Urban Flood Susceptibility Index, Northeastern Illinois (CMAP, 2017)

CMAP developed the Stormwater and Flooding Strategy Paper which informs recommendations made in the ON TO 2050 comprehensive plan to address urban and riverine flooding. The paper presents strategies to reduce flooding impact throughout the region by integrating stormwater management into transportation and land use planning, alongside analysis of damages from past flooding events. To help direct these strategies, CMAP developed urban and riverine Flooding Susceptibility Indexes (FSIs) to identify priority areas across the region for flooding mitigation activities. GIS datasets representing flood susceptibility factors were used to construct the indexes by assessing each factor's influence using a GIS-based frequency ratio approach. The approach, inputs, and results are described in greater detail in the technical appendix of the strategy paper. The values in the raster attribute tables represent low (1) to high (10) flood susceptibility. The inputs are listed below, alongside their sources: Flood locations from FEMA, several counties, and the City of Chicago Topographic Wetness Index (TWI), Urban Only CMAP derived from 5-ft resolution Digital Elevation Model (DEM) Combined sewer service area, received from MWRD and municipalities Elevation differential between property and nearest FEMA Base Flood Elevation (BFE), Urban only Percent Impervious Cover from 2011 National Land Cover Dataset Age of first development from USGS 1974-2012 land use trends dataset, using developed land classes Precipitation variation, precipitation amounts (inches) for the 10-year, 2- hour storm from NOAA Atlas 14