Check out this great resource that provided an overview of some of the floodplain basics in the state of Wisconsin.

Wisconsin Floodplain Management Quick Guide

2020/2021 Preliminary Flood Insurance Rate Maps (FIRMS) and Flood Insurance Study (FIS)

In early 2020, and additionally in early 2021, the City received the follow preliminary Flood Insurance Rate Maps (FIRMS) and Flood Insurance Study (FIS) from FEMA.  For more information on the preliminary maps/study please visit www.fema.gov/preliminaryfloodhazarddata and also view the details provided below.  FEMA also offers a Flood Map Changes Viewer that is an interactive way to compare current vs. proposed floodplain mapping for a specific area/property.

Preliminary Maps (FIRM)

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Preliminary Study (FIS)

Volume 1Volume 2Volume 3Volume 4Volume 5

Preliminary Summary of Map Action (SOMA)

The SOMA document lists the previous Letter of Map Change (LOMC) actions (i.e., Letter of Map Revision (LOMRs), Letter of Map Revision based on fill (LOMR-Fs), and Letter of Map Amendments (LOMAs)) that will or will not still be valid after the preliminary maps become effective.  You will see that most previous LOMC actions are valid, with the exception of five (5) LOMCs that will be superseded by the new mapping.

SOMA - Preliminary

FEMA Public Open House

FEMA will be holding a Public Open House relating to these new maps and study on Wednesday March 4, 2020 at 6:00 p.m. at the Village of Mukwonago Village Hall in the Community Room.  The open house is a means to begin dialogue regarding the Preliminary FIRM and meet with residents in a one-on-one environment.  FEMA is interested in talking directly to property owners, realtors, insurance agents, surveyors, developers, and representatives of lending institution.  The FEMA team will be available to explain site-specific questions for the new maps and provide information on NFIP flood protection standards and flood insurance.

General Floodplain Information 

The purpose of this page is to provide information and resources about floodplain tips, concerns, issues, and mapping in the City of Muskego. Please check back here often as we will try to update this page as often as necessary to keep the residents of Muskego informed on floodplain issues in the City. 

Most floodplain regulations apply to the 1% annual chance (also known as the 100-year) floodplain. The floodplain is made of of two parts. The inner portion of the floodplain in known as the floodway. The floodway is the channel of a river or stream, and those portions of the floodplain adjoining the channel required to carry the regional flood discharge. The floodway is the most dangerous part of the floodplain since it is associated with moving water. The area of the floodplain outside of the floodway is the floodfringe. This area is covered by flood water during the regional flood. The floodfringe is generally associated with standing water rather than flowing water. It is also the part of the floodplain in which some development is allowed subject to the floodplain development standards. 

Floodplain Diagram
Diagram illustrating the different areas of the floodplain (from the DNR).

Floodplain Maps and Documents 

There are a few different types of floodplain maps and documents that are applicable in the City of Muskego. 

Floodplain Zoning Ordinance
The City is required to have an adopted Floodplain Zoning Ordinance that meets the requirements of FEMA and the DNR:

Chapter 386:  Floodplain Zoning 

Official Maps Based on FIS
Flood Insurance Rate Maps (FIRM) are the Official maps produced by the Federal Emergency Management Agency (FEMA) that are nationally recognized maps showing the floodplain per the FIS (Flood Insurance Study). These are the maps that are typically used by lenders to determine is a property is located in the floodplain and if flood insurance may be required for a specific home. These maps identify the various types of floodplains within a certain area. There are 17 of these maps that cover the City of Muskego. These are effective as of November 5, 2014. 

FIS Study Document:

Maps (FIRMs): 



Official Other Studies/Maps:
These are still official studies that have been done commissioned by the City or third parties that have not been acknowledged by FEMA, but are still believed to be more accurate than the FIRMs in certain areas of the City. These maps are typically more restrictive than the FIRMs. These are not typically used by insurance companies to determine if flood insurance is required or not. They are usually used by the City since we believe they are the best information available and all applicable City floodplain regulations apply to these maps, as well as the FIRMs. 


Flood Storage Maps:
These maps were produced by the DNR as part of the revised 2008 FIRMs. These maps were most recently revised on November 5, 2014. These maps show certain floodfringe areas, as shown on the FIRMs, that have an extra layer of protection to ensure that the floodplain storage capacity is preserved in these specially identified areas. 


All of the maps and documents listed above are available at the Community Development Department - Planning Services Division inside Muskego City Hall and some are available through FEMA’s website. 

LOMC (Letter of Map Change) 

Letter of Map Change (LOMC) are documents issued by FEMA that can override and/or clarify what the FIRMs may show. There are a few different types of LOMCs. 

  • LOMA (Letter of Map Amendment) - These are letter issued by FEMA that identify is a specific structure is located in the floodplain or not. FEMA makes these decisions based upon elevation data being submitted to them from review. These are the most common type of LOMCs issued. These letters do not formally change the maps, but the FEMA issued letter supersedes the maps.
  • LOMR-F (Letter of Map Revision Based on Fill) - These are letters, typically with maps/exhibits attached, that formally modify the floodplain boundaries for a certain area. These are used when is being placed within the FIRM mapped floodplain, outside of the floodway.
  • LOMR (Letter of Map Revision) - These are letters, typically with maps attached, that formally modify the floodplain boundaries (floodfringe and/or floodway) for a certain area. These typically involve a new study being done for a certain area. These take a bit more time and have a larger expense associated with them than LOMAs.

Valid LOMCs:
When the revised FIRMs and FIS became effective on November 5, 2014, all previous LOMCs became invalid. On November 6, 2014 FEMA issued a bulk revalidation letter that revalidated any previous LOMC documents that FEMA believed were still valid. The following document lists the previous LOMC documents that are still valid as part of the new mapping. 

LOMC Revalidation Letter 

In addition to the LOMCs issued through the LOMC Revalidation Letter (found above) there have been additional properties that have applied for LOMCs through FEMA. Click the following link to be taken to FEMA’s search page for finding additional LOMCs.

How to Find a LOMC (FEMA) 

The City is on the process of mapping the locations of the properties that have valid LOMCs documents associated with them. The goal is to eventually be able to offer all of the LOMC documents via this website. 

There are also a few other types of floodplain change documents but these are the three most common types. For more information and for copies of all LOMC documents are available through the City of Muskego Community Development Department - Planning Division office and through FEMA’s website

Online LOMC Submittal:
Certain LOMCs can now be submitted to FEMA online. Click here to view the FEMA LOMC online submittal page and find out all of the details relating to submitting a LOMC online. 

Flood Insurance 

Since most standard homeowners insurance policies do not cover flooding, separate flood insurance is often a good tool to help protect against losses due to flooding. The City of Muskego is a participant in the Nation Flood Insurance Program (NFIP). The NFIP was created to help provide a means for property owners to financially protect themselves. The NFIP offers flood insurance to homeowners, renters, and business owners if their community participates in the NFIP. Participating communities agree to adopt and enforce ordinances that meet or exceed FEMA requirements to reduce the risk of flooding. Flood insurance is available to all properties within the community, regardless if they are located within a floodplain or not. This is important since flooding can occur anywhere, even in areas that are not within a mapped floodplain. More information on flood insurance and the NFIP.

More Information 

For more information relating to any floodplain questions, issues, concerns, etc. please feel free to contact the City of Muskego Community Development Department - Planning Services Division. Staff there will try to assist you in any way they can and point you in the right direction if additional information is required. 

You can also always visit the Wisconsin Department of Natural Resources (DNR) Floodplain Management website or FEMA’s website for additional information.