transects: a) facing upstream, b) facing
downstream, c) facing the left bank, d) facing the right bank. Each recording should be an integer value
ranging from 0 to 17. The observer should revolve around the densiometer (i.e., the densiometer
pivots around a point) over the center point of the transect (as opposed to the densiometer revolving
around the observer). Read and record densiometer readings at the top, middle, and bottom of the
reach, for a total of 12 readings (four readings at each of three transects). The indicator is then
recorded as the percent of points covered by shade-casting objects, total points covered divided by
204 and multiplied by 100.
3.8,5 Number of hydrophytic plant species
For the AW and WM SDAMs, hydrophytes are defined as those with a Facultative Wetland (FACW) or
Obligate (OBL) wetland indicator status in the regional National Wetland Plant Lists (NWPL, U.S. Army
Corps of Engineers 2020). The two western NWPL regions (i.e., the Arid West and Western Mountains,
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Valleys and Coasts) are identical to the SDAM regions (AW and WM, respectively). Indicator status for
certain species may differ between regions; therefore, it is important to consult the correct list when
determining indicator status. For example, California corn lily (Veratrum californicum), a common,
widespread herb often found growing in wetlands and riparian zones, is FACW in the AW but only
Facultative (FAC) in the WM. Conversely, mule fat (Baccharis salicifolia) is rated FAC in the AW but
FACW in the WM.
Hydrophytic plant species that exhibit an odd or unusual distribution pattern in the assessment reach
should not be considered among the number of hydrophytic plant species present. Examples of odd or
unusual distribution patterns are described below:
• Isolated individuals, or small patches covering only a small portion of the total assessment area
(e.g., < 2%) and only found in one location (as opposed to plants sparsely distributed
throughout the reach). Hyperlocal hydrologic conditions may support the growth of
hydrophytes in an otherwise unsuitable stream reach. In more arid regions, this can occur at
road crossings, where road runoff increases water availability to vegetation (Figure 12).
• Long-lived species exclusively represented by seedlings or plants less than one-year old. A large
flood may promote the growth of hydrophytes in streams that are normally too dry to sustain
them (Figure 13).
• Old specimens clearly in decline. This scenario may be a sign of major long-term reductions in
water availability due to changes in water use practices or to extreme and/or persistent
drought (Figure 14).
These species may be recorded on the field form, along with notes explaining the unusual distribution
patterns observed, but should not be among the number of hydrophyte species entered for this SDAM
indicator.
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Figure 12. Local conditions that support growth of hydrophytes, In Ridgecrest, California, a culvert at an ephemeral stream
crossing disrupts the movement of water, sustaining the growth of hydrophytes in the immediate vicinity. Photo credit:
Cara Clark.
Figure 13. Long-lived species only
represented by young specimens. Red
alders (Alnus rubra), while abundant at
Mission Creek in the Mojave Desert, were
only observed as seedlings. Photo credit:
Raphael Mazor.
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Section 3: Data Collection
Figure 14. Water-stressed riparian trees near Oro Grande on the Mojave River. Reproduced from Lines (1999).
For this indicator, identify hydrophytic plant species growing within the channel or up to one half-
channel width from the channel of the assessment reach that do not have unusual or odd distribution
patterns. Hydrophytes growing at greater distances from the channel may be supported by local water
sources not related to streamflow in the assessment reach. Once six taxa are identified, counting can
stop; however, where the user may not be confident in all identifications, more species should be
assessed, if possible.
In general, focusing on the most dominant species in the reach is efficient. Take photos of each plant
species, focusing on diagnostic features and photos that illustrate the abundance and environmental
context where the species grows. Where practical, voucher material (e.g., flowers, leaves, etc.) may be
collected and preserved (e.g., in a plant press) for later identification.
If the site is devoid of vegetation, check the box marked "No vegetation within reach."
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Common questions about identifying hydrophytes
Are FACW and OBL plants equally important?
Yes. For this method, OBL and FACW plants are equally important indicators of streamflow duration.
Do Facultative (FAC) or Facultative Upland (FACU) status plants count?
No. Although some applications of the N WPL treat FAC or FACU plants as hydrophytes, they do not
count towards this indicator for the AW or WM SDAM. For instance, some important, high-profile
riparian species are FAC in some or all of the NWPL regions applicable to the West, such as American
sycamore (Platanus occidentalis; AW), eastern cottonwood (Populus deltoides; AW and WM regions),
desert willow (Chilopsis linearis, AW and WM regions), and mule fat (Baccharis salicifolia, AW
region). This exclusion in no way lessens the ecological importance or conservation value of these
plants, but rather it indicates their relative tolerance for drier conditions than FACW or OBL species.
What if a species is not included in the NWPL?
If a plant is not included in the NWPL, assume that it is not a hydrophyte unless environmental
context strongly indicates otherwise. (See "What if I can't confidently identify a dominant plant?"
below.)
Is genus-level identification sufficient?
It depends on the genus. Consult the NWPL. Some genera contain high levels of diversity (e.g.,
Carex), while others are dominated by wetland species (e.g., Ludwigia). For instance, across the AW
and WM, nearly all willow (Salix) species are hydrophytes (although there are a few exceptions), so
genus-level identifications of willows are usually acceptable. Post-sampling confirmation based on
photos or collected specimens is recommended.
What if I can't confidently identify a dominant plant?
It may be acceptable to use environmental context and cues to determine that a plant is a
hydrophyte, even if taxonomic identifications cannot be made. Examples include submerged or
emergent hydrophytes, or plants observed to grow exclusively in saturated soil and absent from
adjacent uplands (Figure 15). Post-sampling confirmation based on photos or collected specimens is
strongly recommended. Photo documentation should convey this context. Photo confirmation is
particularly important if the only hydrophytes observed in an assessment cannot be identified on-
site. Photos can also be used when consulting plant identification applications that use image
recognition (e.g., Seek, iNaturalist).
What if a hydrophytic plant species covers <2% of the assessment area (channel width plus 1A channel
width on both sides of the channel x reach length) or is represented only by seedlings and/or
dead/dying individuals?
Do not consider the species among the number of hydrophyte plant species present in the reach.
The species with such distributions can be photographed and noted for additional information on
the reach.
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Figure 15. Examples of plants determined to be hydrophytes based on context. Left: An emergent hydrophyte growing
within the channel. Right: Sedges and cattails growing exclusively in the streamside zone absent from adjacent uplands.
3.8.6 Prevalence of rooted upland plants in the streambed (AW and WM)
Few plants can tolerate the conditions they would experience on the streambed of a reach with
relatively long flow durations. Prolonged inundation, soil saturation, and sheer stress create an
inhospitable environment for most upland plants, preventing their establishment or perseverance.
Thus, the prevalence of upland plants in the streambed indicates that flows have insufficient
frequency, duration, or severity to limit these species (Figure 16).
For this indicator, upland plants are those with Facultative (FAC), Facultative upland plants (FACU) and
Upland (UPL) species on the most recent regionally appropriate National Wetland Plant List (Lichvar et
al. 2016). Species not listed in the NWPL (No Indicator; Nl) are also considered upland plants.
When assessing this indicator, the focus should be on plants rooted on the entire streambed, including
the thalweg. Upland plants growing on any part of the bank or on upland islands within the OHWM
should not be considered. A user will indicate the prevalence of upland plants growing in the
streambed along the entire reach and identify them on the field form. This indicator is scored as shown
in Table 4. Note that a lower score indicates greater prevalence of rooted upland plants in the
streambed.
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This indicator is derived from the New Mexico Hydrology Protocol (NMED 2020), As with other
indicators derived from the New Mexico Hydrology Protocol, "moderate" scores (i.e., 2) are intended
as an approximate midpoint between the extremes of "poor" and "strong". Half scores (i.e., 0.5, 1.5,
and 2.5), mid-way between the scores shown in Table 4 are appropriate to allow the assessor the
flexibility to characterize this indicator more continuously.
Figure 16. Example of an ephemeral stream with rooted upland vegetation growing in the channel. Where
vegetation is growing within the streambed of Agua Chinon in southern California, it is dominated by mule fat
(Baccharis salicifoiia) which is rated FAC on the National Wetland Plant List for the Arid West region. Chaparral
yuccas (Hesperoyucca whipplei), which is not listed in the NWPL, also grows on the streambed.
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Table 4. Scoring guidance for the Rooted Upland Plants indicator.
Evidence of
Score
perennial
flows
Guidance
0
Poor
Rooted upland plants are prevalent within the streambed/thalweg.
1
Weak
Rooted upland plants are consistently dispersed throughout the
streambed/thalweg.
2
Moderate
There are a few rooted upland plants present within the
streambed/thalweg.
3
Strong
Rooted upland plants are absent from the streambed/thalweg.
3.8.7 Algol cover (AW only)
Visually estimate the extent of algal cover on the strearnbed (from the toe of one bank to the toe of
the other) over the entire assessment reach, Algal cover is based on the entirety of the strearnbed and
is not restricted to the wetted channel. In braided systems, estimate algae cover as a percent of the
strearnbed of the entire active channel. Diagrams in Figure 17 can help visualize increasing levels of
algal cover.
2% 10% 40%
Dispersed
Clustered
Figure 17. Visual guides to assist estimates of algal cover on a strearnbed. The left side shows a relatively dispersed
distribution, whereas the right side shows a more clustered distribution.
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Algae are visible as a pigmented mass or film, or sometimes hair-like growths on submerged surfaces
of rocks, logs, plants, and any other structures within the channel, and may form mats that cover
portions of the streambed. Microscopic algae associated with biofilm can be felt as a slippery film on
substrates, but growth must be extensive enough to be visible to the naked eye to be counted,
Periphyton growth is influenced by chemical disturbances such as increased nutrient (nitrogen or
phosphorus) inputs and physical disturbances such as increased sunlight to the stream from riparian
zone disturbances - observations of these should be noted on the field form under Surrounding Land
Use and Disturbed or difficult conditions, respectively. All macroscopic algal forms (filamentous algae,
mats, periphyton, macroalgal clumps, or microalgae growing as a visible biofilm or mat) count, whether
living, dead, or dying. Estimates should fall into one of the following categories:
• Not detected
• <2% cover
• 2 to 10% cover
• 10 to 40% cover
• >40% cover
Figure 18 shows examples of reaches with high and low algal cover in both flowing and dry conditions.
Figure 18, Examples of low (i.e., <2%; left) and high (i.e., >40%; right) algal cover in flowing (top) and dry (bottom) reaches.
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Live algal mats typically have a dull to bright green color. In contrast, dead algal mats are typically dull
brown under wet conditions or powdery white when desiccated. Include both live and dead algal mats
in the overall estimate of extent. Note that it is possible to observe dead algae mats submerged under
water if a stream has only recently started to flow.
In some circumstances, it may be possible to determine if an algal mat originated locally, or if it washed
in from an upstream location. Sloughed algal mats tend to collect in snags or on top of boulders and
rest unevenly on the streambed, or may be attached to overhanging branches. In contrast, mats with a
local origin are often found in pools, depressions, or areas of flow accumulation. In some cases, algal
mats may wash in from upstream and continue to grow if local conditions are favorable. Indicate on
the field form if evidence suggests that algal mats strictly have an upstream origin. If all algae within
the reach was deposited from upstream reaches, the AW SDAM treats this circumstance as though
there are no algae within the reach.
3.8.8 Differences in vegetation
Stream reaches with longer streamflow durations tend to support a distinct riparian vegetation
community that includes more hydrophytic species compared to surrounding uplands. Even stream
reaches of shorter duration may enable upland species in the riparian corridor to grow more vigorously
in and or near the channel than in surrounding uplands. It is important to note in the context of this
indicator, an 'upland' species does not have the same definition as in 3.8.5 Number of hydrophytic
plant species or 3.8.6 Prevalence of rooted upland plants in the streambed (AW and WM). For this
indicator, an 'upland' species is not defined by its NWPL indicator status, but rather by its location
relative to the channel. For example, cottonwoods (Populus deltoides, which are FAC and would be
considered 'upland' plants for other indicators) found only in the riparian corridor along the length of
the assessment reach, but not in the uplands outside of the riparian corridor, would receive a strong
score for this indicator (see Table 5. Scoring guidance for the Differences in Vegetation indicator.).
When assessing this indicator, consider the entire length of the reach, and choose the score from Table
5 that best characterizes the predominant condition; photos that demonstrate the scoring guidance
are shown in Figure 19. High levels of distinctness in either composition or vigor results in a higher
score. In settings where upland vegetation cannot be assessed due to development in the surrounding
area, consider the upland vegetation growing in comparable areas outside the reach. In settings where
the riparian corridor has been eliminated due to wildfire or management activities (e.g., channel
clearing, mowing), the preferred option is to conduct the assessment after the vegetation has
recovered. When a delay is not an option and the riparian corridor is devoid of vegetation, a score of
zero is appropriate.
This indicator is derived from the New Mexico Hydrology Protocol (NMED 2020). As with other
indicators derived from the New Mexico Hydrology Protocol, "moderate" scores (i.e., 2) are intended
as an approximate midpoint between the extremes of "poor" and "strong". Half scores (i.e., 0.5, 1.5,
and 2.5), midway between the scores shown in Table 5 are appropriate to allow the assessor flexibility
to characterize this indicator more continuously.
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Table 5. Scoring guidance for the Differences in Vegetation indicator.
Score
Evidence of
perennial
flows
Guidance
0
Poor
No compositional or density differences in vegetation are present between
the banks and the adjacent uplands.
1
Weak
Vegetation growing along the reach may occur in greater densities or grow
more vigorously than vegetation in the adjacent uplands, but there are no
dramatic compositional differences between the two.
2
Moderate
A distinct riparian vegetation corridor exists along part of the reach. Riparian
vegetation is interspersed with upland vegetation along the length of the
reach.
3
Strong
Dramatic compositional differences in vegetation are present between the
banks and the adjacent uplands. A distinct riparian vegetation corridor exists
along the entire reach - riparian, aquatic, or wetland species dominate the
length of the reach.
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A. Score: 0 B. Score: 1
C. Score: 2 D- Score: 3
Figure 19, Example photos of reaches that attained different scores for the Differences in Vegetation indicator. A: The
vegetation along the reach is non-hydrophytic and similar in composition and vigor to surrounding uplands (Score: 0). B:
Although the plant community composition is similar, the riparian vegetation is growing with more vigor (Score: 1). C: The
riparian corridor is a mix of upland (e.g., Populus deltoides) and hydrophytic (e.g., Populus angustifolia) vegetation. These
and other hydrophytic species are absent from the surrounding uplands (Score 2). (D) The streambanks are dominated by
hydrophytes (e.g., Alnus viridis, Salixsp., Phalaris arundinacea) that are absent In adjacent uplands (Score 3).
3.8.9 Riffle-pool sequence
A riffle is a zone with a relatively high channel slope gradient, shallow water, and high flow velocity and
turbulence. In smaller streams, riffles are defined as areas of a distinct change in gradient where
flowing water can be observed. The bottom substrate material in riffles contains the largest particles
that are moved by bankfull flow (bedload), A pool is a zone with relatively low channel slope gradient
and deep water that moves at a low velocity and with minimal turbulence. Fine textured sediments
generally dominate the bottom substrate material in pools. A repeating sequence of riffles and pools
can be readily observed in most perennial systems, though the form of this sequence can differ based
on gradient and bed material (riffle-run or ripple-pool in low gradient and sand bed systems, or step-
pool in higher gradient systems). Riffle-run (or ripple-run) sequences in low gradient systems are often
42
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Section 3: Data Collection
created by in-channel woody structures such as roots and woody debris. No matter the form, these
features can be observed even in dry channels by closely examining their local profile and patterns of
sediment deposition (at least for streams with coarser bed material). Score the indicator using the
guidance in Table 6.
This indicator is derived from the New Mexico Hydrology Protocol (NMED 2020). As with other
indicators derived from the New Mexico Hydrology Protocol, "moderate" scores (i.e., 2) are intended
as an approximate midpoint between the extremes of "poor" and "strong". Photos that demonstrate
the scoring guidance are shown in Figure 20. Half scores (i.e., 0.5,1.5, and 2.5), midway between the
scores shown in Table 6 are appropriate to allow the assessor flexibility to characterize this indicator
more continuously.
Table 6. Scoring guidance for the Riffle-Pool Sequence indicator.
Score
Evidence of
perennial
flows
Guidance
0
Poor
No riffle-pool sequences observed.
1
Weak
Mostly has areas of pools or of riffles.
2
Moderate
Represented by a less frequent number of riffles and pools. Distinguishing
the transition between riffles and pools is difficult to observe.
3
Strong
Demonstrated by a frequent number of structural transitions (e.g. riffles
followed by pools) along the entire reach. There is an obvious transition
between riffles and pools.
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Section 3: Data Collection
Figure 20, Examples illustrating scoring levels for the Riffle-Pool Sequence indicator. A: No structural definition is apparent
throughout the reach. Score is 0. B: The reach is largely comprised of pools and transitions to other structures infrequent or
not distinct. Score is 1, C: More structural definition is apparent, but distinctions are subtle. Score is 2. D, A sequence of
structures is present throughout the reach and transitions between them are obvious. Score is 3.
3.8.10 Particle size or stream substrate sorting (WM only)
Well-developed streams that have eroded through the soil profile often have substrate materials
dominated by larger sediment sizes, such as coarse sand, gravel, and cobble, relative to floodplain
sediments and adjacent soils. Finding similar sediment sizes in the stream bed and the adjacent stream
side area may indicate that stream channel-forming processes have not been consistent enough to cut
into the soil profile as typically seen in intermittent and perennial streams. The bed in ephemeral
channels can be soil, having the same or similar texture as areas adjacent to the channel, and can have
differentiated soil horizons.
This indicator can be evaluated in two ways:
1) In channel versus outside channel; Determine if the sediment texture on the bed of the channel
is similar to sediment texture adjacent to the channel (e.g., on banks or adjacent floodplain). If
A. Score:0
B. Score: 1
C. Score 2
D. Score 3
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Section 3: Data Collection
this is the case, then there is evidence that erosive forces have not been active enough to down
cut the channel and support an intermittent or perennial system. Stormflow runoff resulting
from human development can form incised ephemeral or intermittent channels; however,
these channels often show little to no coarsening of the substrate.
2) Substrate sorting: Look at the particle size distribution on the channel bed, are there substrate
differences between the bedforms identified in the Riffle-Pool Sequence indicator? For lower
gradient channels dominated by sand substrate, the user may need to identify sorting across
coarse versus fine sand.
Regardless of the approach used to assess channel sediments (e.g., pebble count, sand-gauge
reference card), evaluate an area adjacent to but not in the channel for comparison purposes. Avoid
adjacent areas with dense vegetation or recent soil disturbance.
Score the indicator using the guidance in Table 7. Photos that demonstrate the scoring guidance are
shown in Figure 21.
This indicator is derived from the New Mexico Hydrology Protocol (NMED 2020). As with other
indicators derived from the New Mexico Hydrology Protocol, "moderate" scores (i.e., 1.5) are intended
as an approximate midpoint between the extremes of "poor" and "strong". Half scores (i.e., 0.75 and
2.25), midway between the scores shown in Table 7 are appropriate to allow the assessor flexibility to
characterize this indicator more continuously.
Table 7. Scoring guidance for Particle Size/Streambed Sorting indicator.
Score
Evidence of
perennial
flows
Guidance
0
Poor
Particle sizes in the channel are similar or comparable to particle sizes in
areas close to but not in the channel. Substrate sorting is not readily
observed in the channel.
1.5
Moderate
Particle sizes in the channel are moderately similar to particle sizes in areas
close to but not in the channel. Various sized substrates are present in the
channel and are represented by a higher ratio of larger particles
(gravel/cobble).
3
Strong
Particle sizes in the channel are noticeably different from particle sizes in
areas close to but not in the channel. There is a clear distribution of various
sized substrates in the channel with finer particles accumulating in the
pools and larger particles accumulating in the riffles/runs.
45
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Section 3: Data Collection
A. Score:0 B. Score: 1.5
C. Score:3
Figure 21, Examples illustrating scoring levels for the
Particle Size/Stream Substrate Sorting indicator. Top- left
photo (A): Dry channel in New Mexico where the in-
channel particle size of material is similar to surrounding
uplands (score of 0). Top-right photo (B): This Wyoming
stream shows signs of increased sorting in the middle of
the channel, with larger particles than surrounding
uplands (score of 1.5). Lower left photo (C): Many
particles in this Arizona channel are much larger
compared to surrounding uplands and a high level of
sorting can be seen in the middle of the photo (score of 3).
3.9 Additional notes and photographs
After assessing and recording all the indicators described above, provide any additional notes about
the assessment, and include photographs in the photo log.
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Section 4: Data Interpretation
Section 4: Data Interpretation and Using the Web Application
The AW and WM SDAMs rely on random forest models to make classifications; therefore, the EPA has
developed a free, open-access web application that runs the model for each assessment reach and is
required to obtain a flow classification. This application allows assessors to input data from an
assessment and obtain a classification. In addition, users have the option to produce a PDF report,
which may be included as documentation of SDAM results.
The web application walks users through three steps in analyzing data from an SDAM. First, the user
selects the desired regional SDAM (either by entering coordinates, clicking on a map, or selecting from
a drop-down list). The coordinates field of the web application uses decimal degrees format of the
World Geodetic System of 1984 (WGS84) datum. Then, the user enters field data on each indicator
required for the selected SDAM. At this point, the user can run the model and obtain the resulting
classification. The third step, report production, is optional. Users may enter additional information
about the assessment (such as date of the site visit, notes, and photos of indicators) and produce a PDF
report. No data entered into the web application is stored or submitted to the EPA or other agencies. A
link at the top of the web application goes to Supporting Materials including User Manuals. Field
Forms. Training Videos and more.
4.1 Outcomes of SDAM classification
As described in 1.1 The SDAMs for the AW and WM. application of the SDAMs can result in one of six
possible classifications:
• Ephemeral
• Intermittent
• Perennial
• At least intermittent
• Less than perennial
• Needs more information
The first three streamflow duration classifications correspond to the three classes of stream reaches
used to calibrate the AW and WM SDAMs. These outcomes occur when the pattern of observed
indicators closely matches patterns in the calibration data measured at reaches directly determined to
have perennial, intermittent, or ephemeral flow durations, and thus a classification can be assigned
with high confidence.
In some cases, the pattern of indicators is associated with multiple classes, and the AW and WM SDAM
models cannot assign an unambiguous classification with high confidence. However, the models may
be able to rule out an ephemeral classification with high confidence or a perennial classification with
high confidence. In the former case, the outcome is at least intermittent, meaning that there is a high
likelihood that the stream is either perennial or intermittent, but not ephemeral. In the latter case, the
outcome is less than perennial, meaning that there is a high likelihood that the stream is either
intermittent or ephemeral, but not perennial. In both cases the two classes (i.e., perennial vs.
47
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Section 4: Data Interpretation
intermittent and intermittent vs. ephemeral) cannot be distinguished with confidence. In some
instances, this information may be sufficient for management decisions, although additional
assessment may be warranted. Two outcomes—at least intermittent and less than perennial—were
rare in the AW and WM SDAM development data sets; at least intermittent occurred at 1.9% of
assessments in both regions and less than perennial occurred at 2.6% of assessments in the WM and
1.2% of the AW. The needs more information outcome is possible and generally occurs when no
classification can be made with confidence, but this did not occur in the development data sets for
either region.
4.2 Applications of the SDAMs outside their intended areas
The AW and WM SDAM are intended only for application to the regions shown in Figure 2. The online
web application allows the user to apply the protocol to reaches outside these regions (e.g., the AW
SDAM may be applied to a site in an adjacent region, such as the Great Plains). However, classifications
resulting from these applications are for informational purposes only; the Great Plains and Pacific
Northwest SDAMs had substantially worse accuracy when applied to the development data sets for the
AW and WM regions compared to when the regionally appropriate SDAM was used.
4.3 What to do when a more specific
classification is needed
If the application of the AW or WM SDAM results in
need more information, it means that no
classification can be made with confidence. If an
assessment's outcome is ambiguous about the
specific flow duration class (i.e., less than perennial
or at least intermittent), it may help to examine
other lines of evidence or conduct additional
evaluations as described below in approximate
order of increasing effort.
4.3.1 Review historical aerial imagery
In many parts of the West (particularly the AW), sequences of aerial imagery can provide information
about streamflow duration. Google Earth's time slider and USGS Earth Explorer offer a convenient
method of reviewing historical imagery, particularly for areas where trees do not obscure channels
(however, Google Earth time slider may not have accurate
image dates). If surface water is observed in all interpretable
images across multiple years (especially during dry seasons),
this may provide evidence that the reach is likely perennial.
If surface water is never observed, even when other nearby
intermittent streams show water, the consistent absence of
surface water may provide evidence that the reach is likely
ephemeral (particularly if images are captured during the
wet season or after major storm events). If surface water is
When a more specific classification is needed:
•
Review historical aerial imagery
•
Conduct additional assessments at the
same reach
•
Conduct assessments at similar nearby
reaches
•
Conduct reach visits during regionally
appropriate wet and dry seasons
•
Collect hydrologic data
Considerations for aerial imagery
• Accurate dates of images
• Changes in reach or watershed
conditions since image was
taken
• Seasonal and recent climatic
conditions for each image
48
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Section 4: Data Interpretation
present in some images and dry in others, the stream may be intermittent. The evidence for perennial
flow is strong if the images with surface water occur in the dry season and do not coincide with recent
storm events. It is also important that users consider whether conditions as reflected by historical
imagery are congruent with current conditions. For example, due to groundwater withdrawals, a
stream that once flowed perennially may now have ephemeral flow; therefore, images from 15-20+
years ago might not be indicative of current flow conditions.
Any time that discrete observations of flow or no flow are used to inform a determination of flow
duration class, such observations should be evaluated in the context of relatively normal climatic
conditions. Doing so ensures that flow duration class is not determined based on observations of flow
or no flow during abnormally wet or abnormally dry periods. The Antecedent Precipitation Tool (U.S.
Army Corps of Engineers 2023) is a useful tool to determine if climate conditions are 'normal' for a
locale (see 3.4 Timing of sampling). However, aerial images may not have high enough temporal
resolution to confidently classify streams as ephemeral or perennial without additional data. See
examples in Figure 22.
49
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Section 4: Data Interpretation
Perennial site: Jemez River near Zia Pueblo, New Mexico.
11/2015: Flowing 4/2017: Flowing 2/2018: Flowing
Intermittent reach: Hassayampa River near Morristown, Arizona.
6/2007: Dry 9/2007: Flowing 12/2014: Flowing
Reach on unnamed wash near Las Vegas, Nevada.
4/2007: Dry 6/2012: Dry 3/2014: Dry
Figure 22. Examples of using aerial imagery to support streamflow duration classification. Images were taken from Google
Earth using the time slider,
4.3.2 Conduct additional assessments at the same reach
Some indicators may be difficult to detect or interpret due to short-term disturbances, floods, severe
drought, or other conditions that affect the sampling event's validity. A repeat application of the
SDAM, even a few weeks later when effects from the disturbance have abated, may be sufficient to
provide a determination. Similarly, conducting an additional evaluation during a different season may
50
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Section 4: Data Interpretation
improve the ability to identify vegetation and collect aquatic macroinvertebrates, leading to a more
conclusive assessment.
4.3.3 Conduct assessments at nearby reaches
Indicators may provide more conclusive results at reaches upstream from the assessment reach or
downstream from the assessment reach, and if those locations represent similar conditions may be
useful for interpreting ambiguous results. For example, there should be no significant discharges,
diversions, or confluences between the new and original assessment locations, and they should have
similar geomorphology. See 3.5 Assessment reach considerations for additional information.
4.3.4 Conduct reach revisits during regionally appropriate wet and dry seasons
A single, well-timed assessment may provide sufficient hydrologic evidence about streamflow duration.
As with observations from aerial imagery, any time onsite observations of flow or absence of flow are
used to inform a determination of flow duration class, such observations should be evaluated in the
context of normal climatic conditions. Doing so ensures that flow duration class is not determined
based on hydrologic observations of flow that occurred during abnormally wet or abnormally dry
periods. The previously mentioned APT can provide this information.
4.3.5 Collect hydrologic data
Properly deployed loggers, stream gauges, or wildlife cameras can provide direct evidence about
streamflow duration at ambiguous assessment reaches. It may be possible to distinguish intermittent
from ephemeral streams in just a single season with these tools, assuming typical precipitation.
51
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Section 5: References
Section 5: References
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Carlson, E. A., D. J. Cooper, D. M. Merritt, B. C. Kondratieff, and R. M. Waskom. 2019. Irrigation canals
are newly created streams of semi-arid agricultural regions. Science of The Total Environment
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Fritz, K. M., T.-L. Nadeau, J. E. Kelso, W. S. Beck, R. D. Mazor, R. A. Harrington, and B. J. Topping. 2020.
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Section 5: References
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Appendix A: Glossary of Terms
Appendix A. Glossary of Terms
Term Definition
Abdomen
The terminal section of an arthropod body.
Active channel
A portion of the valley bottom that can be distinguished based on the
three primary criteria of (i) channels defined by erosional and
depositional forms created by river processes, (ii) the upper elevation
limit at which water is contained within a channel, and (iii) portions of a
channel without mature woody vegetation. Braided systems have
multiple threads and channel bars that are all part of the active channel.
Alluvial
Refers to natural, channelized runoff from terrestrial terrain, and the
material borne or deposited by such runoff.
Assessment reach
The length of reach, ranging from 40 m to 200 m, where SDAM
indicators are measured.
Aquatic
macroinvertebrates
Invertebrate organisms that require aquatic environments for parts or
all of their life cycle and are visible without the use of a microscope (i.e.,
> 0.5 mm body length). Includes bottom dwelling or benthic
macroinvertebrates.
Bank
The side of an active channel, typically associated with a steeper side
gradient than the adjacent streambed, floodplain, or valley bottom.
Bankfull elevation
The elevation associated with a shift in the hydraulic geometry of the
channel and the transition point between the channel and the
floodplain. In unconstrained settings this is the height of the water in the
channel just when it begins to flow onto the floodplain.
Bankfull width
Width of the stream channel at bankfull elevation.
Braided system
A stream with a wide, relatively horizontal channel bed over which
during low flows, water forms an interlacing pattern of splitting into
numerous small conveyances that coalesce a short system downstream.
Same as multi-threaded system.
Canal
An artificial or formerly natural waterway used to convey water between
locations, possibly in both directions. Same as ditch.
Catchment
An area of land, bounded by a drainage divide, which drains to a channel
or waterbody. Synonymous with watershed.
Channel
A feature in fluvial systems consisting of a streambed and its opposing
banks which confines and conveys surface water flow. A braided system
consists of multiple channels, which may include inactive or abandoned
channels.
Confinement
The degree to which levees, terraces, hillsides, or canyon walls prevent
the lateral migration of a fluvial channel.
Culvert
A drain or covered channel that crosses under a road, pathway, or
railway.
Ditch
An artificial or formerly natural waterway used to convey water between
locations, possibly in both directions. Same as canal.
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Appendix A: Glossary of Terms
Dorsal
Upper surface of abdomen, or back when viewed from above.
Ephemeral
Channels that flow only in direct response to precipitation. Water
typically flows at the surface only during and/or shortly after large
precipitation events, the streambed is always above the water table, and
stormwater runoff is the primary water source.
Exuviae
The shed exoskeletons of arthropods typically left behind when an
aquatic larva or nymph becomes a winged adult. Singular: exuvium.
FAC
Facultative plants. They are equally likely to occur in wetlands and non-
wetlands.
FACU
Facultative upland plants. They usually occur in non-wetlands but are
occasionally found in wetlands.
FACW
Facultative wetland plants. They usually occur in wetlands but may occur
in non-wetlands.
Floodplain
The bench or broad flat area of a fluvial channel that corresponds to the
height of bankfull flow. It is a relatively flat depositional area that is
periodically flooded (as evidenced by deposits of fine sediment, wrack
lines, vertical zonation of plant communities, etc.).
Groundwater
Water found underground in soil, pores, or crevices in rocks.
Head
The anterior-most section of an arthropod body, where mouthparts,
eyes, and other sensory organs are located. The head is typically (but not
always) distinct from the rest of the body.
Hydrophyte
Plants that are adapted to inundated conditions found in wetlands and
riparian areas.
Hyporheic
The saturated zone under a river or stream, including the substrate and
water-filled spaces between the particles.
Indicator
For the AW and WM SDAMs, indicators are rapid, generally field-based
measurements that are used to predict streamflow duration class.
Instar
A phase between two periods of molting in arthropods (i.e., insects).
Intermittent
Channels that contain sustained flowing surface water for only part of
the year, typically during the wet season, where the streambed may be
below the water table and/or where the snowmelt from surrounding
uplands provides sustained flow. The flow may vary greatly with
stormwater runoff.
Larva
An immature stage of an insect or other invertebrates. Several insects
have aquatic larval stages, such as mayflies, stoneflies, and caddisflies.
Immature salamanders are sometimes also described as larvae. Plural:
larvae.
Low-flow channel
In braided systems, the main channel with the lowest thalweg elevation.
In intermittent or ephemeral reaches, the low-flow channel typically
retains flow longer than other channels.
57
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Appendix A: Glossary of Terms
Multi-threaded
system
A stream with a wide, relatively horizontal channel bed over which
during low flows, water forms an interlacing pattern of splitting into
numerous small conveyances that coalesce a short system downstream.
Same as braided system.
Nl
Plants that have no assigned wetland indicator (e.g., FACW, FACU) in a
specific National Wetland Plant List region.
OBL
Obligate wetland plants. They almost always occur in wetlands.
Ordinary high-
water mark
(OHWM)
The line on the shore established by the fluctuations of water and
indicated by physical characteristics, such as a clear natural line
impressed on the bank, shelving, changes in the character of the soil,
destruction of terrestrial vegetation, the presence of litter and debris, or
other appropriate means that consider the characteristics of the
surrounding areas. See 33 CFR 328.3. An OHWM is required to establish
lateral extent of U.S. Army Corps of Engineers jurisdiction in non-tidal
streams. See 33 CFR 328.4.
Perennial
Channels that contain flowing surface water continuously during a year
of normal rainfall, often with the streambed located below the water
table for most of the year. Groundwater typically supplies the baseflow
for perennial reaches, but the baseflow may also be supplemented by
stormwater runoff and/or snowmelt.
Pool
A depression in a channel where water velocity is slow and suspended
particles tend to deposit. Pools typically retain surface water longer than
other portions of intermittent or ephemeral streams.
Proleg
Leg-like extensions on the abdomen (never the thorax) of some insect
larvae. Typically, prolegs are unsegmented.
Pupa
An immature stage of insect orders with complete metamorphosis,
occurring between the larval and adult stage. Pupal stages are typically
immobile.
Reach
A length of stream that generally has consistent geomorphological and
biological characteristics.
Riffle
A shallow portion of a channel where water velocity and turbulence are
high, typically with coarse substrate (cobble and gravels). Riffles typically
dry out earlier than other portions of intermittent or ephemeral
streams, and harbor higher abundance and diversity of aquatic
macroinvertebrates.
Riparian
A transitional area between the channel and adjacent upland
ecosystems.
Rooted upland
plants
Plants rooted in the streambed that have wetland indicator statuses of
FAC, FACU, UPL, and Nl.
Runoff
Surface flow of water caused by precipitation or irrigation over
saturated or impervious surfaces.
Sclerotized
Hardened, as in the tough plates covering various body parts in some
arthropods.
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Appendix A: Glossary of Terms
Scour
Concentrated erosive action of flowing water in streams that removes
and carries material away from the bed or banks. Algal and invertebrate
abundance is typically depressed after scouring events.
Secondary channel
A subsidiary channel that branches from the main channel and trend
parallel or subparallel to the main channel before rejoining it
downstream.
Streambed
The bottom of a stream channel between the banks over which water
and sediment are transported during periods of flow.
Thalweg
The line along the deepest flowpath within the channel.
Thorax
The middle section of an arthropod body where legs and wing pads (if
present) are attached.
Tributary
A stream that conveys water and sediment to a larger waterbody
downstream.
UPL
Upland plants. They almost always occur in non-wetlands.
Uplands
Any portion of a drainage basin outside the river corridor.
Valley width
The portion of the valley within which the fluvial channel is able to
migrate without cutting into hill slopes, terraces, or artificial structures.
Ventral
Underside of abdomen, or belly when viewed from below.
Watershed
An area of land, bounded by a drainage divide, which drains to a channel
or waterbody. Synonymous with catchment.
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Appendix B. Guide to Aquatic Invertebrate Orders and Families in the Western United States
Appendix B. Guide to Aquatic Invertebrate Orders and Families in the Western
United States
For the AW and WM SDAMs, assessors need to identify perennial indicator taxa to the family in the
field. They also need to be able to distinguish these families from other invertebrate taxa that may
appear similar but are not used as indicators in the SDAMs. This appendix will help assessors recognize
these taxa and how to distinguish them from other aquatic macroinvertebrates.
Available online resources that have informed this appendix include:
• Macroinvertebrates.org. an online reference for identification of aquatic insects of eastern
North America. Although this website is focused on the East, it covers all the orders and families
of aquatic macroinvertebrates used as indicators in the AW and WM SDAMs.
• NAAMDRC: North America Macroinvertebrate Digital Reference Collection . maintained by the
U.S. Geological Survey (Walters et al. 2017).
Ephemeroptera (mayfly) larvae
Mayflies have plate-like gills along the dorsal side of their abdomen, which typically ends with three
cerci, or "tails" (some species appear to have only two cerci, and cerci may break off during sampling).
Legs always end in a single tarsal claw (never two claws). Mayflies have an aquatic larval stage that
goes through direct metamorphosis into a short-lived terrestrial adult stage. There is no pupal stage.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Perennial indicator Ephemeroptera families
Ephemerellidae (spiny
crawler mayflies)
This family is distinguished
from other mayflies by the
lack of gills in the second
abdominal segment. Overall,
ephemerellid mayflies have
a flattened appearance (but
not nearly so flattened as
the Heptageniidae). A live
larvae feeling threatened
may be observed to assume
"scorpion" posture, raising
its caudal filaments above its
head and wielding them like swords, This specimen is in the genus Serrate I la.
Heptageniidae
(flathead mayflies)
Heptageniidae have a
flattened appearance,
and cling to the
undersides of cobbles
in fast-flowing water.
Still, they have the
single tarsal claws,
abdominal gills, and
three cerci typical of
mayflies. This
specimen is
Rhithrogena.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Leptohyphidae (little stout crawler mayflies)
Leptohyphidae have a pair of enlarged, hardened (i.e., sclerotized) abdominal gills that can cover the
smaller, translucent abdominal gills. The family typically has three cerci, but the right one has broken
off in this specimen. This specimen is a species of Tricorythodes.
Caenidae have similar enlarged gills on abdominal segment two that cover the more anterior gills
("operculate" or "semioperculate" gills). However, in Leptohyphidae, these operculate gills are roughly
triangular or oval, whereas in Caenidae, these gills are square-shaped.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Leptophlebiidae (prong-gilled mayflies)
Prong-gilled mayflies have distinctive gills that either appear as thin, forked filaments, oval double-
layered gills, or small tufts.
Other common Ephemeroptera families
Baetidae (small minnow mayflies)
Baetidae have a streamlined appearance and appears to swim like a minnow. The abdominal gills and
three cerci (tails) are conspicuous in this photo. Wingpads are usually visible. This specimen is Baetis.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Caenidae (square-gilled mayflies)
Like Leptohyphidae. Caenidae have enlarged operculate gills that cover other gills on the abdomen.
However, in Caenidae, these gills are square-shaped, whereas in Leptohyphidae, the gills are triangular
or oval. This specimen is in the genus Caenis.
Ephemeridae (burrowing mayflies)
Ephemeridae prefer to burrow in soft, silty sediments. Although this family is more common in lakes, it
may be found in pools and slow-moving portions of rivers. The long feathery gills and single tarsal
claws make this recognizable as a mayfly. This specimen is Hexagenia limbata.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Plecoptera (stonefly) larvae
Stoneflies have tuft-like gills on the thorax (not along the abdomen), two (not one) tarsal claw at the
end of each leg, and always has two (never three) cerci, making them easily distinguished from
mayflies. Stoneflies have an aquatic larval stage that goes through direct metamorphosis into a short-
lived terrestrial adult stage. There is no pupal stage.
Perennial indicator Plecoptera families
Chloroperlidae (green stoneflies)
Like a few other families of stoneflies, green stoneflies lack gills and have a plain, unpatterned thorax.
Wingpads are parallel to the mainline of the body. Cerci are relatively short (less than three-quarters of
the length of the abdomen). The hind-legs should reach the tip of the abdomen when extended. This
specimen is in the genus Alloperla.
The mouthparts provide an important diagnostic feature of this family: the glossae are much shorter
than the paraglossae.
Glossae
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Chloroperlidae are most likely to be confused with other smaller, unpatterned stoneflies that lack gills:
• Leuctridae have mouthparts with glossae nearly equal in size to the paraglossae, giving the
appearance of three notches on the lower lip, and the hind wingpads are usually much longer
than they are wide. If the hind legs are extended, they do not reach the tip of the abdomen.
• Capniidae have a similar arrangement of mouthparts as Leuctridae. The cerci are usually the
same length as the abdomen. If the hind legs are extended, they do not reach the tip of the
abdomen. In top-view, the margin of the abdomen appears like a zigzag.
Perlidae (common stoneflies)
Perlidae (common stoneflies) are large and conspicuous, often with ornate patterns on the head and
thorax. Wingpads are usually visible. Perlidae have gills on the thorax. This specimen is Claasenia
sabulosa.
Perlodidae look similar but lack gills and have a different arrangement of mouthparts.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Other common Plecoptera families
Leuctridae (roll-winged stoneflies)
Leuctridae resemble Chloroperlidae. in that they lack gills and have an unpatterned thorax. However,
the cerci are typically as long as the abdomen. Leuctridae have mouthparts with glossae nearly equal in
size to the paraglossae, giving the appearance of three notches on the lower lip, and the hind wingpads
are usually much longer than they are wide (similar to Capniidae; see image below). If the hind legs are
extended, they do not reach the tip of the abdomen. This specimen is in the genus Leuctra.
Capniidae (small winter stoneflies)
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Capniidae (smaii winter stoneflies). Capniidae resemble Chloroperlidae. but they have a different
arrangement of mouthparts (with glossae and paraglossae about the same length, as in Leuctridae).
The cerci are usually the same length as the abdomen. If the hind legs are extended, they do not reach
the tip of the abdomen. In top-view, the margin of the abdomen appears like a zigzag. This specimen is
in the genus Allocapnia.
Nemouridae (spring stoneflies)
Nemouridae are relatively small, and this family contains species that are well adapted to intermittent
streams in the West. This specimen is a species of Soyedina.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Perlodidae (springflies)
Paraglossae
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Peltoperlidae (roach-like stoneflies)
Even moreso than other stonefly families, Peltoperlidae have a roach-like appearance. This specimen is
a species of Sierraperla.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Trichoptera (caddisfly) larvae and pupae
Caddisfly larvae have filamentous gills on the ventral side of the abdomen (as opposed to the plate-like
gills on the dorsal side of the abdomen, as seen with mayflies). Their abdomen ends in two anal
prolegs, each with a sclerotized hook, rather than long tail-like cerci. No wingpads are visible, but the
thorax is usually dark and hardened (i.e., sclerotized) on the top, with the abdomen being completely
membranous. Caddisfly larvae are generally C-shaped (less evident in this pudgy specimen).
Many caddisfly larvae build portable cases out of pebbles, sand, or organic matter. Some families live
in fixed retreats. A few families are free-living and build neither cases nor retreats. However, all
caddisflies build cases for their aquatic pupal stage, from which they emerge as short-lived terrestrial
adults.
Perennial indicator Trichoptera families
Brachycentridae (humpless casemakers)
Unlike most other caddisflies Brachycentridae lack a hump on abdominal segment one. The
mesonotum (i.e., the second thoracic segment) is sclerotized, whereas the metanotum (i.e., the third
thoracic segment) is mostly membranous. The distinctive case is made of plant material arranged in
parallel layers, either as a tapered cylinder or a four-sided "log cabin" tube. This specimen is in the
genus Brachycentrus.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Glossosomatidae (saddle casemakers)
The mesonotum and metanotum of Glossosomatidae are both membranous, and each are adorned
with three pairs of setae (hairs). There is a small sclerite on the ninth abdominal segment. The unique
case has a dome made of stones, with a ventral strap made of fine sand. The case has openings on
both the anterior and posterior ends. This specimen is in the genus Glossosoma.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Hydropsychidae (common netspinners)
Hydropsychidae (net-spinner caddisflies). This group lives within nets in fixed locations out of silk,
pebbles, and other materials. These nets are usually located in fast-flowing areas and on large, stable
particles (such as large cobbles and boulders). Like a spider in a web, they wander about the retreat to
catch prey that gets caught in the net. Turning over a boulder typically destroys these nets, but the
larvae may be found crawling among the remains of the net.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Rhyacophilidae (free-iivirig caddisflies)
Rhyacophilidae (free-roaming caddisflies). This family is usually found wandering freely on the
undersides of boulders and cobbles, actively hunting for prey. Abdominal gills are present, but not
evident in this photo. Notice the long anal prolegs, which have large sclerotized claws. Some species of
this family have a striking blue-green coloration, which may fade when preserved in alcohol.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Other common Trichoptera families
Limnephilidae (northern casemakers)
Limnephilids are a large group of roaming caddisflies that build cases out of diverse materials, such as
pebbles, sand, leaf segments, and twigs. This specimen is a mature Dicosmoecus gilvepes.
75
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Lepidostomatidae. This specimen (Lepidostoma
species) has a case made of twigs.
Lepidostomatidae (scaley-
mouthed caddisflies)
Lepidostomatidae. This
specimen (Lepidostoma
species) builds its case out
of leaf segments and silk.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Hydroptilidae (rnicrocadd isfl ies)
These are small caddisflies (2-4 mm long) that build purse-like cases out of sand grains. They may be
very abundant, but hard to see due to their size. This specimen is a species of Hydroptila,
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Helicopsychidae (snail casemaker caddisflies)
Helicopsychidae (snail case-makers) are unusual in that they build spiral-shaped, snail-like cases. This
specimen is Helicopsyche.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Coleoptera (beetle) larvae and adults
Adult beetles are among the most recognizable insects due to their conspicuous hardened forewings
(elytra). The larvae can be identified by their eye spots, the absence of lateral gills (in most families),
and the legs, which typically have 4 or 5 segments.
Perennial indicator Coleoptera families
Elmidae (riffle beetles)
Elmidae (riffle beetles). These small insect larvae have a completely sclerotized body, unlike caddisflies
which only have the thorax sclerotized. Also, there are no gills along the abdomen, as in the caddisflies.
Instead, the gills are found at the tip of the abdomen (where the caddisfly's two anal prolegs with
hooks would be found), within a covered chamber (the lid is called an operculum). This image shows a
Stenelmis larva.
The C-shaped larvae may be confused with the larvae of caddisflies. However, elmid larvae are
completely sclerotized, whereas caddisfly larvae have at most only a few sclerotized abdominal
segments (and sometimes none). Furthermore, Elmidae lack the anal hooks that characterize caddisfly
larvae.
The larvae may also resemble those of the non-biting midges (Diptera: Chironomidae, described
below). Elmid larvae always have three pairs of true (segmented) legs, whereas Chironomidae have
unsegmented prolegs. Additionally, chironomid larvae lack the sclerotization of Elmidae.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Adult riffle beetles are small (~2-4 mm) and typically have distinctive stripes of indentations along their
elytra. Their legs end in 5-segmented tarsi, which end in large claws. They typically have thread-like
antennae. This image shows Stenelmis.
Adult elmid beetles may be confused for other diminutive aquatic beetles, such as some of the smaller
species of Dytiscidae. However, dytiscids have hairs adapted for swimming on their legs, which are
absent from elmids.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Other common Coleoptera families
Dytiscidae (predaceous diving beetles)
Dytiscidae (diving beetles), Larvae of this group lack
the gills and tarsal claws that characterize mayflies
and stoneflies. Their thorax is not as strongly
sclerotized as with caddisflies; conversely, caddisfly
larvae never have sclerotized abdomens, unlike
most beetle larvae. Adults are usually much larger
than Elmidae. Dytiscid adults have hairs on their legs
that help them swim. This specimen is a species of
Agabus.
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Haliplidae (crawling water beetles)
Both adults and larvae of this beetle
family are considered aquatic. Larvae
usually have legs with 4-5 segments
and a single tarsal claw. Instead of
compound eyes, the larvae have eye
spots. Lateral gills are usually absent
and mature (last instar) larvae have
long dorsal projections from thoracic
and abdominal segments. Generally,
beetle larvae can look superficially like
caddisfly larvae (see below); however,
their bodies usually show a greater
degree of sclerotization (including the
abdomen), and they usually have
prominent chewing and/or piercing
mouthparts, though Haliplid larvae
have less prominent mouthparts compared to other beetle families (e.g., Gyrinidae, Dytiscidae, and
Hydrophilidae). Haliplid adults swim slowly and clumsily by moving their legs alternately (rather than in
unison like predaceous diving beetles) and are usually found crawling among vegetation rather than
swimming. Adults usually also have highly patterned (splotchy) elytra (hardened forewings). In
addition, Haliplid adults have expanded hind coaxae (first segment of last leg), which have been
expanded into a broad, flat plate on the ventral surface, covering the first 2 or 3 abdominal segments
and most of the hind femora (third segment of last leg).
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Other Insect Orders
Assessors need to recognize other aquatic insect orders and differentiate them from the EPT orders
shown above. A few commonly encountered insects are shown here. These organisms contribute to
the total count of aquatic macroinvertebrates but are not counted towards the EPT indicator.
Diptera: Chironomidae (non-biting midges)
Culicidae (mosquito
larvae) hang at the
water surface and
breathe air through a
tube at the tip of the
abdomen. When
disturbed, they
"wriggle" and swim
away from the surface
(leading to the
common name
"wrigglers"). Photo
credit is the Missouri
Department of
Conservation.
Superficially, the larvae of this family of true flies
resemble those of Trichoptera. thanks to the C-shaped
body and the posterior prolegs that resemble hooks.
Furthermore, several species are found in tubes of silk
lined with silt and muck, which can resemble a caddis
case. While generally smaller, the sizes of the two
groups can overlap considerably. Chironomidae are best
distinguished from caddisflies by the lack of abdominal
gills, the soft thorax, and the lack of true legs (i.e., three
pairs of sclerotized, jointed legs). Some chironomids
have bright red bodies, thanks to hemoglobin pigment,
which helps them survive in low-oxygen conditions.
Diptera: Culicidae (mosquitos)
*
I
W\
' I
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Appendix B, Guide to Aquatic invertebrate Orders and Families in the Western United States
Megaloptera: Corydalidae (hellgrammites, dobsonflies)
This large, centipede-like insect larva has distinctive lateral filaments along the sides of the abdomen.
They lack the C-shaped bodies of caddisflies, and the lateral filaments contrast with the gills on the
ventral side of the abdomens of caddisflies. Although most species are associated with perennial
streams, some species in California and Arizona persist in intermittent streams by building a chamber
in sandy substrate beneath boulders, where they wait out the dry season; as a result, they are among
the first invertebrates to be observed after the onset of flow.
Other invertebrates
Margaritiferidae and
Unionidae (freshwater
mussels)
Anodonta californiensis
(California floater) is a
freshwater mussel found in
streams throughout the
West. Most freshwater
mussels are imperiled and
should not be collected or
disturbed during
assessments.
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Appendix C. Field Forms
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Appendix CI: Combined field form for the AW and WM SDAMs
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Arid West and Western Mountains SDAMs Field Form
October 2024
Page 1 of 7
Arid West and Western Mountains SDAMs
General site information
Project name or number:
Region ~ Arid West
~ Western Mountains
Site code or identifier:
Assessor(s):
Waterway name:
Visit date:
Current weather conditions (check one): Notes on current or recent
~ Storm/heavy rain weather conditions (e.g.,
~ Steady rain precipitation in prior week):
~ Intermittent rain
~ Snowing
~ Cloudy ( % cover)
~ Clear/sunny
Coordinates at downstream end
(decimal degrees):
Lat (N):
Long (E):
Datum:
Surrounding land-use within 100 m (check one or two):
~ Urban/industrial/residential
~ Agricultural (farmland, crops, vineyards, pasture)
~ Developed open-space (e.g., golf course)
~ Forested
~ Other natural
~ Other:
Describe reach boundaries:
Mean bankfull channel
width (m):
(Indicator 1)
Reach length (m):
40x width
min 40 m
max 200 m
Site photographs:
Enter photo ID or check if completed.
Tod down: Mid down:
Mid up: Bottom up:
Disturbed or difficult conditions (check all that apply):
~ Recent flood or debris flow ~ Drought
~ Stream modifications (e.g., channelization) ~ Vegetation removal/limitations
~ Diversions ~ Other (explain in notes)
~ Discharges ~ None
Notes on disturbances or difficult site conditions:
Observed hydrology: Comments on observed hydrology:
% of reach with surface flow
% of reach with sub-surface or surface flow
# of isolated pools
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Arid West and Western Mountains SDAMs Field Form
October 2024
Site sketch:
Page 2 of 7
1. Mean bankfull channel width (m) (AW and WM) (nearest 0.1 m, copy from first page of field form)
Notes about mean bankfull channel width:
Aquatic macroinvertebrate indicators
Collect aquatic macroinvertebrates from at least 6 locations in the assessment reach, searching all suitable habitats on the
streambed (including dry habitats, if present).
Aquatic macroinvertebrate indicators are used in both the AW and WM SDAMs.
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Arid West and Western Mountains SDAMs Field Form
October 2024 Page 3 of 7
2. Aquatic macroinvertebrates: Abundance of Ephemeroptera, Plecoptera, and Trichoptera (WM
only)
Determine total abundance of individuals in the orders of Ephemeroptera, Plecoptera, and Trichoptera (EPT), such that no
one family counts for more than 11 individuals in the total:
Mark the appropriate box for the number of EPT individuals observed.
~ No EPT detected ~ 10 to 19 EPT individuals
~ 1 to 4 EPT individuals ~ 20 or more EPT individuals
~ 5 to 9 EPT individuals
Check if applicable: ~ No aquatic macroinvertebrates in assessment area
Notes on abundance of EPT indicator:
3. Aquatic macroinvertebrates: Abundance of perennial indicator taxa (AW and WM)
Determine total abundance of individuals in perennial indicator families listed below, such that no one family counts for
more than 11 individuals in the total.
Ephemeroptera Plecoptera Trichoptera Coleoptera
Ephemerellidae (spiny
crawler mayflies)
Heptageniidae (flathead
mayflies)
Leptohyphyidae (little
stout crawler mayflies)
Leptophlebiidae (prong-
gilled mayflies)
Chloroperlidae (green
stoneflies)
Perlidae (common
stoneflies)
Brachycentridae
(humpless casemakers)
Glossosomatidae (saddle
casemakers)
Hydropsychidae
(common netspinners)
Rhyacophilidae (free-
living caddisflies)
Elmidae (riffle beetles)
Mark the appropriate box for the number of perennial indicator individuals observed.
~ No perennial indicator taxa detected ~ 10 to 19 perennial indicator individuals
~ 1 to 4 perennial indicator individuals ~ 20 or more perennial indicator individuals
~ 5 to 9 perennial indicator individuals
Check if applicable: ~ No aquatic macroinvertebrates in assessment area
Notes on perennial indicator taxa:
4. Slope (AW and WM)
Using a clinometer or other device, record the slope as a percent, up to the nearest half-percent.
Notes about slope:
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Arid West and Western Mountains SDAMs Field Form
October 2024
Page 4 of 7
5. Shading (WM only)
At the center of three transects, use a convex spherical densiometer to record the number of points covered by trees,
canyon walls, buildings, or other structures that provide shade (up to 17 points per location). Calculate percent shading as
the percentage of points covered by such structures (total points covered divided by 204).
Percent shading:
Downstream Middle transect Upstream transect
transect
Facing upstream
117
117
117
Facing right bank
117
117
117
Total number of points covered:
Facing downstream
117
117
117
/204 * 100%
Facing left bank
117
117
117
Notes on shading:
6. Number of hydrophytic plant species (AW and WM)
Record up to 6 hydrophytic plant species (FACW or OBL in the appropriate regional wetland plant list, depending on
location) within the assessment area: within the channel or up to one half-channel width outside the channel. Explain in
notes if species has an odd distribution (e.g., one individual or small patch, long-lived species solely represented by
seedlings, or long-lived species solely represented by specimens in decline), or if there is uncertainty about the
identification. Enter photo ID or check if photos are taken.
Number of hydrophytic plant species identified from the assessment reach without odd distribution. Enter
zero if none were found.
Check if applicable: ~ No vegetation in assessment area
Species
Odd
distribution?
Notes
Photo ID
Notes on hydrophytic vegetation:
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Arid West and Western Mountains SDAMs Field Form
October 2024
Page 5 of 7
7. Prevalence of rooted upland plants in the streambed (AW and WM)
8. Algal cover (AW only)
Mark the appropriate percent of the streambed covered by live or dead algae on the streambed.
~ Not detected ~ 10 to 40% cover
~ <2% cover ~ >40% cover
~ 2 to 10% cover ~ Check here if algae exclusively appears to have been deposited from an upstream
source, and no local growth is evident.
Notes on algal cover on the streambed:
9. Differences in vegetation (AW and WM)
(0-3)
Half-scores (0.5,
1.5, 2.5) are
allowed.
Compare the composition and density of plants growing on the banks and riparian areas to plants in
the adjacent uplands. For this indicator, an upland species is not defined by its wetland indicator
status, but rather by its location relative to the channel.
0. (Poor) No compositional or density differences in vegetation are present between the banks and
the adjacent uplands.
1. (Weak) Vegetation growing along the reach may occur in greater densities or grow more
vigorously than vegetation in the adjacent uplands, but there are no dramatic compositional
differences between the two.
2. (Moderate) A distinct riparian corridor exists along part of the reach. Riparian vegetation is
interspersed with upland vegetation along the length of the reach.
3. (Strong) Dramatic compositional differences in vegetation are present between the banks and
the adjacent uplands. A distinct riparian vegetation corridor exists along the entire reach.
Riparian, aquatic, or wetland species dominate the length of the reach.
Notes on differences in vegetation:
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Arid West and Western Mountains SDAMs Field Form
October 2024
Page 6 of 7
10. Riffle-pool sequence (AW and WM)
.(0-3)
Half-scores (0.5,1.5,
2.5) are allowed.
Evaluate the prevalence of riffles, pools, and other microhabitats in the streambed.
0 (Poor) No riffle-pool sequences observed.
1 (Weak) Mostly has areas of pools or riffles.
2 (Moderate) Represented by a less frequent number of riffles and pools. Distinguishing the
transition between riffles and pools is difficult to observe.
3 (Strong) Demonstrated by a frequent number of structural transitions (e.g., riffles followed by
pools) along the entire reach. There is an obvious transition between riffles and pools.
11. Particle size or stream substrate sorting (WM only)
.(0-3)
Half scores (0.75,
2.25) are allowed.
Evaluate the extent of substrate sorting. Compare substrate on the channel bed to the banks and
adjacent floodplain. Look for sorting within the channel bed (e.g., along bars and islands).
0 (Poor) Particle sizes in the channel are similar or comparable to particle sizes in areas close to
but not in the channel. Substrate sorting is not readily observed in the channel.
1.5 (Moderate) Particle sizes in the channel are moderately similar to particle sizes in areas close
to but not in the channel. Various sized substrates are present in the channel and are
represented by a higher ratio of larger particles (gravel/cobble; coarse sand in low-gradient
streams).
3 (Strong) Particle sizes in the channel are noticeably different from particle sizes in areas close
to but not in the channel. There is a clear distribution of various sized substrates in the channel
with finer particles accumulating in the pools, and larger particles accumulating in the
riffles/runs
Notes about substrate sorting:
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Arid West and Western Mountains SDAMs Field Form
October 2024
Page 7 of 7
Photo log
Indicate if any other photographs taken during the assessment:
Photo ID
Description
Additional notes about the assessment:
Model classification:
D Ephemeral
~ At least intermittent
~ Intermittent
~ Less than perennial
~ Perennial
~ Needs more information
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Appendix C2: Field form for the AW SDAM
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Arid West SDAM Field Form
October 2024
Page 1 of 5
Arid West Streamflow Duration Assessment Method
General site information
Project name or number:
Site code or identifier:
Assessor( s):
Waterway name:
Visit date:
Current weather conditions (check one): Notes on current or recent
~ Storm/heavy rain weather conditions (e.g.,
~ Steady rain precipitation in prior week):
~ Intermittent rain
~ Snowing
~ Cloudy ( % cover)
~ Clear/sunny
Coordinates at downstream end
(decimal degrees):
Lat(N):
Long (E):
Datum:
Surrounding land-use within 100 m (check one or two):
~ Urban/industrial/residential
~ Agricultural (farmland, crops, vineyards, pasture)
~ Developed open-space (e.g., golf course)
~ Forested
~ Other natural
~ Other:
Describe reach boundaries:
Mean bankfull channel
width (m):
(Indicator 1)
Reach length (m):
40x width
min 40 m
max 200 m
Site photographs:
Enter photo ID or check if completed.
Tod down: Mid down:
Mid up: Bottom up:
Disturbed or difficult conditions (check all that apply):
~ Recent flood or debris flow ~ Drought
~ Stream modifications (e.g., channelization) ~ Vegetation removal/limitations
~ Diversions ~ Other (explain in notes)
~ Discharges ~ None
Notes on disturbances or difficult site conditions:
Observed hydrology: Comments on observed hydrology:
% of reach with surface flow
% of reach with sub-surface or surface flow
# of isolated pools
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Arid West SDAM Field Form
October 2024
Site sketch:
Page 2 of 5
1. Mean bankfull channel width
m) (nearest 0.1 m, copy from first page of field form)
Notes about mean bankfull channel width:
2. Aquatic macroinvertebrates: Abundance of perennial indicator taxa
Collect aquatic macroinvertebrates from at least 6 locations in the assessment reach, searching all suitable habitats on the
streambed (including dry habitats, if present). Determine total abundance of individuals in perennial indicator families listed
below, such that no one family counts for more than 11 individuals in the total.
Ephemeroptera
Plecoptera
Trichoptera
Coleoptera
Ephemerellidae (spiny
crawler mayflies)
Heptageniidae (flathead
mayflies)
Leptohyphyidae (little
stout crawler mayflies)
Leptophlebiidae (prong-
gilled mayflies)
Chloroperlidae (green
stoneflies)
Perlidae (common
stoneflies)
Brachycentridae
(humpless casemakers)
Glossosomatidae (saddle
casemakers)
Hydropsychidae
(common netspinners)
Rhyacophilidae (free-
living caddisflies)
Elmidae (riffle beetles)
Mark the appropriate box for the number of perennial indicator individuals observed.
~ No perennial indicator taxa detected ~ 10 to 19 perennial indicator individuals
~ 1 to 4 perennial indicator individuals ~ 20 or more perennial indicator individuals
~ 5 to 9 perennial indicator individuals
Check if applicable: ~ No aquatic macroinvertebrates in assessment area
Notes on perennial indicator taxa:
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Arid West SDAM Field Form
October 2024
Page 3 of 5
3. Slope
Using a clinometer or other device, record the slope as a percent, up to the nearest half-percent.
Notes about slope:
4. Number of hydrophytic plant species
Record up to 6 hydrophytic plant species (FACW or OBL in the appropriate regional wetland plant list, depending on
location) within the assessment area: within the channel or up to one half-channel width outside the channel. Explain in
notes if species has an odd distribution (e.g., one individual or small patch, long-lived species solely represented by
seedlings, or long-lived species solely represented by specimens in decline), or if there is uncertainty about the
identification. Enter photo ID or check if photos are taken.
Number of hydrophytic plant species identified from the assessment reach without odd distribution. Enter
zero if none were found.
Check if applicable: ~ No vegetation in assessment area
Species
Odd
distribution?
Notes
Photo ID
Notes on hydrophytic vegetation:
5. Prevalence of rooted upland plants in the streambed
(0-3)
Half-scores (0.5,1.5,
and 2.5) are
allowed.
Evaluate the prevalence of rooted upland plants (i.e., plants rated as FAC, FACU, UPL, Nl, or not
listed in the regionally appropriate National Wetland Plant List) in the streambed.
0 (Poor) Rooted upland plants are prevalent within the streambed/thalweg.
1 (Weak) Rooted upland plants are consistently dispersed throughout the streambed/thalweg.
2 (Moderate) There are a few rooted upland plants present within the streambed/thalweg.
3 (Strong) Rooted upland plants are absent from the streambed/thalweg.
Upland Species
Notes
Photo ID
Notes on rooted upland plants:
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Arid West SDAM Field Form
October 2024
Page 4 of 5
6. Algal cover
Mark the appropriate box for the percent of the streambed covered by live or dead algae on the streambed.
~ Not detected ~ 10 to 40% cover
~ <2% cover ~ >40% cover
~ 2 to 10% cover ~ Check here if algae exclusively appears to have been deposited from an upstream
source, and no local growth is evident.
Notes on algal cover on the streambed:
7. Differences in vegetation
(0-3)
Half-scores (0.
1.5, 2.5) are
allowed.
5,
Compare the composition and density of plants growing on the banks and riparian areas to plants in
the adjacent uplands. For this indicator, an upland species is not defined by its wetland indicator
status, but rather by its location relative to the channel.
0 (Poor) No compositional or density differences in vegetation are present between the banks
and the adjacent uplands.
1 (Weak) Vegetation growing along the reach may occur in greater densities or grow more
vigorously than vegetation in the adjacent uplands, but there are no dramatic compositional
differences between the two.
2 (Moderate) A distinct riparian corridor exists along part of the reach. Riparian vegetation is
interspersed with upland vegetation along the length of the reach.
3 (Strong) Dramatic compositional differences in vegetation are present between the banks and
the adjacent uplands. A distinct riparian vegetation corridor exists along the entire reach.
Riparian, aquatic, or wetland species dominate the length of the reach.
Notes on differences in vegetation:
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Arid West SDAM Field Form
October 2024
Page 5 of 5
8. Riffle-pool sequence
(0-3)
Half-scores (0.5,1.5,
2.5) are allowed.
Evaluate the prevalence of riffles, pools, and other microhabitats in the streambed.
0 (Poor) No riffle-pool sequences observed.
1 (Weak) Mostly has areas of pools or riffles.
2 (Moderate) Represented by a less frequent number of riffles and pools. Distinguishing the
transition between riffles and pools is difficult to observe.
3 (Strong) Demonstrated by a frequent number of structural transitions (e.g., riffles followed by
pools) along the entire reach. There is an obvious transition between riffles and pools.
Notes about riffle-pool sequence:
Photo log
Indicate if any other photographs taken during the assessment:
Photo ID
Description
Additional notes about the assessment:
Model classification:
D Ephemeral
~ At least intermittent
~ Intermittent
~ Less than perennial
~ Perennial
~ Needs more information
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Appendix C3: Field form for the WM SDAM
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Western Mountains SDAM Field Form
October 2024
Page 1 of 6
Western Mountains Streamflow Duration Assessment Method
General site information
Project name or number:
Site code or identifier:
Assessor( s):
Waterway name:
Visit date:
Current weather conditions (check one): Notes on current or recent
~ Storm/heavy rain weather conditions (e.g.,
~ Steady rain precipitation in prior week):
~ Intermittent rain
~ Snowing
~ Cloudy ( % cover)
~ Clear/sunny
Coordinates at downstream end
(decimal degrees):
Lat (N):
Long (E):
Datum:
Surrounding land-use within 100 m (check one or two):
~ Urban/industrial/residential
~ Agricultural (farmland, crops, vineyards, pasture)
~ Developed open-space (e.g., golf course)
~ Forested
~ Other natural
~ Other:
Describe reach boundaries:
Mean bankfull channel
width (m):
(Indicator 1)
Reach length (m):
40x width
min 40 m
max 200 m
Site photographs:
Enter photo ID or check if completed.
Tod down: Mid down:
Mid up: Bottom up:
Disturbed or difficult conditions (check all that apply):
~ Recent flood or debris flow ~ Drought
~ Stream modifications (e.g., channelization) ~ Vegetation removal/limitations
~ Diversions ~ Other (explain in notes)
~ Discharges ~ None
Notes on disturbances or difficult site conditions:
Observed hydrology: Comments on observed hydrology:
% of reach with surface flow
% of reach with sub-surface or surface flow
# of isolated pools
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Western Mountains SDAM Field Form
October 2024
Site sketch:
Page 2 of 6
1. Mean bankfull channel width (m) (nearest 0.1 m, copy from first page of field form)
Notes about mean bankfull channel width:
Aquatic macroinvertebrate indicators
Collect aquatic macroinvertebrates from at least 6 locations in the assessment reach, searching all suitable habitats on the
streambed (including dry habitats, if present).
2. Aquatic macroinvertebrates: Abundance of Ephemeroptera, Plecoptera, and Trichoptera
Determine total abundance of individuals in the orders of Ephemeroptera, Plecoptera, and Trichoptera (EPT), such that no
one family counts for more than 11 individuals in the total.
Mark the appropriate box for the number of EPT individuals observed.
~ No EPT detected ~ 10 to 19 EPT individuals
~ 1 to 4 EPT individuals ~ 20 or more EPT individuals
~ 5 to 9 EPT individuals
Check if applicable: ~ No aquatic macroinvertebrates in assessment area
Notes on abundance of EPT indicator:
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Western Mountains SDAM Field Form
October 2024
Page 3 of 6
3. Aquatic macroinvertebrates: Abundance of perennial indicator taxa
Determine total abundance of individuals in perennial indicator families listed below, such that no one family counts for
more than 11 individuals in the total.
Ephemeroptera Plecoptera Trichoptera Coleoptera
Ephemerellidae (spiny
crawler mayflies)
Heptageniidae (flathead
mayflies)
Leptohyphyidae (little
stout crawler mayflies)
Leptophlebiidae (prong-
gilled mayflies)
Chloroperlidae (green
stoneflies)
Perlidae (common
stoneflies)
Brachycentridae
(humpless casemakers)
Glossosomatidae (saddle
casemakers)
Hydropsychidae
(common netspinners)
Rhyacophilidae (free-
living caddisflies)
Elmidae (riffle beetles)
Mark the appropriate box for the number of perennial indicator individuals observed.
~ No perennial indicator taxa detected ~ 10 to 19 perennial indicator individuals
~ 1 to 4 perennial indicator individuals ~ 20 or more perennial indicator individuals
~ 5 to 9 perennial indicator individuals
Check if applicable: ~ No aquatic macroinvertebrates in assessment area
Notes on perennial indicator taxa:
4. Slope
Using a clinometer or other device, record the slope as a percent, up to the nearest half-percent.
Notes about slope:
5. Shading
At the center of three transects, use a convex spherical densiometer to record the number of points covered by trees,
canyon walls, buildings, or other structures that provide shade (up to 17 points per location). Calculate percent shading as
the percentage of points covered by such structures (total points covered divided by 204).
Percent shading:
Downstream Middle transect Upstream
transect transect
Facing upstream
/17
/17
/17
Facing right bank
117
117
117
Total number of points covered:
Facing downstream
117
117
117
/204 * 100%
Facing left bank
117
117
117
Notes on shading:
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Western Mountains SDAM Field Form
October 2024
Page 4 of 6
6. Number of hydrophytic plant species
Record up to 6 hydrophytic plant species (FACW or OBL in the appropriate regional wetland plant list, depending on
location) within the assessment area: within the channel or up to one half-channel width outside the channel. Explain in
notes if species has an odd distribution (e.g., one individual or small patch, long-lived species solely represented by
seedlings, or long-lived species solely represented by specimens in decline), or if there is uncertainty about the
identification. Enter photo ID or check if photos are taken.
Number of hydrophytic plant species identified from the assessment reach without odd distribution. Enter
zero if none were found.
Check if applicable: ~ No vegetation in assessment area
Species
Odd
distribution?
Notes
Photo ID
Notes on hydrophytic vegetation:
7. Prevalence of rooted upland plants in the streambed
(0-3)
Evaluate the prevalence of rooted upland plants (i.e., plants rated as FAC, FACU, UPL, or not
listed in the regionally appropriate National Wetland Plant List) in the streambed.
Half-scores (0.5,1.5, and
2.5) are allowed.
0 (Poor) Rooted upland plants are prevalent within the streambed/thalweg.
1 (Weak) Rooted upland plants are consistently dispersed throughout the
streambed/thalweg.
2 (Moderate) There are a few rooted upland plants present within the streambed/thalweg.
3 (Strong) Rooted upland plants are absent from the streambed/thalweg.
Upland Species
Notes
Photo ID
Notes on rooted upland plants:
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Western Mountains SDAM Field Form
October 2024 Page 5 of 6
8. Differences in vegetation
(0-3)
Half-scores (0.5,
1.5, 2.5) are
allowed.
Compare the composition and density of plants growing on the banks and riparian areas to plants in
the adjacent uplands. For this indicator, an upland species is not defined by its wetland indicator
status, but rather by its location relative to the channel.
0 (Poor) No compositional or density differences in vegetation are present between the banks
and the adjacent uplands.
1 (Weak) Vegetation growing along the reach may occur in greater densities or grow more
vigorously than vegetation in the adjacent uplands, but there are no dramatic compositional
differences between the two.
2 (Moderate) A distinct riparian corridor exists along part of the reach. Riparian vegetation is
interspersed with upland vegetation along the length of the reach.
3 (Strong) Dramatic compositional differences in vegetation are present between the banks and
the adjacent uplands. A distinct riparian vegetation corridor exists along the entire reach.
Riparian, aquatic, or wetland species dominate the length of the reach.
Notes on differences in vegetation:
9. Riffle-pool sequence
.(0-3)
Half-scores (0.5,1.5,
2.5) are allowed.
Evaluate the prevalence of riffles, pools, and other microhabitats in the streambed.
0 (Poor) No riffle-pool sequences observed.
1 (Weak) Mostly has areas of pools or riffles.
2 (Moderate) Represented by a less frequent number of riffles and pools. Distinguishing the
transition between riffles and pools is difficult to observe.
3 (Strong) Demonstrated by a frequent number of structural transitions (e.g., riffles followed by
pools) along the entire reach. There is an obvious transition between riffles and pools.
Notes about riffle-pool sequence:
-------
Western Mountains SDAM Field Form
October 2024 Page 6 of 6
10. Particle size or stream substrate sorting
(0-3)
Half scores (0.75,
2.25) are allowed.
Evaluate the extent of substrate sorting. Compare substrate on the channel bed to the banks and
adjacent floodplain. Look for sorting within the channel bed (e.g., along bars and islands).
0 (Poor) Particle sizes in the channel are similar or comparable to particle sizes in areas close to
but not in the channel. Substrate sorting is not readily observed in the channel.
1.5 (Moderate) Particle sizes in the channel are moderately similar to particle sizes in areas close
to but not in the channel. Various sized substrates are present in the channel and are
represented by a higher ratio of larger particles (gravel/cobble; coarse sand in low-gradient
streams).
3 (Strong) Particle sizes in the channel are noticeably different from particle sizes in areas close
to but not in the channel. There is a clear distribution of various sized substrates in the channel
with finer particles accumulating in the pools, and larger particles accumulating in the
riffles/runs.
Notes about substrate sorting:
Photo log
Indicate if any other photographs taken during the assessment:
Photo ID
Description
Additional notes about the assessment:
Model classification:
D Ephemeral
D At least intermittent
D Intermittent
D Less than perennial
D Perennial
D Needs more information
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