Effect of Stilling Basin Geometry on Clear Water Scour Morphology Downstream of a Block Ramp
Publication: Journal of Irrigation and Drainage Engineering
Volume 137, Issue 9
Abstract
The scour mechanism downstream of a block ramp in clear water conditions is quite a complex phenomenon that depends on several parameters. Majors role are played by ramp configuration, hydraulic conditions (downstream tailwater level and discharge), material granulometry, and stilling basin geometry. Previous studies analyzed both the scour phenomenon and the effects of all the parameters involved except the last one (i.e., the case in which the ramp has the same width as the downstream stilling basin) and the case of symmetrically expanding stilling basins. This last basin configuration represents an optimal equilibrium between the necessity to dissipate energy and to create a natural pool for the biological species, thus it has a prominent ecological value. The present paper aims to assess the effect of both the width and length of the downstream stilling basin on scour features and flow pattern in clear water conditions. Different scour morphology types are distinguished and classified according to hydraulic and geometric conditions. Simple novel relationships are proposed to evaluate the scour depth and length and the maximum water level in the stilling basin. The results are valid for unsubmerged block ramps.
Get full access to this article
View all available purchase options and get full access to this article.
References
Aderibigbe, O., and Rajaratnam, N. (1998). “Effect of sediment gradation on erosion by plane turbulent wall jets.” J. Hydraul. Res., 124(10), 1034–1042.
Bormann, E., and Julien, P. Y. (1991). “Scour downstream of grade control structures.” J. Hydraul. Eng., 117(5), 579–594.
Bremen, R., and Hager, W. H. (1993). “T-jump in abrupt expanding channel.” J. Hydraul. Res., 31(1), 61–78.
Breusers, H. N. C. (1966). “Conformity and time scale in two-dimensional local scour.” Proc., Symp. on Model and Prototype Conformity, Hydraulic Research Laboratory, Poona, India, 1–8.
Breusers, H. N. C., and Raudkivi, A. J. (1991). Scouring. IAHR hydraulic structures manual series, Vol. 2, Balkema, Rotterdam, Netherlands.
D’Agostino, V., and Ferro, V. (2004). “Scour on alluvial bed downstream of grade-control structures.” J. Hydraul. Eng., 130(1), 1–14.
Dey, S., and Raikar, V. (2005). “Scour in long contractions.” J. Hydraul. Eng., 131(12), 1036–1049.
Hager, W. H. (1992). Energy dissipators and hydraulic jump, Kluwer, Dordrecht, Netherlands.
Herbrand, K. (1973). “The spatial hydraulic jump.” J. Hydraul. Res., 11(3), 205–218.
Hoffmans, G. J. C. M. (1998). “Jet scour in equilibrium phase.” J. Hydraul. Eng., 124(4), 430–437.
Hoffmans, G. J. C. M. (2009). “Closure problem to jet scour.” J. Hydraul. Res., 47(1), 100–109.
Hoffmans, G. J. C. M., and Pilarczyk, K. W. (1995). “Local scour downstream of hydraulic structures.” J. Hydraul. Eng., 121(4), 326–340.
Hoffmans, G. J. C. M., and Verheij, H. J. (1997). Scour manual, Balkema, Rotterdam, Netherlands.
Lee, S. O., and Sturm, T. W. (2009). “Effect of sediment size scaling on physical modeling of bridge pier scour.” J. Hydraul. Eng., 135(10), 793–802.
Ohtsu, I., Yasuda, Y., and Ishikawa, M. (1999). “Submerged hydraulic jumps below abrupt expansions.” J. Hydraul. Eng., 125(5), 492–499.
Oliveto, G., and Comuniello, V. (2009). “Local scour downstream of positive-step stilling basins.” J. Hydraul. Eng., 135(10), 846–851.
Pagliara, S. (2007). “Influence of sediment gradation on scour downstream of block ramps.” J. Hydraul. Eng., 133(11), 1241–1248.
Pagliara, S., and Palermo, M. (2008a). “Scour control downstream of block ramps.” J. Hydraul. Eng., 134(9), 1376–1382.
Pagliara, S., and Palermo, M. (2008b). “Scour control and surface sediment distribution downstream of block ramps.” J. Hydraul. Res., 46(3), 334–343.
Pagliara, S., and Palermo, M. (2010). “Influence of tailwater depth and pile position on scour downstream of block ramps.” J. Irrig. Drain Eng., 136(2), 120–130.
Pagliara, S., Palermo, M., and Carnicina, I. (2009). “Scour and hydraulic jump downstream of block ramps in expanding stilling basins.” J. Hydraul. Res., 47(4), 503–511.
Rajaratnam, N., and Subramanya, K. (1968). “Hydraulic jumps below abrupt symmetrical expansions.” J. Hydraul. Div., 94(2), 481–503.
Tregnaghi, M., Marion, A., and Coleman, S. (2009). “Scouring at bed sills as a response to flash floods.” J. Hydraul. Eng., 135(6), 466–475.
Veronese, A. (1937). “Erosioni di fondo a valle di uno scarico.” Annali Lavori Pubblici, 75(9), 717–726 (in Italian).
Information & Authors
Information
Published In
Copyright
© 2011 American Society of Civil Engineers.
History
Received: Jan 4, 2010
Accepted: Dec 9, 2010
Published online: Dec 11, 2010
Published in print: Sep 1, 2011
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.