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Title:Variation of Manning’s coefficient with channel stage
Author(s):Soong, Ta-Wei; DePue, Perry Michael, II
Contributor(s):University of Illinois at Urbana-Champaign
Subject(s):Water resources center
Water resources center--Illinois
Hydrology and hydraulics
Manning's roughness coefficient
Compound channel
Composite channel
Open channel flow
Flow resistance
Composite roughness
Predictive equation
Geographic Coverage:Illinois (state)
Abstract:Although Manning's roughness coefficient is known to vary with river stage, information on this aspect is limited, and practitioners have to resort to trial-and-error approaches or rely on their judgment to quantify the variation. This research was aimed at investigating the variation patterns of Manning's roughness coefficient over depth. Investigators conducted an extensive laboratory experiment using a fairly long and large channel, in the shape of half of a compound cross section, to simulate natural rivers. This experimental channel allowed a comprehensive investigation of both uniform and composite roughness elements along the channel's wetted perimeter. Data were taken from both cases: when flow was restricted in the main channel (to simulate a prismatic channel) and when it covered the floodplain. In addition, the investigators converted data from other researchers to verify factors not covered in this study. The researchers found that while geometry and roughness patterns can both affect the magnitude of Manning's coefficient over depth, the effects vary in prismatic and floodplain channels. Experimental data were used to identify the variation patterns of Manning's roughness in the floodplain channel as well as the effects of varying roughness distribution in the main channel and floodplains. Investigators also made a number of recommendations regarding the equations that should be used to quantify the variation of the overall Manning's n value for a channel section. Suggestions were made as to the specific use of these equations, including the number of subareas within the channel to be considered, the type of division lines between the subareas, and the ranges of applicability of the equations.
Issue Date:1996-06
Publisher:University of Illinois at Urbana-Champaign. Water Resources Center
Genre:Report (Grant or Annual)
Sponsor:U.S. Department of the Interior
U.S. Geological Survey
Rights Information:Copyright 1996 held by Ta Wei Soong, Perry Michael DePue II
Date Available in IDEALS:2016-05-18

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