Study Reach.--The channel reach under consideration is a meandering, natural river, as shown in quadrangle map on the top left. Seven surveyed cross sections (surveyed by the Illinois Department of Natural Resources, in May 2003) are available in a reach from the Main Street bridge (upstream) to the Deer Path Road bridge (downstream). The study reach, approximately 400 ft long, was selected at the lower portion of this segment that starts from river station (RS) number RS1 upstream passing RS4, where bank vegetation is considered to be consistent in this lower reach. Bank conditions in the vicinity of Main Street were modified during the n-values study. The variations in channel alignment, width and bank conditions, as well as the locations of surveyed cross sections can be viewed in the aerial photo on the top right. Cross-sectional geometries, as described by the 4 downstream surveyed cross sections, are shown in the cross-sectional plot above.
Gage Location.--Lat 41°50’45”, long 88°20’57”, in NW1/4 NW1/4 SE1/4 sec.20, T.39N., R.8E., Kane County, Hydrologic Unit 07120007, on left bank at bridge on Deer Path road, 1.0 mi west of Batavia, and at river mi2.9. The USGS streamgage-station number is 05551330.
Drainage Area.--27.6 sq mi.
Gage Datum and Elevations of Reference Points.--Datum of gage is 685.00 ft. A wire-weight gage (WWG) is attached to the upstream side of Deer Path Road bridge. A reference point for the n-values study (RP-N1) is two file marks on the 2nd I-beam from the left on the downstream side of Main Street bridge upstream from the gage, elevation = 698.794 ft. All elevations are in NGVD 1929 convention.
Stage, Discharge Measurements, and Computed n-Values.--Water-surface elevations are measured from the WWG and from RP-N1 before and after each discharge measurement. Water-surface slope for the study reach is determined to be equal to that between the Main Street bridge and Deep Path Road bridge. Discharge measurements are 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 photo taken at the time of the measurement. The photos are arranged from low stage to high stage in order to illustrate contributing factors of n-values at a particular stage.
| Date of Observation | Discharge (ft3/s) | Average Cross Section Area (ft2) | Hydraulic Radius (ft) | Mean Velocity (ft/s) | Slope | Coefficient of Roughness n |
|---|---|---|---|---|---|---|
| 5/26/2004 | 30.1 | 51.1 | 1.72 | 0.63 | 0.000405 | 0.074 |
| 3/11/2002 | 63.8 | 68.7 | 2.20 | 0.97 | 0.000603 | 0.064 |
| 3/22/2007 | 89.9 | 75.0 | 2.35 | 1.24 | 0.000792 | 0.077 |
| 12/11/2003 | 102.0 | 92.4 | 2.74 | 1.14 | 0.000468 | 0.047 |
Description of Channel.--This channel is natural. The streambed is composed of shifting sand and silt with scattered gravel and cobble riffles in the reach upstream from the Deer Path Road bridge. From upstream to downstream in the study reach, bank materials are mostly clay-sand mixes; tall, flexible weeds (2 ~ 4 ft) grow at the water’s edge and in open area on the flood plains. Clusters of young trees are moderately distributed at water’s edge and on the flood plain. Channel geometry is generally in trapezoidal shape with average bottom width approximately 25 ft; bank heights are from 4- to 6- ft. Top width is approximately 30 ft. Note that the channel downstream from the Main Street bridge is subject to beaver dams and woody debris jams. The study reach includes a complete cycle of meandering bends.
Floods.--Maximum discharge, 1,080 ft3/s, Apr. 23, 1999, gage height, 7.52 ft.
Estimated n-Values using Cowan’s Approach.--0.043 ~ 0.069
U.S. Department of the Interior |
U.S. Geological Survey
URL: http://il.water.usgs.gov/proj/nvalues/db/sites/05551330.shtml
Page Contact Information: David Soong
Page Last Modified: Thursday, 06-Mar-2008 10:49:35 CST
