Lacey Divergence Equations for Alluvial‐Canal Design
Publication: Journal of Hydraulic Engineering
Volume 120, Issue 11
Abstract
Besides discharge and sediment characteristics (size and concentration ), the third physical factor governing hydraulic geometry of an alluvial canal is resistance to erosion of bank material. Lacey formulas provide one set of the parameters of hydraulic geometry through the wetted perimeter , hydraulic mean radius , and slope , with implied values of sediment concentration and maximum safe boundary shear stress t\ds. But with varying values of and t\ds, many other sets of , , and are possible. Defining Lacey divergence as the ratio of actual value to value obtained with the Lacey formula and designating this ratio by subscript , Lacey Divergence relations were obtained for velocity and . Velocity ratio V\dr was found related only to slope ratio S\dr, whereas sediment concentration ratio C\dr was related to both S\dr and boundary shear stress ratio t\dr. Equations were then derived for P\dr, R\dr and S\dr in terms of C\dr and t\dr, which permit determination of , , and when design data in respect of , , , and t\ds are given.
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Copyright © 1994 American Society of Civil Engineers.
History
Received: Jun 18, 1992
Published online: Nov 1, 1994
Published in print: Nov 1994
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