Oregon Streamflow Duration Assessment Method
Interim Version - March 2009
U.S. Environmental Protection Agency, Oregon Operations Office Region
10, and Office of Wetlands, Oceans and Watersheds
U.S. Army Corps of Engineers, Portland District
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Table of Contents
PURPOSE 3
ACKNOWLEDGEMENTS 3
SECTION 1: INTRODUCTION 4
BACKGROUND 5
DEFINITIONS 6
CONSIDERATIONS WHEN USING THE METHOD 7
Spatial Variability 7
The Concept of Scale 8
Reach Selection 8
Recent Precipitation 9
Ditches and Modified Natural Streams 9
Disturbed or Altered Streams 10
CONDUCTING FIELD ASSESSMENTS AND COMPLETING THE ASSESSMENT FORM 10
Suggested Field Equipment 10
General Guidance for Completing the Field Assessment Form 10
Scoring 11
SECTION 2: INDICATORS OF STREAMFLOW DURATION 13
A. GEOMORPHIC INDICATORS 13
1. Continuous Bed and Bank 13
2. In-channel Structure- Coherent, Organized Sequences 15
3. Soil Texture or Stream Substrate Sorting 15
4. Erosional Features 19
5. Depositional Features 20
6. Sinuosity 22
7. Headcuts And Grade Controls 23
B. HYDROLOGIC INDICATORS 25
8. Groundwater (Wet Channel) / Hyporheic Saturation (Dry Channel) 25
9. Springs and Seeps 26
10. Evenly Dispersed Leaf Litter and Loose Debris 27
11. Debris Piles and Wrack Lines 29
12. Redoximorphic Features in the Toe of Bank 30
C. BIOLOGICAL INDICATORS 32
13. Wetland Plants In or Near Streambed 32
14. Fibrous Roots and Rooted Plants in Thalweg (Upland Plants) 33
15. Streamer Mosses or Algal Mats 34
16. Iron-Oxidizing Bacteria, Fungi, or Flocculent Material 35
17. Macroinvertebrates 36
18. Amphibians and Snakes 39
19. Fish 42
20. Lichen Line (Used Only in Arid Regions and Alpine Areas) 43
21. Distinct Riparian Vegetation Corridor (Used Only in Arid Regions) 44
SECTIONS: DRAWING CONCLUSIONS 45
APPENDIX A: REFERENCES CONSULTED 46
APPENDIX B: STREAMFLOW DURATION FIELD ASSESSMENT FORM 52
APPENDIX C: A FIELD GUIDE TO ACCOMPANY THE MACROINVERTEBRATE SCORING PORTION
OF THE OREGON STREAMFLOW DURATION ASSESSMENT METHOD 55
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PURPOSE
The purpose of this manual and accompanying field assessment form is to guide natural
resource professionals in the identification of the geomorphic, hydrological and biological
indicators of stream flow to help distinguish between ephemeral, intermittent and perennial
streams. Section 1 contains an introduction to the method, including definitions of key terms,
method development, scoring, sources of variability, and suggested field equipment. Section 2
describes the indicators assessed by the method and provides guidance for scoring. Section 3
discusses drawing conclusions based on the assessed indicators of flow.
This method and assessment form can be used to distinguish between perennial, intermittent,
and ephemeral streams, but is primarily designed to distinguish ephemeral streams from
intermittent and perennial streams in a single site visit. This method is an assessment tool for
natural resource professionals and should support, but not replace, best professional judgment.
ACKNOWLEDGEMENTS
This manual has come together with the hard work of many people, and was particularly
improved by the critical review and continuing input from participants in the September 2007
field verification workshop: Scott Hoffman Black, The Xerces Society for Invertebrate
Conservation (Xerces Society); Kyle Blasch, United States Geological Survey (USGS) Arizona
Water Science Center; Ken Fritz, United States Environmental Protection Agency (EPA) Office
of Research and Development (ORD); Jim Goudzwaard, United States Army Corps of
Engineers (USAGE) Portland District; Sarina Jepsen, Xerces Society; Jess Jordan, Oregon
Department of State Lands (ODSL); Periann Russell, North Carolina Division of Water Quality;
Yvonne Vallette, EPA Oregon Operations Office; Jim Wgington, EPA ORD; and Molly Wood,
USGS Idaho Water Science Center.
Many others have contributed important review and insight: Scott Leibowitz, Joe Ebersole, and
Randy Cameleo, EPA ORD; Rob Coulombe, Lindsey Webb, Blake Hatteberg, and Shawn
Majors, Dynamac Corporation; Stephen Lancaster, Oregon State University (OSU), Dept. of
Geosciences; Judith Li, OSU, Dept. of Fisheries and Wildlife; Celeste Mazacanno, Xerces
Society; Mark Rains, University of South Florida, Dept. of Geology; Chris Rombough,
Rombough Biological; Nicole Navas, Russ Klassen, and Peter Ryan, ODSL.
Photographs were provided by the following contributors: Rob Coulombe, Lindsey Webb, Blake
Hatteberg, and Shawn Majors (Dynamac Corporation), Jim Wigington and Ken Fritz (EPA
ORD), Jess Jordan and Peter Ryan (ODSL), and Dana Eckard (Bureau of Land Management).
Figures are credited in the document following the title with full citation information in Appendix
A.
To cite this document:
Oregon Streamflow Duration Assessment Method Interim Version. Brian J.D. Topping, Tracie-
Lynn Nadeau, Michael R. Turaski. Public Notice release date, 6 March 2009.
Oregon Streamflow Duration Assessment Method - Interim Version (March 2009)
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Section 1: Introduction
A stream* can be described as a channel containing flowing surface water including:
Stormflow - increased stream flow resulting from the relatively rapid runoff of
precipitation from the land as interflow (rapid, unsaturated, subsurface flow), overland
flow, or saturated flow from surface water tables close to the stream, or;
Baseflow - flow resulting from ground water entering the stream or sustained melt water
from glaciers and snowmelt (observed during long gaps between rainfall events), or;
A combination of both stormflow and baseflow, and;
Contributions of discharge from upstream tributaries as stormflow or baseflow, if present.
*Note: For the purposes of this method the descriptor 'stream' is attached to the
channel, and applies regardless of whether flow dries up seasonally or otherwise.
As a stream flows from its origin, water may be derived primarily from stormflow, baseflow, or
some combination of the two. Streams typically continue to accumulate water from stormflow,
baseflow and other tributaries as they flow downstream. As streams accumulate flow they
commonly transition along a gradient from ephemeral to intermittent and perennial; but
sometimes quickly transition from ephemeral to perennial in high gradient systems, or transition
from perennial to ephemeral to total cessation of flow on the surface. Often these changes are
gradual and may not be obvious to the casual observer. There are, however, several indicators
of stream flow that collectively can be used to characterize the flow duration of a stream along a
particular reach as ephemeral, intermittent or perennial. In this manual duration is used to
encompass the concept of the cumulative time period of flow in a year, which may vary
interannually with climate, groundwater withdrawal or streamflow diversion, and other patterns.
This manual describes these indicators and presents a method for assessing and drawing
conclusions from these indicators in the state of Oregon.
Stream systems can be characterized by interactions among hydrologic, geomorphic (physical)
and biological processes. Variations in these attributes along the length of a stream are used as
indicators of the dominant processes related to flow duration (Figure 1). To identify the
indicators and distinguish ephemeral streams from intermittent streams or intermittent streams
from perennial streams using the information presented in this manual, the field evaluator
should have experience making geomorphic, hydrologic and biologic observations in streams.
Figure 1. Hydrologic and geomorphic
characteristics in relation to drainage area
(FISRWG 1998).
Drainage Area (downstream distance^)
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This method and assessment form are designed to help the USAGE Portland District Regulatory
Program and EPA Region 10, and Oregon Department of State Lands distinguish between
ephemeral, intermittent and perennial streams. This method is designed to be used throughout
Oregon; however, the climatic and hydro-geomorphic variation across Oregon requires that
local conditions and the potential strength of an indicator be considered when assessing
indicator strength. For example, the arid regions of eastern Oregon will not produce thick wrack
lines as will the deciduous forests of western Oregon in fall, but both systems can produce
"strong" wrack lines. In addition, one indicator - presence of a clear riparian vegetated corridor -
is used only in arid regions of Oregon (defined for this method as those areas that occur within
the Arid West Region described in the Regional Supplement to the 1987 USAGE Wetland
Delineation Manual). Another indicator, presence of a lichen line on stream bed rocks or on the
bank, is used only in arid regions and alpine areas.
Background
This method has been developed, in part, based on the experiences and progress of the North
Carolina Division of Water Quality on their Identification Methods for the Origins of Intermittent
and Perennial Streams.1 The North Carolina Stream Identification Method (NC Method) was
developed and tested based on documented scientific principles in hydrology, geomorphology
and biology. Version 1 of the method was implemented in 1998 after extensive review from the
academic and regulatory community. Since 1998, several major revisions have been made as
experience and science advanced. The NC Method is viewed as an evolving document, and will
continue to change over time. Since the NC Method is a regulatory tool used to guide rapid
assessment of intermittent and perennial streams, it is used as a guide only and does not
replace best professional judgment. As a regulatory tool, the NC Method facilitates consistent
stream identification across many scientific disciplines, and evaluators must be certified by
passing a state-legislated four-day training course.
Starting from that base, experts in relevant academic and professional fields have been
consulted in the development of the Oregon Streamflow Duration Assessment Method (Oregon
Method). A team of experts from the USAGE Portland District, USEPA Region 10 Oregon
Operations Office and Office of Research and Development, USGS Idaho and Arizona Water
Science Centers, Oregon Department of State Lands, and North Carolina Division of Water
Quality conducted a one week field assessment of the method in the five major physiographic
and climatic regions of Oregon. The field assessment compared the Oregon Method to known
flow durations for headwater streams in the Coast Range, Wllamette Valley Lowlands,
Cascades Range, Great Basin, and the High Desert Plateau. In addition, several other efforts
have informed selection of appropriate indicators, identification of potential problems in the field,
and development of meaningful indicator descriptions and scoring, including: review of the
scientific literature; beta-testing by the USAGE Portland District, USEPA Oregon Operations
Office, and Oregon Department of State Lands; development of a Xerces Society report "Using
Aquatic Macroinvertebrates as Indicators of Streamflow Duration;" external peer-review; and
results of the first phase of a USEPA field verification study of the OR Method including more
than 170 streams from both sides of the Cascade Range. This interim version of the
Streamflow duration assessment method will be used, evaluated, and refined as experience and
scientific understanding advances.
Application of this method requires that users receive training in the identification and
rating of these indicators to ensure accuracy and consistency in results.
1 http://h2o.enr.state.nc.us/ncwetlands/documents/NC Stream ID Manual.pdf
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Definitions
As used by this method:
Channel forming flow is the discharge that maintains the channel form and transports the
greatest quantity of sediment over time (commonly referred to as bankfull flow). For streams
with active floodplains, the channel forming flow can be defined as the point at which the flow
just begins to enter the floodplain. Thus there are a variety of indicators that can be used to
identify this point. For example, on some streams without active floodplains the distance
between the lower limit of rooted terrestrial vegetation on each bank can be used (Dunne &
Leopold, 1978).
Channel is an area that contains flowing water (continuously or not) that is confined by banks
and a bed.
Dry Channel is an area confined by banks and a bed that at times contains flowing
water, but at the time of assessment does not contain flowing water (it may contain
disconnected pools with no sign of connecting flow).
Wet Channel is an area confined by banks and a bed that contains flowing water at the
time of assessment (flow may be interstitial).
Ephemeral Stream flows only in direct response to precipitation. Water typically flows only
during and shortly after large precipitation events.,. An ephemeral stream may or may not have
a well-defined channel, the stream bed is always above the water table, and stormwater runoff
is the primary source of water. An ephemeral stream typically lacks biological, hydrological, and
physical characteristics commonly associated with the continuous or intermittent conveyance of
water.
Groundwater occurs at the subsurface under saturated conditions and contains water that is
free to move under the influence of gravity, often horizontally to stream channels when a
confining layer blocks downward percolation.
Hyporheic Zone is the zone under and adjacent to the channel where stream water infiltrates,
mixes with local and/or regional groundwater, and returns to the stream. The dimensions of the
hyporheic zone are controlled by the distribution and characteristics of alluvial deposits and by
hydraulic gradients between streams and local groundwater. It may be up to two to three feet
deep in small streams, and is the site of both biological and chemical activity associated with
stream function.
Intermittent Stream is a channel that contains water for only part of the year, typically during
winter and spring when the stream bed may be below the water table and/or when snowmelt
from surrounding uplands provides sustained flow. The channel may or may not be well-defined.
The flow may vary greatly with stormwater runoff. An intermittent stream may lack the biological
and hydrological characteristics commonly associated with the continuous conveyance of water.
Normal Precipitation is defined as the 30-year average, provided by NOAA National Climatic
Data Center, computed at the end of each decade. These data are available as annual and
monthly means.
Perennial Stream contains water continuously during a year of normal rainfall, often with the
stream bed located below the water table for most of the year. Groundwater supplies the
baseflow for perennial streams, but flow is also supplemented by stormwater runoff and
snowmelt. A perennial stream exhibits the typical biological, hydrological, and physical
characteristics commonly associated with the continuous conveyance of water.
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Stream Origin is the point where flow first appears on the land surface with enough force to
disturb the substrate creating a lasting sign of flow. Stream origins are often wetlands, springs,
seeps or headcuts.
Swales can be wetlands or uplands (when assessed under the USAGE 1987 Wetlands
Delineation Manual or appropriate regional supplements) and primarily serve as a vegetated
flow path occurring in a slight depression in the landscape but lacking differentiation between
bed and bank. Swales often connect uplands to wetlands or streams, connect wetlands
together, or connect upstream and downstream reaches of small streams that flow through a
colluvial fan or an abrupt change in grade.
Thalweg is the deepest part of a stream channel and the last part of the stream to contain
flowing water as a stream dries up. As used in this method, the thalweg comprises the "lowest
flow" pathway and typically spans approximately 5 to 20% of the channel width.
Water Table is the surface elevation of the saturated zone below which all interconnected voids
are filled with water and at which the pressure is atmospheric, commonly identified as the top of
the local (i.e., floodplain) or regional groundwater aquifer.
Considerations When Using the Method
Spatial Variability
Spatial variations in stream indicators occur within and among stream systems. Sources of
variation between stream systems in Oregon are due primarily to physiographic province
(geology and soils) and climate (seasonal patterns of precipitation and evapotranspiration). For
example, riffles and pools result from in-channel structures and these structures can vary
between rocks and boulders in the mountains and roots and wood debris in the alluvial valleys.
The method was designed to apply to all stream systems within the diverse physiographic and
climatic regions of Oregon.
A substantial amount of variability can also occur along the length of a given stream system.
Common sources of variation within a stream system include:
Longitudinal changes in stream indicators related to increasing duration and volume of
flow. As streams gain or lose streamflow, the strength of indicators changes.
Longitudinal changes due to variables such as channel gradient and valley width, which
affect physical processes and thus directly or indirectly affect many indicators.
Temporal variation of flow related to precipitation and evapotranspiration seasonality.
For instance, in western Oregon the strong seasonal rainfall pattern - several months of
wet weather followed by several months of dry weather - supports the establishment of
intermittent streams. Due to these long periods of rain many of the intermittent streams
in Oregon carry 80 - 90 percent of the yearly discharge associated with a perennial
stream of the same size. This large yearly discharge results in very strong
geomorphological development of the stream channel relative to the flow duration when
compared with intermittent streams in other parts of the country.
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The Concept of Scale
For the purposes of applying this method perhaps the most important type of variation between
streams, however, is simply the size of the stream. Streams develop different channel
dimensions due to differences in flow magnitude, landscape position, land use history, and other
factors. When assessing a stream, it is of paramount importance to consider scale when
determining the strength of indicators. For instance, depositional features or channel
structures of a given size may be insignificant (i.e., "weak") in a large stream, while features of
the same size in a small stream may be a clear expression of physical processes and thus merit
a score of "strong." Section 2 provides specific guidance for considering the scale of features
when assessing individual indicators; some indicators are scale-independent, in which case no
additional commentary on scale is provided.
Reach Selection
This manual lays out a method for assessing geomorphic, hydrologic, and biologic indicators of
stream flow duration. However, flow characteristics often vary along the length of a stream,
resulting in gradual transitions in flow duration. Recognizing that in many streams flow duration
exists on a continuum, choosing the reach on which to conduct an assessment can influence
the resulting conclusion about flow duration.
Assessments should be made for a representative reach, rather than at one point of a stream.
A representative reach for stream assessments is equivalent to 35 - 40 channel widths of
the stream. For narrow streams, the length of the assessment reach should be a minimum of
30 meters.
Assessments should begin by first walking up and down the channel, from the stream origin to
the downstream confluence with a larger stream (to the extent feasible). This initial review of
the site allows the evaluatorto examine the overall form of the channel, landscape, and parent
material, and variation within these attributes as the channel develops or disappears upstream
and downstream. Walking the channel also allows the assessor to observe characteristics of
the watershed such as land use and sources of flow (e.g. stormwater pipes, springs, seeps, and
upstream tributaries). Once these observations are made, the assessor can identify the areas
along the stream channel where these various sources (stormflow, tributaries or groundwater) or
sinks (alluvial fans, abrupt change in bed slope, etc.) of water may cause abrupt changes in flow
duration. Similarly, the assessor can identify if the stream segment in question is generally
uniform or should be assessed as two or more distinct reaches.
For regulatory purposes the reach in question will often be predetermined by property
ownership or proposed activities; the above process for assessing the stream should be
followed to the extent possible, and if the reach in question is generally uniform one assessment
is appropriate. If the reach in question is not uniform, two or more assessments are
recommended to fully describe the changes along the reach. Regardless of the number of
reaches assessed, decisions should be made in conjunction with "best professional judgment"
to reach a conclusion on flow duration as ephemeral, intermittent, or perennial.
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Recent Precipitation
The rate and duration of flow in stream channels is influenced by climate and by recent weather.
Recent (within 48 hours) rainfall can influence scoring; therefore it is strongly
recommended that field evaluations be conducted at least 48 hours after the last
significant rainfall.
However, note that this assessment method has been designed with redundancy to allow for
reasonably accurate ratings even after a recent rainfall. Evaluators should note recent rainfall
events on the assessment form and take them into consideration when drawing conclusions and
assessing the applicability of individual indicators.
Ditches and Modified Natural Streams
This method can be used, in combination with best professional judgment, to assess the flow
duration of natural streams, modified natural streams, and ditches dug in wetlands or uplands.
When assessing a reach that is a ditch or modified natural stream, it is important to walk the
entire reach and locate the inflow point or origin as well as the downstream terminus of flow
(most often a confluence with another channel). Similarly, any disturbance or modifications to
the stream channel should be noted on the assessment form - especially if it means one or
more indicators are not applicable (Figure 2). For highly modified streams, and many ditches, it
may be necessary to use an alternative method to identify flow duration based on the presence
of one or two key indicators that were not affected by the modifications; it may also be
appropriate to visit the site multiple times or conduct hydrologic monitoring. For all
assessments, disturbances or modifications to the stream or its catchment that may
affect the presence and/or strength of the stream indicators should be noted.
Figure 2. Example of a
modified stream. Several
indicators are apparent in this
reach, but assessor should note
the strength of indicators in
upstream or downstream
segments that are not directly
affected by the road. Such field
notes will more fully describe
the site and may be useful in
determining flow duration.
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Disturbed or Altered Streams
Assessors should be alert for natural or human-induced disturbances that affect streamflow
duration and/or the strength of indicators. Streamflow duration can be directly affected by flow
diversions, urbanization and stormwater management, septic inflows, agricultural and irrigation
practices, vegetation management, or other activities. The strength of indicators can be affected
by changes in streamflow, and can also be affected by disturbances that may not substantially
affect streamflow (for instance, a channel could be graded, thus removing many indicators even
without changing the flow duration; other examples include grazing, logging, recent fire, beaver
activity, riparian management, culvert installation, bank stabilization). Such disturbances
should be described in the "Notes" section of the field assessment form. Similarly,
natural sources of variation should also be noted such as fractured bedrock, volcanic parent
material, recent or large relic colluvial activity (landslides or debris flows), and drought or
unusually high precipitation.
Conducting Field Assessments and Completing the Assessment
Form
Suggested Field Equipment
This guidebook.
Amphibian and macroinvertebrate field guides: (e.g. Amphibians of Oregon, Washington
and British Columbia, Corkran and Thomas, 1996, Lone Pine Publishing, Redmond, WA;
Macroinvertebrates of the Pacific Northwest, Adams and Vaughan, 2003, The Xerces
Society, Portland, OR)
Plant identification guide and current wetland indicator status list2
Global Positioning System (GPS) - used to identify the boundaries of the reach
assessed.
Camera - used to photograph and document site features.
Clinometer - used to measure channel slope.3
Tape measure
Calculator
Kicknet or small net and tray - used to sample aquatic insects and amphibians.
Hand lens
Munsell Soil Color Chart - used to classify the color of various soils and distinguish
redoximorphic features.
Polarized sun glasses - for eliminating surface glare when looking for fish, amphibians,
and macroinvertebrates.
Soil auger and/or soil probe - used to examine soils in the toe of the bank and determine
if the hyporheic zone is saturated.
Rock hammer or equivalent - useful for digging into the hyporheic zone.
General Guidance for Completing the Field Assessment Form
The Oregon Streamflow Duration Assessment Method relies upon the assessment of up to 21
indicators of flow duration and on the assessor's understanding of the site. As described in the
2 The 1988 plant list and 1993 Region 9 supplement are the currently applicable lists for use in Oregon.
3 Channel slope can also be determined from topographic maps or surveys.
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Ditches and Modified Natural Streams section above, modifications to the site or areas
upstream of the site may affect the presence or strength of the indicators. Similarly, natural
variation such as interannual variation in precipitation can affect the year to year depth to
groundwater, stream discharge, and the presence of the indicators used in this method.
Therefore, it is important to accurately complete the field assessment form, including
information for date, project, evaluator, waterway name and location, recent
precipitation, observed hydrologic status, and channel gradient and width. Furthermore,
the evaluator should indicate whether she has participated in a classroom "orientation" to the
method, a field-based training class, or both.
If the stream does not have defined a channel (i.e., bed and banks are not apparent), estimate
the width of the flow path and describe in the "Notes" section. Any other relevant observations
should also be recorded in the "Notes" section of the form. These may include the local geology,
runoff rates, hydrologic unit codes, evidence of stream modifications or hydrologic alterations
upstream of the assessment area (e.g. dams, diversions, stormwater discharge), and recent
land clearing activities upstream. All pertinent observations should be recorded on the form,
including a clear and repeatable way of identifying the boundaries of the reach being assessed
and the reasons for choosing those boundaries.
Scoring
Identification of stream type is accomplished by evaluating up to 21 different indicators of
streamflow duration and assigning a score to each. The scoring sheet is used to tally the scores
for each indicator and determine the total numeric score for the stream. The total score reflects
the persistence of flow, with higher scores indicating intermittent and perennial streams.
Thresholds for total scores separate perennial, intermittent and ephemeral streams, but local
conditions including disturbances and modifications made to the stream should be taken into
account when using best professional judgment to reach a flow duration conclusion for a
stream. If a quick or comprehensive assessment leads to an overall score within a point or two
of the threshold for flow duration category, the assessor should carefully review the indicators
and the potential disturbances and modifications made to the stream before reaching a final
conclusion on flow duration category, carefully documenting rationale for the conclusion on the
assessment form or supporting documents.
A four-tiered scheme is used for scoring each indicator or attribute while accounting for the
variability of streams. The scores, "Absent", "Weak", "Moderate", and "Strong" are applied to
sets of geomorphic, hydrologic and biological indicators.4 Each score reflects the evaluator's
judgment of the average degree of an indicator's development along the stream reach being
evaluated.
The range of scores is intended to allow the evaluator flexibility in assessing indicators that exist
along a continuum, instead of relying simply on presence/absence of an attribute. The small
increments in scoring between gradations also will help reduce the range in scores between
different evaluators.
It is important to note that "Moderate" scores are intended as an approximate qualitative
midpoint between the two extremes of "Absent" and "Strong." The remaining
description, "Weak", represents gradations between "Absent" and "Moderate" that will
often be observed in the field.
4 The scoring system includes both primary and secondary indicators: the secondary indicators are
weighted less than the primary indicators.
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Natural disturbances such as recent landslides and wildfires could mask the presence of some
indicators. Similarly, human modifications to streams, such as toxic pollution or cement lined
channels, could also preclude some indicators from forming. These situations should be
explained in the "Notes" section of the assessment form.
General definitions of "strong", "moderate", "weak", and "absent" are provided in Table 1. These
definitions are intended as overall guidelines. The evaluator must select the most
appropriate score for each indicator based primarily upon specific guidance (see Section
2) and secondarily upon experience and professional judgment, observations of the
stream, and characteristics of the watershed and physiographic region.5
Scoring of the indicators is based on observations and should not include predictions of what
could or should be present. Disturbances and modifications to the stream should be described
in the notes section of the assessment form and taken into consideration when drawing
conclusions from the information collected. It is also important to explain the rationale behind
conclusions reached, and when necessary that rationale should be supported with photos and
other documentation of the reach condition and any disturbances or modifications that were
taken into consideration.
Table 1. General Guide to Scoring Categories
Category Description
Absent The indicator is not observed
Weak The indicator is present but not common
Moderate The indicator is common but not ubiquitous
Strong The indicator is present throughout the reach
5 Physiographic region is an important consideration when assessing the presence of certain indicators.
For example, assessment of the strength of indicators 10 - Leaf litter / loose debris and 11 - Debris piles
or wrack lines in the arid eastern half of Oregon should reflect the vegetation present and the potential for
accumulation.
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Section 2: Indicators of Streamflow Duration
A. Geomorphic Indicators
1. Continuous Bed and Bank.
Throughout the length of the stream reach, is the channel clearly defined by having a
discernable bank and stream bed? (Figures 3, 4, 5, and 6)
The bed of a stream is the physical confine of the baseflow; it often also confines stormflow, but
it will always confine the baseflow. The lateral constraints (channel margins) during all but flood
stage are known as the stream banks. In fact, a flood occurs when a stream overflows its banks
and partly or completely fills its flood plain.
As a general rule, the bed is that part of the channel below the "normal" water line, and the
banks are that part above the water line; however, because water flow varies, this differentiation
is subject to local interpretation. In perennial and intermittent streams the bed is usually kept
clear of terrestrial vegetation, whereas the banks are subjected to water flow only during
infrequent high water stages, and therefore can support vegetation much of the time.
This indicator will lessen and may diminish or become fragmented upstream as the stream
becomes ephemeral. This feature may also be weak or absent when a stream passes over
waterfalls, long stretches of exposed bedrock, or when it enters a water control or conveyance
structure - in such cases those confounding factors should be noted on the assessment form,
as should the presence of a bed and bank where they had the potential to form (immediately
upstream or downstream). Artificially created bed and banks should still be assessed for their
presence and degree of confinement along the reach. For heavily incised channels, assess the
active channel's bed and banks, not the relic incision.
Note: If the aquatic feature does not have a bed and banks it may be more appropriate to
consider the feature as a swale or a wetland (if it meets hydrology, soils, and vegetation
criteria).
Strong - There is a continuous bed and bank present throughout the length of the stream
reach.
Moderate - The majority of the stream has a continuous bed and bank. However, there are
obvious interruptions.
Weak- The majority of the stream has obvious interruptions in the continuity of bed and bank.
However, there is still some representation of the bed and bank sequence.
Absent - There is little or no ability to distinguish between the bed and bank.
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Figure 3. "Weak" discontinuous bed and
bank (western Cascades, channel width
0.7m)
Figure 4. "Weak" poorly defined bed and
bank (Blue Mountains, flow path width 0.5 m)
Figure 5. "Moderate" bed and bank (Blue
Mountains, channel width 0.7 m)
Figure 6. "Strong" bed and bank (western
Cascades, channel width 0.6 m)
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2. In-channel Structure - Coherent, Organized Sequences
Is there a regular sequence of coherent, organized fluvial erosion/deposition structural
features in the channel indicative of recurring high flows? (Figures 7, 8, 9, and 10)
A repeating sequence of riffle/pool (riffle/run in lower-gradient streams, riffle/pool in sand bed
streams, or step/pool in higher gradient streams) can be readily observed in many but not all
perennial streams. This morphological feature is almost always present to some degree in
higher gradient mountain streams. Riffle-run (or ripple-run) sequences in low gradient streams
are often created by in-channel woody structure such as roots and woody debris. When present,
these characteristics can be observed even in a dry stream bed or in small streams by closely
examining the local profile of the channel. Streams with particularly course beds may lack in-
channel structure.
A riffle is a zone with relatively high channel gradient, shallow water, and turbulence. In smaller
streams, areas of a distinct change in gradient where flowing water can be observed are often
identified as riffles. The substrate material in riffles contains the largest sediment particles that
are moved by bankfull flow (bedload). A pool is a zone with relatively low channel gradient, deep
water, and low turbulence during low flow periods. Fine textured sediments may dominate the
substrate material in pools where a fine sediment supply exists. Along the stream reach, take
notice of the spacing and frequency of the riffles and pools or other types of in-stream
structures. This feature may also be absent or not well defined when a stream passes over long
stretches of exposed bedrock, or when it enters a water control or conveyance structure. In
such cases those confounding factors should be noted, as should the presence of an in-stream
structure where it had the potential to form (i.e. immediately upstream or downstream).
Strong - Stream has a coherent and organized sequence of fluvial erosion/deposition structural
features along the entire reach. There is an obvious transition between structural features.
Moderate - Stream has a sequence of fluvial erosion/deposition structural features along the
reach but distinguishing between the features is difficult or they do not occur over the entire
reach.
Weak - Stream has some fluvial erosion/deposition structural features but not a coherent
sequence, mostly one structural form.
Absent - There are no fluvial erosion/deposition structural features in the stream.
3. Soil Texture or Stream Substrate Sorting
Has channel downcutting penetrated through the soil profile, such that the texture of the
stream substrate different (i.e. much coarser) than that of the soil in the adjacent
floodplain? Is there evidence of sorting of the stream substrate materials, indicative of
frequent high flows? (Figures 11,12, 13, and 14)
This feature can be examined in two ways. The first is to determine if the soil texture in the bed
of the stream channel is similar to the soil texture outside the channel. If the soil texture is
similar, then there is evidence that erosive forces have not been active enough to down cut
through the soil profile as expected in an intermittent or perennial stream. Soils in the bed of
ephemeral channels typically have the same or similar texture as the soils adjacent to the
channel (Figure 11). Accelerated stormflow resulting from development, for example, may
produce deep, well-developed ephemeral or intermittent channels but which have little or no
coarse bottom materials indicative of upstream erosion and downstream transport (i.e.,
alluvium). The substrate of intermittent or perennial streams often has accumulations of coarse
sediment,
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Figure 7. "Weak" geomorphic sequences;
channel is dominated by a single structural
form (Blue Mountains, channel width 2.6 m)
Figure 8. "Weak" development of riffle/pool
structure (Crooked River basin, channel
width 1.7 m)
Figure 9. "Moderate" frequency of riffle/run
sequences (Blue Mountains, channel width
2.2m)
Figure 10. "Strong" set of step-pool
sequences (foothills of western Cascades;
channel width 2.0 m)
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either from deposition or winnowing away of fines leaving behind the coarse sediments.
Bedrock streams may lack any sediment on the bed for significant reaches.
The second way this feature can be examined is to look at the distribution of sediment in the
substrate in the stream channel. Is there an even distribution of various sized particles
throughout the reach, or is the sediment sorted into discrete patches of different grain sizes
(Table 2; Figures 12 and 14)? In the arid area of eastern Oregon one may need to look for size
variations among sand grains - for instance, coarse versus fine sand. The occurrence of
depositional features may be infrequent in intermittent streams. Perennial streams, on the other
hand, tend to exhibit larger depositional features, with cobble/gravel/boulders being localized in
riffles and runs, and may have accumulations of fine sediments settling out in slow water areas.
Notes: The usefulness of this attribute may vary among physiographic provinces. For instance,
in parts of eastern Oregon dominated by fine-textured parent materials (such as volcanic ash)
the variability in the size of soil particles may be less than in the mountains and valleys.
Assessors should also note if the deposits are potentially colluvial (i.e. from rock slides and
other terrestrial movements outside of stream flows) and therefore not indicative of flow
duration.
Table 2. Standard USDA Particle Sizes
Description
fine sand
medium sand
coarse/very coarse sand
pebbles (gravel)
cobbles
stones
boulders
Diameter
millimeters
0.1-0.25
0.25-0.5
0.5-2.0
2-75
75-250
250-600
>600
inches
.004-.01
.01-.02
.02-.08
.08-3.0
3.0-9.8
9.8-23.6
>23.6
Strong - There is a well-developed channel through the soil profile with relatively coarse-
textured substrate compared to riparian zone soils; for instance, course sand, gravel, or
cobbles on the coast or in the valleys; gravel, cobbles, stones, or boulders in the mountain
regions. OR - There is clear evidence of sediment sorting, soil texture differs between the
stream substrate and adjacent land.
Moderate - There is a well-developed channel but it has not incised through the soil profile. Soil
texture differs somewhat between the stream substrate and adjacent land. Some coarse
sediments are present. OR - There is relatively little sorting of fine material from coarser
materials.
Weak- The channel is poorly developed through the soil profile. Soil texture differs little
between the stream substrate and adjacent land. OR - Some coarse sediments are present, but
substrate sorting is not readily observed. There may be some small depositional features
present on the downstream side of obstructions (large rocks, etc.).
Absent - The channel is poorly developed, very little to no coarse sediments are present, and
substrate sorting is absent. No difference between soil texture in the stream substrate and
adjacent land is observed.
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Figure 11. Both substrate sorting and soil
texture differentiation are "weak" (Willamette
Valley, channel width 0.7 m)
Figure 12. "Strong" sorting of particle sizes
amongst stream substrate (Willamette
Valley, channel width 1.2 m)
Figure 13. "Weak" substrate sorting (Blue
Mountains, channel width 0.9 m)
Figure 14. Example of different patches of
sorted particles (pine needles are approx.
10 cm long).
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4. Erosional Features
Is there evidence of fluvial erosion? Does the channel show evidence of fluvial erosion in
the form of undercut banks, scour marks, channel downcutting, or other features of
channel incision? (Secondary Indicator) (Figures 15 and 16)
Undercut banks and scour marks are the most common signs of fluvial erosion for streams in a
floodplain system. In steeper landscapes, channel downcutting and incision may occur. Other
weaker signs of erosion include the scour marks on the downstream side of boulders and other
obstructions.
Assess the erosional features within the active channel; relic channel incision that is not part of
the active channel should not be assessed. Human modifications to armor or stabilize the bed
or banks of the stream (e.g. root wads and riprap) should be considered an indicator of fluvial
erosion. Note that bank sloughing is not directly caused by fluvial processes and should not be
considered an erosional feature.
Note: Erosion and deposition processes differ between bedrock and alluvial channels. The
field assessment form includes a check box to denote if the streambed consists of more than
50% exposed bedrock. This information is used to interpret indicator scores and document best
professional judgment.
Strong- Fluvial erosion is obvious throughout the reach, or there are some substantial
erosional features present.
Moderate - Fluvial erosion is present throughout most of the reach, or there are some
moderate erosional features present.
Weak- Fluvial erosion is infrequent along sampling reach and the features are weak.
Absent- Fluvial erosion is completely lacking.
Figure 15. "Weak" lateral erosion is not
continuous along length of reach, and banks
are relatively stable (Northern Basin and
Range, approximate channel width 1.8 m)
Figure 16. "Strong" erosional feature is
continuous along length of reach, and bank
is actively undercutting (Blue Mountains,
channel width 2.4 m)
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5. Depositional Features
Are there depositional features such as bars or fresh deposits of alluvial materials in the
stream channel or on the floodplain? Is there an active floodplain at the bankfull
elevation? (Figures 17, 18, and 19)
When a stream channel conveys perennial flow, the forces of channel scouring and deposition
create distinct erosional and depositional features. Alluvium may be deposited as sand, silt,
gravel and cobble. There are several different types of depositional features, all of which are
assessed with this one indicator and should be scored based on the presence of depositional
features along the reach of stream being assessed. Observing depositional feature(s) along
only a third of the reach would be weak, but depositional feature(s) along the entire length of the
reach would be strong.
Bars are accumulations of sand or silt in a stream channel which may or may not be covered
with vegetation. These include point bars, lateral bars and mid-channel bars. The presence of
depositional bars suggests that the channel transports sediment and is in or near dynamic
equilibrium with the shaping forces of its water/sediment load. Depositional bars also indicate a
relatively continuous hydrologic regime.
Floodplains are relatively flat areas that accumulate organic matter and inorganic alluvium
deposited during flooding, and are usually located outside of and adjacent to the stream
channel. An active floodplain (at current bankfull elevation, such that it is inundated on an
approximate 2-year recurrence interval) shows characteristics such as drift lines, sediment
deposits on the surface or surrounding plants, or flattening of vegetation. The floodplain of
incised streams may be restricted to within the channel itself and the previous floodplain (now a
terrace) may be inundated rarely or infrequently. In these instances, look for indicators along the
sides and within the incised channel. Floodplains on smaller order, incised streams may not be
continuous but rather may be present in some locations and absent in others. In many cases
there should be evidence of a floodplain if the stream has perennial flow.
Depositional features are often absent in very small channels. Sometimes there may be
depositional features along the side of the channel or on the lee side of obstructions in the
channel (e.g. in the hydraulic shadow of logs, boulders, etc.), the tops of which are below
bankfull elevation. These features should not score as highly as well-developed bankfull
depositional features, but are nonetheless evidence of deposition.
Strong- Depositional features are obvious throughout the reach, or there are some substantial
depositional features present.
Moderate - Depositional features are present throughout most of the reach, or there are some
moderate depositional features present.
Weak- Depositional features are infrequent along sampling reach, and the features are weak.
Absent- Indications of depositional bar, floodplain connection, or other depositional features
are lacking.
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Figure 17. Example of depositional feature
in small stream (channel width 0.5 m)
Figure 18. Point bar (Willamette Valley,
approximate channel width 3 m). Also note
seep areas (on right), indicated by oxidized
iron.
Figure 19. "Strong" depositional features in
a small headwater stream (western
Cascades, channel width 0.9 m)
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6. Sinuosity
Measure the stream's sinuosity. (Figure 20)
Sinuosity is a measure of a stream's "crookedness." Specifically, it is the total stream length
measured along the stream thalweg divided by the straight line valley length (Figure 20). Higher
ratios indicate more and/or larger curves in the stream. Sinuosity is related to the gradient, but
can also be influenced by parent material and obstructions (natural or otherwise). Typically
higher gradient streams are less sinuous than lower gradient streams, and perennial streams
are more sinuous than intermittent or ephemeral streams. Sinuosity is the natural result of the
stream dissipating the force of its flow.
Note: Sinuosity may not be an applicable indicator for highly modified or managed streams, but
even so, sinuosity is sometimes evident in the path of the thalweg in the bottom of a cement
lined canal. Any modifications or artificial restrictions on a stream's sinuosity should be noted
on the assessment form and taken into consideration when drawing conclusions from the total
score for the reach.
Strong- Ratio > 1.2. (i.e., stream has numerous, closely-spaced bends, very few straight
sections)
Moderate- 1.1 < Ratio < 1.2. (i.e.., stream is a combination of sinuous and straight sections)
Weak- 1.03 < Ratio < 1.1. (i.e.,., stream has very few bends and mostly straight sections)
Absent- Ratio < 1.03. (i.e., the stream is essentially straight)
7
Figure 20. Varying degrees of sinuosity, from left to right: "absent" (sinuosity of
1.01), "weak" (1.07), "moderate" (1.14), "strong" (1.27), and "strong" (2.18)
(Upper Klamath Lake basin). (These pictures are used for illustrative purposes;
alterations to streams should be noted on the assessment form.)
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7. Headcuts And Grade Controls
Is there a headcut at the upstream end of the reach being evaluated? Are there one or
more headcuts within the reach being evaluated? Are there grade controls within the
reach being evaluated? (Secondary Indicator) (Figures 21, 22, 23, 24, and 25)
A headcut is an active erosion feature expressed as an abrupt vertical drop in the bed of a
stream. It often resembles a small intermittent waterfall (or a miniature cliff) and may have a
deep pool at the base resulting from the turbulent scour produced during high flows. Head cuts
are transient structures of the stream and often exhibit relatively rapid upstream movement
during periods of high flow. Intermittent or perennial streams sometimes begin at a head cut,
particularly common in the drier east side and in the mountains. Groundwater seepage may also
be present from the face or base of a headcut.
A grade control is a structural feature in the channel that separates an abrupt change in grade
of the stream bed or a point where a headcut has been stopped by an obstruction. Grade
controls may consist of bedrock outcrops, large stones or large roots which extend across the
channel, or accumulations of large woody debris (Figures 21 and 23). Sediment typically
accumulates immediately upstream of grade controls. Pipes and hard bottomed culverts can
also serve as grade control - and should be counted when they are functioning as grade
control. These structures separate an abrupt change in grade of the stream bed.
The strength of this indicator is based on the number and relative size of the features compared
to the channel size and bed slope. Assess these features by comparing the dimensions of the
headcut/grade control to the dimensions of the channel, and by determining if the feature affects
the direction of the thalweg flow path.
Note: To be considered as "grade control," sediment particles should be larger than the vast
majority of other sediment particles in the channel, such that they are not mobilized during
channel-forming flows (i.e., boulders may provide grade control in a sand-bed stream, but are
unlikely to provide a similar function in a high-energy cobble-bed stream). Structural features
comprised of coarse sediment organized fluvially in repeating sequences should be evaluated
using Indicator 2 (In-channel Structure).
Strong-One or more large headcuts or grade
control features are present within the reach.
Moderate - One or more medium or several
small headcuts or grade control features are
present within the reach.
Weak- One or two small headcuts or grade
control features are present within the reach.
Absent- No headcuts or grade control features
are present within the reach.
^ 1
Figure 21. Grade control comprised of very
large sediment particles (channel width 2.8
m). This is a medium-sized feature, given
the channel dimensions.
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Figure 22. Stream channel with headcuts
and grade controls "absent" (Blue
Mountains, channel width 2.4 m)
Figure 24. Headcut, viewed from
downstream (Blue Mountains, approximate
channel width outside of the scour zone is
0.5 m). This is a large feature, given the
channel dimensions.
Figure 23. Grade control of woody debris
and roots (western Cascades, channel width
0.7 m). This is a medium-sized feature,
given the channel dimensions.
Figure 25. Headcut, viewed from upstream
(Upper Klamath Basin, approximate channel
width outside of the scour zone is 0.8 m).
This is a medium-sized feature, given the
channel dimensions.
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B. Hydrologic Indicators
8. Groundwater (Wet Channel) / Hyporheic Saturation (Dry Channel)
Groundwater discharge to a stream indicates longer flow durations and more sustained
baseflow between precipitation events. Observing flow in a channel does not conclusively
indicate groundwater discharge to the channel within the reach being observed. Similarly,
observing a dry stream bed does not conclusively indicate that the channel does not receive
groundwater discharge. So separate assessment measures are used for this indicator when the
channel is wet, versus when the channel is dry. When assessing this indicator, choose the
location along the reach that will be most likely to show the presence of groundwater or
hyporheic saturation (e.g., tails of riffles, deep pools). This assessment strategy indicates
whether there are groundwater inputs anywhere along the reach, not whether groundwater is
entering the stream throughout the entire reach.
When the channel is wet: Are there signs of groundwater discharge to the stream along
the reach, or is there a seasonal high water table?
Groundwater Table: the presence of a seasonal high water table or groundwater discharge (i.e.
seeps or springs) from the bank indicates a relatively reliable source of baseflow to a stream.
The presence of pools or standing water are indicators of the height of the water table. A water
table can also be inferred by the presence of wetlands in close proximity to the stream (i.e.,
within 2 channel widths) above the elevation of the streambed. The height of the water table
can also be observed by digging a hole in the adjacent floodplain approximately one channel
width away from the streambed (to avoid intercepting bank storage). The presence of water
standing in the hole above the elevation of the channel bottom after waiting for at least 30
minutes (longer for clayey soils) indicates the presence of the water table. This hole can be dug
with a shovel, auger, or probe. If soil conditions prevent digging an adequately deep hole,
assess this indicator as best you can and note the depth of refusal in the "Notes" section.
Strong - Groundwater table higher than stream height is readily observable adjacent to the
reach, or pools or standing water are apparent along the reach.
Moderate - Groundwater table present, but nearly equal to the stream height.
Weak - Groundwater table present, but well below the stream height or indicators of
groundwater discharge are present, but require considerable time to locate.
Absent- No indication of groundwater table in close proximity to stream bed elevation (within
30 cm of streambed surface).
When the channel is dry: Is the streambed / hyporheic zone saturated?
Hyporheic Saturation: even when there is no visible flow above the channel bed, there may be
flow in, or groundwater discharge into, the hyporheic zone (Figure 26).
The hyporheic zone is the site of groundwater discharge to the stream, downstream flow, and
biological and chemical activity associated with aquatic functions of the stream. The presence of
hyporheic saturation can be assessed by making a hole in the thalweg (where possible) and
seeing whether the hole fills with water (similar to the method for observing water table height
described above). The hole may be dug with a shovel, but using an auger, probe, or pounding
in a steel bar are recommended to minimize disturbance to the channel. If soil conditions
prevent digging an adequately deep hole, assess this indicator as best you can and note the
depth of refusal in the "Notes" section.
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Strong- Hyporheic zone is saturated (i.e., standing water visible in excavated hole) to
streambed surface.
Moderate- Hyporheic zone is saturated in close proximity to stream bed elevation (within 10
cm of channel bottom for channels < 1 meter wide; within 20 cm for channels with width
between 1 and 5 meters; within 30 cm for channels > 5 meter wide).
Weak- Hyporheic zone is saturated well below streambed surface.
Absent- No saturation of the hyporheic zone within 50 cm of the streambed surface.
water
table
impermeable
layer-
Figure 26. Idealized depiction of hyporheic zone and groundwater
aquifer (from FISRWG, 1998).
9. Springs and Seeps
Are springs or seeps observed or mapped in the reach being evaluated or in an upstream
reach? (Figure 27)
Springs and seeps often are present at toeslopes of adjacent hillslopes but may also be present
at the heads of secondary channels, at the toe of stream banks, and at grade controls and
headcuts. The presence of springs and seeps suggest that the stream is supported at least
partly by groundwater except during droughts. Score this category based on the abundance of
these features observed within the reach. USGS and other maps often identify springs; however
the accuracy with which these features are identified is often greater in arid and semi-arid areas,
and less so in forested areas and wetter climates.
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Note: If a spring or seep exists within the assessment reach, indicate the location of that feature
on the assessment form. If a spring within or upstream from the reach is mapped, check USGS
and state or local records for any discharge data and attach that to the field assessment form.
Strong - A spring or seeps occur within the stream reach or a mapped spring occurs within the
reach. If a spring is mapped in the reach but is not observed in the reach, this indicator should
be rated moderate.
Moderate - A spring or seeps are observed immediately upstream of the reach or a mapped
spring occurs within a mile upstream of the assessment reach.
Weak-A spring or seeps are observed upstream of the reach, or a mapped spring occurs
more than a mile upstream of the assessment reach
Absent- No springs or seeps are mapped or observed within, or upstream of, the reach.
Figure 27. Seep discharging from
fractured bedrock on channel margins.
10. Evenly Dispersed Leaf Litter and Loose Debris
Are leaves (freshly fallen or older leaves that may be "blackish" in color and/or partially
decomposed) or other available aerially deposited debris accumulating in the thalweg?
(Secondary Indicator) (Figures 28, 29, and 30)
Perennial streams (with deciduous riparian vegetation) should continuously transport plant
material through the channel. Leaves and other aerially deposited debris will occur throughout
the length of non-perennial stream channels, whereas there will be little to no leaves or debris
present in the stronger flowing areas (riffles) with small accumulations on the upstream side of
obstructions. Assessing this indicator may be more difficult during autumn in deciduous forests
when sampling between rain events. In areas where vegetation is non-deciduous, or is sparse
or absent, the presence of other forms of light debris that could be aerially deposited uniformly
on the landscape should be assessed (Figure 30).
Dry channels: The distribution of aerially deposited debris should be assessed for the thalweg,
comparing the distribution of debris in the thalweg to the surrounding channel and uplands.
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Note: The scoring range is reversed for this indicator. "Strong" indicates less flow and receives
fewer points than "Absent".
Strong- Leaf or other aerially deposited litter is present and abundant throughout the length of
the stream.
Moderate - Leaf litter or other aerially deposited debris is present throughout most of the
stream's reach with some accumulation on the upstream side of obstructions and in pools.
Weak- Leaf litter or other aerially deposited debris is present, mostly located in small packs
along the upstream side of obstructions and in pools.
Absent- Leaf litter or other aerially deposited debris is not present in the fast moving areas of
the reach, but there may be some present in the pools.
Figure 28. "Weak" distribution of leaf litter,
with accumulations at discrete locations
(western Cascades, channel width 1.7 m)
Figure 29. "Strong" abundance and
distribution of leaf litter (Klamath Mountains,
approximate channel width 1.5 m)
Figure 30. "Strong" distribution of light
organic debris (Blue Mountains, channel
width 0.8)
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11. Debris Piles and Wrack Lines
Are there accumulations of debris in piles or lines in the channel or on the active
floodplain? (Secondary Indicator) (Figures 31, 32, and 33)
Debris piles are defined as twigs, sticks, logs, leaves, trash, plastics, and any other floating
materials piled up on the upstream side of obstructions in the stream, on the stream bank, in
overhanging branches, and/or in the floodplain that indicate high stream flows. Wrack lines are
twigs, sticks, logs, leaves, trash, plastics, and any other floating materials piled up/deposited in
lines parallel to the channel's direction of flow. Ephemeral streams usually exhibit fewer or no
drift lines within their channels unless downstream of a storm drain or extensive urban runoff.
The magnitude of the accumulation of drift may be influenced by watershed characteristics and
sources of debris. For example, streams in watersheds dominated by herbaceous vegetation
may not exhibit large drift piles. When assessing the strength of coverage by debris piles look
at all the obstructions in the reach that could support a debris pile and assess strength based on
the percentage of obstructions that actually have a debris pile.
Dry channels: Focus the assessment of debris piles on the thalweg.
Strong- Debris piles are prevalent along the upstream side of most obstructions within the
channel and / or wrack lines are prevalent in the floodplain along the length of the reach.
Moderate- Debris piles are on the upstream side of many obstructions and dispersed
throughout the reach or wrack lines are present along parts of the reach.
Weak- Small debris piles are present on the upstream side of one or two of the obstructions or
one wrack line exists along the reach.
Absent- No debris piles or wrack lines are present.
Figure 31. "Weak" abundance of debris
piles; most debris is distributed rather than
aggregated (Blue Mountains, channel width
0.8m)
Figure 32. "Weak" abundance of debris
piles (foothills of the western Cascades;
channel width 0.5 m)
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Figure 33. Example of debris pile.
12. Redoximorphic Features in the Toe of Bank
Are there redoximorphic features present in soils at the toe of the bank, at the base of
head cuts above the streambed, or in the hyporheic zone? (Secondary Indicator) (Figures
34 and 35)
Soils with sufficient periods of inundation or saturation that contain iron (Fe) and manganese
(Mn) may develop distinctive color features. Such redoximorphic ("redox") features form by the
processes of reduction, translocation, and/or oxidation of iron and manganese oxides. Thus, the
presence of redox features in soils in the stream bed or bank provides evidence of extended
annual periods of base flow. Types of redox features include:
Redox concentrations: Bodies of apparent accumulation of Fe-Mn oxides. Includes soft
masses and pore linings, but does not include nodules and concretions.
Redox depletions: Bodies of low soil chroma (< 2) having values of 4 or more where Fe-
Mn oxides have been stripped or where both Fe-Mn oxides and clay have been
stripped. Redox depletions contrast contrast distinctly or prominently with the soil
matrix6.
Reduced matrix: A soil matrix that has low chroma and high value, but in which the color
changes in hue or chroma when the soil is exposed to air.
Gleyed matrix: A soil matrix that has bluish, greenish, or grayish colors, and high
values and low chroma. While technically not a "redoximorphic feature," the presence of
gleyed soils is a strong indicator of saturated soil conditions.
Soils immediately adjacent to the stream bed along the stream bank may have redoximorphic
features. Use an auger, soil probe or spade to obtain at least a 30- to 35-cm (12- to 14-inch)
deep core and examine the soil pedon for redoximorphic features. The soil sample should be
representative of the major streambed/bank soil type observed throughout the assessment
The soil matrix is the dominant soil volume that is continuous in appearance. When three colors occur,
such as when a matrix, depletions, and concentrations are present, the matrix may represent less than 50
percent of the total soil volume.
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reach. Look for redoximorphic features in the surface and in the subsoil. Note that in cumulic
(alluvial) soils with thick surfaces, redoximorphic features may only be found much deeper in the
profile. Also, redoximorphic features can be masked by the presence of high organic matter
concentrations (i.e. N 2.57, 2.5Y 2.5/1 colors in the Munsell Soil Color Charts).
Saturated soils, such as those found in the streambeds of perennial streams, have limited or no
contact with oxygen and will remain reduced, thereby producing low chroma or gleyed soils.
Soils subject to repeated periods of alternating aerobic and anaerobic conditions, such as those
found along the banks of perennial streams, often have a dark colored matrix with brightly
colored redoximorphic features.
Note: While this indicator does not assess the presence or absence of hydric soils, the
definition and discussion of redoximorphic features in the guide Field Indicators of Hydric Soils
in the United States is nonetheless a useful reference.7
C^v*'
mm<
Figure 34. Masses of oxidized iron in a
sandy soil (from NRCS, 2006).
Figure 35. Soil matrix that has been
depleted of iron and manganese oxides
(scale in inches). Concentrations of
oxidized iron are also present (from NRCS,
2006).
7 http://www.usace.army.mil/cw/cecwo/reg/techbio.htm under the Plants and Soils heading
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C. Biological Indicators
13. Wetland Plants In or Near Streambed
What is the wetland indicator status of hydrophytic plants found in the streambed or
within one-half channel width of the streambank?
The USAGE wetland delineation procedure uses a plant species classification system which
identifies hydrophytic plants. This same system can be used as an indicator of the duration of
soil saturation in stream channels. Small, low gradient, low velocity intermittent and perennial
streams with adequate sunlight will often have Obligate (OBL) and Facultative Wetland (FACW)
plants or Submerged Aquatic Vegetation (SAV) growing in the stream bed. SAV grows
completely underwater (Figure 36).
Wetland plant designations can be found in the National List of Plant Species that Occur in
Wetlands: Northwest R9 (1988) and the 1993 Northwest Region 9 Supplement. The score for
this indicator is based on the most hydrophytic wetland plant found in the assessed reach (e.g.,
if both FACW and OBL species are found, the score for this indicator would be 1.5).
Note: Abundance and prevalence throughout the reach is not a factor in scoring this indicator,
but if the reach is covered with wetland species and the stream scores very low overall the site
may be more appropriately considered as a wetland than a stream.
Figure 36. Example of
submerged aquatic vegetation.
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14. Fibrous Roots and Rooted Plants in Thalweg (Upland Plants)
Are fibrous roots of woody upland plants present in the thalweg of the stream? Are
rooted herbaceous upland plants growing in the thalweg of the stream? (Figure 37)
Fibrous roots are small diameter (<1 cm or < 0.25 in), shallow, wide spreading roots without
bark that often form dense masses in the top few inches of the soil. Fibrous roots of perennial,
woody plants (i.e., trees and shrubs) are those which provide for water and nutrient uptake.
Because oxygen is needed for respiration, fibrous roots are intolerant of saturation, unless they
are roots of water tolerant plants. Thus, in substrates where water is persistent, or frequent high
energy flows disturb the bottom substrate, fibrous roots may be infrequent or absent.
Because streamflow often deters upland plant establishment by removing seeds, scouring
plants, and preventing aeration of roots, herbaceous upland plants are also generally absent in
the thalweg of perennial streams.
Observe the bottom of the stream and determine if very small (fibrous) roots are present. Focus
on the presence of rooted plants in the thalweg of the stream. Fibrous roots or plants growing
on any part of the bank of the stream should not be considered. Note that during dry periods
and in the growing season, fast growing fibrous roots may grow across the bottom of a dry
stream that would not be present or survive during normal flow.
Note: The scoring range is reversed for this indicator. A higher score is given for the absence
of upland fibrous roots and rooted plants.
Strong- Fibrous roots or rooted upland plants are present in many places along the reach.
Moderate - Fibrous roots or rooted upland plants are present in approximately half of the reach.
Weak- Fibrous roots or rooted upland plants are present in one or two places along the reach.
Absent- Fibrous roots or rooted upland plants are not present in the reach.
Figure 37. Example of an
upland plant's fibrous roots
growing in a stream channel.
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15. Streamer Mosses or Algal Mats
Are there streamer mosses present in the streambed? Are algal mats present in the
reach? (Secondary Indicator) (Figures 38, 39, 40, and 41)
Bryophytes (mosses and liverworts) are long-lived, non-vascular (without lignin) plants which
inhabit a wide range of habitats. Some bryophytes have growth forms that trap moisture for
survival; however some growth forms do not efficiently trap moisture and require a sustained (or
recurring) presence of water in order to survive. Mosses of the streamer morphology - with
long flowing stems - indicate a sustained or recurring presence of water (Figures 38 and 39).
Algal matting is another indicator of duration of inundation. Look for clumps of filamentous algae
attached to the streambed or substrate (Figure 40). Algal mats are also evident in dry channels
(especially dry pools), and appear as a crust-like layer on top of the streambed. The crust-like
layer often appears to be salts or other minerals left behind when the last remaining water
evaporated out of the pool, but upon closer inspection may reveal a dried mat of filamentous
algae rather than a crystalline/mineral residue. Algal matting often occurs in association with
prismatic cracking of the streambed, which indicates high clay content in the streambed and is
another sign of water loss through evaporation (Figure 41). The presence of algal matting
indicates that the stream held water long to support algal growth sufficient to form a mat.
Note: Only the presence of streamer mosses and attached or matted filamentous algae are
being assessed - growth of other mosses (cushion, turfs, etc.) or algae (non-filamentous,
floating, etc.) should not be considered for this indicator.
Strong - Streamer mosses are present throughout the reach.
Moderate - Streamer mosses are present in approximately half of the reach, and / or attached
filamentous algae are present throughout the reach.
Weak- Streamer mosses and / or attached filamentous algae are present in the reach.
Absent -Streamer mosses and / or attached filamentous algae are not present.
xl
T
Figure 38. Example of desiccated streamer
mosses (Blue Mountains).
Figure 39. "Strong" abundance of streamer
mosses (Northern Basin and Range,
channel width 0.8 m).
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Figure 40. Example of dried attached
filamentous algae.
Figure 41. Example of algal mat on top of
fine-textured streambed.
16. Iron-Oxidizing Bacteria, Fungi, or Flocculent Material
In slow moving or stagnant areas of the stream, are there clumps of "fluffy" rust-red
material in the water? Are orange-red flocculent materials or stained rocks present in the
stream? Are there red or rust colored stains (usually an "oily sheen" or "oily scum" will
accompany these areas) on the bank or in the streambed? (Figures 42 and 43)
Iron-oxidizing bacteria and fungi, and associated flocculent material, are often associated with
groundwater. Iron-oxidizing bacteria/fungus in streams derive energy by oxidizing iron,
originating from groundwater, from the ferrous form (Fe2+) to the ferric form (Fe3+). In large
amounts, iron-oxidizing bacteria and fungi discolor the stream substrate, giving it an orange-red
appearance. In small amounts, it can be observed as an oily sheen on the water's surface. This
indicates that the stream is being recharged by groundwater, and these features are most
commonly seen at seeps or springs.
Filmy deposits on the surface or banks of a stream are often associated with the greasy
"rainbow" appearance of iron-oxidizing bacteria. This is a naturally occurring phenomenon
where there is iron in the groundwater, but can also be caused by organic acids associated with
leaf litter and septic tanks. A sudden or unusual occurrence may indicate a petroleum product
release or septic tank problem. One way to differentiate iron-oxidizing bacteria from petroleum
releases is to trail a small stick or leaf through the film. If the film breaks up into small islands or
clusters, it is most likely bacterial in origin; if the film swirls together, it is most likely a petroleum
product.
Note: Springs or seeps with iron-oxidizing bacteria, fungus or flocculent materials present
should be assessed for both Indicator 9 (Springs and Seeps) and Indicator 16 - (Iron-Oxidizing
Bacteria, Fungi, Flocculent Material).
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Strong- Iron-oxidizing bacteria, fungi or flocculent materials are present in many places in the
reach.
Moderate- Iron-oxidizing bacteria, fungi or flocculent materials are present in a few places in
the reach.
Weak- Iron-oxidizing bacteria, fungi or flocculent materials are present in one or two small
places in the reach.
Absent - There are no iron-oxidizing bacteria, fungi or flocculent materials present in the reach.
1
mm
iASBi£~?:£»-.^_ A j
-^ ..'.' ^"T1*"---
A'
Figure 42. Example of iron-oxidizing
microorganisms.
Figure 43. "Strong" abundance of iron-
oxidizing microorganisms.
17. Macroiinvertebrates
Is there evidence of aquatic macro-invertebrates within the reach? (Figures 44 and 45;
Also see Appendix C)
Many macroinvertebrates require the presence of water, and in many cases flowing water, for
their growth and development. Such macroinvertebrates are good indicators of streamflow
duration because they require aquatic habitat to complete specific life stages. For example,
clams cannot survive outside of water, in contrast to some stoneflies or alderflies that resist
desiccation in some seasons of the year by burrowing into the hyporheic zone. Some
macroinvertebrates can survive short periods of drying in damp soils below the surface, or in
egg or larval stages resistant to drying. Others are quick to colonize temporary water and
complete the aquatic portion of their life cycle during the wettest part of the year when sustained
flows are most likely.
This indicator includes the range of macroinvertebrates typically associated with stream habitats
including: Coleoptera (aquatic beetles), Diptera (true flies), Ephemeroptera (mayflies),
Megaloptera (dobsonflies and alderflies), Mollusca (snails and clams), Odonata (dragonflies and
damselflies), Plecoptera (stoneflies), Trichoptera (caddisflies), and Astacoidea (crayfish).
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Macro! nvertebrates of the Pacific Northwest (Adams and Vaughan, 2003)8 provides a useful,
compact and inexpensive field guide for general identification of several aquatic
macroinvertebrate families found in Oregon streams. A condensed field guide for use with this
method is included in Appendix C.
The scoring system for this indicator was informed by a literature review and synthesis
completed by the Xerces Society for Invertebrate Conservation (Mazzacano and Black, 2008).9
Several taxa and lifestages have been identified as either "Perennial Indicators" or "Intermittent
Indicators" (Table 3); there is a high level of confidence that these indicator taxa are associated
with the prolonged presence of water. (These taxa are also "Single Indicators"; see Section 3.)
Table 3. Indicator status of various macroinvertebrate taxa
Perennial Indicator Taxa / Lifestage
Juga spp. (pluerocerid snail)
Freshwater mussels (Margaritiferidae, Unionidae); less likely in small high-gradient
streams
Larvae/pupae of:
Philopotamidae (finger-net caddisfly)
Hydropsychidae (net-spinning caddisfly)
Rhyacophilidae (freeliving caddisfly)
Glossosomatidae (saddle case-maker caddisfly), esp. in forested headwater streams
Nymphs of:
Pteronarcyidae (giant stonefly)
Perlidae (golden stonefly)
Larvae of:
Elmidae (riffle beetle)
Psephenidae (water penny), esp. in eastern regions
Larvae/nymphs of:
Gomphidae (clubtail dragonfly) -^
Cordulegastridae (biddies) kesp. in larger streams in eastern Oregon
Calopterygidae (broadwinged damselfly) j
Intermittent Indicator Taxa / Lifestage
Larvae/pupae of:
Limnephilidae (Northern caddisfly)
Nymphs of:
Capniidae (small winter stonefly)
Nemouridae (forestfly)
Larvae/adults of:
Dytiscidae (predaceous diving beetle)
Hydrophilidae (water scavenger beetle)
Larvae/nymphs of:
Lestidae (spread-winged damselfly)
Ephemeral Indicator Taxa / Lifestage
Larvae/pupae of:
Culicidae (mosquito)
8 Published by The Xerces Society. Portland, OR (www.xerces.org)
9 Available at http://www.xerces.org/aquatic-invertebrates/
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This indicator is assessed using a minimum 20-minute search time to sample the range of
habitats present, including water under overhanging banks or roots, accumulations of organic
debris (e.g. leaves), woody debris, and the substrate (pick up rocks and loose gravel, also look
for empty clam shells washed up on the bank in the coarse sand). A kicknet or D-frame net
and a hand lens are required to collect and identify specimens. Place the kicknet
perpendicular against the streambed and stir the substrate upstream of the net for a minimum of
one minute, empty contents of the net into a white tray with fresh water for counting and
identification. Many individuals will appear the same until seen against a contrasted color
background, and some bivalves and other macroinvertebrates can be pea-sized or smaller.
Sweeping grass and shrubs in the riparian zone immediately adjacent to the active channel with
a funnel-shaped insect net may collect emergent aquatic insects such as stoneflies or
caddisflies.
Dry channels; Focus the search on the sandy channel margins for mussel and aquatic snail
shells, any remaining pools for macroinvertebrates, and under cobbles and other larger bed
materials for caddisfly casings. Casings of emergent mayflies or stoneflies may be observed on
dry cobbles or on stream-side vegetation.
Notes:
Time estimates for scoring do not reflect time spent on identifying individuals, rather they are
wholly focused on searching / gathering effort.
This indicator does not differentiate between live organisms and shells, casings, and
exuviae (i.e., the external coverings of the larvae and nymphs). In other words, mussel
shells are treated the same as live mussels, and caddisfly cases are treated the same as
live caddisflies (Figure 45)
The assessment is based only on what is observed, not on what would be predicted to occur
if the channel were wet, or in the absence of disturbances or modifications. Disturbances
and modifications should be described in the notes section and taken into account when
drawing conclusions.
For greatest efficiency macroinvertebrates should be searched concurrently with the
amphibian search (Indicator 18).
Strong - At least one of the Perennial Indicator taxa is present, or at least 5 families within the
orders of Ephemeroptera, Plecoptera, or Trichoptera (EPT) are present.
Moderate - At least one of the Intermittent Indicator taxa is present, or at least 2 families within
the EPT orders are present, or at least 5 taxa of aquatic macroinvertebrates are present.
Weak-At least one aquatic macrovinvertebrate is present.
Absent- No aquatic macroinvertebrates are found.
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Figure 44. Example of caddisfly casings of
the Limnephilidae family. Note that presence
of these casings would meet the "single
indicator" criteria for macroinvertebrates.
A vr
Figure 45. Abundant caddisfly casings from
in the Blue Mountains. Note that presence
of these casings would meet the "single
indicator" criteria for macroinvertebrates.
18. Amphibians and Snakes
Are amphibians and snakes that require aquatic habitats present in the reach?
(Secondary Indicator) (Figures 46 and 47)
Amphibians by definition are associated with aquatic habitats, and some amphibians require
aquatic habitat for much or all of their lives. In Oregon, there are likewise three snake species
that require aquatic habitat for significant portions of their life history. This indicator focuses on
the life history stages of salamanders, frogs, toads, and snake species, which require aquatic
habitat by indicating life history stages for these species as FAC, FACW, or OBL (see Table 4).
This indicator is assessed using a minimum 20-minute search time to sample the range of
habitats present and can be searched concurrently with the macroinvertebrate search
(Indicator 17) for greatest efficiency. Various life stages of frogs, salamanders, and tadpoles
can be found under rocks, on stream banks and on the bottom of the stream channel. They may
also appear in benthic samples. Using kicknets or smaller nets and tubs for specimen
collection and identification is recommended. Frogs will alert you of their presence by
jumping into the water for cover, usually following an audible "squeak". Certain frogs and
tadpoles, as well as adult and larval salamanders typically inhabit the shallow, slower moving
waters of stream pools and near the sides of the bank. Amphibians of Oregon, Washington and
British Columbia (Corkran and Thomas, 2002)10 is a useful field guide for identifying amphibians
of the Pacific Northwest.
10
Amphibians of Oregon, Washington and British Columbia (1996). C. Corkran and C. Thomas, Lone
Pine Publishing, Redmond, WA.
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Many of the obligate frog (tadpole-adult) and salamander species such as the Tailed frog
(Figure 46), the Torrent salamanders, and the two Giant Salamander species will be found in
the fast flowing portions of a stream. The three snake species listed in the table below will
usually be found along the streambank, within the wetted margin of the stream, or on exposed
rocks within the stream channel11.
Amphibian eggs, also included for this indicator, can be located on the bottom of rocks, attached
to vegetation in backwaters or along the stream margin, and in or on other submerged debris
(Figure 47). They are usually observed in gelatinous clumps or strings of eggs, unlike snail and
insect eggs, which are also often found on the bottom of rocks or attached to debris.
Table 4 lists amphibians and snakes likely to be found in Oregon and the water-dependent life
history stages for each. All egg masses, tadpoles, or salamander larvae count as OBL for a
water-dependent life stage. Please note amphibian breeding adults require water, therefore
adult FACW and FAC species found breeding should be scored as OBL. For instance, the adult
Western Toad is listed as FAC, but would be scored as OBL if found breeding.
Table 4. Water-dependent Life Stages of Amphibians and Snakes of the Pacific
Northwest (Note: OBL: Obligate, requires surface or hyporheic water; FACW: Facultative Wet,
strong preference for surface or hyporheic water; FAC: Facultative, uses but does not depend
on surface or hyporheic water.)
Species
Common Name
Water-Dependent Life Staqes
Eggs
Larva/
Tadpole
Juve.
Adult
Aquatic Salamanders
Ambystoma gracile
Ambystoma
macrodactylum
Ambystoma tigrinum
Taricha granulosa
Dicamptodon cope;
Dicamptodon tenebrosus
Rhyacotriton spp.
Northwest Salamander
Long-toed Salamander
Tiger Salamander (rare)
Roughskin Newt
Cope's Giant Salamander
Pacific Giant Salamander
Torrent Salamanders
(rare)
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
FACW
FACW
FACW
FAC
OBL
OBL
OBL
FACW
FACW
FACW
FAC
OBL
FACW
OBL
Frogs and Toads
Ascaphus truei
Spea intermontana
Tailed Frog
Great Basin Spadefoot
(Eastern Oregon)
OBL
OBL
OBL
OBL
OBL
FAC
OBL
FAC
11 Reptiles of the Northwest: California to Alaska; Rockies to the Coast (2002), A. St. John, Lone Pine
Publishing, Redmond, WA.
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Species
Bufo boreas
Bufo woodhousii
Pseudacris regilla
Rana aurora
Rana boylii
Rana cascadae
Rana catesbeiana
Rana pretiosa
Rana luteiventris
Common Name
Western Toad
Woodhouse's Toad
(Eastern Oregon)
Pacific Treefrog
Red-Legged Frog
Foothill Yellow-Legged
Frog
Cascades Frog
Bullfrog
Oregon Spotted Frog
Columbia Spotted Frog
Water-Dependent Life Staqes
Eggs
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
Larva/
Tadpole
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
Juve.
FAC
FAC
FACW
FACW
OBL
FACW
FACW
OBL
OBL
Adult
FAC
FAC
FAC
FACW
OBL
FACW
FACW
OBL
OBL
Snakes
Thamnophis atratus
Thamnophis elegans
Thamnophis sirtalis
Western Aquatic Garter
Snake (SW Oregon)
Wandering Garter Snake
Common Garter Snake
OBL
FACW
FACW
OBL
FACW
FACW
OBL
FACW
FACW
Notes:
Time estimates do not reflect time spent identifying individuals, rather they are wholly
focused on searching / gathering effort.
The assessment is based only on what is observed, not on what would be predicted to
occur in the absence of disturbances or modifications. Disturbances and modifications to
the stream should be described in the notes section and taken into account when
drawing conclusions.
For greatest efficiency, the amphibian/ snake search should be done concurrently with
the macroinvertebrate search (Indicator 17).
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Strong-At least one individual, egg or egg mass of an OBL water-dependent life stage or two
or more individuals, eggs or egg masses of at least two species listed as FACWfor any water-
dependent life stage is present.
Moderate - At least one individual, egg or egg mass of a FACW water-dependent life stage or
two or more individuals, eggs or egg masses of one or more species listed as FAC for any
water-dependent life stage is present.
Weak - At least one individual, egg or egg mass of a water-dependent life stage is present.
Absent- No water-dependent amphibian or snake life stages are found.
Figure 46. Tailed frog (Ascaphus truei), an
"obligate" species whose presence would
meet the "single indicator" criteria for
amphibians.
Figure 47. Amphibian egg mass found on
the underside of a rock.
19. Fish
Are there fish in the stream?
Fish are an obvious indicator of flow presence and duration. Fluctuating water levels of
intermittent and ephemeral streams provide unstable and stressful habitat conditions for some
fish communities. However, the strongly seasonal precipitation pattern in Oregon means
intermittent streams may flow continuously for several months; thus, some native fish species
have evolved to use intermittent streams for significant portions of their lifespan.
When looking for fish, all available habitats should be searched, including pools, riffles, root
clumps, and other obstructions (polarized sunglasses are helpful to reduce surface glare). In
small streams, the majority of species usually inhabit pools and runs. Also, fish will seek cover
once aware of your presence, so be sure to look for them slightly ahead of where you are
walking along the stream. Check several areas along the stream sampling reach, especially
underneath undercut banks.
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Strong - Several fish or a few different species of fish are found in the reach.
Moderate - A few fish or two different species are found in the reach.
Weak- One or two fish are found in the reach.
Absent- No fish are found in the reach.
20. Lichen Line (Used Only in Arid Regions and Alpine Areas)
Is there a line on the rocks in the stream bed, or on the banks, below which no lichen
grows? (Secondary Indicator) (Figures 48 and 49)
Lichens are a symbiotic association of fungi and algae growing together. Generally, they are
tolerant of dry conditions and temperature extremes and can colonize bare rock and survive in
arctic and alpine conditions. However, they grow very slowly and are not very tolerant of
physical abrasion or inundation. Lichens may occur on rocks, large woody debris, live trees and
other hard surfaces extending out of the streambed. If lichens are present, identify whether
there is a distinct horizontal line below which the substrate does not change but no lichens grow
(Figure 49). This indicator applies only in arid regions and alpine areas.
Note: As used below, "height" means elevation above the streambed at a cross-sectional point
along the reach. The "height" of the lichen line may vary between locations along the length of
the reach.
Strong- Lichens are present along the length of the reach and form a line at approximately the
same height.
Moderate - A few lichens are present in the reach and most stop at the same height above the
streambed.
Weak- Lichens are present, but they do not form a clear height line along the reach.
Absent- Lichens are not present in or near the channel, or if present are found throughout the
reach, including in the thalweg.
Figure 48. Example of lichen line.
Figure 49. "Strong" distribution of lichen
lines (Columbia Plateau, approximate
channel width 4 m).
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21. Distinct Riparian Vegetation Corridor (Used Only in Arid Regions)
Is there a distinct change in vegetation between the surrounding uplands and the
riparian corridor along the stream channel?
Especially in arid regions, intermittent and perennial streams often support riparian areas that
contrast markedly with adjacent plant communities. A distinct change in vegetation between the
surrounding lands and the riparian area (top of bank and immediately adjacent areas within a
channel width) may indicate the presence of seasonal moisture. Such changes may be
evidenced by the occurrence of less drought tolerant species, vegetation types, or plant
communities.12 For instance, upland grasses and shrubs may transition abruptly or gradually to
riparian vegetation (e.g. willows, cottonwood, sedges, etc.).
Note: This indicator applies only in the Arid West Region. Also note on the assessment form
any reasons why this indicator would not be present, for example livestock grazing.
Strong-A distinct riparian vegetation corridor exists along the entire stream reach.
Moderate - A distinct riparian vegetation corridor exists along part of the stream reach or there
is some change in vegetation towards less drought tolerant species along the entire stream
reach.
Weak- There is some change in vegetation towards less drought tolerant species along parts
of the stream reach.
Absent - There is no change in vegetation towards less drought tolerant species along the
stream reach.
Figure 50. Riparian corridor is "absent"
along this drainageway (Northern Basin and
Range).
Figure 51. "Strong" riparian corridor, as
indicated by distinct transition from upland
to riparian species and continuity of riparian
vegetation along entire stream reach.
12 Wetland Plants of Specialized Habitats in the Arid West (Lichvar and Dixon, 2007) lists wetland and
upland plants (and their wetland indicator status) in the arid west, grouped by habitat.
(http://www.crrel.usace.army.mil/library/technicalpublications-2007.html)
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SECTION 3: Drawing Conclusions
The results of the field assessment are used to make a finding as to whether the weight of the
observations indicates perennial, intermittent, or ephemeral streamflow.
The method indicates the stream is perennial when the following criteria is met:
1. A numerical value of at least 25 points.
If the stream segment being evaluated does not meet the above criteria, the method
indicates the stream is intermittent when any of the following criteria are met:
2. A numerical value of at least 13 points.
Or
3. One or more fish are found in the segment.
Or
4. One or more individuals of an amphibian or snake life stage identified as Obligate or
Facultative Wet (Table 4) are present.
Or
5. Two or more individuals classified as "Perennial Indicator" or "Intermittent Indicator" (Table 3)
are present; or, two or more caddisfly cases, mussel shells, or aquatic invertebrate exuviae (i.e.,
the external coverings of the larvae and nymphs) associated with the sustained presence of
water are present.
If the stream has a bed and banks but does not meet any of the above criteria, the
method indicates the stream is ephemeral. If the stream does not have a bed and banks
and does not meet any of the above criteria, it may be more appropriate to consider the
stream as a swale, wetland, or upland.
As discussed in the introductory sections on Ditches and Modified Natural Streams and Scoring,
if the channel does not meet any of the above criteria and the practitioner believes the channel
to be perennial or intermittent s/he must clearly describe on the assessment form the evidence
supporting this assertion. This may occur in highly polluted or recently manipulated streams. In
those cases the actual observed indicators should be scored as usual, and the indicators that
could potentially be there were it not for the pollution/manipulation should be described and the
"Notes" section of the datasheet.
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Appendix A: References Consulted
Adams, Jeff and Vaughan, Mace. 2003. Macroinvertebrates of the Pacific Northwest: A Field Guide. TheXerces
Society, Portland, OR.
Adams, Jeff; Vaughan, Mace; Black, Scott Hoffman. 2004. Stream Bugs as Biomonitors: Guide to Pacific Northwest
Macroinvertebrate Monitoring. The Xerces Society, Portland, OR.
Adams, M.J. and R.B. Bury. 2002. The endemic headwater stream amphibians of the American Northwest:
associations with environmental gradients in a large forested preserve. Global Ecology & Biogeography
11:169-178.
Anderson, Russel J.; Bledsoe, Brian P.; Hession, W. Cully. 2004. Width of streams and rivers in response to
vegetation, bank material, and other factors. Journal of American Water Resources Association. 1159-1172.
Arp, Christopher D.; Gooseff, Michael N.; Baker, Michelle A.; Wurtsbaugh, Wayne. Surface-water hydrodynamics and
regimes of a small mountain stream-lake ecosystem. Journal of Hydrology. 329:500- 513.
Barbour, M.T., J. Gerritsen, B.D. Snyder, and J.B. Stribling. 1999. Rapid Bioassessment Protocols for Use in Streams
and Wadeable Rivers: Periphyton, Benthic Macroinvertebrates and Fish, Second Edition. EPA 841-B-99-
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Oregon Streamflow Duration Assessment Method - Interim Version (March 2009) 51
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Appendix B: Streamflow Duration Field Assessment Form
The Field Assessment Form is provided on the following two pages
Oregon Streamflow Duration Assessment Method - Interim Version (March 2009) 52
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Oregon Streamflow Duration Field Assessment Form (Interim Version - March 2009)
Project # / Name
Address
Waterway Name
Reach Boundaries
Precipitation w/in 48 hours (cm) Channe
"Dry Channel"
E valuator
Attended O Orientation O Field Training
Date
Coordinates at Lat. N
downstream end
(ddd.mm.ss) Lon9' W
I Gradient (%) Channel Width
"Wet Channel"
Obseived s- ->, ^- >
Hydrology: D Water Q No surface flow but at Q Surface flow present but Q Continuous
Absent least one pool present not spatially continuous surface flow
D Disturbed Site /Difficult Situation (Describe in "Notes") | Absent Weak Moderate Strong
1. Continuous Bed and Bank
Do CM D2 Ds
2. In-channel Structure /Organized Sequences fj0 CM D 2 d 3
§" 3. Soil texture or stream substrate sorting
.i 4. Erosional Features n check this box if >5
o 5. Depositional Features of exposed bedrock
2 6. Sinuosity
7. Headcuts And Grade Controls
DO CM D2 DS
3% DO DO. 5 D 1 D 1-5
DO CM D2 DS
Do no.5 CM CM.5
GEOMORPHOLOGY SUBTOTAL:
8. Groundwater (Wet) / Hyporheic (Dry)
>, 9. Springs And Seeps (Note Locations)
DO CM D2 DS
DO CM D2 DS
° 10. Evenly Disbursed Leaf Litter / Loose Debris T d 1.5 d 1 d 0.5 d 0
o
^ 11. Debris Piles And Wrack Lines
12. Redoximorphic Features In Toe Of Bank
Do DO. 5 D 1 D 1.5
D Absent = 0 Q Present = 1 .5
HYDROLOGY SUBTOTAL:
13. Wetland Plants In / Near Streambed D FAC 0.5 D FACW 0.75 D OBL 1 .5 D SAV 2 D None
14. Fibrous Roots / Rooted Plants In Thalweg
15. Streamer Mosses And Algal Mats
Yd3 C|2 CM DO
Do no.5 CM CM.5
16. Iron Oxidizing Bacteria, Fungus, Flocculent d 0 CM Cl 2 d 3
g 17. Macroinvertebrates
~ 18. Amphibians
19. Fish
20. Lichen Line (Arid Regions and Alpine Areas Only)
21 . Riparian Corridor (Arid Regions Only)
ClFish
Single D Amphibians
Indicators:
D Macroinvertebrates
Note: Scoring scale is reversed
for indicators marked with T.
Do CM D2 Ds
Do Do. 5 CM CM.5
Do CM D2 Ds
Do Do. 5 CM CM.5
Do CM D2 Ds
BIOLOGY SUBTOTAL:
* TOTAL SCORE:
Flow Duration (select only one)
Ephemeral Q Total Score < 13
Intermittent Q Total Score > 13 or Single Indicator
Perennial Q Total Score > 25
Oregon Streamflow Duration Assessment Method - Interim Version (March 2009)
53
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Notes (explanation of any single indicator conclusions, description of disturbances or modifications that may
interfere with indicators, etc.)
Difficult Situation- Describe situation. For disturbed streams, note extent,
type, and history of disturbance.
n Prolonged Abnormal Rainfall / Snowpack
D Below Average
n Above Average
D Natural or Anthropogenic Disturbance
D Other:
Describe and Explain any Indicators of Questionable Applicability:
Other Notes (sketch of site, description of photos, depth of observed groundwater, etc.)
Oregon Streamflow Duration Assessment Method - Interim Version (March 2009) 54
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Appendix C: A field guide to accompany the
macroinvertebrate scoring portion of the Oregon Streamflow
Duration Assessment Method
The Field Guide is provided on the following four pages
Oregon Streamflow Duration Assessment Method - Interim Version (March 2009) 55
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This page intentionally blank
Oregon Streamflow Duration Assessment Method - Interim Version (March 2009) 56
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Str eamf low Du ration
. . " . r: ""% "?'*». - .. --'-=1 :, " ~ "" -;'?*. "'v-K
of Ihc Or gon^treamflo i an Assessment Method *
-'.>," .- ***- -' , -...». * _ * » ,....._ ' . - -'-'i . ' -v,. ,-= '>.,-.? '*'"
EPHEMEROPTERA: MAYFLIES
Larvae (nymphs): elongated body, may be cylindrical or flattened, 3-20 mm (0.1-0.8 in.); tip of abdomen with three (sometimes two) long
slender cerci ("tails"); developing forewing pads visible; plate-like, feathery, or fringed gills at sides of abdomen; some types have larger
fore-gills that form a shield like cover over other gills; conspicuous eyes; slender antennae
Heptageniidae
(flathead mayfly)
Baetidae
(small minnow mayfly)
Ephemeridae
(common burrower
mayfly)
Isonychiidae
(brush-legged mayfly)
Leptophlebiidae
(prong gill mayfly)
Ephemerellidae
(spiny crawl@repft'Streamflow Duration Assessment Method - Interim Version (March 2009)
Caenidae
(little squaregill mayfly)
57
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MOLLUSCA: MUSSELS & SNAILS
Freshwater mussels, Margaritiferidae (Margaritifera spp), Unionidae
(Anodonta & Gonidea spp.): bivalved shell with two oblong halves; can reach
>15 cm (6 in.); more common in larger rivers with softer substrate
Juga snails: dark reddish-brown to black shell,
smooth or ridged; pale lines may spiral with
coils; 10-30 mm (0.4-1.2 in.)
Gonidea angulata
(western ridged mussel)
Anodonta nuttaltiana
(winged floater)
Margaritifera falcata
(western pearlshell)
PLECOPTERA: STONEFLIES
Larvae (nymphs): elongate, slightly flattened body with "roachlike" appearance; 5-35 mm (0.2-1.4 in.); long slender antennae; two pairs of
wing pads visible on older larvae; tip of abdomen has two "tails" (cerci); fingerlike or filamentous gills may be visible on bases of the
legs, thorax, or underside of abdomen
Perlidae (golden stonefly)
Pteronarcyidae
(giant stonefly)
Capniidae (snowfly)
Peltoperlidae
(roachfly)
TRICHOPTERA: CADDISFLIES
Larvae: elongate, caterpillar-like body; antennae reduced & inconspicuous; no wing pads; tip of abdomen has pair of short, clawed, anal
prolegs, but no "tails" (cerci); 2-40 mm (0.08-1.6 in.); filamentous gills may be present in some types; some are free-living & spin silken nets,
others build elongated, cylindrical, coiled, or saddle-shaped portable cases from stones, twigs, leaves, & other organic material; cases may
persist in dry channels
Glossosomatidae
(saddle case-maker)
Limnephilidae
(Northern caddisfly)
Philopotamidae
(finger-net caddisfly)
Helicopsychidae
(snail case-maker)
Hydropsychidae
(net-spinning caddisfly)
Rhyacophilidae
(green rockworm)
Leptoceriade
(longhorned case-maker)
Oregon Streamflow Duration Assessment Method - Interim Version (March 2009)
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COLEOPTERA: AQUATIC BEETLES
Larvae: body shapes vary; most types elongated, cylindrical, some dome-shaped; may have long filaments at the sides or tip of
abdomen; well-developed, tough head and mouthparts; no wing pads; 2-70 mm (0.08-2.8 in.)
Adults: body shapes vary; often oval and slightly flattened, some types cylindrical; forewings form hard smooth shiny covers
(elytra) when folded, meet in straight line down the back, covering membranous hindwings and most of abdomen; legs may be
flattened or fringed with swimming hairs; 1-40 mm (0.04-1.6 in.)
Dytiscidae (predaceous
diving beetle, adult (top)
& larva)
Gyrinidae
(whirligig beetle,
larva (left) &
adult)
Psephenidae (water penny,
larvae)
Hydrophilidae (water
scavenger beetle, adult)
Elmidae (riffle beetle, larva and
adults)
Haliplidae (crawling water
Beetle, adult)
ODONATA: DRAGONFLIES & DAMSELFLIES
Larvae (nymphs): dragonflies = stout, cylindrical to flattened body; abdomen ends in 3 short stiff points; damselflies = slender elongated
body with 3 flattened leaf-like gills at tip of abdomen; both have large eyes, wing pads, long extendable "lower lip" (labium) that masks the
lower part of head when not in use
Gomphidae
(clubtail dragonfly)
Calopterygidae
(broadwinged damselfly)
"'.
Aeshnidae
(darner dragonfly)
Macromiidae
(river skimmer dragonfly)
Libellulidae
(skimmer dragonfly)
Coenagrionidae
(narrowwinged damselfly)
Dregon Streamflow Duration Assessment Method - Interim Version (March 2009)
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HEMIPTERA: AQUATIC TRUE BUGS
Larvae (nymphs) & adults: body slender, oval to elongate, may be flattened; 1-65 mm (0.04-2.6 in.); cone- or needle-like beak arises
from front of head, folded under body when not in use; have developing wing pads (nymphs) or wings (adults); adult forewings thickened
& leathery at the base, membranous at the tips, cross at tips when folded; legs may be flattened like oars or fringed with swimming hairs
Gerridae (water strider, nymph)
Nepidae (water scorpion, adult)
Chironomidae (non-
biting midge, pupa &
larvae)
Notonectidae
> (backswimmer, adult)
Corixidae
(water boatman, adult)
Belostomatidae
(giant water bug, nymph)
DIPTERA: AQUATIC & SEMI-AQUATIC TRUE FLIES
Dixidae (dixid midge, larva)
Ceratopogonidae (biting midge, larva)
Athericidae (watersnipe fly, larva)
Tipulidae (crane fly, larvae)
Culicidae (mosquito,
larva
Blepharicidae (netwinged
midge, larva)
ADDITIONAL GROUPS OF AQUATIC INVERTEBRATES
Class Oligochaeta
(aquatic earthworm)
Class Turbellaria
(flatworms)
Subclass Hirudinea
(leeches)
Phylum Nematomorpha
(horsehair worm)
Order Isopoda (aquatic sowbug)
Order Decapoda (crayfish)
Order Amphipoda (scud, side
swimmer)
Order Megaloptera, Family Corydalidae
(dobsonfiy/fishfiy larva, left) & Family
Sialidae (alderfly larvae, right)
To read the complete report, "Macroinvertebrates as Indicators of Stream Duration", visitwww.xerces.org/aquatic-invertebrates/
All photos copyrighted by The Xerces Society, unless otherwise noted.
The Xerces Society for Invertebrate Conservation, 4828 SE Hawthorne Blvd., Portland OR 97215, 503-232-6639
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