City of Prior Lake, MN
City of Prior Lake, MN

Flooding

CITY HALL LOCATION

City of Prior Lake
4646 Dakota St. SE
Prior Lake, MN 55372
   (952) 447-9800

FLOOD CONTACTS

Prior Lake Public Works
  (952) 447-9896
Scott County Dispatch
   (952) 445-1411

FLOOD RESPONSE DOCUMENTS

Floodplain FAQs
Flood Response Policy
Flood Protection Map
High Water No Wake Restrictions
Scott County Mitigation Plan
2016 Flood Mitigation Study

Flood at Watzl's

The Federal Emergency Management Agency (FEMA) recently established a new 100-year floodplain elevation for Prior Lake. The City of Prior Lake and the Prior Lake-Spring Lake Watershed District (PLSLWD), in collaboration with Spring Lake Township, completed a Flood Study in 2016. One of the significant components of the Flood Study is a watershed flood model that accurately characterizes the nature of flooding for the areas draining to Prior Lake. The previous flood model was developed in the 1970s and updated in 1997. FEMA used these old flood models to set the 100-year floodplain elevation for Prior Lake at 908.9. The 2016 Flood Study found that the 100-year flood elevation for Prior Lake should be 906.9. The difference of 2 feet is primarily due to the presence of the Prior Lake Outlet Channel (PLOC); Prior Lake was previously a landlocked lake having no natural outlet. The 1997 FEMA update did not consider the presence of the PLOC.

FLOODING POTENTIAL
The watershed draining into Spring Lake and Prior Lake encompasses approximately 19,000 acres (30 square miles). Prior Lake does not have a natural outlet and lake levels have fluctuated by more than 15 feet, from extreme low levels in the 1930s and 1980s to the flooding of the 1960s and record-setting flood of 2014. The Prior Lake-Spring Lake Watershed District (PLSLWD) completed the Prior Lake Outlet Structure and Prior Lake Outlet Channel in 1983 which provides significant relief from flooding. The historic average lake level elevation is about 902 feet, and the 100-year flood elevation is 906.9 feet. The 100-year flood elevation is more accurately referred to as the 1% flood, since it is a flood that has a 1% chance of being equaled or exceeded in any given year.

FLOOD LEVELS
Body of Water OHW 100-Year Flood RFPE
Prior Lake 903.9 ft. 906.9 ft. 907.9 ft.
Spring Lake 912.8 ft. 914.4 ft. 915.4 ft.

The Ordinary High Water (OHW) level for a lake is an elevation delineating the HIGHEST water level that has been maintained for a sufficient period of time to leave evidence upon the landscape, commonly the point where the natural vegetation changes from predominantly aquatic to predominantly terrestrial. The OHW is set by the Department of Natural Resources. The Regulatory Flood Protection Elevation (RFPE) refers to an elevation 1 foot (minimum) above the 100-year flood. In Prior Lake the flood plain regulations require that the elevation of the surface of the lowest floor of a dwelling be at or above the regulatory flood protection elevation. The listed 100-year Flood and RFPE elevations are effective as of July 9, 2018.

PRIOR LAKE FLOOD RESPONSE POLICY
The City of Prior Lake Flood Response Policy defines and outlines the City’s response to lake flooding within the City. The City’s primary responsibility during a flooding event is to protect public safety. The City Council prioritizes the following goals:

  1. Protect public safety – maintain emergency vehicle access
  2. Protect public health and safety – protect public infrastructure (i.e., sanitary sewer and water distribution)
  3. Maintain traffic flow through the County Road 21 corridor
  4. Maintain access to private property through public rights-of-way

Private property owners are responsible for protecting their own private property during flooding events. Property owners may use City flood protection efforts to enhance private property protection efforts; an example of this would be connecting private sandbag walls to road right-of-way barriers.

City flood response for Spring Lake and Prior Lake is based on lake elevation trigger points, weather forecasting, watershed conditions, and overall system flow. Lake elevations are determined by the PLSLWD. Please review the Flood Response Policy for more information about lake elevation trigger points and City responses.

SAND BAGS
The City of Prior Lake, in accordance with the Flood Response Policy, does not offer sandbags for sale until the level of Prior Lake or Spring Lake reaches its Ordinary High Water (OHW) elevation. When these conditions are met, property owners on Prior Lake and Spring Lake can order sandbags, at the front desk at City Hall or by calling the Public Works at (952) 447-9896. The City will provide sand to residents at designated locations and in a stockpile at the City Maintenance Center. Residents are encouraged to utilize these services if they feel there is a need to protect their property. North Dakota State Univ. has developed a brochure on building strong effective sandbag walls for Fargo, ND that helps calculate the number of sandbags needed and how to anchor and reinforce the wall.

FLOOD INSURANCE RATE MAP (FIRM)
FEMA publishes maps, called Flood Insurance Rate Maps (FIRMs), that show the areas in the community that have a 1 % or greater chance of flooding in any given year, known as Special Flood Hazard Areas (SFHAs). FIRMs are the result of engineering studies that are performed by engineering companies, other federal agencies, or the community and are reviewed and approved by FEMA. The Community Development Department has copies of FIRMs for the City available for review. You may also obtain property flood information by calling the Community Development Department at (952) 447-9810. General flood information, including ordering of FIRM maps, is available on the FEMA website.

LETTER OF MAP AMENDMENT (LOMA)
AND LETTER OF MAP REVISION BASED ON FILL (LOMR-F)
If you are a homeowner and believe your property is not located in the designated 100-year flood plain (also known as the Special Flood Hazard Area (SFHA)), as shown on the effective Flood Insurance Rate Map or Digital Flood Insurance Rate Map for Prior Lake and you would like FEMA to make an official determination regarding the location of your property relative to the SFHA, you may request a LOMA or LOMR-F. For more information on how to apply for a LOMA or LOMR-F visit the FEMA website dedicated to LOMA and LOMR-F.

VOLUNTARY EVACUATION
Should you decide to evacuate please see the guidance for securing your home. If you need assistance in plugging your sewer please call the City at the numbers listed above. We also ask that you inform the City of your decision so that we are aware of the vacancy.

WEATHER
The National Weather Service provides accurate warnings and forecasts for Scott County and Prior Lake. If you observe a sudden rise in water or something unusual with a storm pond, creek, stormwater drain, sanitary sewer manhole, or street with flooding notify Prior Lake Public Works at (952) 447-9896 during regular business hours. Call Scott County dispatch at (952) 445-1411 after 4:30 p.m. or weekends.

MORE INFORMATION
For general information about flooding visit the Homeland Security and Emergency Management website.