Experimental investigation of the effect of height and crest slope of bendway weirs on flow pattern in a 90 degree bend

Document Type : Research Paper

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Abstract

Bendway weirs are an important tool in multi-purpose erosion control and are implemented to control erosion, restore streams, and improve habitat. These structures create a hydraulic effect that reduces erosion on the outer bank of a bend by reducing flow velocities near the outer bank and reduce the concentration of currents on the outer bank creating better current alignment through the bend. In this research the effect of bendway weirs on flow pattern in a 90 degree mild bend has been investigated experimentally. Experimental tests were conducted in a curved flume with relative radius of 3.3 (R/b=3.3) and with 24 m length and 0.92 m width at three flow discharges (55, 66 and 77 l/s). Series of bendway weirs (7 weirs) were constructed at the outer bank side of the bend at three weir height ratios (0.3, 0.5 and 0.7 of water depth), three crest slopes (0%, 5% and 10%), while inclination angle (60°) and distance between weirs (equal to 3 times of weir length) were kept fixed. Velocity measurements around weirs were performed in two levels, near the bed and close to the water surface. The research results showed that the velocity magnitude decreased in the outer bank by more than 70% and increased in the inner bank side by more than 50%, after bendway weirs installation. Weirs with height of 0.5y and with crest slope of 5% were more effective in deceleration of velocity at the outer bank side. On the other hand, weirs with height of 0.7y and also weirs with flat crest slope were more efficient in velocity magnitude increment at the inner bank side, especially in the head of the bend. Generally, the present research results revealed that the bendway weirs with crest slope of 5% and with height of 0.5y are the most suitable design options in such bends. 

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References

Acharya, K. and Gautam, M. (2012). Evaluation of bendway weir bank stabilization techniques for stream restoration. International Journal of River Basin Management, 10(2), 171- 176.
Brown, S.A. (1985). Design of spur-type streambank stabilization structures. FHWA, Report No. FHWA/RD-84.101, Final Report, 98 p.
Darrow, J. (2004). Effects of bendway weir characteristics on resulting flow conditions. M.S. Thesis, Colorado State University, Fort Collins, CO.
Fischenich, J. C. and Allen, H. A. (2000). Stream management. ERDC/EL SR-W-00-1, U.S. Army Engineer Research and Development Center, Vicksburg, MS.
FHWA, (1997). Bridge scour and stream instability countermeasures (SI). Federal Highway Administration, Hydraulic Engineering Circular Number 23, FHWA HI-97-030.
Jarrahzade, F. and Shafai Bejestan, M. (2011). Comparison of maximum scour depth in Bank line and nose of submerged weirs in a sharp bend. Scientific Research and Essays, 6(5), 1071-1076.
Jarrahzade, F. and Shafai Bejestan, M. (2013). Experimental investigation of thalweg under effect of submerged weirs in a 90 degree sharp bend. Watershed Management Research (Pajouhesh & Sazandegi), 97, 17-29. (In Farsi)
Julien, P. Y. and Duncan, J. R. (2003). Optimal design criteria of bendway weirs from numerical simulation and physical model studies. Technical paper, Colorado State University, Civil Engineering.
Hemmati, M. (2012). Experimental investigation on the effect of angle, length and crest slope of bendway weirs on sediment process and flow pattern in meander river. Ph. D. dissertation, University of Shahid Chamran, Ahvaz, Iran. (In Farsi)
Hemmati, M., Ghomeshi, M.,  Kashefipour, S. M., Shafai-Bejestan, M. and Lanzoni, S. (2012).  Experimental investigation of the effects of angle and length of bendway weirs on scouring and sedimentation in a meander river.  Journal of American Science, 8(9), 912-917.
Hemmati, M., Ghomeshi, M. and Kashefipour, S. M. (2013a). Experimental investigation on the effect of angle of bendway weirs on erosion and sedimentation pattern in meander river. Journal of Iranian Water Resource Research,  8(3), 66-73. (In Farsi)
Hemmati, M., Kashefipour, S. M. and Ghomeshi, M. (2013b). Experimental Study on the Effects of Bendway Weirs Length on Sediment Process and Water Level in a Meandering River. Journal of Civil and Environmental Engineering, 43(1), 51-60. (In Farsi)
Hemmati, M., Ghomeshi, M., Ahmadi, H. and Lanzoni, S. (2015). Scour depth around flat and sloped crest bendway weirs: a laboratory study. International Journal of River Basin Management. DOI: 10.1080/ 15715124. . 1085870.
Heintz, M.L. (2002). Investigation of bendway weir spacing. M.S. Thesis, Colorado State University, Fort Collins, CO.
Kinzli, K. (2005). Effects of bendway weir characteristics on resulting eddy and channel flow conditions. M.S. Thesis, Colorado State University, Department of Civil Engineering, Fort Collins, CO.
Lagasse, P. F., Clopper, P. E., Pagan-Ortiz, J. E., Zeverbergen, L. W., Arneson, L. A., Schall, J. D., and Girard, L. G. (2009). Bridge scour and stream stability countermeasures. 3rd ed., vols. 1 and 2, 64 HEC-23, FHWA-NHI-09-111, Federal Highway Administration, U. S. Dept. of Transportation, Washington, D. C.
Lagrone, D.L., and Remus II, J.I. (1998). Nontraditional erosion control projects constructed on the Missouri river. In: Proceedings of the 1998 International Water Resources Engineering Conference, Part 1 of 2, 3-7 Aug., Memphis TN, PP. 399-404.
Lyn, D. A. and Cunningham, R. (2011).  A laboratory study of bendway weirs as a bank erosion countermeasure. Joint Transportation Research Program. Paper 1107. http://docs.lib.purdue.edu/jtrp/1107.
Mashkooriniya, H., Jarrahzade, F., Ramesh, S. and Shafai-Bejestan, M. (2010). Experimental investigation of the effect of bendway weirs length on outer bank erosion in a 90 degree sharp bend. In: Proceedings of 9th Iranian hydraulic conference, Tarbiat Modares University, 9-11 November, Tehran, Iran. (In Farsi)
Maza Alvarez, J. A. (1989). Design of groynes and spur dikes. In: Proceedings of the 1989 National Conference on Hydraulic Engineering, 14-18 Aug., New Orleans, Louisiana, USA, PP. 296-301.
Ramesh, S., Jarrahzade, F., Mashkooriniya, H. and Shafai-Bejestan, M. (2010). Experimental investigation of the effect of distance between bendway weirs on bed scour in a 90 degree sharp bend. In: Proceedings of 9th Iranian hydraulic conference, 9-11 Nov., Tarbiat Modares University, Tehran, Iran. (In Farsi)
Rhoads, B. L. (2003). Protocols for geomorphic characterization of meander bends in Illinois. Dept. of Geography, Univ. Illinois Urbana-Champaign.
Shields, F.D. Jr., Knight, S.S., and Cooper, C.M. (1998). Addition of spurs to stone toe protection for warm water fish habitat. Journal of the AmericanWater Resources Association, 34, 1427–1436.
Iranian Journal of Soil and Water Research
Volume 47, Issue 3
November 2016
Pages 505-516

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