Estimating Manning's Roughness Coefficients for Natural and Man-Made Streams in Illinois

U.S. Geological Survey: David T. Soong, Crystal D. Prater, Teresa M. Halfar
Illinois Department of Natural Resources: Loren A. Wobig

:: Introduction :: Contact Information :: Acknowledgements :: Notes from the Authors ::


The Manning's roughness coefficients (n-values) presented in these Web pages are averaged reach-wise n-values.  These n-values are computed using flow, water surface slope, and channel geometry data collected from selected streams in Illinois. Only in-bank flows are considered at the present time.  In order to provide information for estimating n-values under other hydraulic and/or geometric conditions, the site- and event-specific data are organized into data pages using a format similar to the Barnes report (1967), which is known as the visual approach for estimating n-values. The stream reaches that are presented here are those representing natural or man-made cross sections with natural or artificial surface roughness found in rural or urban settings. Efforts are made to include a range of n-values computed using hydraulic data collected at different stages at each site. Attempts are also made to enhance the presentation of the topographic features of a study reach and to describe the geometric and hydraulic factors pertaining to the computed n-values in the site descriptions.

The U.S. Geological Survey-Illinois Water Science Center (USGS-ILWSC) and the Illinois Department of Natural Resources-Office of Water Resources (IDNR-OWR) conducted this study. Using links provided at the left-hand-side of the Web page, readers can view or download selected site pages, compute n-values using various methods that can be found in literature, and search for sites that have n-values within a specified range. Readers can also find links to reports of similar studies conducted by other USGS Water Science Centers and agencies. Other search or computational functions will be provided when feasible.

These Web pages are being continuously revised in order to provide information to users in the most clear and useful form. Please forward any comments to David T. Soong, Crystal D. Prater, or Teresa M. Halfar (USGS), or Loren Wobig (IDNR-OWR).


David T. Soong:, phone: 217 328 9717, fax: 217 328 9770
Crystal D. Prater:, phone: 217 328 9730, fax: 217 328 9770
Teresa M. Halfar:, phone: 217 328 9714, fax: 217 328 9770

Loren A. Wobig:, phone: 217 782 9130, fax: 217 785 5014


This project has been conducted by the USGS-ILWSC in cooperation with the IDNR-OWR. We want to give our thanks to the many private landowners who gave us permission to conduct field measurements on their properties. Data collection and surveying of channel cross sections has been conducted by USGS-ILWSC staff. Channel cross-sectional geometry and datum has also been obtained from IDNR-OWR, Illinois Department of Transportation, U.S. Army Corps of Engineers Chicago, Rock Island, and St. Louis Districts, and from municipalities and private consultant firms. Former USGS-ILWSC student employees Megan A. Jupin and King Shan Kwok made tremendous contributions to the data analysis and maintenance of these Web pages.


These Web pages are still under construction. Many Web functions will be developed in the future. Provisional data are for review/comment only. Your comments and suggestions are invaluable to us for providing better, more accurate information/results.

USGS data on this page have not received Director's approval and as such are provisional and subject to revision. The data are released on the condition that neither the USGS nor the United States Government may be held liable for any damages resulting from their use.

Data from other agencies are displayed for informational purposes only. The USGS is not involved with the collection, checking, and analysis of other agency data. Questions and/or comments concerning other agency data should be directed to the respective agency.

Convert this page to PDF

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo logo U.S. Department of the Interior | U.S. Geological Survey
URL:[an error occurred while processing this directive]?
Page Contact Information: David Soong
Page Last Modified: December 19, 2012