Public Waters are defined as all lakes, rivers, streams and waterways which are or were navigable and are open or dedicated to public use including all bayous, sloughs, backwaters and submerged lands connected by water to the main channel or body of water during normal flows or stages. The Public Waters shown on this map are identified in 17 Ill. Adm. Code, Chapter I, Section 3704, Appendix A Public Bodies of Water.

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Public Waters identified in 17 Ill. Adm. Code, Chapter I, Section 3704, Appendix A Public Bodies of Water are shown on the map, along with Federal Navigable Waters that extend beyond the Illinois Public Waters. Federal Navigable Waters (Section 10) of the United States are waters that have been used in the past, are now used, or are susceptible to use as a means to transport interstate or foreign commerce up to the head of navigation.

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The 100-year floodplain represents that portion of the topography that would be inundated during a flood event which has a 1% chance of occurrence in any given year. The mapped 100-year floodplain area represents the best available data as of July 2009.

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Stream gages monitor streams and collect information such as water height and discharge. This information is useful for flood prediction, water management, recreation and navigation purposes. The location of stream gages maintained by the USGS and IDNR Office of Water Resources are shown on this map. The map also shows the stream gages in relation to the underlying topography, major watershed boundaries and streams.

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Levees are usually earthen embankments that contain, control, or divert the flow of water to provide some level of protection from flooding. Levees in this map were located based on information from the US Army Corps of Engineers and IDNR Office of Water Resources.

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