Appendix B: Bioengineering for Streambank Erosion Control -- Guidelines
Table 2.
Local flow velocities sustained by and recorded for various
bioengineering treatments monitored by this project.
Location
Type of Bioeng'r
Maximum
Notes
Treatment
Velocity
(fps)
Recorded
10.0
Logs anchored in the bank with
Roaring Fork
Log revetment with
heavy duty cables. Rock jetties
River, CO
coir geotextile roll
used for hard points at strategic
and grass seeding
points
above roll (See
Figures 17 & 18)
Lack of maintenance during
Snowmass Creek,
Root wads with
8.7
spring, 1994 (additional root wads
CO
large root pads
at scour points) caused partial
(clumps) of willow
washout of the upper meander
(See Figures 19 &
during spring flood of 1995.
20)
4.0
Lower velocities measured in and
Upper Truckee
Root wads with
around bioengineering treatment
River, CA
large clumps of
than further out into channel; this
willow (Figures 19
can be attributed to larger
and 20)
roughness coefficient
3.1
4 rows of willow posts on 4-ft
Court Creek, IL
Dormant willow
centers; 10-15 -ft long cedar trees
posts with rock toe
between 1st two rows of willow;
(Figures 34 and
coir geotextile roll and riprap
35)
placed at toe along meander
apex.
Notes: These are local flow velocities noted in this table and were measured by a flow meter; All
treatments were in their second growing season after major flood events when these measurements
were taken.
Table 2 shows maximum local flow velocities around a root wad structure with willow
root pads to be 4.0 and 8.7 fps for two different treatments at two geographic locations,
Upper Truckee River, CA, and Snowmass Creek, CO. It is suspected that these kind of
structures, if properly installed, could sustain velocities much higher than these. It was noted
earlier in this report that D. Rosgen5 measured local flow velocities around root wads on the
Blanco River, CO, to be 12.0 fps.
Some of the treatments noted in Table 2 had some partial failures even though at least half
of the reaches where these were installed remained intact and the treatments continued to
function. The treatment containing the log revetment with coir geotextile roll on the Roaring
1
Rosgen, Dave. President, Wildland Hydrology, Pagosa Springs, CO, Jul 1996, personal
communication.
B-69
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