Arid Southwest BMP 27

Brush Mattress POLLUTANTS ADDRESSED: Sediments, Nutrients and Organics, Salinity

DESCRIPTION: A brush mattress is a mat of live branches of willow or similar tree species placed along the slope of an eroding stream bank to reduce erosion and to filter surface water flowing into the stream. To hold the mattress in place, the lower end is placed in a trench and anchored by bundles of cuttings (fascines). Further stability is achieved by securing the mattress to the stream bank with a grid of ropes tied to wooden stakes. Over time, branches will take root and provide long-term bank protection.

LOAD REDUCTION MECHANISM: Organics/Nutrients Management - Nutrients and organics in water flowing across the land are taken up by plants before they reach the stream. Sediment Reduction - Dense matrix of willow roots provides cohesion for sediment, reducing erosion. Salinity Reduction – Dissolved salts are taken up by plants.

LAND USE CLASSIFICATION: Agricultural and grazing lands where nutrients and organic materials may be carried into adjacent streams. Urban areas where organic pollutants may be released and where impervious surfaces increase runoff.

ADDITIONAL BENEFITS: Rooted plants protect bank from erosion. Brush mattresses help maintain natural channel configuration. POTENTIAL TREATMENT AREAS: Stream banks ALTERNATIVE MANAGEMENT MEASURES: Pole/Post Planting Vertical Bundle Willow Fascines Brush or Tree Revetment PERMITTING REQUIREMENTS: As required under Sections 404 and 401 of the Clean Water Act. Contact county regional flood control district.

Arid Southwest BMP 28

Brush Mattress POLLUTANTS ADDRESSED: Sediments, Nutrients and Organics, Salinity

Level 300: MODERATE ENGINEERING LOAD REDUCTION POTENTIAL:

LOW MEDIUM HIGH ESTIMATED TIME FOR LOAD REDUCTION:

IMMEDIATE MONTHS- > 2 YEARS 2 YEARS EXPECTED MAINTENANCE:

LOW MEDIUM HIGH ESTIMATED COST:

LOW MEDIUM HIGH PLANNING AND IMPLEMENTATION:

1. This technique works best on stream slopes no steeper than 2H:1V.

2. Brush mattresses can be washed out by strong flooding events, so the flow regime of the stream should be known.

3. Use branches from native species to avoid introducing invasive plants to the riparian community. Gathering of live branches should not damage other ecosystems.

4. Prepare the slope of the stream bank by clearing away large debris. Do not, however, remove woody debris from the stream channel because this provides important fish habitat.

5. Excavate a horizontal trench, 8 to 12 inches deep, at the toe (bottom) of the stream bank along the length of the area to be treated.

6. Place willow cuttings in the trench. Make sure the cut ends reach the bottom of the trench. Spread the cuttings along the face of the slope until a thickness of 4 to 6 inches is achieved.

7. Pound a grid of 36-inch long wooden stakes into the mattress 3 to 4 feet apart. Use longer stakes in less cohesive soil. Secure the brush mattress by using 3/8-inch rope. Tie the cord in horizontal runs and then diagonally between each row of stakes. After tying the mattress, drive the stakes further into the ground to compress the mattress tightly against the stream bank.

8. Construct a bundle of branches (a fascine) the

length of the area to be treated. Place the fascine across the base of the mattress in the

trench. 9. Backfill around the fascine and mattress by

using material excavated from the trench, making sure to work soil between the branches. Use buckets of water to wash the soil down into the stems. Key the upstream end of the mattress and fascine into the stream bank to prevent high flows from getting behind the mattress. It is a good idea to protect this area with a revetment, large rocks, or tree trunks.

Riparian Planting Zone: Toe Zone