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.
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Minimum releases from Beaver increased from 950 cfs to 1,900 cfs when Beaver Lake is in flood pool and conditions downstream allow.
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Table Rock must be below elevation 917 feet
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Combined Beaver, Table Rock, and Bull Shoals less than 50 percent flood storage
2. Deeper Drawdown After Surcharge (release to prevent gates from overtopping).
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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
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Provides extra 0.5 to 0.75-inch runoff storage
3. Revised Guide Curves at Newport and Georgetown.
Winter:
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Regulate to 24 feet stage at Newport
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Delay transition to springtime target stage by two weeks
Springtime:
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When system storage is LOW, use current low target (blue)
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When system storage is HIGH, use current high target (green dash), and
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When system storage is VERY HIGH, use current late springtime (May) target (red dots).
Summer/Fall:
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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
Additional Beaver Lake Dam IRRMs (Non-Operational)
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Physical Improvements to Dam Equipment
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Gate mechanical / electrical waterproofing
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Equipment wave run-up protection
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Added sensors for remote operation
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Preparedness Improvements
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Emergency flood barriers for control house and power house
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Increased monitoring for potential seepage
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Downstream warning system for Carroll County, Arkansas and Branson, Missouri
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Communication
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Regular emergency exercises with stakeholders
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