Premium
Use of the discharge‐weighted average velocity in studies of the frictional energy loss of streamflow
Author(s) -
Lewis Nathan K.
Publication year - 1997
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/(sici)1096-9837(199704)22:4<329::aid-esp669>3.0.co;2-k
Subject(s) - streams , streamflow , range (aeronautics) , hydrology (agriculture) , cascade , geology , environmental science , mathematics , mechanics , statistics , geotechnical engineering , materials science , physics , drainage basin , computer network , cartography , computer science , composite material , geography , chemistry , chromatography
The discharge‐weighted average velocity of streamflow is proposed as an alternative to the more commonly used area‐weighted average for uses where frictional energy losses are evaluated. Using experimental data from Mink Brook, NH, and data published by Marchand et al. (USGS Open File Report 84–733, 1984), the theoretical framework developed here indicates that, through the use of the area‐weighted average velocity. Manning's n overestimates frictional effects by 2–156 per cent in certain common situations. Variance in the vertical axis, from a sample of various streams in Colorado, creates an additional overestimation of 6–25 per cent. A sample velocity distribution for a smooth walled, straight, trapezoidal channel creates an overestimation of 24 per cent. Similar overestimation may partially explain the roughness multiplier applied to the Nikuradse K in gravel‐bed streams where particle size approaches or exceeds mean depth. A generalized resistance equation is proposed that may assist in evaluating the range of conditions found in the natural world. © 1997 by John Wiley & Sons, Ltd.