Floodplain

Development in Floodplains

The City of Johnston participates in the National Flood Insurance Program (NFIP) and has adopted regulations to manage development in floodplains. The floodplain regulations adopted by the City of Johnston establishes a flood fringe (FF) overlay district and a flood way (FW) overlay district. The regulations are found in Chapter 169 of the Zoning Ordinance, which outline permissible development in those areas. A floodplain development permit is required.

The Iowa Department of Natural Resources issues floodplain development permit also and a permit may also be required from them based upon the type of construction proposed.

To determine if your property is within the floodplain, review the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Maps. Copies are available at Johnston City Hall for review. Electronic copies of the maps are also available from FEMA.


Floodplain Regulations

Because of the city's floodplain regulations, residents in the city are eligible to purchase flood insurance from the National Flood Insurance Program, please contact your insurance agent about flood insurance or review this link for more information.

For additional floodplain information, please contact the Community Development Department at 515-727-7778 or by email.

Preliminary FEMA Floodplain Maps Released


The current FIRM maps regulating properties within Johnston were adopted on July 19, 2000.  However, over the last couple of years FEMA has been working to update all FIRM maps within Johnston based upon:

  • Updated hydrologic and hydraulic analysis of portions of Little Beaver Creek, affecting flood hazard areas generally north of NW 70th Avenue and east of NW 86th Street; and,
  • Re-delineation of flood hazard areas using updated topographic information, affecting all flood hazard areas within Johnston.  The 2000 FIRM maps were prepared using 10 foot topographic contour data, while the preliminary maps use 2 foot topographic contour data.
As a result of this work, FEMA has published preliminary FIRM maps and an FIS for Johnston dated June 17, 2015.  In order to continue to participate in the NFIP, the City is required to officially adopt these updated maps, with this approval expected in 2017.

A link to the Preliminary FIRM Map and Flood Study for Johnston dated June 17, 2015:

Preliminary Flood Study for Polk County – Volume 1
Preliminary Flood Study for Polk County – Volume 2
Preliminary Flood Study for Polk County – Volume 3

Panel Guide – Johnston Maps are provided on multiple panels, this is a guide to the location of each panel (panels are provided in the links below):


A map, prepared by City staff, that generally shows the comparison of the 2000 FIRM maps and the preliminary 2015 FIRM maps by identifying locations of areas added to or deleted from flood designated areas.  Please note this is not an official FEMA map, nor should it be used to determine if your property is or is not within a flood hazard area, rather it’s been prepared to assist you in determining the general effect of the preliminary FIRM maps.

A Summary of Actions pertaining to previously approved Letters of Map Revisions (LOMR) or Letters of Map Amendments (LOMA).  LOMR and LOMA’s are property specific studies prepared to show that the property and/or structures on the property are located above the flood designated areas shown the FIRM maps.  This summary notes how previously approved LOMA and LOMR’s, issued between July 19, 2000 and June 17, 2015, where addressed on the preliminary FIRM maps for Johnston; and, Summary of Map Actions.

A copy of the preliminary FIRM maps and Flood Study, and all of the information noted above, is also available for review in the Community Development Office at Johnston City Hall, located at 6221 Merle Hay Road.  You may stop in anytime during regular office hours from 8 a.m. – 5 p.m. to review this information.  Should you desire to discuss this information with a staff member, it is suggested that you schedule an appointment in advance by calling 515-727-7778.

If you do not already have flood insurance through the NFIP, the City strongly encourages you to contact your insurance agent to discuss the options best suited for your property.  Should you have any questions, please feel free to contact David Wilwerding at 515-727-7775 or by email.