skip to main content
The County of DuPage
Wheaton, Illinois

Floodplain Mapping

Program Overview

DuPage County has grown dramatically over the last half decade. From 1950 to 2002 DuPage County saw a 600% increase in population alone. This rapid urbanization from what was mostly agricultural land to large residential, commercial, and industrial areas have had a profound impact on many of DuPage County's rivers and streams. The Stormwater Management Program was therefore established to address existing issues and to prevent future flood damages along the county's waterways. Since its inception, the Stormwater Management Division has striven to provide accurate flood plain information to property owners, regulators, and developers.

In the late 1970s and early 1980s the Federal Emergency Management Agency issued Flood Insurance Rate Maps (FIRM) that established the 1% annual chance (100-year) floodplains for DuPage County. These and other FIRMs have since been rendered obsolete due to changes in land use, topography, modeling standards and technologies but can still be viewed at FEMA's Map Service Center website by using the "Product Catalog". The Stormwater Division has been conducting new watershed studies that will conform to current topographical conditions and meet today's standards and practices in hydrologic and hydraulic analysis.

View DuPage County Regulatory Floodplain Maps (RFM) or DuPage County effective FEMA issued Digital Flood Insurance Rate Maps (DFIRM)

Preliminary / Revised Preliminary Data

FEMA issued preliminary maps on June 3, 2015, to all communities in DuPage County. Revised Preliminary maps were issued on June 1, 2017.  Printed floodplain maps were mailed to the CEO of each community along with a CD containing the FIS report, FIRM database, and Preliminary Summary of Map Actions (PSOMAs) lists.  The DuPage County Board Chairman received this information on behalf of the County. For more information please visit the County's Revised Preliminary Data webpage.

2/22/2019 - The Pending FEMA map products for DuPage County, IL – FIRM panels, FIRM database, and FIS – are now posted to to be viewed or downloaded.  They are not yet posted to the FEMA Flood Map Service Center (MSC), but they have passed all FEMA reviews and should be posted to the MSC within the next few weeks.

Watershed Planning and Modeling

The Stormwater Management Division utilizes a specific methodology when developing watershed plans. The Hydrologic Simulation Program (HSPF) is used to create the required hydrologic inputs. The hydraulic analysis is achieved using the dynamic flood routing model known as Full Equations (FEQ) to determine flood elevations. Once the hydrologic and hydraulic analysis is complete the results are used as inputs to a statistical program called Peak To Volume Statistics (PVSTATS) which then determines the 100-year and other frequency flood elevations. View a detailed explanation and a map showing model progress.

Request for Information

  • Flood Elevation Request Form (PDF) - Please download this form to your computer. Opening the form within a web browser will DISABLE the "Send via Email" button.
  • Data/Map Request Form (PDF) - Please download this form to your computer. Opening the form within a web browser will DISABLE the "Send via Email" button.