EPA841-F-05-002A
Measuring Physical Habitat in Streams
Why Measure Physical Habitat?
> The physical structure of streams is key to understanding the stream biota.
> Alteration of stream physical habitat is among the leading human alterations to streams.
> Setting goals for maintaining and restoring physical habitat in streams is a key to
improving stream quality.
Goals
What Dimensions of Physical Habitat will be Evaluated?
Produce a report
on the condition
of wadeable
streams of the U.S.
by December 2005
•
Promote
collaboration
across
jurisdictional
boundaries in the
examination and
assessment of
water quality
•
Build State
capacity through
use of survey
design and
comparability of
methods or
indicators
How Many Measurements Do We Need?
Residual pools are a critical habitat feature of
streams
Measurements must be taken frequently enough
to be accurate
Reducing protocol from 100 depth measures to
40 measures reduces accuracy from 99% to70%
WSA protocol is sufficient to provide values
that are a minimum of 99% of the true value.
Instreamfish cover
Riparian Vegetation &
Human Disturbance
Substrate and Channel
Measurements
Channel/Riparian
Cross section
Transect
Thalwegprofile
intervals
4 \aABj
Woody Debris Tally /
(between transects) ^~k \
3
Downstream end of '5
sampling reach J
Residual Pools - Effort Return
a
0)
<
0)
3
s_
"o
^
100
on
BO
Aft
20
n
* = Data points
• ,
' -^
» „
" • . «
100 40 20 10
# of Measurements
-------
Key Indicators of Physical Habitat
Channel Dimension
Habitat space may be the most important attribute
(width, depth, bank measurements, Thalw eg profile,
residual pools).
Riparian Vegetation Cover and Structure
Determine stream temperature, organic inputs and
channel morphology (riparian cover measurements,
structure).
Channel Gradient
Provides insights into the hydraulic energy of a
stream (percent slope for the entire reach and
between individual transects).
Substrate Size and Type
Important for fish, benthos and periphyton, an
important determinant of what can live there and
provides clues to potential stressors (Wolman pebble
count, embeddedness).
Channel-Riparian Interaction
Channel characteristics are altered by riparian and
catchment land use, which in turn influence
terrestrial-aquatic interactions (bank full height,
incision, sinuosity from compass bearings).
Anthropogenic Alteration
Among the markers for diagnosing stream
disturbance and "reference condition " (human
disturbance tally).
Complexity and Cover
Determines niche diversity and cover from predation
(woody debris count, fish cover variables).
How Good is our Information on Habitat?
Can We Detect Signals?
> Signal must be greater than measurement noise
> Signal noise calculated by repeat visits at sites
over the variability across all the sites.
> WSA quantitative habitat metrics are consistently
above 5 (i.e., 5 times as much signal as noise).
For more information contact:
Susan Holds-worth, USEPA
202-566-1187
holdsworth.susan@epa.gov
Mean Substrate dia.
% Canopy Density
Residual Pool Area
% Sand + Fines
Bed Stability
Riparian Agriculture
% Undercut Bank (visual)
% Pool Habitat (visual)
Qualitative Habitat Score Z]
0
Metric Signal to Noise
1 1 1
1
1
1
1
•
1
1
•
5 10 15 20
Signal: Noise Ratio
25
------- |