Sugar Creek at Main St at Normal, IL




Study Reach.--The channel reach is a concrete-paved channel in an urban setting, as shown in the quadrangle map on the top left. The study reach, approximately 530 ft long, is located between the North Main Street bridge as the upstream end and Amtrak Railroad bridge as the downstream end. The North Central Street bridge is located in between. There are eight channel cross sections, surveyed by the USGS-ILWSC in October 2007, available for evaluating the geometric characteristics of the study reach. Locations of the surveyed cross sections are shown in the aerial photograph on the top right. Shapes of four cross section; at river stations (RS) 1, 3, 4, and 6 are plotted to illustrate the channel geometry of the study reach (see plots above).

Gage Location.--Lat 40°29'55", long 88°59'41" (NAD 1983), in NW1/4 SE1/4 NW1/4 sec.33, T.24N., R.02E., Mc Lean County, Hydrologic Unit 07130009, a temporary gage datum is file marks chiseled in concrete on the west side of the North Main Street bridge, 31 feet south of the north end of the concrete foot railing and at river mile 51.8. The gage is located 0.7 miles north of the intersection of Illinois Route 51 and Illinois Route 9. The USGS streamflow gage number is 05580830.

Drainage Area.--16.13 sq mi.

Gage Datum and Elevations of Reference Points.--A reference point, RP-1, on the Main St. bridge, is file marks chiseled in concrete on the west edge of the North Main Street bridge, approximately 31 ft south of the north end of the concrete foot railing, elevation=768.74 ft. RP-2, on the North Center Street bridge, is file marks chiseled in concrete on the west side of the bridge, 53 feet south of the north end of the concrete rail, elevation=772.73 ft. RP-3 is file marks chiseled in wood on the east edge of the railroad bridge, 35.5 feet south of the north edge of the wood ties spanning the creek, elevation=782.97 ft. All elevations are referenced to NAVD88.

Stage, Discharge Measurements, and Computed n-Values.--Water-surface elevations were measured with tape-downs from each of the reference points by recording a continuous series that started before and ended after each discharge measurement. Discharges were measured with a SonTek FlowTracker following conventional method or with a tethered boat Acoustic Doppler Current Profiler (ADCP). Discharges were measured at RS 4, immediately downstream of RP-2. When possible, multiple discharge measurements were made during a rise and recession to provide data for calculating n-values over a range in stage. 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. The photographs are arranged from low to high discharge in order to illustrate the contributing factors of n-values at a particular discharge.

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
12/11/2007 176.2 73.5 1.98 2.52 0.002712 0.042
12/11/2007 210.0 78.2 2.07 2.81 0.002439 0.037
12/11/2007 234.1 82.7 2.16 2.94 0.002181 0.035
1/8/2008 734.0 121.2 2.83 6.32 0.001423 0.017
1/8/2008 755.0 122.7 2.85 6.43 0.001458 0.017
1/8/2008 779.0 124.3 2.88 6.55 0.001470 0.017
1/8/2008 782.0 125.5 2.90 6.51 0.001485 0.017
1/8/2008 897.0 129.0 2.95 7.31 0.001532 0.015


Description of Channel.--The study reach is concrete-paved with trapezoidal cross sections in a straight reach. The bed material consists of concrete slabs, approximately 4 ft by 8 ft each. Bottom width is about 40 ft. Banks are approximately 7 ft high and extend at 45º angles from each side with the bottom 4 ft. paved with concrete and turf grass above. Top width measured from the top edge of the concrete slab on each side is approximately 44 ft, but when measured from the top of the bank width varies from 70 ft. upstream to 55 ft. downstream. Bridge piers at N. Main Street and N. Central Street bridges do not constrict the flow unless the river stage exceeds the concrete part of the channel. Extreme high flow events may extend beyond the concrete channel and include some turf grass banks.

Floods.--Maximum discharge, 897 ft3/s, January 8th, 2008.

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Page Last Modified: February 4, 2013