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 for the Skokie River is 625.3 NAVD 1988, which is generally consistent throughout the limits of Winnetka (between Hill Road and the northern Village Limits), but does vary south of Hill Road. The BFE and Flood Zone Designation for Lake Michigan have recently undergone revisions. Based upon the results of the Great Lakes Coastal Flood Study, FEMA has revised the BFE for Lake Michigan to a variable BFE ranging from 587 to 594 NAVD 1988, depending upon where the property is situated along the lake front in Winnetka. The Flood Zone Designation will also change from Zone AE to Zone VE, which is a coastal flood zone that takes into account wave action.
Any grade that is equal to or below this elevation is considered in the floodplain, when tributary to that floodplain. This elevation is referenced from the North American Vertical Datum (NAVD) of 1988.