Independent Technical Review and 

Analysis of Hydraulic Modeling and 

Hydrology Under Low-Flow Conditions of 

the Des Plaines River Near Riverside, Illinois

Open-File Report 2012–1143

U.S. Department of the Interior

U.S. Geological Survey
Photo on covers shows a USGS Hydrologist obtaining water-surface elevations along 

the Des Plaines River near Riverside, Illinois with a Global Positioning System (GPS). 

(Photo by Jon Hortness, USGS–llinois Water Science Center).
Independent Technical Review and 

Analysis of Hydraulic Modeling and 

Hydrology Under Low-Flow Conditions 

of the Des Plaines River Near Riverside, 

Illinois 

By Thomas M. Over, Timothy D. Straub, Jon E. Hortness, and Elizabeth A. Murphy

Open-File Report 2012–1143

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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Suggested citation:

Over, T.M., Straub, T.D., Hortness, J.E., and Murphy, E.A., 2012, Independent technical review and analysis of 

hydraulic modeling and hydrology under low-flow conditions of the Des Plaines River near Riverside, Illinois: U.S. 

Geological Survey Open-File Report 2012–1143, 73 p.
iii

Contents

Background.....................................................................................................................................................3

Field Data Collection During Low-Flow Conditions..................................................................................8

Hydraulic Model Verification .....................................................................................................................15

Hydrology Review/Analysis........................................................................................................................20

Hydraulic Model Results.............................................................................................................................32

Summary of USGS Activities......................................................................................................................44

Hydrologic Analysis: Additional Methods and Results Slides .............................................................50

Hydraulic Appendix .....................................................................................................................................67

Selected References...................................................................................................................................73
iv

Conversion Factors and Abbreviations

Inch/Pound to SI

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Flow rate

cubic foot per second (ft3/s or cfs) 0.02832 cubic meter per second (m3/s)

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Abbreviations

+/– Plus or minus

% Percent

7Q10 7-day annual minimum discharge with 10-year return period

Addison.Ck Addison Creek at Bellwood, Illinois

Ck Creek

CY Calendar year

DPR Des Plaines River

DPR.abvSalt.DAadj Des Plaines River above Salt Creek with adjustment of 

discharge for ungaged drainage area

DPR.abvSalt.noDAadj Des Plaines River above Salt Creek without adjustment of 

discharge for ungaged drainage area

DPR.abvSalt.MWRDdiv.DAadj Des Plaines River above Salt Creek with Salt Creek diversion 

computed with MWRD rating and with adjustment of Salt 

Creek discharge for ungaged drainage area

DPR.abvSalt.MWRDdiv.noDAadj Des Plaines River above Salt Creek with Salt Creek diversion 

computed with MWRD rating and without adjustment of Salt 

Creek discharge for ungaged drainage area

DPR.DesPlaines Des Plaines River near Des Plaines, Illinois

GPS Global positioning system

HEC-RAS Hydrologic Engineering Center-River Analysis System
v

IDNR Illinois Department of Natural Resources

ISWS Illinois State Water Survey

MWRD Metropolitan Water Reclamation District of Greater Chicago

N/A Not available

OLS Ordinary least squares

OWR Office of Water Resources

Q7 7-day annual minimum discharge

SaltCk.at.div.DAadj Salt Creek at diversion with adjustment of discharge for 

ungaged drainage area

SaltCk.at.div.noDAadj Salt Creek at diversion without adjustment of discharge for 

ungaged drainage area

SaltCk.MWRDdiv.DAadj Salt Creek diversion computed with MWRD rating with 

adjustment of discharge of Salt Creek at diversion for 

ungaged drainage area

SaltCk.MWRDdiv.noDAadj Salt Creek diversion computed with MWRD rating without 

adjustment of discharge of Salt Creek at diversion for 

ungaged drainage area

SaltCk.WSprings Salt Creek at Western Springs, Illinois.

USACE U.S. Army Corps of Engineers

WWTP Wastewater Treatment Plant

WY Water year
 1

Independent Technical Review and Analysis of Hydraulic 

Modeling and Hydrology Under Low-Flow Conditions of 

the Des Plaines River Near Riverside, Illinois 

By Thomas M. Over, Timothy D. Straub, Jon E. Hortness, and Elizabeth A. Murphy

Introduction

The U.S. Geological Survey (USGS) has operated a streamgage and published daily flows for the Des Plaines River at Riverside since Oct. 1, 1943. A HEC-RAS model has been developed to estimate the effect of the removal of Hofmann Dam near 

the gage on low-flow elevations in the reach approximately 3 miles upstream from the dam. The Village of Riverside, the Illinois 

Department of Natural Resources-Office of Water Resources (IDNR-OWR), and the U. S. Army Corps of Engineers-Chicago 

District (USACE-Chicago) are interested in verifying the performance of the HEC-RAS model for specific low-flow conditions, 

and obtaining an estimate of selected daily flow quantiles and other low-flow statistics for a selected period of record that best 

represents current hydrologic conditions. Because the USGS publishes streamflow records for the Des Plaines River system 

and provides unbiased analyses of flows and stream hydraulic characteristics, the USGS served as an Independent Technical 

Reviewer (ITR) for this study.
Independent Technical Review 

and Analysis of Hydraulic 

Modeling and Hydrology Under 

Low-Flow Conditions of the 

Des Plaines River Near 

Riverside, Illinois

U.S. Department of the Interior

U.S. Geological Survey
Background

 Hofmann Dam

 Low-head dam on the Des Plaines River in 

Riverside

 Constructed by the State of Illinois in 1950

 The U. S. Army Corps of Engineers – Chicago 

District (USACE) has developed plans to remove 

the dam.

 HEC-RAS model

 Developed by the U. S. Army Corps of Engineers – 

Chicago District 

 Model the effects of the removal of Hofmann Dam 

 Study area is Hofmann Dam to 26th Street 

(approximately 3 mi)
What is the USGS?

 U.S. Geological Survey

 Department of Interior

 Nation’s largest earth science agency

 No regulatory responsibility

 Created by Congress in 1879

 Mission

 Provide the Nation with reliable, impartial

information about the Earth

 Data collection and interpretive projects
Streamflow Data within Area of Detailed Study

 USGS streamflow-gaging station 05532500 

on Des Plaines River

 Downstream of Hofmann Dam (Millbridge Road)

 Continuous streamflow data since 1943
Components of the Technical Review/Analysis 

Under Low-Flow Conditions

 Field data collection

 Hydraulic model verification (using field 

data collected)

 Hydrology review/analysis

 Hydraulic model results (using flows 

determined in hydrologic analysis)
Study Area 

Map

Direction of flow
Field Data Collection 

Under Low-Flow Conditions

 Flow measurements

 Water-surface elevations

 Manning’s Roughness observations
Flow

Measurements 

(May 17, 2012)  Measurement accuracy 

is +/–5%

 Measurement locations 

chosen to identify 

changes in flows 

 Value at USGS 

streamflow-gaging 

station 05532500 is 

average of two 

measurements (made 

at beginning and end 

of data collection) 

Direction of flow
Salt Creek Diversion Structure

 Constructed in 1960

 Inlet modified in 1967

 Main purpose: flood protection along Lower Salt 

Creek

 Flow in the diversion is controlled by the water level 

of Salt Creek

Flow from Salt Creek into 

diversion structure

Flow from diversion structure 

into Des Plaines River
Water-Surface 

Elevations 

(May 17, 2012)  GPS accuracy +/– 

0.07 ft

 Small errors 

possible due to 

difficulties holding 

equipment at water 

surface

 Computed drop in 

water surface 

between 26th Street 

and Hofmann Dam 

was 0.92 ft

Direction of flow
Manning’s Roughness (n-value) 

 A measure of flow resistance based on 

several factors including: channel 

material, channel shape, vegetation, etc.

 Used in hydraulic models to represent 

the resistance to flow in the channel

 Typical values in natural channels range 

from 0.025 to 0.070 (Chow, 1959)
 Bed material seems to be mainly fine-grained 

sands, silts, and clays.

 Most river banks are made up of silts and clays 

with minimal vegetation up to the floodplain.

 Woody debris is common along many of the banks.

Manning’s Roughness:

General Observations
Manning’s Roughness: Summary

 Manning’s roughness in the study reach 

should likely range from approximately 

0.035 to 0.045.

 These values are relevant for flows within 

the main channel; values during flood 

conditions would be substantially 

different.
Hydraulic Model Verification

 Comparison of modeled and observed 

water-surface elevations

 Manning’s roughness sensitivity analysis
Observed Water 

Surface 

Locations 

and 

Corresponding 

Selected Model 

Cross Sections

Direction of flow
Water Surface Elevations Modeled With Flows 

Measured on May 17, 2012

Manning’s roughness = 0.035

26 Salt Creek th St

confluence Railroad Bridge 31st St

Red dots

indicate 

observed 

water surface

Streambed (vertically exaggerated)

Modeled 

water surface

Hofmann Dam

Millbridge Rd

Forest Ave
Comparison Among Manning’s Roughness 

Coefficients

Main-channel Manning’s roughness of 0.035 

selected based on comparison of errors

Manning's 

Roughness

Coefficient

1 Error

(ft)

0.035 +/- 0.16

0.040 +/- 0.21

0.045 +/- 0.30

1

root mean square error

Dam to 31st Street

1Root mean square error
Observed Flows Modeled

Modeled with flows measured on May 17, 2012

Manning’s roughness = 0.035

Salt Creek

confluence

Railroad Bridge 31st St 26th St

Streambed (vertical exaggeration) 

Existing

Proposed

Millbridge Rd

Forest Ave

Hofmann Dam
Hydrology Review/Analysis

 Purpose: Compute flow statistics for use 

in hydraulic modeling

 Overview of tasks

 Computation of daily flows

 Trend analyses of flow statistics to determine 

appropriate period of record

 Computation of flow statistics
Flow Statistics Computed

 Daily flows with 80% (low), 50%, and 20% 

exceedance probabilities

 7Q10: annual 7-day minimum flow (Q7) 

with 10-year return period

Only low flows results will be presented: 

80% exceedance daily flow and 7Q10
Streamflow

-

gaging 

Stations and

Des Plaines 

River Study 

Reaches 

Direction of flow

Beginning of complete 

water years (WY) of 

published daily streamflow

record:

05531500: 10-1-1945

05532000: 10-1-1951

05532500: 10-1-1943

Note:

132 of 150 mi

2 (88%) of 

Salt Creek watershed is 

gaged.
Flow Data Computations

Reach A: Flow measurements from 

gage near Hofmann Dam

Reach B: Reach A flow – Salt 

Creek flow

Reach C: Reach A flow – Salt 

Creek flow – Salt Creek diversion 

flow
Salt Creek Diversion Ratings

0

500

1000

1500

2000

2500

0 2000 4000 6000 8000

Diversion discharge (ft

3/s)

Salt Creek discharge upstream from 

diversion (ft3/s) 

MWRD

Notice major disagreement Figure provided by Rick Gosch, IDNR-OWR

at low flows:

• OWR rating has 1 ft3/s 

diverted at 700 ft3/s in 

Salt Creek = 0.14% ~ 0.

• MWRD rating has 

1280/2850 = 44.9% 

diverted up to 2850 ft3/s 

in Salt Creek.

• Our 5/17/12 measurement 

suggests low-flow rating 

is somewhere in the 

middle.

 Because of this 

uncertainty, flows based 

on both ratings were 

computed, providing a 

range of possible values.
Flow Data Computation:

Uncertainties Considered

Adjustment for ungaged portion of 

Salt Creek at confluence affects 

flow computation for reaches B

and C

Rating of Salt Creek diversion

affects flow computation for reach 

B 
Trend Analysis of Annual Minimum 7-Day 

Flow (Q7), WY 1952–2010

DPR aboveSalt Ck, adjusted for ungaged area

Salt Ck at Western Springs (05531500) DPR at Riverside (05532500)

DPR aboveSalt Ck, MWRD diversion rating, 

adjusted for ungaged area DPR above Salt Ck, adjusted for ungaged area 
Trend Analysis of Annual Minimum 7-day 

Flow (Q7):

Conclusions

 Trended upward in the 1950s and 1960s 

and then jumped during the mid-to-late 

1970s

 Trends since 1980 are small and not 

statistically different than zero

Estimate 7Q10 from 1980–2010 Q7 data
7Q10 Computation Results 

(ft3/s)

Reach C: [47.3 – 62.0] (88*) 

Reach B: [47.3 – 101] (90*) 

Reach A: 131 (133*) 

*Values in italics are from the 

Illinois State Water Survey (2003), 

included for comparison.
Trend Analysis of Annual Quantiles of 80% 

Exceedance Daily Flow (Q0.80)

Salt Ck at Western Springs (05531500) DPR at Riverside (05532500)

DPR above Salt Ck, adjusted for ungaged area

DPR above Salt Ck, MWRD diversion rating, adjusted for 

ungaged area
Trend Analysis of Daily Flow Quantiles:

Conclusions

 Trends in quantiles of interest are generally 

positive throughout the period of record 

(1952–2010).

 As with the Q7 data, there is a break in the 

trend in mid-to-late 1970s.

 Unlike the Q7 data, trends since 1980 are 

positive.

Use data from 2000–20101 to compute daily 

flow quantiles.

1This time period is a compromise between being recent 

and having enough data to estimate the flow value with 

reasonable accuracy.
80% Exceedance Daily Flow 

Computation Results (ft3/s)

Reach C: [149 – 160] (161*) 

Reach B: [149 – 199] (161*) 

Reach A: 245 (246*) 

*Values in italics are from OWR 

presentation, Sept. 2011.
Hydraulic Model Results

Water-surface elevations were modeled using:

 Manning’s roughness of 0.035

 USGS computed flows (no diversion and diversion added)

Results are presented as:

 Longitudinal profiles (80% exceedance and 7Q10)

 Cross section views (7Q10)

 Tables (80% exceedance and 7Q10)
Conditions Modeled

 Hofmann Dam current conditions

 150-ft notch in Hofmann Dam

Proposed (no diversion)

Proposed (diversion added)

Existing (no diversion)

Existing (diversion added)
Hydraulic Model 

Result Locations 

26th to 31st Street 

31st to Railroad 

Bridge 

Railroad Bridge to

Salt Creek 

Salt Creek to 

Hofmann Dam

Direction of flow
Longitudinal Profile

80% Exceedance 

Existing (no diversion)

Existing (diversion added)

Proposed (no diversion)

Proposed (diversion added)

26th St

Salt Creek

confluence

Railroad Bridge 31st St

Hofmann Dam Streambed (vertical exaggeration)

Millbridge Rd
Longitudinal Profile

80% Exceedance 

26th St

Salt Creek

confluence

Railroad Bridge 31st St

-0.38 -1.79 -1.43 -3.83

Average 

depth

change

Existing-project

(at field locations)

Streambed (vertical exaggeration)

Existing (no diversion)

Existing (diversion added)

Proposed (no diversion)

Proposed (diversion added)

Hofmann Dam

Millbridge Rd
Longitudinal Profile

7Q10 

26th St

Salt Creek

confluence

Railroad Bridge 31st St

-0.56 -4.23 -2.29 -1.89

Streambed (vertical exaggeration)

Average 

depth

change

Existing-project

(at field locations)

Existing (no diversion)

Existing (diversion added)

Proposed (no diversion)

Proposed (diversion added)

Hofmann Dam

Millbridge Rd
Hydraulic Model 

Result Locations 

26th to 31st Street 

31st to Railroad Bridge

Railroad Bridge to 

Salt Creek 

Salt Creek to 

Hofmann Dam

Direction of flow Direction of flow
Example Cross Section Plot and Line Legend

1500 1550 1600 1650 1700

600

602

604

606

608

Elevation (ft) 

Station (ft) 

XS 14792

Existing (no diversion)

Existing (diversion added)

Proposed (no diversion)

Proposed (diversion added)
7Q10 

 

26th to 31st

Street 

Average 

top width 

change = 

–14.58 ft 

Average 

maximum 

depth 

change = 

–0.56 ft

XS 16197

XS 14792

XS 13666

XS 12492
7Q10 

 

31st Street 

to 

Railroad 

Bridge 

Average 

top width 

change = 

–27.04 ft

Average 

maximum 

depth 

change = 

–1.98 ft

XS 11518

XS 10592

XS 9682

XS 8907
7Q10 

 

Railroad 

Bridge to 

Salt Creek 

Average 

top width 

change = 

–46.57 ft

Average 

maximum 

depth 

change = 

–2.29 ft

XS 7978

XS 7387

XS 6042

XS 5688
7Q10 

 

Salt Creek 

to Hofmann 

Dam

Average 

top width 

change = 

–123.11 ft

Average 

maximum 

depth 

change =

–4.23 ft

XS 4804

XS 3542

XS 2691

XS 1682-Existing XS 1682-Proposed
Summary of USGS Activities
Summary of Field Data Collection

 Data collected for model verification

 Flow measurements collected for model 

verification 

 Water-surface elevations collected for 

model verification

 Field-estimated Manning’s roughness 

ranged from 0.035 to 0.045

 Observed flow in Salt Creek diversion 

consistent with measured value
Summary of Model Verification

 Hydraulic model verified from 31st Street to 

Hofmann Dam 

 Observed to modeled error +/– 0.16 ft

(for 0.035 Manning’s roughness model)

 Manning’s roughness of 0.035 selected 

 The USACE model value was 0.040

(error +/– 0.21 ft ) 

 Both values are within range of field 

estimations
Summary of Hydrologic Analysis

 Analysis of annual flow statistics indicated:

 Increasing flows in all statistics throughout 

1950s–70s 

 Use of flow data from 1980–2010 for annual 7-

day minimum and 2000–10 for 20%, 50%, and 

80% exceedance daily flow quantiles

 Range of flow statistic values estimated for 

reaches above Salt Creek confluence 

depending on:

 diversion rating

 Salt Creek unmeasured drainage area
Summary of Hydraulic Analysis:

Change in Top Width

 16 cross sections total (four in each reach)

7Q10 Flows 80th Percentile Flows

(project minus existing) (project minus existing)

Reach Location 

Average Top Width 

Change (ft)

Average Top Width 

Change (ft)

31st Street to 26th Street -14.58 -9.86

Railroad to 31st Street -27.04 -19.00

Salt Creek to Railroad -46.57 -39.30

Hofmann Dam to Salt Creek -123.11 -116.09
Summary of Hydraulic Analysis:

Change in Maximum Depth

 16 cross sections total (four in each reach)

7Q10 Flows 80th Percentile Flows

(project minus existing) (project minus existing)

Reach Location 

Average Maximum 

Depth Change (ft)

Average Maximum 

Depth Change (ft)

31st Street to 26th Street -0.56 -0.38

Railroad to 31st Street -1.98 -1.43

Salt Creek to Railroad -2.29 -1.79

Hofmann Dam to Salt Creek -4.23 -3.83
Hydrologic Analysis: 

Additional Methods and Results Slides

 Specific details on the methods and results of the 

hydrologic and hydraulic analyses are presented in 

the following slides including:

 Detailed information on hydrologic analysis 

methods and specific results for the 50 and 20 

percentiles

 Detailed summary tables of all model results for 

the 80%, 50%, and 20% exceedance daily flow 

quantiles and 7Q10 flow statistics
Wastewater Treatment Plant Effluent Flows

Table from Singh and Ramamurthy (1993) 

Also note online information indicates MWRD Kirie

WWTP, which discharges to Willow Creek. Kirie WWTP 

discharge enters the Des Plaines River below USGS 

streamflow-gaging station 0552900 but above the study 

area and began operation in 1980.
ISWS 7Q10 Maps

1993

 2003 

Notes: 

• Channel losses in Lower Salt Creek in 1993 map but not 2003.

• Decrease in Kirie WWTP flows from 1993 to 2003, which explain 

part but not all of Des Plaines River decreases from 1993 to 2003.
Flow Data Sources and Computation Methods: 

Des Plaines River

Location Data Source or Computation Method

Reach A: DPR below Salt Ck 

confluence QDPR.Riverside

Reach B: DPR above Salt Ck 

confluence / below Salt Ck 

diversion

QDPR.abvSalt.MWRDdiv = QDPR.Riverside – QSaltCk.conf

Reach C: DPR above Salt Ck 

diversion QDPR.abvSalt = QDPR.Riverside – QSaltCk.conf – Qdiv

Notes: 

• Stylized Q indicates estimated quantity; others are measured.

• QDPR.Riverside: daily streamflow at USGS streamgage 05532500. 

• QSaltCk.conf: daily streamflow at Salt Creek confluence with DPR

• Qdiv: daily streamflow in Salt Creek diversion
Flow Data Sources and Computation Methods: 

Salt Creek

Location Data Source or Computation Method

Salt Creek at 

confluence

QSaltCk.conf = KDA.adj.conf[QSaltCk.WSprings + QAddisonCk] – Qdiv, where 

KDA.adj.conf = DASaltCk.conf/(DASaltCkWSprings + DAAddisonCk) = 

150.4/(116.3+16.2) = 1.135; 

KDA.adj.conf = 1 for no ungaged area adjustment.

Salt Creek diversion Qdiv = Krating

*QSaltCk.at.div

Krating = 0.449 (MWRD) or 0.0 (IDNR-OWR)

Salt Creek at 

diversion

QSaltCk.at.div = KDA.adj.div[QSaltCk.WSprings + QAddisonCk], where

KDA.adj.div = DASaltCk.at.div/(DASaltCkWSprings + DAAddisonCk) = 

145.3/(116.3+16.2) = 1.0966; 

KDA.adj.div = 1 for no ungaged area adjustment.

Notes: 

• Stylized Q indicates estimated quantity; others are measured.

• QAddisonCk: daily streamflow at USGS streamgage 05532000. 

• QSaltCk.WSprings: daily streamflow at USGS streamgage 05531500. 

• DA: drainage areas in square miles from USGS StreamStats. 
Trend Analysis: Annual Minimum 7-Day Flow (Q7), 

WY 1980–2010 

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Trend with Standard Error (ft

3/s/year) 
Computation of 7Q10:

log-Pearson type 3 (LP3) Method

 Determine a homogeneous period (here 1980–2010)

 Compute moments (mean, stdev, skewness) of log10

of annual minimum 7-day flow (log10Q7) series

 Fit to “Pearson type 3” distribution using moments to 

constrain parameters (in this study function quape3() 

from version 1.6.1 of lmomco package (Asquith, 

2012) of R language was used for this fit).

 Note: Flood frequency computations are usually 

done essentially the same way (Interagency Advisory 

Committee on Water Data, 1981).
Computation of 7Q10: Example Fits

Salt Ck at WesternSprings (05531500) DPR at Riverside (05532500)

DPR above Salt Ck, adjusted for ungaged area

DPR above Salt Ck, MWRD diversion 

rating, adjusted for ungaged area
Computation of 7Q10: Results

Applicable Des 

Plaines River

reach

Drainage area 

adjustment

Salt Creek 

diversion

included

Estimated 

7Q10: this 

study (ft3/s)

Estimated 

7Q10: ISWS 

2003 (ft3/s)

Reach A: 

below Salt Ck N/A N/A 131 133

Reach B: 

above Salt Ck, 

below diversion

No Yes 101 90

Yes Yes 94.5 90

No No 62.0 90

Yes No 47.3 90

Reach C: 

above Salt Ck, 

above diversion

No N/A 62.0 88

Yes N/A 47.3 88
Daily Flow Quantiles: Computation Example

DPR.Riverside (05532500), WY 2000–2010
Trend Analysis of Daily Flow Quantiles

Method 

 Example computation plot in previous slide used 

11 years of data.

 To analyze trends, daily flow quantiles were 

obtained from each water year’s data separately to 

obtain quantiles on an annual basis. 

 Example results of trend analysis of these annual 

quantiles for 50% and 20% exceedance probabilities 

are given in the following slides; 80% exceedance

results were given in main body of presentation.
Trend Analysis: Annual Quantiles of 50% 

Exceedance Daily Flow

Salt Ck at Western Springs (05531500) DPR at Riverside (05532500)

DPR above Salt Ck, adjusted for ungaged area

DPR above Salt Ck, MWRD diversion rating, adjusted for 

ungaged area
Trend Analysis: Annual Quantiles of 20% 

Exceedance Daily Flow

Salt Ck at Western Springs (05531500) DPR at Riverside (05532500)

DPR above Salt Ck, adjusted for ungaged area

DPR above Salt Ck, MWRD diversion rating, adjusted 

for ungaged area
Trend Analysis: Annual Quantiles of 80% 

Exceedance Daily Flow, WY 1980–2010 

-4.0

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

Trend with Standard Error (ft

3/s/year) 
Trend Analysis: Annual Quantiles of 50% 

Exceedance Daily Flow, WY 1980–2010 

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

Trend with Standard Error (ft

3/s/year) 
Trend Analysis: Annual Quantiles of 20% 

Exceedance Daily Flow, WY 1980–2010 

-20

-15

-10

-5

0

5

10

15

20

Trend with Standard Error (ft

3/s/year) 
Computation of Daily Flow Quantiles: Results 

Location Applicable Des Plaines 

River reach

Q0.80

(ft3/s)

Q0.50

(ft3/s)

Q0.20

(ft3/s)

DPR.Riverside Below Salt Ck (Reach A) 245

(246)

508

(507)

1170

(1170)

DPR.abv.SaltCk.

0WRDdiv.noDAadj Above Salt Ck, below 

diversion (Reach B)

199 425 1000

DPR.abv.SaltCk.

0WRDdiv.DAadj 191 412 977

DPR.abv.SaltCk.no

DAadj Above Salt Ck, above

diversion (Reach C) or no 

diversion (Reach B)

160

(161)

358

(358)

863

(863)

DPR.abv.SaltCk.

'$adj 149 339 816

Note: Values in italics are from IDNR-OWR presentation (Sept. 2011) and were 

computed using data from CY2000–9. These values are included for comparison 

purposes only. 
Hydraulic Appendix
Summary Table for 80th Percentile Flows

Location and Cross Section

Flow (ft3

/s) Top Width (ft) Maximum Depth (ft)

Diversion 

Added

No

Diversion

Diversion Added

Existing Project

No Diversion

Existing Project

Diversion Added

Existing Project

No Diversion

Existing Project

31st Street to 26th Street

16197 149 149 169.60 167.53 165.48 162.06 5.33 5.18 5.07 4.88

14792 199 149 120.42 115.97 112.81 106.96 5.59 5.43 5.32 5.11

13666 199 149 90.70 86.93 87.04 82.16 3.10 2.87 2.88 2.58

12492 199 149 119.33 93.85 114.95 86.00 2.44 1.64 2.33 1.35

Average --- --- 125.01 116.07 120.07 109.30 4.12 3.78 3.90 3.48

Railroad to 31st Street

11518 199 149 121.65 110.95 120.91 107.37 3.79 2.8 3.70 2.5

10591 199 149 95.41 78.79 94.84 70.58 3.79 2.43 3.74 2.18

9682 199 149 148.95 117.66 147.78 115.09 4.62 3.15 4.57 2.94

8907 199 149 98.48 87.51 98.17 86.26 6.24 4.73 6.21 4.53

Average --- --- 116.12 98.73 115.43 94.83 4.61 3.28 4.56 3.04

Salt Creek to Railroad

7978 199 149 139.56 104.90 138.65 100.59 4.59 3.04 4.56 2.86

7387 199 149 115.59 80.81 114.75 79.19 4.33 2.61 4.31 2.49

6042 199 149 190.33 137.59 190.22 136.85 4.79 2.97 4.79 2.90

5688 199 149 159.61 127.52 159.59 126.43 4.12 2.24 4.11 2.20

Average --- --- 151.27 112.71 150.80 110.77 4.46 2.72 4.44 2.61

Hofmann Dam to Salt Creek

4804 245 245 99.05 77.65 --- --- 4.74 2.51 --- ---

3542 245 245 94.22 57.53 --- --- 6.08 3.3 --- ---

2691 245 245 226.96 91.79 --- --- 6.65 2.77 --- ---

1682 245 245 368.43 97.33 --- --- 7.86 1.42 --- ---

Average --- --- 197.17 81.08 6.33 2.50
Summary Table for 50th Percentile Flows

Location and Cross Section

Flow (ft3/s) Top Width (ft) Maximum Depth (ft)

Diversion 

Added

No

Diversion

Diversion Added

Existing Project

No Diversion

Existing Project

Diversion Added

Existing Project

No Diversion

Existing Project

31st Street to 26th Street

16197 339 339 176.29 175.97 175.50 175.12 6.44 6.32 6.15 6.01

14792 425 339 140.29 138.57 136.32 134.25 6.64 6.50 6.33 6.16

13666 425 339 106.35 103.09 101.93 98.06 4.06 3.86 3.79 3.55

12492 425 339 135.63 125.67 132.03 119.91 3.31 2.78 3.12 2.47

Average --- --- 139.64 135.83 136.45 131.84 5.11 4.87 4.85 4.55

Railroad to 31st Street

11518 425 339 128.41 123.39 127.04 120.97 4.61 4.00 4.44 3.7

10591 425 339 103.05 94.34 101.83 90.65 4.52 3.69 4.41 3.44

9682 425 339 160.08 143.09 158.74 137.26 5.31 4.4 5.21 4.18

8907 425 339 104.12 96.11 103.41 94.57 6.91 5.96 6.82 5.77

Average --- --- 123.92 114.23 122.76 110.86 5.34 4.51 5.22 4.27

Salt Creek to Railroad

7978 425 339 147.86 129.23 147.27 124.11 5.22 4.24 5.16 4.06

7387 425 339 159.56 99.75 154.46 98.20 4.91 3.79 4.87 3.68

6042 425 339 199.42 155.74 199.12 152.43 5.33 4.11 5.31 4.05

5688 425 339 163.04 155.20 162.98 154.95 4.64 3.38 4.63 3.34

Average --- --- 167.47 134.98 165.96 132.42 5.03 3.88 4.99 3.78

Hofmann Dam to Salt Creek

4804 508 508 106.22 85.36 --- --- 5.19 3.63 --- ---

3542 508 508 98.63 65.46 --- --- 6.42 4.19 --- ---

2691 508 508 239.04 108.35 --- --- 6.93 3.59 --- ---

1682 508 508 369.21 143.10 --- --- 8.12 2.25 --- ---

Average --- --- 203.28 100.57 6.67 3.42
Summary Table for 20th Percentile Flows

Location and Cross Section

Flow (ft3/s) Top Width (ft) Maximum Depth (ft)

Diversion 

Added

No

Diversion

Diversion Added

Existing Project

No Diversion

Existing Project

Diversion Added

Existing Project

No Diversion

Existing Project

31st Street to 26th Street

16197 816 816 320.33 254.84 181.93 180.06 8.3 8.19 7.92 7.79

14792 1000 816 161.14 160.37 158.56 157.64 8.45 8.32 8.03 7.88

13666 1000 816 138.03 135.98 134.81 129.50 5.78 5.60 5.41 5.20

12492 1000 816 171.67 154.94 153.20 149.31 5.05 4.76 4.73 4.39

Average --- --- 197.79 176.53 157.13 154.13 6.90 6.72 6.52 6.32

Railroad to 31st Street

11518 1000 816 143.72 139.57 139.87 136.82 6.29 5.97 6.01 5.63

10591 1000 816 122.30 115.38 117.27 112.53 6.1 5.7 5.88 5.43

9682 1000 816 244.26 183.13 227.21 171.20 6.82 6.4 6.64 6.16

8907 1000 816 116.49 112.75 115.17 110.94 8.37 7.93 8.21 7.71

Average --- --- 156.69 137.71 149.88 132.87 6.90 6.50 6.69 6.23

Salt Creek to Railroad

7978 1000 816 223.45 160.45 201.88 153.68 6.62 6.14 6.49 5.97

7387 1000 816 281.22 225.01 261.04 215.40 6.24 5.70 6.16 5.58

6042 1000 816 226.26 215.59 225.61 214.21 6.57 5.96 6.54 5.90

5688 1000 816 174.83 166.99 174.21 166.76 5.85 5.21 5.84 5.18

Average --- --- 226.44 192.01 215.69 187.51 6.32 5.75 6.26 5.66

Hofmann Dam to Salt Creek

4804 1170 1170 120.58 109.93 --- --- 6.24 5.42 --- ---

3542 1170 1170 111.55 89.16 --- --- 7.15 5.70 --- ---

2691 1170 1170 249.84 141.52 --- --- 7.51 4.90 --- ---

1682 1170 1170 370.71 158.79 --- --- 8.61 3.57 --- ---

Average --- --- 213.17 124.85 7.38 4.90
Summary Table for 7Q10 Flows

Location and Cross Section

Flow (ft3

/s) Top Width (ft) Maximum Depth (ft)

Diversion 

Added

No

Diversion

Diversion Added

Existing Project

No Diversion

Existing Project

Diversion Added

Existing Project

No Diversion

Existing Project

31st Street to 26th Street

16197 47.3 47.3 157.36 148.81 140.80 123.46 4.63 4.41 4.28 3.83

14792 101 47.3 102.09 96.88 92.39 85.42 4.93 4.72 4.59 4.12

13666 101 47.3 81.27 74.82 75.60 63.43 2.53 2.24 2.28 1.71

12492 101 47.3 103.56 77.36 101.90 68.16 2.05 1.03 1.98 0.71

Average --- --- 111.07 99.47 102.67 85.12 3.54 3.10 3.28 2.59

Railroad to 31st Street

11518 101 47.3 118.73 96.78 118.24 82.43 3.43 2.07 3.37 1.56

10591 101 47.3 91.75 64.17 91.06 59.33 3.49 1.64 3.46 1.23

9682 101 47.3 141.35 108.29 140.68 103.55 4.34 2.38 4.31 2.03

8907 101 47.3 96.19 82.65 96.01 80.48 5.97 3.97 5.95 3.64

Average --- --- 112.01 87.97 111.50 81.45 4.31 2.52 4.27 2.12

Salt Creek to Railroad

7978 101 47.3 131.85 91.15 131.34 80.92 4.33 2.31 4.31 2.00

7387 101 47.3 104.55 70.40 104.37 65.89 4.09 1.9 4.08 1.70

6042 101 47.3 187.84 129.79 187.80 128.61 4.57 2.29 4.57 2.17

5688 101 47.3 158.41 113.12 158.40 112.11 3.90 1.57 3.89 1.48

Average --- --- 145.66 101.12 145.48 96.88 4.22 2.02 4.21 1.84

Hofmann Dam to Salt Creek

4804 131 131 95.97 72.41 --- --- 4.54 1.82 --- ---

3542 131 131 92.14 52.85 --- --- 5.93 2.72 --- ---

2691 131 131 217.97 79.90 --- --- 6.51 2.25 --- ---

1682 131 131 367.55 76.04 --- --- 7.73 1.00 --- ---

Average --- --- 193.41 70.30 6.18 1.95
Summary of Simulated Changes in Average Top 

Width and Maximum Depth

20th Percentile 50th Percentile 80th Percentile 

Flows Flows Flows 7Q10 Flows

(project minus (project minus (project minus (project minus 

existing) existing) existing) existing)

Average Average Average Average Average Average Average Average 

Top Maximum Top Maximum Top Maximum Top Maximum 

Width Depth Width Depth Width Depth Width Depth 

Reach Location 

Change 

(ft)

Change 

(ft)

Change 

(ft)

Change 

(ft)

Change 

(ft)

Change 

(ft)

Change 

(ft)

Change 

(ft)

31st Street to 26th 

Street -12.13 -0.19 -4.21 -0.27 -9.86 -0.38 -14.58 -0.56

Railroad to 31st 

Street -18.00 -0.42 -10.79 -0.89 -19.00 -1.43 -27.04 -1.98

Salt Creek to 

Railroad -31.30 -0.58 -33.01 -1.18 -39.30 -1.79 -46.57 -2.29

Hofmann Dam to 

Salt Creek -88.32 -2.48 -102.71 -3.25 -116.09 -3.83 -123.11 -4.23
Selected References

 Asquith, W.H., 2012, lmomco---L-moments, trimmed L-moments, L-comoments, censored 

L-moments, and many distributions, in R package (version 1.6.1): Lubbock, Texas Tech 

University, accessed at http://www.cran.r-project.org/package=lmomco. 

 Chow, V.T., 1959, Open channel hydraulics: New York, McGraw-Hill, 680 p. 

 Easterling, D.R., and Peterson, T.C., 1995, A new method for detecting undocumented 

discontinuities in climatological time series: International Journal of Climatology, v. 15, p. 

369–377. 

 Illinois State Water Survey, 2003 (rev. Feb. 2003), 7-day 10-year low flows, Map 2, 

Northeastern Illinois Streams.

 Interagency Committee on Water Data, 1981, Guidelines for determining flood flow 

frequency: Bulletin 17B of the Hydrology Subcommittee, U.S. Department of the Interior, 

Geological Survey, Reston, Virginia [variously paged]. 

 Singh, K. P., and Ramamurthy, G.S., 1993, 7-day, 10-year low flows of streams in 

northeastern Illinois: Illinois State Water Survey Contract Report 545, 24 p. 

 U.S. Army Corp of Engineers, Hydrologic Engineering Center, 2010, HEC-RAS river 

analysis system, hydraulic reference manual: version 4.1, various chapters plus 

appendixes. 

 U.S. Geological Survey, Illinois StreamStats: accessed in May 2012 at 

http://streamstatsags.cr.usgs.gov/il_ss/default.aspx.