FLOOD TRACKING CHART FOR THE ILLINOIS RIVER BASIN

For real-time data, access the U.S. Geological Survey "Home Page" at http://il.water.usgs.gov
NOTE: Stage graphs are only shown for main-stem stations and selected tributary stations to the Illinois River.


Open-File Report 98-390
Prepared by Charles Avery , Robert R. Holmes, Jr. and Jennifer B. Sharpe

This Flood Tracking Chart for the Illinois River Basin in Illinois can be used to record and compare the predicted or current flood-crest stage to past flood-crest information. This information can then be used by residents and emergency-response personnel to make informed decisions concerning the threat of flooding to life and property. The chart shows a map of the Illinois River Basin (see below), the location of real-time streamflow-gaging stations in the basin, graphs of selected historical recorded flood-crest stages at each of the stations, and sea-level conversion (SLC) factors that allow conversion of the current or predicted flood-crest stage to elevation above sea level. Each graph represents a streamflow-gaging station and has a space to record the most current river stage reported for that station by the U.S. Geological Survey (USGS). The National Weather Service (NWS) predicts flood crests for many of the stations shown on this chart.

During a flood, the USGS provides current river-stage information to the public through news releases. The Illinois Water Science Center of the USGS displays near real-time river-stage data on the World Wide Web at the following Internet address:

http://il.water.usgs.gov

The NWS has direct access to all information collected by the USGS for use in their flood-crest forecasting models and routinely broadcasts the forecast information to the news media and on shortwave radio. The radio frequencies are 162.475 Mhz (megahertz) in Peoria, Ill., 162.400 Mhz in Springfield, Ill., and 162.550 Mhz in Champaign, Ill.

The potential threat of flooding to life and property can be evaluated by first determining the approximate elevation of the threatened property and recording that elevation in the box at the lower left corner of the map along with the elevation of the "key gaging stations." The "key gaging station" is the station closest to the threatened property. For example, people in Peoria, Ill., probably should use the station on the Illinois River at Kingston Mines as their "key gaging station". Record the current river stage or predicted flood-crest information for each station, especially the "key gaging station," and convert the stage to sea level (see the example in the lower left corner of the map). The SLC factor is shown on the corresponding graph for each station and can be added to the current river stage and also to the historical recorded peak stages to convert the information to elevation above sea level. Compare the predicted flood crest converted to elevation above sea level to the elevation of the property to know immediately if the property is threatened by flooding. One must be cautioned that the surface of flowing water is not flat but has a slope downstream. Therefore, the surface-water elevation near a threatened property might not be the same as the surface-water elevation at the "key gaging station."

The network of streamflow-gaging stations in the Illinois River Basin in 1998 is operated by the USGS in cooperation with these agencies: U.S. Army Corps of Engineers, Illinois Department of Natural Resources, Bloomington and Normal Water Reclamation District, Kankakee County Soil and Water Conservation District, Forest Preserve District of Cook County, Forest Preserve District of Du Page County, Du Page County Department of Environmental Concerns, Kane County Development Department, Lake County Stormwater Management Commission, McHenry County Conservation District, Wonder Lake Master Property Owners Association, City of Decatur, City of Monticello, City of Springfield, and Village of Oak Brook.

For additional information about USGS Programs in Illinois write to:

District Chief
U.S. Geological Survey
221 N. Broadway Avenue
Urbana, IL 61801
Phone: (217) 344-0037
E-mail: dc_il@usgs.gov

8-digit station numbers on the above map correspond to the station numbers shown at the top of each graph below.