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 Appendix B: Bioengineering for Streambank Erosion Control -- Guidelines
Figure 18.
Installed log revetment with coir
geotextile roll combination,
Roaring Fork River, Colorado.
Wetland vegetation is seeded or
planted in backfilled soil placed
in a depression between the
revetment and the land. Rock is
placed on top to prevent scour.
Root wads are live or dead logs with root masses attached (Figure 19, see Bowers, Land
and Water, 1992). These are also used in the toe zone to protect it from undercutting, but
must be used in combination with other materials. The fans of the root wads provide an
interlocking wall protecting the streambank from erosion. The voids within and between the
root wads are filled with a soil mix and planted with live, willow clumps or root pads. The
root wads are laid on top of a keyed-in shelf of stone and support logs. This shelf includes
a layer of bottom support logs flush with one another, shingled together, and running parallel
to the streambank. The root mass should be a minimum of 5-ft in diameter and angled slightly
upstream towards stream flow. This treatment should be placed at a base elevation that is
consistent with water levels during the major part of the growing season, i.e., June through
September. The bottom two-thirds of the root wad should be in water during that period of
time. The upstream and downstream ends of the root wad treatment should be tied into hard
points made from rock or some natural hard feature so as to prevent flanking.
Figure 20 shows a treatment using root wads on the Upper Truckee River in California
near South Lake Tahoe, where this treatment and others were monitored for a couple of
growing seasons (see also Volume II). Various local flow velocities were measured along the
treatment on the fall of the hydrograph. These ranged from 1.6 to 4.0 fps at .6 depth of flow
and 4 ft out from the right bank. The root wads sufficiently reduced local flow velocities so
that vegetation had a chance to get established and stabilize the bank despite a
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