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Flood Plain Information

The Village of Winnetka's Flood Plain

When we speak of the flood plain, we are referring to the land that is typically adjacent to a body of water that has its ground elevation at or below the BFE (100-year flood frequency elevation).  In Winnetka, there are two sources of flood plain, the Skokie River and Lake Michigan.  The BFE for the 100-year flood event for the Skokie River is 625.3 NAVD 1988 (or 625.5 NGVD 1929). The mapped BFE for Lake Michigan is 585 NAVD 1988. The BFE for both water bodies is generally consistent throughout the limits of Winnetka.  The BFE for the Skokie River does vary, south of Hill Road. The flood plain is made up of two components, the flood way and the flood fringe. The flood way is a more restrictive development area than the flood fringe. All of the residential areas within the Village of Winnetka that are located within the flood plain are located within the flood fringe. 

About the Flood Plain

A flood plain is a land area that will flood in a storm event that has a 1% chance of occurring in any given year. Flood plains are designated by the Federal Emergency Management Agency (FEMA) and cover parts of Winnetka. Much of the Village west of downtown was originally marsh land. The Skokie Marsh was actually reclaimed and filled in the 1920’s and 1930’s, but the marsh area encroached into what are now residential areas. A flood plain is susceptible to be inundated with floodwater in the event of a major storm. For a house built in the flood plain, a 100-year storm event potential translates into a 26% chance of flooding occurring over the life of a typical 30-year household mortgage. FEMA commonly refers to the 100-year flood plain as the Special Flood Hazard Area (SFHA).

Within these high risk areas, the National Flood Insurance Program’s (NFIP) flood plain management regulations must be enforced within the SFHA by the Village, as a condition of participation in the flood insurance program. All home and business owners within an SFHA (with mortgages from federally regulated or insured lenders) are required to buy flood insurance. Homeowners with questions about flood plain locations and insurance can view FEMA’s maps directly online.

The flood plain is composed of a flood way and a flood fringe. The flood way is typically determined to be the channel of a river or stream and the overbank areas adjacent to the channel. The flood fringe is the area to either side of the flood way that is subject to flooding, but conveys little or no flow. Most of the flooding experienced in Winnetka is not river flooding because the river water is contained through a system of levees. Most often, this community experiences flash flooding, which is less predictable than river flooding. There is little time to prepare for a flash flood, so pre-planning is essential for safety and home protection.

Flood Plain's Natural and Beneficial Functions

The original function of the flood plain and waterway served to provide for a variety of needs. Rivers provided for transportation, water supply, a source of energy, and even a source of waste disposal.  However, after hundreds of years, the character of the rivers and flood plains has changed and the natural function of the riparian ecosystems (the vegetated areas adjacent to the streams) has been significantly altered by human action.

Flood plain resources, including wetlands, have experienced increased pressure from development.  Expanding urbanization of our watershed deliver increased amounts of surface water runoff into the receiving water bodies. The straightening and channelization of streams allow for increased water velocities, which with the increase in storm water runoff from past developments have created increased bank erosion, loss of wildlife habitat and detrimental changes in water quality. However, over the past several years, the Village of Winnetka has taken significant steps toward minimizing storm water runoff from developments, as well as requiring that storm water quality management techniques be implemented for each development. Every permit issued in the Village of Winnetka that results in an alteration of the existing drainage pattern requires that some form of storm water management and water quality control be implemented as part of the design.  All permits issued in the flood plain require that no net fill be placed in the flood plain in order to maintain the existing capacity of our flood plain storage without having to increase its boundaries.

The Federal Emergency Management Agency has classified the natural resources of flood plains into three groups: water resources; biological resources; and cultural resources. Water resources include both the maintenance of natural flood and erosion control characteristics as well as the maintenance of water quality. Benefits from these include the reduction of flood velocities and peaks; the reduction of erosion potential and impacts; the stabilization of soils; the reduction of sediment loads and the amount of sediments entering the stream; the filtering of nutrients and impurities from the storm water prior to entering the stream; and protecting the physical, biological and chemical integrity of the water.  Biological resources include the support and diversification of flora and the provision of fish and wildlife habitat. Cultural resources include the provision of recreational opportunities, scientific study and outdoor education areas, and an improved economic base for the community by improving property values and stimulating natural resource activities and businesses.

Village of Winnetka Flooding

Although the Village of Winnetka has not witnessed a 100-year flood event in recent history, we have experienced several 100-year plus storm events, most recently in April of 2013, July of 2011 and September of 2008.  There have also been several river bank overtopping events, but not up to the 100-year BFE.  As a point of reference, if one were standing near the intersection of Hibbard Road and Ash Street, the elevation of a 100-year flood event would be approximately 2.3 feet deep, well above the knee of an adult. A third, and probably the most common source of flooding, occurs during heavy rainstorm events when the capacity of the storm sewers has been exceeded due to the increase of storm water flow. This situation can readily worsen if the storm sewer inlet structures or other storm water conveyance systems are covered or blocked with leaves, or other debris, as well as ice. Once storm water starts ponding on the street surface, the potential for that water to infiltrate into the sanitary sewer system increases. As a result, basement back-ups can occur for those homes with a gravity sanitary sewer.

Do not dump or throw anything into ditches, swales, streams or other water conveyance systems, including storm inlets and manholes.  Dumping or altering grades is in violation of the Village’s ordinance Sections 9.16.020.B.11; 14.04.130.A.1; 15.32.080.G and L; and 15.68.  Even grass clippings, mulch and branches can accumulate and block drainage.  To read the entire ordinance on-line, view the Village's Code of Ordinances.

Changes to the National Flood Insurance Program (NFIP)

On April 1, 2016 the Homeowner Flood Insurance Affordability Act was implemented, resulting in changes to the National Flood Insurance Program. Below are additional resources outlining changes to the NFIP:

Village Accepted into CRS Program, Entered at Class 6

The Village of Winnetka is pleased to announce their acceptance into the National Flood Insurance Program's Community Rating System. CRS is a national incentive program that results in discounted premium rates for flood insurance measured on Village participation in various floodplain management activities. Such activities include providing flood protection information/assistance, maintaining flood data, implementing outreach projects,  and many more.

The Village is entering the program at a Class Six Rating which affords 20% discount on flood insurance rates for Special Flood Hazard Area (SFHA) policy holders within the Village. Non-SFHA policy holders will be discounted 10% based on the current rating. Those discounts provide an incentive for new flood protection activities that can help save lives and property in the event of a flood.  Discounts are applied automatically however those with flood insurance are encouraged to contact their agent for more information.

Village of Winnetka Resources, Services and Contact Information

The Village of Winnetka has produced several documents to advise people about the flood hazard, flood insurance and flood protection.

As a public service, the Village of Winnetka will continue to provide you with the following information upon request:

  • Whether a property is located in or out of the Special Flood Hazard Area (SFHA) as shown on the current Flood Insurance Rate Map (FIRM) of the Village.  Please note, in many cases, this determination can only be conclusive with a topographic survey of the property in question.  If there is a topographic survey on file with the Village of Winnetka, we will utilize that information, in addition to the FIRMs. Otherwise, the property owner would be obligated to provide a copy of a topographic survey for analysis. The Village of Winnetka does not perform engineering/surveying services for private entities.
  • Additional flood insurance data for a site, such as the FIRM zone and the base flood elevation (BFE), if shown on the FIRM.
  • Provision of flood insurance purchase requirements that can help people who need a mortgage or loan for a property in the SFHA.
  • Information on non-floodplain drainage issues and historical flooding, if they are on file.
  • Access to available completed FEMA Elevation Certificates for new or substantially improved structures constructed in the 100-year flood plain.

For inquiries regarding the flood plain or properties within it, please provide the Village with the street address of the property in question.  Inquiries can be directed to the Engineering Division of the Village of Winnetka, and can be made in person, by telephone, or by e-mail. The Engineering Division is located at the Village Yards, 1390 Willow Road, Winnetka. While any of our Engineering Staff can answer your questions, our Flood Plain Manager is Susan Chen, Assistant Village Engineer. For general questions or concerns regarding local flooding, drainage issues, sewer back-ups, or to schedule on on-site visit, contact 847-716-3568, and your call can be directed to the appropriate Public Works staff.

You can obtain copies of a FIRM, view a  FIRM online and gain access to many other sources of flood plain information by visiting the National Flood Insurance Program. Also, the Village has an Interactive Mapping site. When visiting the site, click on LAYERS and select WINNETKA, and then select either FEMA Flood Hazard Advanced Legend or Basic Legend, and an overview of the entire town with the FIRM’s overlaid will be presented. In order to find information about a specific address, type in the address under FIND, located in the upper left hand corner of the page. The Village Yards facility also has paper copies of the FIRM’s for viewing purposes in the Engineering Department.

To obtain any paper copies of information, a Freedom of Information Act (FOIA) form must be completed with the request. The FOIA can be obtained at the Yards or online by going here.

Rainfall Data Websites

Cook County Precipitation Network - Village of Winnetka is Station #2

Recent Rainfall Data

Historic Rainfall Data

Flood Plain Resources

Click below to view the Village of Winnetka's Informational Flood Hazard Pamphlets, prepared by the Public Works Engineering Department.

Repetitive Loss Area Analysis

Click below to view the Village of Winnetka's Repetitive Loss Area Analysis Reports, prepared by Baxter and Woodman Consulting Engineers.

FEMA Resources for Residents

Additional Links

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