» Research Note « Incipient Motion of Sediment in a U-shape Rigid Boundary Channel

Document Type : Technical Note



Sediment transport is one of the essential aspects in hydraulic design of rigid boundary channels. Urban drainage systems, irrigation canals and other water transport systems are examples of rigid boundary channels. Channel cross-section shape is one of the effective parameters in sediment transport in rigid boundary channels. In this experimental study, incipient motion of sediment in a U-shape rigid boundary channel is investigated. Experimental data are analyzed based on critical shear stress and critical velocity approaches and new relationships for computing required shear stress and velocity for initiation of sediment motion are presented. The developed relationships are compared with corresponding models available in the literature for loose and rigid boundary channels. It is found that in rigid boundary channels, sediment particles require lower incipient shear stress and velocity in comparison with loose boundary channels. Comparison of incipient motion relationships based on critical velocity approach in rigid boundary channels indicates that among U-shape, circular, rectangular and rectangular with V-bottom cross-section channels, higher incipient motion velocity is required for U-shape channel. 


صفری، م. ج. ص.؛ محمدی، م. ع. و گیلانی­زاده­دیزج، گ.؛ (1392). "بررسی آستانه نهشته شدن و حرکت دانه‌های رسوبی در مجاری باز جدارصلب، "مجله دانش آب و خاک، دوره 23، شماره 3، ص.ص. 13-24.
Bong, C.H.J., Lau, T.L. and Ab Ghani, A. (2013). “Verification of equations for incipient motion studies for a rigid rectangular channel.” Water Sci. Technol. 67(2): 395-403.
Butler, D., May, R. W. P. and Ackers, J. C. (1996). “Sediment transport in sewers. Pt. 2: design.” P. I. Civil Eng-Mar. En. 118(2): 113-120.
Butler, D. and Davies, J., (2004). Urban drainage. CRC Press, Boca Raton.
Dey, S. (1999). “Sediment threshold.” Appl. Math. Model. 23(5): 399-417.
Dey, S. (2003). “Threshold of sediment motion on combined transverse and longitudinal sloping beds.” J. Hydraul. Res. 41(4), 405-415.
Dey, S. and Papanicolaou, A. (2008). “Sediment threshold under stream flow: A state-of-the-art review.” KSCE J. Civ. Eng. 12(1): 45-60.
El-Zaemey, A. K. S. (1991). “Sediment transport over deposited beds in sewers.” PhD Thesis, University of Newcastle upon Tyne.
Engelund, F. A. (1964). “Flow resistance and hydraulic radius.” ISVA, Technical Univ. of Denmark. Basic Research Progress Rep. No. 6.
Ippen, A. T. and Verma, R. P. (1953). The motion of discrete particles along the bed of a turbulent stream. Proceedings of Minnesota International Convention, Minneapolise, Minn.
Kramer, H. (1935). “Sand mixtures and sand movement in fluvial levels.” Trans. ASCE, 100, 798-838.
Knight, D. W., Demetriou, J. D. and Hamed, M. E. (1984). “Boundary shear in smooth rectangular channels.” J. Hydraul. Eng. 110(4), 405–422.
Lavelle, J. W. and Mofjeld, H. O. (1987). “Do critical stresses for incipient motion and erosion really exist?” J. Hydraul. Eng. 113(3): 370-385.
Mohammadi, M. (2005). “The initiation of sediment motion in fixed bed channels.” Iran. J. Sci. Technol. B. 29(B3): 365-372.
Novak, P. and Nalluri, C. (1975). “Sediment transport in smooth fixed bed channels.” J. Hydraul. Div. ASCE 101(HY9): 1139-1154.
Novak, P. and Nalluri, C. (1984). “Incipient motion of sediment particles over fixed beds.” J. Hydraul. Res. 22(3): 181-197.
Omid, M. H., Narayanan, R. and Nalluri, C. (2002). “Erosion of a sediment deposit from a rigid rectangular channel by clear water.” Proc. Inst. Civ. Eng., Waters Maritime Engineering, 154(1): 63-73.
Ota, J. J. and Perrusquia, G. S. (2013). “Particle velocity and sediment transport at the limit of deposition in sewers.” Water Sci. Technol. 67(5): 959-967.
Paphitis, D. (2001). “Sediment movement under unidirectional flows: an assessment of empirical threshold curves.” Coast. Eng. 43(3): 227-245.
Pilotti, M., Menduni, G. and Castelli, E. (1997). “Monitoring the inception of sediment transport by image processing techniques.” Exp. Fluids. 23(3): 202-208.
Rouse, H. (1965). “Critical analysis of open-channel resistance.” J. Hydr. Eng. Div., ASCE, 91 (4), 1–23.
Safari, M. J. S., Mohammadi, M. and Manafpour, M. (2011). “Incipient motion and deposition of sediment in rigid boundary channels.” Proceedings 15th International Conference on Transport &
Sedimentation of Solid Particles, 6-9 September, Wroclaw, Poland, 63-75.
Safari, M. J. S., Mohammadi, M. and Gilanizadehdizaj, G. (2014). “On the effect of cross sectional shape on incipient motion and deposition of sediments in fixed bed channels.”J. Hydrol. Hydromech. 62(1): 75-81.
Safari, M. J. S., Aksoy, H. and Mohammadi, M. (2015). “Incipient deposition of sediment in rigid boundary open channels.” Environ. Fluid Mech. 15 (5): 1053-1068.
Safari, M. J. S., Aksoy, H. and Mohammadi, M. (2016). “Artificial neural network and regression models for flow velocity at sediment incipient deposition.” J Hydrol. 541, 1420-1429.
Safari, M. J. S., Aksoy, H., Unal, N. E. and Mohammadi, M. (2017). “Non-deposition self-cleansing design criteria for drainage systems.” J. Hydro-environ. Res. 14: 76-84.
Shields, A. (1936). “Application of similarity principles and turbulence research to bed-load movement.” Preussiischen Research Institute of Hydraulic Engineering, Berlin, Germany, Issue 26.
Yen, B. C. (2002). “Open channel flow resistance.” J. Hydraul. Eng. 128 (1), 20–39.