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The following is an
exerpt from: Environmental Monitoring and Assessment Program, Surface
Waters: Western Pilot Study, Field Operations Manual for Wadeable Streams,
Peck, D.V., J.M. Lazorchak, and D.J. Klemm (editors), U.S. Environmental
Protection Agency, Washington, D.C.
In the broad sense,
physical habitat in streams includes all those physical attributes that
influence or provide sustenance to organisms within the stream. Stream
physical habitat varies naturally, as do biological characteristics;
thus, expectations differ even in the absence of anthropogenic disturbance.
Within a given physiographic-climatic region, stream drainage area and
overall stream gradient are likely to be strong natural determinants
of many aspects of stream habitat, because of their influence on discharge,
flood stage, and stream power (the product of discharge times gradient).
Summarizing the habitat results of a workshop conducted by EMAP on stream
monitoring design, Kaufmann (1993) identified seven general physical
habitat attributes important in influencing stream ecology:
- Channel Dimensions,
- Channel Gradient,
- Channel Substrate
Size and Type,
- Habitat Complexity
and Cover,
- Riparian Vegetation
Cover and Structure,
- Anthropogenic
Alterations,
- Channel-Riparian
Interaction.
All of these attributes
may be directly or indirectly altered by anthropogenic activities. Nevertheless,
their expected values tend to vary systematically with stream size (drainage
area) and overall gradient (as measured from topographic maps). The
relationships of specific physical habitat measurements described in
this section to these seven attributes are discussed by Kaufmann (1993).
Riparian vegetation, and large woody debris are included in this and
other physical habitat assessments because of their role in modifying
habitat structure and light inputs, even though they are actually biological
measures. The field physical habitat measurements from this field habitat
characterization are used in the context of water chemistry, temperature,
and other data sources (e.g., remote sensing of basin land use and land
cover). The combined data analyses will more comprehensively describe
additional habitat attributes and larger scales of physical habitat
or human disturbance than are evaluated by the field assessment alone.
A comprehensive data analysis guide (Kaufmann et al., 1999) discusses
the detailed procedures used to calculate metrics related to stream
reach and riparian habitat quality from field data collected using the
EMAP field protocols.
Literature cited:
Kaufmann, P.R. (ed.), 1993, Physical Habitat, pp. 59-69, in R.M.
Hughes (ed), Stream Indicator and Design Workshop, EPA/600/R-93/138,
U.S. Environmental Protection Agency, Office of Research and Development,
Corvallis, Oregon. |
