Flood Plain & Floodway Considerations

Similar to many areas in the country, there are areas in the Village of Carol Stream that are within the flood plain. This means that they are in an area of land where there is an increased risk of flooding.  Flood plains are divided into several “Zones” to show various degrees of risk. The predominant “Zones” in the Village are as follows:

Zone A:  This zone contains areas where the risk is the highest, (1% chance of flooding in a given year). No Base Flood Elevations determined.

Zone AE:  This zone contains areas where Base Flood Elevations are determined for the 1% annual chance of flooding.

Zone X (Un-dotted):  This zone contains areas that are outside the 0.2% annual chance of flooding.

Zone X (Dotted):  This zone contains areas that are within 0.2% annual chance of flooding as well as areas of 1% annual chance of flood with average depths of less than 1 ft. or with drainage areas less than 1 square mile.

In order to determine which one of these zones a parcel of land or a residence is located in, Flood Insurance Rate Maps (FIRMs) are used that are developed by FEMA, (the Federal Emergency Management Agency) in 2004 showing the flood plain areas within the Village of Carol Stream.

In order to reduce the insurance costs of flooding as well as for the safety of the people who live within the flood plain or very close to it, there are restrictions placed on building or adding to existing buildings within the high risk areas of the flood plain. The underlying reason for this is that in case of a flood, there would be less property to be damaged and also there would be less buildings to displace the volume which the flood water would occupy, since more buildings would mean flood waters would rise to higher levels and damage even greater number of homes and structures.

It is however possible to build within the flood plain, but the regulations surrounding this issue can make the matter difficult, costly or sometimes physically impossible.  For example: current regulations require the creation of compensatory storage by the removal of 1.5 times the volume of soil from an area in the back yard (within the flood plain) where a building addition occupies one volume of flood plain below the Base Flood Elevation (BFE).  This would make it difficult for a small back yard that backs into Klein Creek for example to lose that much soil because they added a room addition or a swimming pool.

FEMA also has a regulation that is known as the "50% rule" or "substantial improvement and substantial damage rule".  The rule is this; “If the cost of improvements or the cost to repair the damage exceeds 50 percent of the market value of the building, it must be brought up to current flood plain management standards.”  This means that a substantial improvement or a repair to an existing building must meet all the current requirements for construction in the flood plain, just as if it were new construction.  For DuPage County municipalities, the improvement costs are considered to be cumulative.  This will only effect a homeowner that is wanting to make repairs or improvements to their home.

What does this mean for your property?  A substantial improvement or repair of damage to a residential building would require that the structure (including the basement) be elevated to at least three feet above the BFE in order for a building permit to be issued for improvements or the repair of damages.  If the structure is not elevated the building permit would be denied.  Elevating a structure can be expensive, especially after major flood or fire damage.  Because DuPage County only requires structures to be elevated one foot above the BFE, and FEMA only above the BFE, variances may be granted to this requirement.  If the basement is not elevated, it would need to be filled or it would be considered uninhabitable and thus not insured.  Non-residential buildings could either be elevated or flood- proofed.  Residential buildings have stricter limitations to provide a higher degree of protection.

The purpose of FEMA’s 50% rule is to limit the amount of damage and therefore the amount of insurance claims paid out in the event of a flood.   The Village is a participant in the National Flood Insurance Program (NFIP) which operates by a mutual agreement between the FEMA and the community.  The Federal Government makes available guaranteed flood insurance in communities that agree to regulate development in their mapped flood plains.

The Village is required to track building improvements and damages to ensure properties are in compliance with FEMA requirements including the 50% rule.  If violations are found and the Village does not enforce FEMA's regulations, we run the risk of losing our status in the NFIP.  If the Village dropped out of the NFIP, hundreds would lose flood insurance protection.  The Village would require a structure to be elevated if it was found to be substantially improved without a building permit.

In addition to the flood plain issues, there are floodway regulations that restrict development in the regulatory floodway.  FEMA defines the regulatory floodway as "the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height.  Communities must regulate development in these floodways to ensure that there are no increases in upstream flood elevations."

The FIRM (maps) governing the Village of Carol Stream has the following “Community-Panel Numbers effective date 12/16/2004" These can be viewed through the following links.

17043C0106H

17043C0109H

17043C0204H

17043C0207H

17043C0208H

17043C0501H

17043C0502H

In order to determine if your property is in the flood plain, you can contact the Village of Carol Stream Engineering Department at (630) 871-6220. Also, copies of these maps are available for viewing at the Engineering Department.

A negative determination made by using a FIRM can be challenged. A resident can apply for a review by FEMA by submitting all the evidence including a topographic survey of the lot and the appropriate forms required. 

After reviewing the documents FEMA will issue a “Letter of Determination” indicating their final opinion on that particular lot. This type of challenge usually can be made in cases where the location of the lot, the house or structure on it cannot be precisely determined due to proximity to a less flood risk area on the flood plain map. A resident who intends to challenge the FIRM with regard to his or her property and initiate a review process should contact the FEMA Regional Office in Chicago at (312) 408-5500.

 Please ask for: “a checklist package for submittal to request a letter of determination” to receive the correct forms for this purpose. These forms can also be downloaded and printed through the following link: 

Elevation Certificate

If you have any questions concerning flood plain or floodway regulations you can contact us at (630) 871-6220.  Further information can also be obtained by going to FEMA's web site.