Kaskaskia River at Shelbyville, IL




Study Reach.--The channel reach is constructed with riprap on both banks. The study reach, approximately 600 ft long , extends from upstream of the gage house to the upstream side of the State Highway 16 Bridge, as shown in the quadrangle map on the top left. Seven surveyed cross sections are available to describe the channel geometries. The channel alignment, approximate variations in channel width and bank conditions, and locations of surveyed cross sections are shown in the aerial photograph on the top right. Cross-sectional geometries vary gradually and continuously upstream to downstream. Seven surveyed cross sections (surveyed by the U.S. Army Corps of Engineers 1980) are available to describe channel geometry. The general shapes of cross sections in the study reach are illustrated with four selected cross sections, (see plots above).

Gage Location.--Lat 39°24'26", long 88°46'53" (revised WY 2000), in SE1/4 SW1/4 sec.8, T.11N., R.4E., Shelby County, on the left bank 700 ft upstream from the bridge on State Highway 16 in Shelbyville, 700 ft downstream from Shelbyville dam, 0.5 mi upstream from the railroad bridge, 7 mi upstream from Robinson Creek, and at river mi 197.5. The USGS streamgage station number is 05592000.

Drainage Area.--1,054 sq mi.

Gage Datum and Elevations of Reference Points.--Datum of the gage is 530.00 ft. Reference point, RP-4, is two file marks on the top of the upstream side of the ladder at the cleanout doorsill of the stilling well at the USGS station, elevation=554.935 ft. Two reference points (RP-N) were established for the n-value study. RP-N1 is the top of the lag bolt on the streamward side of the downstream, streamward post of the observation deck 450 ft downstream of the gage, elevation=547.31 ft. RP-N2 is the top of the nut on the concrete anchor bolt set in the downstream face of the concrete guardrail on the bridge for the east bound lanes of State Highway 16 at station number 122, elevation=565.834 ft. All elevations are referenced to NGVD29.

Stage, Discharge Measurements, and Computed n-Values.--Water-surface elevations were measured at the gage house and the RP-Ns for each discharge measurement. Corresponding water-surface slopes were obtained by dividing the differences in water-surface elevations by the distance between the selected locations. Discharge measurements were made using the conventional current meter or tethered boat Acoustic Doppler Current Profiler (ADCP). Because this site has a stable stage-discharge rating curve, discharge for an event could be determined from the rating curve if the surveyed water stage is within the range of stable rating. The computed n-values are listed in the following table. Whenever possible, the computed n-values are associated with a photograph taken at the time of the measurement.

Date of Observation Discharge (ft3/s) Average Cross Section Area (ft2) Hydraulic Radius (ft) Mean Velocity (ft/s) Slope (ft/ft) Coefficient of Roughness n
11/21/2003 724.0 1709.8 8.70 0.42 0.000023 0.071
7/21/2004 988.0 1831.5 9.09 0.54 0.000023 0.056
4/19/2004 1490.0 2081.5 9.82 0.71 0.000034 0.053
1/6/2004 2880.0 2780.6 11.51 1.04 0.000115 0.078
1/6/2004 2930.0 2806.5 11.57 1.05 0.000115 0.077
1/13/2004 3110.0 2915.8 11.82 1.07 0.000115 0.076
1/16/2004 3280.0 2903.1 11.79 1.13 0.000092 0.063
4/17/2006 3775.0 3050.3 12.12 1.24 0.000082 0.070




Description of Channel.--This channel is constructed with riprap paved banks. Bed materials consist of boulders and cobbles and bank materials consist of boulder and cobble sized riprap. The banks are about 30 ft high and have a top width of about 325 ft. The cross-sectional shape is trapezoidal with a bottom width of approximately 150 ft. The study reach is straight.

Floods.-- Maximum discharge, 25,900 ft3/s, June 29, 1957, gage height, 28.15 ft., present datum. Maximum stage since construction of Shelbyville Reservoir, 18.94 ft, present datum, on Mar. 20, 1982. Maximum discharge since construction of Shelbyville Reservoir, 5,580 ft3/s Mar. 22, 1998, gage height 18.77 ft, present datum. Flood of June 1, 2002, discharge, 4,920 ft3/s, gage height 17.65 ft, present datum.

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Page Last Modified: February 4, 2013