GIF images are not cartographic products; they portray the general nature of the data.
This feature dataset contains feature classes that show the general areal extent of major bedrock aquifers to various depths, major sand and gravel aquifers, and potential water-bearing unconsolidated strata to a depth of 50 feet. ISGS.
Flood Zones for Unincorporated Areas, One-Hundred and Five-Hundred Year
Statewide polygon feature class of 100 and 500 year flood zones for unincorporated areas of Illinois as indicated on Federal Emergency Management Agency (FEMA) National Flood Insuranc Program (FIRM) maps and Flood Hazard Boundary maps. ISWS.
Potential of Agricultural Chemical Contamination of Aquifers
A statewide dataset for evaluating the potential for contamination of shallow aquifers by pesticides and nitrate. The sources of this data set were published and digitized at 1:250,000; however, the soils map and depth to aquifer map (stack-unit map) were generated from source data mapped at 1:15,000 and 1:64,000, respectively. This aquifer sensitivity map was published at 1:500,000 (statewide map), and 1:250,000 (county maps). Nominal scale is 1:250,000. ISGS.
Sinkhole Areas (an indicator of karst terrain)
Distribution of areas that contain one or more sinkholes throughout the state of Illinois. Areas that contain sinkholes are susceptible to aquifer contamination and may also lack the stability required for certain land-uses. Sinkholes are one of the major indicators of karst terrains. This map provides basic data for land-use planning and decision making. ISGS.
Streams and Shorelines
Wetlands, National Wetlands Inventory, 1987