Silver Creek at Armitage Ave at Franklin Park, IL (Reach 3)




Study Reach.--The channel reach contains luncker structures at the toe of the bank and is in an urban environment. The study reach, 900 ft long, is located from the downstream side of the Palmer Street bridge to the upstream side of the Armitage Avenue bridge, as shown in the quadrangle map on the top left. Five surveyed cross sections (surveyed by the Illinois Department of Natural Resources in 1995) are available for evaluating the longitudinal and cross-sectional characteristics in the reach. Locations of these surveyed cross sections can be seen in the aerial photograph on the top right. The general shapes of the channel geometries are represented using main channel cross sections at river stations (RS) 139.41, 135.21, 132.41, and 130.41 (see plots above). Shape of the luncker structures is not included in the plots. The lucker structures at this location are wooden rectangular boxes 1 ft. high and 3 ft. deep that are continuous throughout the study reach.

Gage Location.-- The location where discharge measurements are taken is lat 41°54’54”, long 87°52’04”. The general location of the site is at SW1/4 SE1/4 NE1/4 sec.33, T.40N, R.12E Cook County, Hydrologic Unit 07120004. The USGS stream gage station number is 05530680.

Drainage Area.--9.54 sq mi.

Gage Datum and Elevations of Reference Points.--Two reference points (RP-N) were established for the n-values study. The upstream reference point, RP-N6, is the top of a bolt located on the downstream face of the Palmer Avenue bridge left of mid-channel, elevation=639.53 ft. Downstream, RP-N5 is two file marks located on the outer edge of the right-most green gate brace on the upstream face of the Armitage Street bridge, elevation=633.68 ft. All elevations are referenced to NGVD29.

Stage, Discharge Measurements, and Computed n-Values.-- The water-surface elevations were measured from the established reference points using a weighted tape before, during, and after each discharge measurement. Discharge measurements were made using the conventional current-meter method. 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
5/2/2006 20.3 29.8 1.49 0.71 0.000259 0.046
6/26/2006 37.0 36.6 1.72 1.05 0.000315 0.038
4/25/2007 95.9 66.5 2.19 1.48 0.000239 0.028
1/13/2005 172.0 84.2 2.50 2.09 0.000330 0.026




Description of Channel.--This channel is constructed and contains luncker structures at the toe of the bank. Bed materials consist of small to large cobbles in a sand-gravel mixture. Above the luncker structures, the banks are grass and weed covered. Channel cross sections are trapezoidal in shape with a bottom width (between lunckers) of approximately 14 ft, a top width of 40 ft, and a bank height of 5 ft. The stream is straight.

Floods.--Maximum discharge, 15,500 ft3/s, Apr. 13, 1994, gage height, 20.46 ft.

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Page Contact Information: David Soong
Page Last Modified: February 4, 2013