What is an Interim Risk Reduction Measure (IRRM)?

Public Workshop Dates

An IRRM is a series of temporary actions implemented by engineers designed to reduce the risk to downstream populations that may be associated with high water elevations at a USACE reservoir. Since 2017, a series of IRRMs have been implemented at Beaver Lake Dam. These IRRMs ranged from updated emergency action plans to water-proofing the operational equipment at the dam (gate controls) to faster, more effective evacuation of the water from the flood pool. Updating these flood pool evacuation operations was performed in a series of three steps, which are described below. 

IRRM Operational Changes

1. Double flood risk management minimum release after floods.

  • Minimum releases from Beaver increased from 950 cfs to 1,900 cfs when Beaver Lake is in flood pool and conditions downstream allow.

  • Table Rock must be below elevation 917 feet

  • Combined Beaver, Table Rock, and Bull Shoals less than 50 percent flood storage

 

2. Deeper Drawdown After Surcharge (release to prevent gates from overtopping).

  • Drawdown of 1.0 to 1.5 feet from top of flood pool (from elevation 1,130.0 to 1290.0 or 1,128.5 feet depending on the time of year) after flood event

  • Provides extra 0.5 to 0.75-inch runoff storage

3. Revised Guide Curves at Newport and Georgetown.

Winter:

  • Regulate to 24 feet stage at Newport

  • Delay transition to springtime target stage by two weeks

Springtime:

  • When system storage is LOW, use current low target (blue)

  • When system storage is HIGH, use current high target (green dash), and

  • When system storage is VERY HIGH, use current late springtime (May) target (red dots).

Summer/Fall:

  • When system storage is above 30 percent, regulate to higher summer target (red dots).

Dec. 16 - Searcy, AR

White County EM Office

5p.m. - 8p.m.

Jan. 24 - Rogers, AR

City of Rogers

City Hall Community Room

5p.m. - 8p.m.

Jan. 25 - Branson, MO
Dewey Short Visitor's Center

5p.m. - 8p.m.

 

Jan. 31 - Jacksonport, AR

State Park Visitor's Center

5p.m. - 8p.m.
 

Feb. 1 - Mountain Home, AR

Arkansas State University

Vada Sheid Community Development Center

5p.m. - 8p.m.

Newport and Georgetown IRRM Plans

Georgetown Graph 6-16-2022.JPG

Additional Beaver Lake Dam IRRMs (Non-Operational)

  • Physical Improvements to Dam Equipment

    • Gate mechanical / electrical waterproofing 

    • Equipment wave run-up protection

    • Added sensors for remote operation

  • Preparedness Improvements

    • Emergency flood barriers for control house and power house

    • Increased monitoring for potential seepage

    • Downstream warning system for Carroll County, Arkansas and Branson, Missouri

  • Communication​

    • Regular emergency exercises​ with stakeholders

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