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CMAP has developed a Stormwater and Flooding strategy paper, which will inform the recommendations made in ON TO 2050 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 has 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 contained within the raster attribute table represent low (1) to high (10) flood susceptibility. The inputs are listed below, alongside their sources:Reported Flood Locations: FEMA National Flood Insurance Program Claims, FEMA Individual Assistance Grants, FEMA Discovery Data, City of Chicago 311 Standing Water Locations, MWRD Detailed Watershed Plans, DuPage County GIS, Kendall County Department of Planning, Lake County Stormwater Management Commission.Topographic Wetness Index: CMAP analysis of Illinois State Geological Survey (ISGS) Light Detection and Ranging (LiDAR) data.Combined sewer service areas: Metropolitan Water Reclamation District; IL EPA; municipalities with combined sewers outside of Cook County.Elevation differential between property and nearest Base Flood Elevation (BFE): CMAP analysis of ISGS LiDAR data and FEMA BFE data.Impervious cover: 2011 National Land Cover Dataset.Impervious cover of watershed catchment: CMAP analysis of NLCD and National Hydrography Program data.Age of first development: U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Wall-to-Wall Anthropogenic Land Use Trends (NWALT) 1974-2012 land cover.Precipitation variation: NOAA Atlas 14 10-year, two hour storm event. |