HomeMy WebLinkAbout6A Prior Lake Floddplain Update PresentationPRIOR LAKE FLOODPLAIN
ELEVATION UPDATE
City Council Meeting
May 7, 2018
Floodplain Acronyms & Definitions
•FEMA: Federal Emergency Management Agency. Federal government agency that coordinates
the federal government’s role in preparing for, preventing, mitigating the effects of, responding
to, and recovering from all domestic disasters…
•100-year Flood. Water elevation that has a 1% chance of being equaled or exceeded in any
given year.
•FIS: Flood Insurance Study. A compilation and presentation of flood risk data for specific flood
hazard areas within a community. When a flood study is completed, the information and maps
are assembled into an FIS. The FIS report contains detailed flood elevation data.
•FIRM: Flood Insurance Rate Map. The official map of a community on which FEMA has
delineated both the special hazard areas and risk premium zones applicable to the community.
•LOMR: Letter of Map Revision. FEMA’s modification to an effective FIRM.
•LOMA: Letter of Map Amendment. An official amendment for an individual property that
establishes a property’s location in relation to the floodplain. LOMAs are usually issued
because a property has been inadvertently mapped in a floodplain, or as an update after a
home has been raised out of the floodplain.
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Prior Lake Floodplain History
•1978 –FIS approved
(100-year flood elevation 909.0’)
•1983 –Prior Lake Outlet Channel(PLOC) operational
•1997 –FIS revised (100-year flood elevation 908.9’)
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Prior Lake Floodplain History
Top 5 Prior Lake Flood Elevations
(MN DNR records)
1.906.17 (June 30, 2014)
2.905.68 (July 20, 1983)
3.904.78 (May 27, 1999)
4.904.64 (July 12, 1993)
5.904.40 (July 10, 1998)
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Prior Lake Stormwater Management
and Flood Mitigation Study (2016)
Study Goals:
1.Update the flood model (to help establish flood
levels)
2.Summarize efforts already accomplished
3.Identify flood reduction strategies
4.Evaluate cost/benefit of strategies and define
community goals for flood protection
5.Develop an implementation plan
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Prior Lake Stormwater Management
and Flood Mitigation Study (2016)
Study Results:
1.Modeling considers new factors including the
effect of the Prior Lake Outlet Structure and
Outlet Channel
2.City and PLSLWD have both implemented
short-term options
a.City: Flood Response Policy
b.PLSLWD: Actively manage Prior Lake Outlet
3.PLSLWD continues to work on long-term
implementation of the upper watershed
storage option to reduce 100-year flood level
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Prior Lake Stormwater Management
and Flood Mitigation Study (2016)
Study Results:
1.Modeling considers new factors including the
effect of the Prior Lake Outlet Structure and
Outlet Channel
a.Effects of the PLOS/PLOC
b.Updated precipitation record set (Atlas 14)
c.Accurate topography data (LiDAR)
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Study concludes that the 100-year
floodplain elevation for Prior Lake should be
906.9 instead of 908.9
LOMR for Prior Lake
•A LOMR is required to update the
existing FIRM to reflect the new flood
elevation
•Barr Engineering retained to complete
the LOMR process
•Detailed agency review required
•Interagency Hydrology Review Committee
(IAHRC), consisting of MnDNR, USACE, USGS,
and USDA; approved in April 2017
•FEMA approved LOMR with effective date of
July 9, 2018
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Implications for Residents
Flood Insurance
•Mortgage companies may require flood insurance for homes
located within the floodplain
•This change may remove this requirement for some homes based
on their elevation (may need to complete a LOMA)
•Those outside the 100-year floodplain who wish to purchase flood
insurance may still do so at a substantially reduced rate
•Insurance implication information will be available at the Open
House on May 17th at 6:00 p.m. at City Hall
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Implications for Residents
Building Permits
•The City requires the lowest floor elevation of new or reconstructed
homes to be at least one foot above the 100-year floodplain
•This change would require these homes to have a lowest floor
elevation of at least 907.9 (currently 909.9)
•Building to an elevation higher than the minimum would still be an
option
•Information to be presented at the Open House on May 17th at 6:00
p.m. at City Hall
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Floodplain Update Open House
May 17th at 6:00 p.m. at Prior Lake City Hall
•Representatives from the City, PLSLWD, and Barr Engineering will
be present
•Large-scale maps, insurance implication information, and building
permit information will be available
•Staff can review specific properties with residents using a map tool
that shows the updated floodplain
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