Sediment Concentration below Free Overfall
Publication: Journal of Hydraulic Engineering
Volume 120, Issue 9
Abstract
Time‐varying sediment concentration exiting a plunge pool is analyzed by considering the effect of free‐overfall jet diffusion on sediment detachment and scour. The analysis results in dimensionless relationships between scour volume, sediment concentration, maximum scour depth, and time. Sediment concentration is at a maximum near the initiation of scour, when the eroding bed is at the tip of the impinging jet's potential core. Thereafter, sediment concentration decreases as a function of time and scour‐hole geometry, expressed as maximum scour depth. Dimensionless geometric relationships show that the scour volume per unit width can be expressed as twice the square of the maximum scour depth at the corresponding time for the cohesive and noncohesive soils tested. Analytical relationships between sediment concentration and time are verified by laboratory experiments of scour below a free overfall on two sand‐bed materials (one coarse and one fine) and on one cohesive soil, each replicated several times. The agreement between measured and predicted values is best for the noncohesive sands.
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References
1.
Albertson, M. L., Dai, Y. B., Johnson, R. A., and Rouse, H. (1950). “Diffusion of submerged jets.” Trans., ASCE, 115, 639–697.
2.
Akashi, N., and Saitou, T. (1986). “Influence of water surface on scour from a vertical submerged jet.” J. Hydrosci. and Hydr. Engrg., 4(2), 55–69.
3.
Begin, Z. B., Meyer, D. F., and Schumm, S. A. (1980a). “Knickpoint migration due to base level lowering.” J. Wtrway., Port., Coast. and Oc. Div., ASCE, 106(3), 369–389.
4.
Begin, Z. B., Meyer, D. F., and Schumm, S. A. (1980b). “Sediment production of alluvial channels in response to base level lowering.” Trans., American Society of Agricultural Engineers, 23(5), 1183–1188.
5.
Beltaos, S. (1972). “Normal impingement of plane turbulent jets on sooth walls,” MS thesis, University of Alberta, at Edmonton, Alberta.
6.
Beltaos, S. (1974). “Turbulent impinging jets,” PhD dissertation, University of Alberta, at Edmonton, Alberta.
7.
Beltaos, S. (1976). “Oblique impingement of plane turbulent jets.” J. Hydr. Div., ASCE, 102(9), 1177–1192.
8.
Beltaos, S., and Rajaratnam, N. (1973). “Plane turbulent impinging jets.” J. Hydr. Res., 11(1), 29–59.
9.
Blaisdell, F. W., and Anderson, C. L. (1988a). “A comprehensive generalized study of scour at cantilevered pipe outlets, Pt. 1.” J. Hydr. Res., 26(4), 357–376.
10.
Blaisdell, F. W., and Anderson, C. L. (1988b). “A comprehensive generalized study of scour at cantilevered pipe outlets, Pt. 2.” J. Hydr. Res., 26(5), 509–524.
11.
Blaisdell, F. W., Anderson, C. L., and Hebaus, G. G. (1981). “Ultimate dimensions of local scour.” J. Hydr. Div., ASCE, 107(3), 327–337.
12.
Bormann, N. E., and Julien, P. Y. (1991). “Scour downstream of grade control structures.” J. Hydr. Engrg., ASCE,117(5), 597–594.
13.
Chee, S. P., and Kung, T. (1971). “Stable profiles of plunge basins.” Water Res. Bull., 7(2), 303–308.
14.
Chee, S. P., and Yuen, E. M. (1985). “Erosion of unconsolidated gravel beds.” Can. J. Civ. Engrg., 12(3), 559–566.
15.
Foster, G. R., Meyer, L. D., and Onstad, C. A. (1977). “An erosion equation derived from basic erosion principles.” Trans., American Society of Agricultural Engineers, 20(4), 678–682.
16.
Gardner, T. W. (1983). “Experimental study of knickpoint and longitudinal profile in cohesive, homogeneous material.” Geol. Soc. Amr. Bull., 94(5), 664–672.
17.
Hanson, G. J. (1989). “Channel erosion study of two compacted clays.” Trans., American Society of Agricultural Engineers, 32(5), 485–490.
18.
Holland, W. N., and Pickup, G. (1976). “Flume study of knickpoint development in stratified sediment.” Geol. Soc. Amr. Bull., 87(1), 76–82.
19.
Kobus, H., Liester, P., and Westrich, B. (1979). “Flow field and scouring effects of steady and pulsating jets impinging on a moveable bed.” J. Hydr. Res., 17(3), 175–192.
20.
Laursen, E. M. (1952). “Observations on the nature of scour.” Proc. 5th Hydr. Conf., University of Iowa, Iowa City, Iowa, 179–197.
21.
Mason, P. J., and Arumugam, K. (1985). “Free jet scour below dams and flip buckets.” J. Hydr. Engrg., ASCE, 111(2), 220–235.
22.
Nearing, M. A., Foster, G. R., Lane, L. J., and Finkner, S. A. (1989). “A process‐based soil erosion model for USDA water erosion prediction project technology.” Trans., American Society of Agricultural Engineers, 32(5), 1587–1593.
23.
Rajaratnam, N. (1976). “Turbulent jets.” Development in Water Science 5. Elsevier Scientific Publishing Co., Amsterdam, the Netherlands.
24.
Rajaratnam, N. (1981). “Erosion by plane turbulent jets.” J. Hydr. Res., 19(4), 339–359.
25.
Rajaratnam, N. (1982). “Erosion by unsubmerged plane water jets.” Proc. Applying research to hydraulic practice, ASCE, New York, N.Y., 280–288.
26.
Robinson, K. M. (1989a). “Hydraulic stress on an overfall bounday.” Trans., American Society of Agricultural Engineers, 32(4), 1269–1274.
27.
Robinson, K. M. (1989b). “Stress distribution at an overfall.” Trans., American Society of Agricultural Engineers, 32(1), 75–80.
28.
Rouse, H. (1940). “Criteria for similarity in the transportation of sediment.” Proc. 1st Hydraulic Conf., State University of Iowa, Iowa City, Iowa, 33–49.
29.
Stein, O. R. (1990). “Mechanics of headcut migration in rills,” PhD dissertation, Colorado State University, at Fort Collins, Colo.
30.
Stein, O. R., and Julien, P. Y. (1991). “Measurement of rill erosion sediment detachment.” Paper No. 91‐2086, American Society of Agricultural Engineers, St. Joseph, Mo.
31.
Stein, O. R., and Julien, P. Y. (1993). “A criterion delineating the mode of headcut migration.” J. Hydr. Engrg., ASCE, 119(1), 37–50.
32.
Stein, O. R., Julien, P. Y., and Alonso, C. V. (1993). “Mechanics or jet scour downstream of a headcut.” J. Hydr. Res., 31(6), 723–738.
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Copyright © 1994 American Society of Civil Engineers.
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Received: May 23, 1993
Published online: Sep 1, 1994
Published in print: Sep 1994
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