5 Less than 5 percent of surface area of gravel, cobble, and boulder particles
covered by fine sediment
4 Five to 25 percent of surface area of gravel, cobble, and boulder particles covered
by fine sediment
3 Twenty-six to 50 percent of surface area of gravel, cobble, and boulder particles
covered by fine sediment
2 Fifty-one to 75 percent of surface area of gravel, cobble, and boulder particles
covered by fine sediment
1 Over 75 percent of surface area of gravel, cobble, and boulder particles covered
by fine sediment
0 No gravel, cobble, or boulder particles present
To determine how much of the surface area
of large particles is covered in order to provide a rating, select five
relatively large (gravel to boulder size) substrate particles at the three
sampling points along the transect and examine them on the sides. Note
the percentage of each particle's height that was buried in sediment by
the extent of discoloration on the particle. The rating is based on the
percentage of coverage of fine sediment as determined from the average
percentage of coverage for the five particles. In turbid wadeable reaches and in nonwadeable
reaches, a sample of the substrate is obtained using an appropriate device
such as a shovel, Ponar sampler, or Ekman dredge.
- 21. Canopy angle: Canopy angle is formed by the angles
from mid-point of the transect (midpoint of the channel width) to the
visible horizon. From the midpoint of the transect, use a clinometer to
determine the angle from the line of sight of the investigator to the
tallest structure (for example, tree, shrub, building, or grass) on the
left bank (in the general area of the transect). The same procedure is
done at the right bank. The sum of these angles is computed and
subtracted from 180 degrees. The result is the canopy angle (fig. 8).
- 22. Aspect: Record the aspect (0 to 360 degrees) of the
downstream flow of the stream using a compass. At the midpoint of the
transect, face downstream and point a compass parallel to streamflow.
Record the compass reading.
- 23. Habitat features: Determine the type and amount (two-dimensional area)
of all habitat features that are partly or wholly within a 2-m zone on
either side of the transect. Habitat features consist of any mineral or
organic matter that produces shelter for aquatic organisms to rest, hide,
or feed, and include natural features of a stream such as large boulders,
woody debris, undercut banks, and aquatic macrophyte beds, as well as
artificial structures such as discarded tires, appliances, and parts of
automobiles. Habitat features are not counted when they are in
insufficient depth (usually less than 20 cm). For example, a woody debris
accumulation in 5 cm of water is not considered to be a significant
habitat feature. Habitat-feature type is noted using the following
two-letter code: