Streambank Revegetation and Protection: A Guide for Alaska
Revegetation Techniques: Live Siltation
Live siltation is a revegetation technique used to secure the toe of a slope, trap sediment and create fish rearing habitat. This technique may be installed behind other toe-of-slope protection. The practice can be constructed as a living brushy system at the water's edge. This technique is particularly valuable for providing immediate cover and fish habitat while other revegetation plantings become established.
Collection, storage and planting information are described in Dormant Cuttings under the Plant Care and Preparation section. The dormant branches need to be a minimum of 3 feet long with side branches still attached. Feltleaf, Pacific or Sitka Willow is recommended for dormant cuttings (see Plant Species Selection List, Shrubs and Trees)
Construct a v-shaped trench above the ordinary high water (OHW) level, with hand tools or a backhoe. Excavate a trench so that it parallels the toe of the streambank and is approximately 2 feet deep. Lay a thick layer of willow branches (8"-10" before compaction) in the trench so that 1/3 of the length of the branches are above the trench and the branches angle out toward the stream. Place a minimum of 40 willow branches per yard in the trench. Of the 2/3 buried willow, not more than 1/2 should fall in permanently moist soil.
Backfill over the branches with a gravel/soil mix and secure the top surface with large washed gravel and/or bundles (see Bundles / Coir Logs sections). Both the upstream and downstream ends of the live siltation construction need to transition smoothly into a stable streambank to reduce the potential for the technique to wash out. More than one row of live siltation can be installed.
- Provides good fish habitat
- Provides bank stability in low velocity areas
- Provides good riparian vegetation
- Requires shallow water and slope
- Requires relatively low velocity
- Critical to know OHW (ordinary high water)