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Floodplain & LPDAs

Table 1: Contact information.
Contact Telephone
Public Works (630) 434-5460
Julie Lomax, Stormwater Administrator (630) 493-8821

What is a Floodplain?

Explanation of 500 and 100 year flood water situations.

The Federal Emergency Management Agency (FEMA) has delineated areas that have a 1% chance of flooding in any given year, commonly referred to as the "100-year flood plain" or the Special Flood Hazard Area (SFHA). Areas within the SFHA are regulated by FEMA and are typically low lying areas, usually bordering a water body, which floods during storm events. There are many misperceptions that these areas should "only" flood once every 100 years. This is actually a statistical probability that translates to a 26% chance of flooding within the life of a 30-year mortgage and a 67% chance of flooding within a span of 100 years. It is possible to have more than one 100-year flood in a single year.

For more information on floodplains and how they are mapped, see this publication from the U.S. Geological Survey: https://pubs.usgs.gov/gip/106/pdf/100-year-flood-handout-042610.pdf

Is My Property Located in a Floodplain?

Aerial photograph of a residential neighborhood with floodplain layers colored in red, blue, and yellow.
To determine whether your property is in or near a floodplain, visit the Village's Parcel Navigator map. 

  1. Enter your address in the search box in the upper left hand corner. 
  2. Go to the bottom of the page and click on the "Layers" icon A black circle with three white squares stacked on top of each other. to open the list. 
  3. Click once on the box next to the "Drainage" layer so it changes color A blue square with a white check mark inside. and to make the Floodplain boundaries visible. If the "Drainage" text is greyed out, this means you are zoomed out too far. 

You can also use FEMA's Flood Hazard Viewer and input your address. Please keep in mind this service is for the entire nation and results may take a minute to load.

The current FEMA Floodplain maps became effective August 1, 2019.

Please note: Tthe location of the floodplain on the maps is approximate and based on elevations. To determine the exact location of the floodplain on your property, a topographic survey is required. For more information contact the Village Stormwater Administrators at 630-434-5460 or email stormwater@downers.us.  

Why Protect Flood Plains?

Floodplains play a valuable role in providing natural and beneficial functions to Downers Grove. Undeveloped floodplains provide protection for buildings and properties, natural erosion & sediment control, and improved habitat for a variety of plants and animals.  Flood waters can spread over a large area providing benefits such as:

  • Slowing water down (higher speeds cause more damage).
  • Storing flood water that would otherwise be sent towards downstream properties.
  • Allowing water to soak into the ground and recharge the groundwater aquifer.
  • Moderating flood water temperatures, reducing the possibility of harmful effects on aquatic plants, fish, and animals.

National Flood Insurance Program (NFIP)

Floods are fairly common events that cause the most destruction of all natural hazards, and more than three quarters of national emergency funding spent is due to flood events. Despite this, flooding is not included in a typical house insurance policy, and most insurance companies will not supply it. The primary supplier of flood insurance is provided through the National Flood Insurance Program (NFIP). As a condition of participation in the NFIP, floodplain management regulations must be enforced within the SFHA by local communities. These regulations restrict new construction within the SFHA, with the goal of significantly reducing the number of insurance claims over time. 

An aerial photo of a residential neighborhood that has a blue, dashed line indicating an LPDA area.What is an LPDA?

LPDA stands for "Localized Poor Drainage Area." The Village identified these areas as locations prone to flooding due to topography. In other words, LPDAs are areas of land that are bowl-shaped. Stormwater runoff that cannot infiltrate the ground tends to accumulate in LPDAs, creating flooding or standing water. Although LPDAs are not recognized by FEMA, Village codes regulate both LPDAs and floodplains similarly.

Is My Property Located in a LPDA?

To determine whether your property is in or near an LPDA, visit the Village's Parcel Navigator map. 

  1. Enter your address in the search box in the upper left hand corner. 
  2. Go to the bottom of the page and click on the "Layers" icon A black circle with three white squares stacked on top of each other. to open the list. 
  3. Click once on the box next to the "Drainage" layer so it changes color A blue square with a white check mark inside. and to make the Floodplain boundaries visible. If the "Drainage" text is greyed out, this means you are zoomed out too far. 

Please note the location of the LPDA on the maps is approximate. To determine the exact location of the LPDA on your property, a topographic survey is required.

For more information contact the Village Stormwater Administrators at 630-434-5460 or email stormwater@downers.us.

Why does the Village regulate LPDAs while FEMA does not?

The purpose of regulating LPDAs is to help ensure that any new construction will be reasonably safe from flooding and that the work will not adversely affect other properties. Filling in a portion of an LPDA, similar to filling in a portion of a floodplain, may increase the flood elevation, potentially leading to a higher chance of flooding to properties. 

Are There Any Restricted Property Uses in an LPDA?

A bulldozer pushing soil closer to the stream to build up land to compensate and offset the excavated area on the other side of the stream.

General and recreational use of the property is unrestricted. Landscaping and gardening that does not include fill is generally allowed, provided that stormwater drainage patterns are not blocked and erosion does not become a problem. Fill is only allowed within the LPDA if an equivalent volume can be provided on the same parcel.  Any permanent structure, including swing sets and other playground equipment, requires a permit when placed in an LPDA.  Please refer to Chapter 26, Section 1303 of the Municipal Code for more information.

Buildings constructed near, or adjacent to an LPDA have restrictions regarding lowest opening elevations and basements. For more detailed information, refer to Chapter 26, Section 505 of the Municipal Code.