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The 100-year flood plain, also known as the Special Flood Hazard Area (SFHA), is an area of land that has been determined by the Federal Emergency Management Agency (FEMA) as having a 1% chance of flooding in any given year. 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.
The Village of Winnetka’s Flood Hazard Protection Ordinance is Chapter 15.68 in the Municipal Code. In addition, the Metropolitan Water Reclamation District (MWRD) Watershed Management Ordinance (WMO) contains flood plain regulations that all municipalities within Cook County are required to comply.
The Base Flood Elevation (BFE) is the elevation below which areas are at risk of flooding for the 100-year flood event. The current BFE for the 100-year flood event, throughout most of Winnetka (between Hill Road and the northern Village Limits), is at an elevation of 625.3. Any grade that is equal to or below this elevation is considered in the flood plain, when tributary to that flood plain. This elevation is referenced from the North American Vertical Datum (NAVD) of 1988.
The Flood Protection Elevation (FPE) is the elevation to which any structures within the flood plain are required to be protected. In compliance with the MWRD WMO, the Flood Protection Elevation is two feet above the BFE. Within the Village of Winnetka, the FPE is 627.3 NAVD 1988.
If any grade adjacent to the foundation of the house is at or below the Base Flood Elevation (BFE), the entire house is determined to be in the flood plain, and must comply with the Village’s Flood Hazard Protection Ordinance.
In addition, the Metropolitan Water Reclamation District (MWRD’s) Watershed Management Ordinance (WMO) stipulates that if a home is within 100 feet of the mapped BFE, any permit applicant who is wanting to construct a new home or make substantial improvements to an existing home must prove, by means of a topographic survey, that all grades adjacent to the home are above the BFE (by at least 0.1 feet) to be considered outside of the flood plain.
FEMA completed two remappings of Winnetka’s flood plains, one in November 2000 and one in August 2008. Due to increased rainfall intensities and various other topographic changes, the Base Flood Elevation rose approximately 9 inches, as part of the 2000 remapping. In addition, the 2008 remapping and modernization more accurately reflects the flood plain limits north of Willow Road.
Anyone in Winnetka can purchase flood insurance, even if the property (a building and/or its contents) is not located within the flood plain. However, if your property is located within the 100-year flood plain, and you have a federally backed loan or mortgage on the property, you are required by law to purchase flood insurance.
Yes, construction is permitted in the flood plain in accordance with the Village of Winnetka’s Flood Hazard Protection Ordinance. Improvements to existing homes are permitted as long as the total cost of the improvements are less than 50% of the current market value of the structure, excluding the land. By law, the cost of the improvements is calculated cumulatively over the remaining life of the structure.
Construction of a new home with a basement may be permitted in the flood plain, if a Letter of Map Revision - Fill (LOMR-Friday) is first obtained from FEMA. The LOMR-Friday can be obtained if engineered fill has been placed and compacted on the site to create a clay building pad for the home. All work must be done in accordance with the Village’s Flood Hazard Protection Ordinance. A LOMR-Friday, removes that portion of the property that was filled from the flood plain, thereby allowing a home to be constructed with an engineered basement. Otherwise, if site constraints do not allow for a LOMR-Friday, a home with a floodable crawlspace (no basement) may be constructed.
Compensatory storage must be provided to offset any fill that is placed in the flood plain, under any circumstance. Compensatory storage must equal a minimum of 110% Fill volume.
The Metropolitan Water Reclamation District (MWRD’s) Watershed Management Ordinance (WMO) requires that new home construction and/or substantial improvements to existing homes need to prove, by means of a topographic survey, that the existing/new home and/or improvements are above the Base Flood Elevation (BFE) by at least 0.10 feet.
Regardless, if you are considering constructing a new home that is within 100’ of the BFE, the following design criteria must be met:
These requirements include:
There are two main criteria:
There are additional criteria that must be met, but they are more material-related.
Yes, as long as the Flood Hazard Protection Ordinance criteria are met. Read the complete requirements.
Compensatory storage is an artificially excavated storage volume within the 100-year flood plain that is required to offset the loss of natural storage capacity caused by the placement of fill, structures, or other materials above the existing natural grade. Compensatory storage must meet the following requirements:
Call Emily Grimm at 847-716-3532: as the Flood Plain Manager in the Village of Winnetka, she will be able to read the Flood Insurance Rate Maps and give an approximation of whether your property is within a flood zone. However, in order to make an exact determination, a topographic survey would need to be obtained by either an Illinois Licensed Land Surveyor or Professional Engineer.