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Ik "\'>' 20' NOVEMBER 1973 A ~' v (l = average raindrop velocity; x, y, z ~ coordinates (Fig. I); y c = critical depth at outlet; al' CXl' cx) = eigenvalues of A; ~ I' ~2'~' ~ eigenvalucs of B; 9 x' 9 y' 9 z = angles of inclination that gravitational force makes wid! x., Yw, and z-axes, respectively; . e = watershed slope angle in direction of main channel (FiJ.- I); v = kinematic viscosity of fluid; p = mass density of fluid;' {J = maximum eigenvalue of either A or B; T.1' T Z = boundary shears in x- and z-directions, respectively; 4> = watershed slope angle in direction perpendicular to maia -: channel (Fig. I); and * = superscript for normalized quantities. ,< ~. " ~, f4 ~ I ~ " ~ f! ~ " " t: ~ i: !. h ~ , I i 1 t ~-. I "i I' ). ~1 JOURNAL OF THE HYDRAULICS DIVISION NOVEMBER 1973 ,!i ~ SEDIMENT TRANSPORT: NEW ApPROACH AND ANALYSIS By Peter Ackers 1 and William Rodney Wbite2 IHmooUCTION The transport of noncohesive sediments by a steady uniform flow of fluid in an open channel is a complex process, and the physics of this two-phase motion is as yet incompletely understood. Many theories have been put forward in attempts to provide frameworks for the analysis of data on sediment transport, ., some being based on the physics of particle motion and others on similarity 1>' principles or dimensional arguments. Very different answers may result from , Ibe use of available predictive equations and some are complicated to apply. There has been an academic preference for shear stress as the main parameter defining the stream's transporting power. However, the total shear on a deformed ,,~ bed (rippled or duned) is in part composed of the along-stream components of the normal pressures on the irregular bed profile. Although these normal pressures may contribute indirectly to sediment motion through suspension, many methods separate the bed shear into the non transporting form loss and the shear on the grains. As the rate of transport is very sensitive to transporting power, inaccuracy in this separation procedure may give large errors of prediction. :., In engineering practice, this factor is important because few natural streams have a plane bed. Several researchers have suggested that shear stress is not the most convenient, nor the most rational, basis of a sediment transport function, and have proposed methods of correlation that use average stream velocity in preference to shear stress. Note.-Discussion open until April 1, 1974. To extend the closing date one month, a written request must be filed with the Editor of Technical Publications, ASCE. This paper is part of the copyrighted Journal of the Hydraulics Division, Proceedings of the American SociNy of Civil Engineers, Vol. 99, No. HYll. November, 1973. Manuscript was submitted for review for possible publication on April 4, 1973. IConsultant, Binnie and Partners, London, England; previously Asst. Dir., Hydr. Research Sta., Wallingford, England. 2Principal Sci. Officer, Hydr. Research Station, Wallingford, England. 2041 l II, } ! I ! ,. I J 1 , .' .;; I j '!', ',I. h" if