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Flood Plain & LPDA Information

Individuals interested in floodplain elevation, floodway, wetland, LPDA or past history of a property may contact;

Table 1: Contact information.
Contact Telephone
Public Works (630) 434-5460
Julie Lomax, Stormwater Administrator (630) 493-8821
Kerry Behr, Stormwater Administrator (630) 434-5489

What is a Flood Plain?

Floodplains are low lying land areas, usually bordering a water body, which floods during storm events. 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.  Despite 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. Though the chance is low, it is possible to have more than one 100 year flood in a single year.

For more information on floodplains go to this link: https://pubs.usgs.gov/gip/106/pdf/100-year-flood-handout-042610.pdf

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 Floodplain Insurance Program

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. 

Is My Property Located in a Floodplain?

To determine whether your property is in or near a floodplain, visit the Village's Parcel Navigator map. Enter your address in the search box in the upper left hand corner. Go to the bottom of the page and click on the "layers" icon (it looks like a stack of papers) to open a box. Click on the "drainage" layer in that box to make the floodplain boundaries visible.

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

Please note: the 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 Administrator at 630-434-5460.  

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. Although LPDAs are not recognized by FEMA, Village building codes regulate both LPDAs and floodplains similarly.

LPDAs are primarily located in older neighborhoods (before the late 1970s) that were built up before stormwater regulation codes requiring stormwater detention existed. The purpose of detention basins is to temporarily store excess water during and after a storm that might otherwise flood structures in the area. LPDAs help serve this function as a naturally formed detention basins. 

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 theoretically increases the flood elevation, potentially leading to a higher chance of flooding to adjacent properties.

Are There Any Restricted Property Uses in an LPDA?

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 Section 26.1303 of the Village Code for more information.

Buildings constructed near, but just outside, an LPDA must have the lowest adjacent grades (the lowest ground elevation next to the foundation) a minimum of one foot above the 100-year flood elevation. For more detailed information, refer to Section 26.505 of the Municipal Code.

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.  Enter your address in the search box in the upper left hand corner. Go to the bottom of the page and click on the "layers" icon (it looks like a stack of papers) to open a box. Click on the "drainage" layer in that box to make the LPDA boundaries visible.

Please note the 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 Administrator at 630-434-5460.