As you can see from the photo, this is
a single-thread channel. Field measurements determined an entrenchment ratio of
1.7. The ratio of bankfull width to mean bankfull depth is 16. The sinuosity,
calculated from aerial photographs is 1.3. At this point in the classification process, it
can be seen that this reach classifies as a B channel, commonly called a step-pool stream.
The measured slope on
this reach is .034 feet per foot. The slope
numbers on the diagram are in feet per foot
units. These numbers multiplied by 100 will
yield percent slope; or multiplied by 5,280
will yield feet per mile slope. Measurements
of channel materials, commonly called "pebble
counts", indicate that 50% of the surface
substrate is equal to or less than 52 millimeters
in size. This size material falls within the
gravel range. This reach is therefore a B4 stream
type.
Comparison of measured values from this
stream with values from known B4 references reaches provides the basis for determining if
this reach is stable. The reference reach concept is beyond the scope of this
presentation. However, all the measurements in the exercise presented here
indicates the B4 reach is a stable B4, and will tend to adjust back towards a B4 as a
consequence of alteration.
