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The County of DuPage
Wheaton, Illinois

Floodplain Identification in DuPage County

It is important to understand the regulatory issues that are associated with properties located in a floodplain. Flood insurance and special permit requirements may add complexity to ownership of a property located in a floodplain. Floodplain maps may be used to help determine whether or not a DuPage County property is located in the regulatory floodplain.  

Flood Insurance


The current effective Digital Flood Insurance Rate Maps (DFIRMs), issued by the Federal Emergency Management Agency (FEMA), identify various flood zones and are used by the National Flood Insurance Program (NFIP) for rating flood insurance policies and enforcing federal mandatory insurance purchase requirements.

Revised Preliminary DFIRM

On June 1, 2017, FEMA issued Revised Preliminary DFIRMs to all communities in DuPage County. It is projected that these maps will become effective sometime in 2018 or later. It should be noted that while the current effective DFIRMs are based on the National Geodetic Vertical Datum (NGVD) of 1929, the Revised Preliminary DFIRMs are based on the North American Vertical Datum of 1988 (NAVD 88).  DuPage County has created a  Revised Preliminary DFIRM Map Compare Application that allows the public to quickly compare the new Revised Preliminary DFIRMs to the 2004 DFIRMs.

Development in the Floodplain

The DuPage County Regulatory Flood Maps (RFMs) are for use in administering the DuPage Regulatory Flood Program. For all development in the floodplain, it is required that users consult the current RFM, current effective DFIRM and the Preliminary DFIRM.

The DuPage County RFMs were created using the same information used to create the 2004 DFIRMs. The maps are used as a planning tool only and cannot be used to definitively determine whether or not a property is located in the floodplain. Floodplain maps do not necessarily identify all areas subject to flooding. Site specific floodplain, depressional storage areas and local drainage sources of small size are not always represented on the floodplain maps. Actual floodplain boundaries may be slightly different than those shown on the maps due to variations in topography. The community map repository should be consulted for possible updated or additional flood hazard information, such as FEMA Letter of Map Change (LOMC) or Letter of Map Revision (LOMR) information. Please reference the DuPage County Countywide Stormwater & Flood Plain Ordinance for regulatory information.