Following is a description of the installation methods and materials used to construct the Composite Brush Siltation Weirs:

Weir construction materials consisted of brushy vegetation collected on site (using thinnings of selected existing woody plants) and lashed together with heavy sisal or coir twine.  Plenty of brushy materials were available immediately adjacent to the site.  Brushy materials consisted of the following:  (1) Heteromeles arbutifolia (toyon); (2) Adenostoma fasiculatum (chamise); (3) Baccharispilularis consanguinea (coyote brush); (4) Aesculus californica ( California buckeye); (5) Populus fremontii (cottonwood); and Rhomnus californica (coffeeberry).

In this dryland, riparian site, there is an ebb and flow of water from year to year with corresponding flushes or die-back in plant growth.  Consequently, brushy plant material has grown up over wet seasons and then died back when water was lacking.  Thinning these plants encourages new growth if conditions are favorable, and reduces total leaf area of the plants so that they are more capable of surviving droughty periods.

Brush trimmings were cut with chain saws and stacked alternating the butt ends of the brush in both directions.  The stacks were tightly bundled and secured with twine made of natural sisal.  The finished bundles were approximately 2.6 meters (8 feet) long and 0.5-0.6 meters (18 inches-2 feet) in diameter.  Trenches were dug into the graded bench area on the landward side of the LPSTP, perpendicular to the stream channel, in preparation for placement of the CBSW’s.

Direct Seeding:
Prior to placement of the Brush Weirs, the trenches were direct seeded with toyon, coffeeberry, and California buckeye.  Buckeyes should be direct seeded when they are fresh or have been stored in a cool and moist area, as they germinate and grow most successfully when gathered and planted in the same season they have fallen from the trees.
The composite brush bundles were then installed into these trenches with the lower half of the bundle buried and secured in place with pole cuttings and stakes cut from 2 x 4's.

Live Pole Planting:
Live pole planting refers to planting a cut section of an easily rootable plant directly into the ground.  Cottonwood was chosen for this site.  The cottonwood poles ranged from 20 mm to 37 mm (3/4" to 1 1/2") in diameter and are approximately 0.6 m (2') long.  It is vitally important to keep the top/bottom orientation of the plant correct.  To keep this orientation correct, the bottom end of the pole cutting is cut at an angle and the top end is cut straight across.

Pole cuttings were taken from dormant, healthy specimens of cottonwood and planted within 24 hours of cutting.  Poles were planted so that no more than 75-100 mm (3-4") of the cutting protruded above the ground, again to prevent desiccation.  The 75-100 mm (3-4") sections of the cuttings above ground level had at least 2 nodes where dormant buds could break and grow.  The pole cuttings were firmly tamped and watered in so that there were no air pockets around the stem, assuring good plant to soil contact.

The vegetative components of this project were installed during the month of March, 1999.  Weather patterns for this area at this time of year were such that temperatures were beginning to warm up and there was not a great deal of rain fall that occurred after the construction window.  Ideally, the revegetation for this project should have been implemented in December or early January, when there was more moisture to give a greater opportunity for establishment.  This was particularly critical on this site due to the long, hot dry summers.

Subsequent visits to the site have shown about 50% of the live pole plantings to be sprouting.  None of the direct seeded areas within the Composite Brush Siltation Weirs have shown any signs of seedling emergence.  The CBSW's did not experience any periods of inundation from high flows during the spring of 1999.  The desired revegetation is expected to occur during the next few years as the CBSW's trap sediment, creating a more hospitable medium for native plant colonization, and as a percentage of the direct seeding and seeds naturally found in the CBSW’s begin to germinate.  This process is already beginning to occur in the silt deposits left in the backwater zones of the bendway weirs.

Davinroy, R.D., Rapp, R.J., and R.E. Myhre 1998. “Hydroacoustic Study of Fishes in Bendway Weir Fields of the Middle Mississippi River”.  Proceedings of the ASCE conference Wetlands Engineering and River Restoration Conference 1998.

Derrick, D.L., 1995.  Case Study:  "Harland Creek Bendway Weir/Willow Post Bank Stabilization Demonstration Project".  In Water Resources Engineering, Proceedings, First International Conference on Water Resources Engineering, ASCE, New York.

McCullah, J., 1998. "Biotechnical Soil Stabilization". Training Manual for Caltrans, California.

Shields, Jr. F.D., Knight, S.S., and Cooper, C.M. 1995.  “Streambank Protection and Habitat Restoration”.  Volume 1 of the ASCE conference, The First International Conference on Water Resources Engineering, San Antonio, TX. p. 721-725