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Alliance for Aquatic Resource Monitoring
Visual Assessment
Manual
February 2009
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Assessment Manual. Is licensed under the Creative Commons
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TABLE OF CONTENTS
Background on ALLARM ........................................................................................................................... 3
Background on Visual Assessment ........................................................................................................... 3
Quantifying Your Results .......................................................................................................................... 4
Site Description and Diagram ................................................................................................................... 4
Categories.................................................................................................................................................. 7
Channel Condition ............................................................................................................................. 7
Bank Stability ...................................................................................................................................... 8
Riparian Zone ..................................................................................................................................... 9
Water Appearance ........................................................................................................................... 10
Nutrient Enrichment ........................................................................................................................ 11
Fish Barriers ...................................................................................................................................... 12
In-Stream Fish Cover ........................................................................................................................ 12
Insect/Invertebrate Habitat ............................................................................................................. 13
Embeddedness ................................................................................................................................. 14
Canopy Cover .................................................................................................................................... 15
Manure Presence ............................................................................................................................ 15
Sewage ............................................................................................................................................. 15
Assessment Scores ................................................................................................................................... 16
Problem Diagram Sample......................................................................................................................... 17
Problem Diagram ..................................................................................................................................... 18
Glossary .................................................................................................................................................... 19
References and Acknowledgements ........................................................................................................ 21
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Background on ALLARM:
The Alliance for Aquatic Resource Monitoring (ALLARM) is a project of the Environmental Studies
Department at Dickinson College. Since its founding in 1986, ALLARM has become a nationally
recognized technical and programmatic support center for
community organizations interested in watershed
assessment, protection, and restoration. ALLARM program
goals are to:
1) Enhance local action for the protection and
restoration of Pennsylvania watersheds by
empowering communities with scientific knowledge
and tools to implement watershed assessments;
2) Provide Dickinson College students with
opportunities to participate in community-based
participatory research thereby enhancing the
quality of undergraduate science education; and
3) Be the leader in volunteer monitoring in
Pennsylvania and a national model for college-
community partnerships.
Through the work of student and professional staff, ALLARM
offers comprehensive services to enable groups to use critical scientific tools to enhance environmental
quality and fully participate in community decision-making. The program staff includes a Director, an
Assistant Director, a faculty Science Director, and 12-14 undergraduate student staff.
For more information on please visit: www.dickinson.edu/allarm or email: allarm@dickinson.edu
Background on the USDA Visual
Assessment Protocol:
The USDA Visual Assessment Protocols, or "streamwalks,"
allow watershed groups to evaluate stream sites based on
the physical conditions of the stream. This is very useful in
the early stages of the study design process, as the
streamwalk can be used as a reconnaissance tool to evaluate
the condition of the aquatic ecosystem within the stream.
Streamwalks can help identify problem areas and allow you
to narrow the scope of your monitoring sites. It is important
to conduct streamwalks in addition to chemical and biological
monitoring, as stream ecosystems are based on interactions
of physical, biological, and chemical processes.
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ALLARM uses this protocol to train volunteers on physical monitoring. This manual is a culmination of
tools and resources ALLARM has developed to complement training workshops using the USDA
protocol.
Project funding provided by the Foundation for Pennsylvania Watersheds.
Quantifying Your Results:
The assessment portion of the streamwalk is divided into twelve categories that evaluate different
aspects of stream habitat. Each category is rated with a value between 1 and 10. Remember to rate
only those categories appropriate to the stream reach, as some may not apply (i.e. manure presence
and sewage). Record the score that best fits your observations based on the description provided. At
the end, the scores are summed, averaged, and assigned a rating of:
Rating Condition
≤ 6.0 Poor
6.1 – 7.4 Fair
7.5 – 8.9 Good
≥ 9.0 Excellent
Site Description and Diagram:
The first step in conducting a streamwalk is to identify the boundaries of the reach to be evaluated. A
reach is a length of the stream that has consistent or representative conditions. The end of a reach is
determined by a change in the ecosystem (primarily due to land use), such as a change from farmland to
a parking lot. Remember: There is an area in your forms for problem diagrams within your reach, so you
do not need to change forms for every little change. Large bridges or overpasses are examples of what
constitutes a new form.
The site description section includes basic information about the stream, including the evaluator's name,
location of reach, and surrounding land uses. If you do not know the longitude and latitude of your
reach, write down road names or defining characteristics of your reach so you can locate the site later
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on. For Dominant Substrate, choose the rock type that is dominant in the stream and approximate the
percentage of the total substrate that it makes up.
In the Site Diagram space, sketch out the reach of your stream and make sure to note the direction of
flow, riffles, pools, large woody debris, and trees. You should illustrate potential problem areas, such as
road crossings, discharge pipes, bank erosion, etc. We recommend that you sketch your diagram after
you have walked the entire reach and have evaluated it.
Figure 1. Site diagram example.
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Monitor’s name: ____________________________ Date: ______________________________________
Stream name: _____________________________________ Owner’s name: _____________________________
Reach location: Latitude___________________________ Longitude__________________________________
Land use (%): Row crop_________ Grazing/pasture __________ Forest _________
Residential________ Conservation Reserve______ Park __________
Industrial_________ Commercial______________ Other _________
Weather conditions: Today______________________ Past 2-5 days________________________________
Active channel width (bankfull): _____________________ Approximate reach length: ___________________
Dominant substrate: Boulder ______ Cobble ______ Gravel ______ Sand ______ Silt ______ Mud______
(>10 in) (2.5-10 in) (0.5-2.5 in) (<0.5 in)
Site Diagram:
Notes:
6
CATEGORIES:
Assessment Tip: This manual refers to different portions of the stream channel as baseflow, bankfull,
and floodplain (Figure 2). In order to conduct a successful visual assessment, it is important to
understand these terms. Baseflow is the water flowing over the stream bottom under normal low-flow
conditions. The bankfull stage, or "active channel width,” forms and controls the shape of the active
channel as larger volumes of water move through the channel during large storm events. Look for a
break in the slope of the bank, changes in vegetation, substrate, debris, or signs of raised water flow as
indicators of the bankfull stage. When the stream level rises above bankfull, water spills out into the
surrounding floodplain.
Figure 2. Stream cross-section identifying baseflow, bankfull, and floodplain.
CHANNEL CONDITION
Channel condition helps to understand historic and current
uses as well as alteration of the stream. Indicators of
channelization (man-made alteration) or straightening of the
stream can include unnaturally straight sections of the
stream, high banks, dikes, or a lack of flow diversity. Look for
signs of down cutting (a deepening of the channel), lateral
cutting (a widening of the channel), or aggradation (the
stream bottom is raised in multiple locations by deposited
sediments). You also want to look for artificial banks – man-
made rock walls built to stabilize the bank, called riprap.
Channelized streams are common but do not allow natural
stream mobility or vegetation growth for the riparian zone.
Other signs of channelization include drop structures (such as
check dams), culverts, and irrigation diversions.
Example of lateral cutting.
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Natural channel: • Evidence of past Altered channel: • Channel is actively
• No man-made channel alteration, • <50% of the reach downcutting or
influences but with significant has riprap and/or widening
• No evidence of recovery of channelization • >50% of the reach
downcutting or channel and banks • Excess aggradation has riprap or
excessive lateral • Stream-control o braided channel channelization
cutting structures are set • Dikes or levees • Dikes or levees
back to provide restrict floodplain prevent access to
access to a width the floodplain
floodplain
10 7 3 1
Keys: Look for down cutting, lateral cutting, altered or widened sections, dikes, levees or other obstructions.
BANK STABILITY:
Areas with degraded riparian zones, channel alteration, or changes in hydrology and sediment load can
undergo excessive bank erosion. The roots of trees and woody vegetation in the riparian zone help to
stabilize banks by holding the soil together. Look for areas of exposed soil on the banks, as well as high
and steep banks which are more susceptible to erosion or collapse. As water flows around bends in the
stream, the velocity is higher on the outside of the bend, and causes erosion.
Banks are stable: Moderately stable: Moderately unstable: Unstable:
• Banks are low (at • Banks are low (at • Banks may be low, • Banks may be low,
elevation of active elevation of active but typically are but typically are
floodplain) floodplain) high (flooding high
• 33% or more of • Less than 33% of occurs 1 year out • Some straight
eroding surface eroding surface of 5, or less reaches and inside
area of banks in area of banks in frequently) edges of bends are
outside bends is outside bends is • Outside bends are actively eroding as
protected by roots protected by roots actively eroding well as outside
that extend to the that extend to the (overhanging bends
baseflow elevation baseflow elevation vegetation at top (overhanging
of bank, some vegetation at top
mature trees of bare bank
falling into the • Numerous mature
stream trees falling into
• Some slope failures the stream
apparent • Numerous slope
failures apparent
10 7 3 1
Keys: Even the most stable streams may have 50% of the outside bend banks bare and eroding.
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RIPARIAN ZONE:
Riparian zones are the vegetated areas adjacent to streams and are important for maintaining a healthy
ecosystem and stabilizing streambanks. These zones act as a buffer between the stream and nearby
lands, and should contain a variety of natural woody vegetation such as sedges or rushes, tall grasses,
shrubs, understory trees, and overstory trees. Lawns are not considered part of the riparian zone, as
mowed grass is rather impervious and will not absorb surface runoff as readily as natural vegetation. If
one side of the stream is lacking a healthy riparian zone, the entire reach of the stream will be affected.
A healthy riparian zone:
• Absorbs and slows surface runoff and reduces the amount of pollutants entering the stream.
• Helps to control erosion by holding the soil together with root systems.
• Provides habitat and food for macroinvertebrates.
Natural Natural Natural Natural Natural
vegetation vegetation vegetation vegetation vegetation less
extends at least extends one extends half of extends one third than one third of
two bankfull bankfull width on the bankfull width of the bankfull the bankfull width
widths on each each side on each side width on each on each side
side or side or
If less than one or Lack of
width, covers Filtering function regeneration
entire floodplain is moderately or
compromised
Filtering function
is severely
compromised
10 8 5 3 1
Healthy Riparian Zone – 10 Unhealthy Riparian Zone - 1
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WATER APPEARANCE:
This category accounts for the turbidity, color, and visual characteristics of the water. Water clarity is a
measure of the ability of sunlight to penetrate the water. Degraded water clarity is usually caused by
soil particles, organic matter, or algae suspended in the water. Keep in mind that many streams will not
be deep enough to evaluate water clarity as described in the box below.
Some streams are naturally tea-colored from tannins in leaves, greenish due to algae communities, or
orange from acid mine drainage. Excess nutrients can cause a thick algal film to coat the stream bottom.
In degraded streams, surface scum, floating algal mats, and oil may be present.
• Very clear, or clear • May have slight • Considerable • Very turbid or
but tea-colored green color cloudiness most of muddy appearance
• Objects visible at • Occasionally cloudy, the time most of the time
depths of 3 to 6 ft especially after • Objects visible to • Objects visible to
(less if slightly storm events, but depths of 0.5-1.5 ft depths <0.5 ft
colored) clears rapidly • Slow sections may • Slow moving water
• No oil sheen on • Objects visible at appear pea-green may be bright-
surface depths of 1.5 to 3 • Bottom rocks or green
• No noticeable film ft submerged objects • Other obvious
on submerged • No oil sheen on covered with water pollutants
objects or rocks water surface heavy green or present
olive-green film or • Floating algal mats,
moderate odor of surface scum,
ammonia or rotten sheen or heavy
eggs coat of foam on
surface or strong
odor of chemicals,
oil, sewage, or
other pollutants
10 7 3 1
Tip: It can be difficult to determine the color of the water due to algae coating the rocks or glare on the water
surface. Take a sample of water in a clear bottle and hold it up to the light.
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NUTRIENT ENRICHMENT:
Low levels of nutrients are essential to support aquatic ecosystems, but an abundance can cause
problems. High levels of nutrients, particularly phosphorus and nitrogen, can cause an overgrowth of
aquatic algae and macrophytes (floating and rooted aquatic plants). Excessive algae growth can hurt
stream life as it can block the sun from penetrating the water, preventing other plants from producing
dissolved oxygen through photosynthesis. Dissolved oxygen is also lowered as bacteria decompose
dead plant matter. These low oxygen conditions can stress and even kill fish and other aquatic life.
Evidence of nutrient enrichment includes a greenish water color, thick mats of algae, and a low diversity
of aquatic plants.
• Clear water along • Fairly clear or • Greenish water • Pea green, gray or
entire reach slightly greenish along entire reach brown water along
• Diverse aquatic water along entire • Abundant algal entire reach
plant community reach growth, especially • Severe algal blooms
• Little algal growth • Moderate algal during warmer create thick algal
present growth months mats in stream
10 7 3 1
Keys: Look for algae and other aquatic vegetation. A little is good, but should not be excessive.
Figure 3. The left side has clear water and diverse aquatic plants, while the right side shows a degraded
environment due to thick algal mats and green-brown water.
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FISH BARRIERS:
Barriers, both natural and manmade, can prevent the movement of fish and other aquatic organisms.
These barriers can prevent migrations, block access to important breeding and feeding areas, and isolate
populations of fish and other organisms. Barrier types include waterfalls, boulder dams, small or sloped
culverts, concrete drop structures, or any other obstacle that would impair the movement of aquatic
organisms.
No barriers Seasonal water Drop structures, Drop structures, Drop structures,
withdrawals culverts, dams or culverts, dams or culverts, dams or
inhibit movement diversions (<1ft diversions (>1ft diversions (>1ft
within the reach drop) within the drop) within 3 drop) within the
reach miles of reach reach
10 8 5 3 1
Keys: Look for withdrawals, culverts, dams and diversions. Anything that is imposed or constructed by humans
that would impede fish passage is considered a barrier.
IN-STREAM FISH COVER:
Fish need a variety of different habitat and cover types in order to maintain a healthy population. Cover
types include:
• Logs/large woody debris: Fallen trees or parts of trees that provide structure and attachment
for macroinvertebrates and hiding places for fish.
• Deep pools: Characterized by a smooth undisturbed surface, generally slow current, and deep
enough to provide breeding areas for fish (deeper than the prevailing stream depth).
• Overhanging vegetation: Trees, shrubs, vines, etc. that hang over the stream surface providing
shade and cover.
• Boulders/cobble: Boulders are rounded stones more than 10 inches in diameter; cobbles are
stones 2.5 – 10 inches in diameter.
• Undercut banks: Eroded areas extending horizontally beneath the surface of the bank forming
underwater pockets used by fish for hiding and protection.
• Thick root mats: Dense mats of roots (generally from trees) at or beneath the water.
• Dense macrophyte beds: Thick beds of emergent, submerged aquatic vegetation.
• Riffles: Area characterized by broken water surface, moderate or swift current, and relatively
shallow depth (usually less than 18 inches).
• Isolated/backwater pools: Areas disconnected from the main channel or connected as a "blind"
side channel, characterized by a lack of flow except in periods of high water.
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>7 cover types 6 to 7 cover types 4 to 5 cover types 2 to 3 cover types None to 1 cover
available available available available type available
10 8 5 3 1
Cover types (check when present):
(B) Logs/large woody debris ______ (A) Deep pools ______ (D) Overhanging vegetation ______
(B,C) Boulders/cobbles ______ (C) Riffles ______ Isolated/backwater pools ______
(A) Thick root mats ______ (A) Undercut banks ______ (E) Dense beds of aquatic plants ______
Other ______
Figure 4. Stream cross-section with types of in-stream fish cover.
INSECT/INVERTEBRATE HABITAT:
Macroinvertebrates need a variety of substrates to have an optimal habitat for colonization. These
substrates include fine woody debris, submerged logs, leaf packs, undercut banks, cobble, boulders, and
coarse gravel.
• At least 5 types of • 3 – 4 types of • 1 – 2 types of 0 – 1 types of habitat
habitat available habitat habitat
• Habitat is at a stage • Some potential • The substrate is
to allow full insect habitat exists, such often disturbed,
colonization as overhanging covered,
(woody debris and trees, which will deposited, or
logs not freshly provide habitat, removed by high
fallen) but have not yet stream velocities
entered the stream
10 7 3 1
Habitat Examples (check when present):
Fine woody debris ______ Submerged logs ______ Leaf packs ______ Cobbles _____
Boulders _______ Coarse gravel ______ Undercut banks ______ Other ______
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EMBEDDEDNESS:
Embeddedness measures the extent to which rocks are sunken into the stream bottom or buried by fine
sediments (Figure 6). The less embedded a cobble, the more habitat variety for fish,
macroinvertebrates, and other stream biota. The substrates that make up the stream bottom are
classified by size:
Substrate Size (in.) Particle Size Description
Silt/Clay/Mud Fine, sticky feeling
Sand < 0.2 Gritty, pea
Gravel 0.1 – 2 Pea to marbled
Cobble 2 – 10 Tennis to basketball
Boulder > 10 Basketball to car
Bedrock Solid rocks bigger than a car
Figure 5. Estimating
embeddedness.
How to measure: Remove a cobble from the stream, retain it spatial orientation, and estimate the height
that is embedded, often a visible line on the rock (Figure 5). Repeat this for several cobbles and record
the estimate.
Gravel or cobble Gravel or cobble Gravel or cobble Gravel or cobble Completely
particles are <20% particles are 20 - particles are 30 - particles are >40% embedded
embedded 30% embedded 40% embedded embedded
10 8 5 3 1
Figure 6. Cross-section of cobble embeddedness.
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CANOPY COVER:
Large mature trees with overhanging branches provide canopy cover for streams. Shading of the stream
is important because it keeps water cool, and limits algal growth by limiting the amount of sunlight
available for photosynthesis. Cooler water has a greater oxygen holding capacity than warmer water,
thus providing better conditions for aquatic life. Within the reach, estimate the portion of the water
surface that is shaded by trees and vegetation in the riparian zone. As weather, time of day, and time of
year can affect shading, assume that the vegetation is fully leaved and the sun is directly overhead.
• >75% of water 50% shaded in reach 20 to 50% shaded <20% of water surface
surface shaded or in reach shaded
• 2 – 3 miles >75% in reach, but
upstream generally upstream 2 to 3 miles
well shaded poorly shaded
10 7 3 1
Keys: This category only pertains to waterways where channel is 50 feet wide or less.
MANURE PRESENCE (if applicable):
Livestock manure can enter the water from runoff of grazing lands or if livestock have access to the
stream. Manure can increase the nutrient load, increase biological oxygen demand, and cause
eutrophication. Well-worn livestock paths near the stream suggest manure presence in the water.
(Intentionally blank) Livestock have access Occasional manure in Extensive amount of
to riparian zone stream manure on banks or in
or stream
Waste storage or
structure located on Untreated human
the floodplain waste discharge pipes
present
5 3 1
SEWAGE (if applicable):
(Intentionally blank) • Noticeable odor • Noticeable odor • Visible pipe with
• Excess plant growth • Excess plant growth effluent
• Siltation • Questionable pipe • Heavy odor
• Black stream
substrate
5 3 1
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ASSESSMENT SCORES
CHANNEL CONDITION
BANK STABILITY
RIPARIAN ZONE
WATER APPEARANCE
NUTRIENT ENRICHMENT
FISH BARRIERS
INSTREAM FISH COVER
EMBEDDEDNESS
INSECT/INVERTEBRATE HABITAT
CANOPY COVER
SEWAGE
(If applicable)
MANURE PRESENCE
(If applicable)
< 6.0 Poor
Overall Score 6.1 – 7.4 Fair
(Total divided by number scored) ____________ 7.5 – 8.9 Good
> 9.0 Excellent
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PROBLEM DIAGRAM SAMPLE:
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PROBLEM DIAGRAM
Type of problem: _________________________________________________________________________
Pictures: Y / N Where are the pictures stored? _____________________
Should this site be sampled? Y / N
If yes, why? _________________________________________________________________
____________________________________________________________________________
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GLOSSARY
Active Channel Width: Elevation of bank marking the normal maximum water flow before flooding
occurs.
Aggradation: The stream bottom or floodplain is raised in elevation by the deposition of material.
Algae: A chlorophyll-containing plant ranging from one to many cells in size that lives in fresh or salt
water.
Bankfull width: The width of the stream that is formed by the bankfull discharge (flow rate, such as
cubic feet per second), which occurs once every 1.5 years on average.
Baseflow: The portion of stream flow that is derived from groundwater; average stream discharge
during low flow conditions.
Benthic (Bottom-dwelling): The plant and animal life whose habitat is the bottom of a sea, lake, or river.
Biological Oxygen Demand: A measure of the amount of oxygen used by microorganisms to decompose
waste.
Channelization: Straightening of a stream channel to make water move faster.
Channelized: The straightening and deepening of streams. Channelization reduces the ability of the
stream to assimilate waste and disturbs fish breeding areas.
Cover: Overhanging or instream structures (such as tree roots, undercut stream banks, or boulders)
that offer protection from predators, shelter from strong currents, and/or shading.
Culvert: A channel used for draining water, often enclosed in steel, concrete, or plastic; can be used to
allow water to pass underneath a road or embankment.
Current: The velocity (speed) of the flow (of water).
Ecosystem: The interacting system of a biological community (plants, animals) and its non-living
environment.
Effluent: The wastewater from a municipal or industrial source that is discharged into the water.
Embeddedness: The degree to which objects in the stream bottom are surrounded by sediment.
Erosion: The wearing away of the land surface by wind or water.
Eutrophication: A process where water bodies receive excess nutrients that stimulate excessive plant
growth.
Floodplain: The flat area of land adjacent to a stream that is formed by flood processes.
Gradient: The slope or steepness of the stream.
Macrophytes: Aquatic plants, growing in or near water that are either emergent, submergent, or
floating.
Macroinvertebrate: Organisms found attached to rocks or within the sediments of the stream bed,
often larval stages of insects, and are indicative of stream health.
Non-Point Source Pollution: “Diffuse” pollution, generated from large areas with no particular point of
pollutant origin, but rather from many individual places. Urban and agricultural areas generate non-
point source pollutants.
Nutrient: Any substance, such as fertilizer, phosphorus, and nitrogen compounds, which enhances the
growth of plants and animals.
Point Source Pollution: A discharge of water pollution to a stream or other body of water, via an
identifiable pipe, vent, or culvert.
Pool: An area of relatively deep slow water in a stream that offers shelter to fish.
Quality Control (QC): The system of checks that are used to generate excellence, or quality, in a
program, such as a monitoring program.
19
Quality Assurance (QA): Quality Assurance is the larger system to see that QC is maintained. QA asks if
we are doing the right things (in our case are we monitoring the right things to detect changes in water
quality).
Reach: A stream section with fairly similar characteristics.
Riffle: A shallow, gravely area of streambed with swift current where water is breaking over rocks,
wood, or other partly submerged debris and producing surface agitation.
Riprap: A sustaining wall built of rocks.
Riparian Zone: An area, adjacent to and along a watercourse, which is often vegetated and constitutes
a buffer zone between the nearby lands and the body of water.
Run: A stretch of fast smooth current, deeper than a riffle.
Runoff: The portion of rainfall, melted snow, or irrigation water that flows across the ground surface
and eventually returns to streams. Runoff can pick up pollutants from the air or the land and carry them
to streams, lakes, and oceans.
Sediment: Fine soil or mineral particles that settle to the bottom of the water or are suspended in the
water.
Stormwater Runoff: Water that washed off the land after a rainstorm. In developed watersheds it
flows off of roofs and pavement into storm drains which may feed directly into the stream; often carries
concentrated pollutants.
Substrate: The material that makes up the bottom layer of the stream, such as gravel, sand, or bedrock.
Suspended Sediments: Fine material or soil particles that remain suspended by the current until
deposited in areas of weaker current. They create turbidity and, when deposited, can smother fish eggs
or early plant growth.
Topographic: The configuration of a surface area including its relief, or relative elevations, and the
position of its natural and man-made features.
Turbidity: Cloudiness of the water, caused by suspended sediments or excess organic matter.
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REFERENCES & ACKNOWLEDGEMENTS
This protocol is a modified version of the USDA Stream Visual Assessment Protocol: Tier 1. The visual
assessment worksheet consists of two main sections: site description and assessment.
The original version of the USDA Visual Assessment Protocol is available from:
http://www.nrcs.usda.gov/technical/ECS/aquatic/svapfnl.pdf
Figures were illustrated by Matthew Freedman, ALLARM, 2008.
This manual is produced by the Alliance for Aquatic Resource Monitoring with project support from the
Foundation for Pennsylvania Watersheds.
ALLARM
Environmental Studies Dept.
Dickinson College
P.O. Box 1773
Carlisle, PA 17013
717.245.1565
allarm@dickinson.edu
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