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AS7 - Habitat Assessment
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This activity is performed as part
of AS6 A catchment study.
The site description is easy to do and
consists of observing and noting the main features of your site.
It is useful for
·
learning about the aquatic environment and
·
identifying grossly degraded sites.
Things to do at the site
Take a walk.
Determine the extent of the area to
be assessed. Pace 10m upstream and 10m downstream from a point of
reference such as a tree or rock. Walk the 20m area along the stream
bank and become familiar with the features of the site and surrounding
land.
2. Fill in the details of the top
portion of the Site Description Sheets.
You must give a name to the waterway,
preferably as it appears on the map. If it is a stream but does
not have a name then record which water body it flows into. Indicate
the type of water body, its elevation from the map and the name
of the nearest town. The brief description of the site must include
precise details of access and location.
Make a Sketch
Make a sketch of the area on your Site
Description Sheet. Sketches are a useful means of keeping a visual
record of your stream. Drawing the site will help you to ‘see’
the landscape and features of the site, and provide a record for
future school visits.
Draw the shape of the stream channel
from a ‘birds-eye’ view, looking down from above.
Note on the sketch features such as:
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tributaries, dams, roads, etc;
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direction of true north;
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direction of water flow;
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riffles, logs and log jams, vegetation
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photo sites and direction of photo;
·
any important features outside of the 20m area which may
affect the site, for example a recently burnt area.
Filling out the details of your Site Description
Sheets
Appearance of the water. Pay
particular attention to the appearance of the water as this can
indicate pollution.
The smell of water can also indicate
pollution.
Rating the Health of the Site Habitat
This section describes how you can rate
the health of the habitat on a scale of excellent, good, fair or
poor. This survey is designed for assessing the health of stream
habitats but can be used for wetlands, lakes and ponds. Simply ignore
the rating for riffles pools and bends when completing the survey.
How to carry out the survey
To assess the health of the habitat
around the stream you are monitoring, you will need to consider
four indicators described below. For each indicator, survey a total
distance of 20m on both banks (if possible). Riparian vegetation
and instream cover are more important in determining the health
of the habitat than either bank erosion and stability or riffles,
pools and bends. This is reflected in the weighting of scores given
in the table.
Riparian vegetation. The riparian
zone is an area up to about 30m wide directly adjoining the waterway
and can include vegetation such as trees, shrubs and grasses.
In-stream Cover. In-stream cover
includes overhanging banks and aquatic vegetation, snags, fallen
trees, logs and rocks. Streams with a rich diversity of in-stream
cover allow fish and macro-invertebrates to shelter from the current,
feed and reproduce. Aquatic plants provide food and oxygen, and
protruding snags provide roosting and preening sites for birds.
Bank Erosion and Stability. Streams
naturally erode on the outside of bends (meanders) and deposit sediment
on the inside of the bend. However, changes in nearby land uses
can cause a stream to become unstable, resulting in continuous erosion
along its channel. You may find steep walled gullies, bank collapse,
slumping and hanging roots from riparian vegetation. If the stream
has been channelled or stabilised with concrete banks, it will obviously
be stable with little erosion, but has little or no vegetation cover
and few habitats needed by macroinvertebrates to live.
Riffles, Pools and Bends. A riffle
is a section of a river or stream where shallow water flows over
rocks in rapid turbulent flow. As the water flows downstream the
stream bed may deepen and form a quiet pool. Larger, slow-flowing
rivers may not have any riffles or pools but bends will be present.
As water flows around the outside of bends it cuts into the
bank deepening the bed.
Streams that have a number of pools
and riffles are able to support a greater variety of species than
those that do not vary in character at all.
Instructions
Read the descriptions above and become
familiar with the terms used and how to distinguish between them.
Examine 20m length of waterway on both
banks at your site.
Go to table 1 and select a category
(excellent’, ‘good’, ‘fair’ or ‘poor)
that is most like your habitat. If the information does not match,
try another category.
A score is given for each category.
The scores are higher for the more important conditions affecting
stream health. Record your score on the ‘Stream habitat rating
sheet’.
To obtain an overall assessment of the
site, add up each score to obtain a total. The total gives an overall
indication of habitat condition.
Table 1 Description of Habitat Ratings
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Habitat
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Excellent
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Good
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Fair
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Poor
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Riparian Vegetation
(Examine vegetation from the water to about 30 m back)
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8
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6
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4
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2
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Mainly undisturbed native plants on both sides of river.
Introduced species are absent or insignificant. Riparian zone
up to 30m wide.
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Native vegetation on both sides of river in generally good
condition. Some intrusion of introduced species. Wide riparian
zone.
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Mixture of native and exotic species on both banks, or one
side may be cleared and the other side undisturbed native
plants or narrow corridor of native plants on both sides.
Other impacts may be present eg fire, stock grazing in riparian
zone
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Any native vegetation present is severely modified on both
sides by grazing or human access. Cleared land both sides
(eg agriculture, housing). Species present are virtually all
exotics (willow, pines, introduced grass).
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In-stream cover
(aquatic plants, snags logs, bank overhangs and overhanging
vegetation)
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8
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6
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4
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2
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High cover on banks. Abundant in-stream, and overhanging
vegetation. Abundant snags and logs or boulders. Bank overhangs
present.
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Good cover on the banks, moderate areas of in-stream and
overhanging vegetation. Some snags, logs or boulders.
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Some cover. Some areas of in-stream or overhanging vegetation.
Invasion of bank vegetation by terrestrial grasses. Few
snags, logs or boulders.
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Little or no cover. No overhanging vegetation or in-stream
plants. The stream is largely cleared with rare or no snags,
logs. Any boulders present are submerged. Site may have
rock or concrete lining.
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Bank erosion & stability
(roots, bare soil, slumping, erosion, fall-ins, cracking
of bank)
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4
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3
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2
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1
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Stable. No erosion or deposition evident. No slumping of
banks. Lower banks completely covered with root mat, grasses,
reeds or shrubs.
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Very occasional and very localised erosion. Little slumping
or undercutting of bank. No significant damage to bank. Good
vegetation cover.
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Some erosion evident but localised. No continuous damage
to bank structure. Moderate vegetation cover.
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Extensive areas of erosion. Unstable, extensive areas of
bare ground, bank failure such as cracks and fall-ins. Little
vegetation cover. Despite stability of concrete channels
they score only 1.
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Riffles pools & bends.
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4
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3
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2
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1
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Wide variety of habitats. Riffles and pools of varying depths
present. Bends present.
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Good variety of habitat eg. riffles and pool or bend and
pool. Variations in depth of riffle and pool.
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Some variety of habitats eg. occasional riffle or bend.
Some variation in depth.
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Uniform or only slight variety of habitat. All riffles or
pools with uniform or only slight variation in depth eg. channelled
stream.
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Site Description
For each site you will need to complete
a copy of this work sheet, in the future it will be used to assess
if there have been any changes in or around the site and to help
assess the health of the site. Describe the area 10m upstream and
10m downstream from where you are standing.
Name of water body: …………….
UBD Map reference:
Date: Time:
Name of Group:
Name of Investigators:
Type of water body: pond/wetland
estuary lake/dam cement channel
river stream
Position in the catchment: upper
middle lower
Estimated elevation: ………………………………………………………………………………………………………
Name of suburb:
Brief description of site:
……………………………………………………………………………………………………………
Bird’s
eye view of site
Sketch a bird’s eye view (a view
looking down from above) of your stream site, showing curves in
the stream, adjacent land on both sides etc. Mark areas of vegetation,
eroded banks, fences, roads, drains, etc. Try to draw about 20 metres
of stream length. Remember, it is only a rough sketch. Label the
sketch where possible. Mark and number any photo sites and draw
an arrow to show the direction from which each photograph was taken.
Show the direction of stream flow.
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Bird’s eye view of your survey site
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General features of waterway
1. Appearance of the water
clear
muddy milky
stained green
foamy / frothy oily sheen stained brown reddish
Other (describe) _________________________________________________________
2. Smell of water
sewage fishy
chlorine rotten eggs
none
Other (describe)_________________________________________________________
Stream Habitat Rating
Circle the appropriate score for
each part of the habitat below:
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Habitat
Rating
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Riparian
Vegetation
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In-stream
Cover
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Erosion &
Stability
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Pools, Riffles
& Bends
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Excellent
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8
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8
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4
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4
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Good
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6
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6
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3
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3
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Fair
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4
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4
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2
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2
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Poor
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2
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2
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1
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1
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How to get an overall assessment
of the site.
If you wish to get a general rating
for the site then add up all the numbers you circled for a total
score. The minimum total score is 6 and the maximum is 24. Compare
the total score with the range of scores below to find a description
of the general condition of your stream habitat
Stream Habitat Rating
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Total Score
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Rating
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Condition of habitat
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21 - 24
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Excellent
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Site in natural or virtually natural condition; excellent
habitat condition.
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16 -20
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Good
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Some alteration from natural state; good habitat conditions.
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11 -15
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Fair
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Significant alterations from the natural state but still
offering moderate habitat; stable.
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6 - 10
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Poor
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Significant alterations from the natural state to very degraded.
May have moderate to severe erosion or sedimentation problems
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Stream Habitat
Rating:
Total Score:
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