Rock Weir

Rock Weir POLLUTANTS ADDRESSED: Nutrients and Organics, Sediments

DESCRIPTION: This is a grade control structure constructed from large rocks.

POTENTIAL TREATMENT AREAS: Streamside

LOAD REDUCTION MECHANISM: Nutrients/Organics Management- Reduces sediment which has the ability to transport Nutrients and Organics

ALTERNATIVE MANAGEMENT MEASURES: Irrigation Water Management Water Facilities

PERMITTING REQUIREMENTS: Permits are required under Sections 404 and 401 of of the Clean Water Act.

Sediment Reduction – Reduce bank erosion and protect against channel incision or downcutting

Contact county regional flood control district.

LAND USE CLASSIFICATION: Stream Bank Protection

ADDITIONAL BENEFITS: The rock weir can also be used as a diversion for off channel watering facilities.

Arid Southwest BMP

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Rock Weir POLLUTANTS ADDRESSED: Nutrients and Organics, Sediments

Level 500: INTENSE ENGINEERING

LOAD REDUCTION POTENTIAL: LOW

MEDIUM

PLANNING AND IMPLEMENTATION:

HIGH

1. Rock weirs can be used to stabilize incising channels and to provide more stable diversion systems for irrigation and livestock water.

ESTIMATED TIME FOR LOAD REDUCTION: IMMEDIATE

MONTHS2 YEARS

2. Rock weirs must be very carefully designed and installed. They should only be installed in the transition or riffle sections of stream between meanders. The structure is keyed into both banks to reduce the chance of the stream eroding around it. At the banks the structure elevation should be higher than the floodplain to allow high flows to spread. The weir arms are angled sharply upstream at a 20째 - 30째 from the bank as it dips down to the channel bed elevation.

> 2 YEARS

EXPECTED MAINTENANCE: LOW

MEDIUM

HIGH

ESTIMATED COST: LOW

MEDIUM

HIGH

3. Weirs can be constructed of large rock, generally 2 - feet in diameter, angular rock riprap, logs, or upright posts. It is critical that the structure extend below the level of stream scour in the channel bed to protect from undermining and failure.

4. These structures are more stable than traditional flat topped diversion dams because they maintain natural water and sediment transport.

The central flow also allows fish passage.

Riparian Planting Zone: Base flow and Toe Zone.

Photo courtesy of ADEQ Streambank Stabilization Plan

Arid Southwest BMP

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