Indiana Floodplain Mapping FAQs

The term “100-year flood” is misleading. It is not the flood that will occur once every 100 years; rather, it is the flood that has a one percent chance of being equaled or exceeded annually. It is based on probabilities, not predictions. Thus, the 100-year flood could conceivably occur multiple times in a year, or not at all over a period of 150 years or more. Because the term “100-year flood” is misleading, FEMA has also defined it as the one-percent-annual-chance flood. The “one-percent-annual-chance flood” is the term that is now used by most Federal and State agencies and by the National Flood Insurance Program (NFIP). It can also be interpreted as 26% chance of flooding over the life of a 30-year mortgage.

A Base Flood Elevation (BFE) is the elevation the floodwaters will reach during the one-percent annual chance flood. A property owner can obtain Base Flood Elevation (BFE) through the Indiana Floodplain Information Portal (INFIP).

The Special Flood Hazard Area (SFHA) is the portion of the floodplain subject to inundation by the base flood (1% annual chance) and/or flood-related erosion hazards. Riverine SGHAs are shown on FIRMs as Zones A, AE, AH, AO, AR, and A99. Older FIRMs may have Zones A1-A30.

A Flood Insurance Rate Map (FIRM) is an official map of a community on which FEMA has delineated both the Special Flood Hazard Areas and the risk premium zones applicable to the community. More information can be found in the FEMA Floodplain Mapping Section

The DNR maps were developed to show the extents of unmapped floodplains and to provide information about flood-prone areas along Indiana’s rivers and streams, where little or no information previously existed. Information provided by the DNR maps is used by communities and local governments to administer their floodplain regulations (ordinances) and by those seeking a DNR permit for construction in the floodway.

Best Available Data includes the FEMA FIRM and DNR studies.

Through the Indiana Floodplain Information Portal (INFIP) you can request a review of the information shown as well as provide additional technical information to justify your change. You can also submit your own revised modeling data to update the floodplain information shown.

Indiana DNR serves as a Cooperating Technical Partner (CTP) with FEMA. This programs mission is to strengthen the effectiveness of the National Flood Insurance Program (NFIP) and support FEMA’s mitigation objectives. The CTP Program leverages partnerships to deliver high-quality hazard identification and risk assessment products, provide outreach support and empower communities to take action to reduce risk based on informed, multi hazard-based data and resources. By participating in the program IDNR can actively work to identify and map flood risks while incorporating this information into official FEMA flood hazard data.

With respect to the Flood Insurance Rate Maps, there is a formal process for getting new or updated floodplain information on the maps. FEMA recognizes the need for updating mapping based on new topography, new hydrology, and incorporation of any projects that have been completed since the last comprehensive update.

There are a number of touch points through the FEMA mapping process:

1. Discovery Meeting - These meetings are held with community officials to gather any existing issues with the maps and identify areas where floodplain information is needed. These meetings are summarized in Discovery Reports.
2. Flood Risk Review Meetings - These meetings are held, with local floodplain administrators to review draft versions of new maps and bring any concerns they have with new floodplain mapping. If there are concerns, then we work to address them before the maps go to preliminary.
3. Community Consultation Officer (CCO) Meetings - These meetings are held with local officials to provide an overview of the Preliminary Maps. At this meeting, local officials are also provided information on the appeal and ordinance update process.
4. Flood Risk Open Houses - These open houses, which follow the CCO meetings, are where the public is invited to view the maps, ask questions, and provide comments. IDNR sends out notices to affected landowners (not a FEMA requirement), to invite them to the Open House. We also take concerns at these meetings and will review specific issues before we go into the appeal period.

After the open house, there is a 90-day appeal period which begins with newspaper notifications in a local newspaper. Once the appeal period has ended and any appeals are resolved, the mapping products will be finalized. When completed, FEMA will issue a Letter of Final Determination which sets a 6-month period for maps to be adopted by communities before the maps become final.

There are two options:

1. Appeal Process - An appeal is a formal objection to new or revised Base Flood Elevations (BFEs) shown on a Preliminary Digital Flood Insurance Rate Map (DFIRM) or Flood Insurance Study (FIS) report. Predicted flood elevations can be appealed if they are shown to be scientifically or technically incorrect.

   If you would like to appeal new or revised floodplain information, we highly recommend contacting an engineering or surveying firm to assist with the highly technical information needed.

2. Comment Process - Any submittal that does not meet the criteria to be consider an appeal is processed as a comment. Comments are generally regarding the delineation of the updated floodplain and/or floodway boundaries, corporate limits, road names, and road locations.

Resolution of Appeal and Comment Petitions

After the appeal period has closed, FEMA will review submitted data to determine if it constitutes a valid Appeal or Comment. Letters will be sent to communities explaining the resolution of any Appeals or Comments. If a formal petition supports a revision FEMA will update the Preliminary Maps and issue Revised Preliminary Maps.

Visit the Indiana DNR Department of Natural Resources on floodmaps.

Or contact us at:

Indiana Department of Natural Resources
Division of Water
402 W. Washington Street, Room W264
Indianapolis, IN 46204
317-232-4160
877-928-3755 (Toll Free)

For exemption from the mandatory flood insurance purchase requirement, a property owner would need to file for a Letter of Map Amendment (LOMA). A LOMA is a letter that officially revises an effective FEMA floodplain map and establishes that a specific property or building is not located in the Special Flood Hazard Area. The LOMA does not physically revise the map, but rather amends the map. The letter is an official statement from FEMA stating that the specific property in question is not located in the Special Flood Hazard Area

For buildings constructed before the publication of the first FEMA flood map that identified the structure as being in the Special Flood Hazard Area, it must be shown that the lowest ground elevation where it touches the foundation on the outside of the building – what FEMA refers to as the lowest adjacent grade – is above the base flood elevation. An entire lot or parcel can be removed from the Special Flood Hazard Area if the lowest ground elevation within the boundaries of the parcel is at, or above, base flood elevation.  FEMA requires that property owners hire a licensed surveyor or professional engineer registered in Indiana to obtain the surveyed elevations of the lowest adjacent grade in order to complete application. FEMA does not charge any fees to process and review MT-EZ forms for a LOMA.  However, since FEMA requires property owners to obtain survey data to complete a LOMA, property owners are responsible for the cost of hiring a licensed surveyor or professional engineer registered in Indiana.