An analytical approach to the estimation of optimum river channel dimensions

Document Type : Article


Faculty of Civil, Water and Environmental Engineering, Shahid Beheshti University, Tehran, P.O. Box 16765/1719, Iran.


Extremal hypotheses without bank stability constraint typically over-predict and under-predict channel width in large rivers and natural streams, respectively. In general, results obtained from unconstrained extremal hypotheses are indicative of inappropriate agreement between predicted and observed dimensions of the rivers. One of the important factors in disparity of the data may be lack of appropriate relationships to assess bank vegetation of the rivers. For this reason, a modified analyticalmodel has been developed to reduce the effect of bias by considering bank stability and vegetation. The model takes into account channel shape factor, a wide range of bed load equations in the form excess shear stress and vegetation quantification is able to predict optimal channel geometry dimensions. Finally, developed model was calibrated using the field data of the United Kingdom and Iran. In addition to indicating the effect of bank stability and vegetation on estimation of the geometric characteristics of the channel, obtained results also confirmed the efficiency of the constrained model in comparison to the unconstrained model. This study also provides support for the use of the concepts of maximum sediment transporting capacity and minimum stream power for understanding the operation of alluvial rivers.


Main Subjects

1. Bray, D.I. Regime equations for gravel-bed rivers", In Gravel-bed Rivers: Fluvial Processes, Engineering and Management, R.D. Hey, J.C. Bathurst and C.R. Thorne, Eds., John Wiley and Sons, Chichester, pp. 517- 552 (1982b). 2. ASCE Task Committee on Hydraulics Bank Mechanics and modeling of river width adjustment", I: Processes and Mechanisms, J. Hydraul. Eng. ASCE, 124(9), pp. 881-902 (1998). 3. Leopold, L.B. and Langbein, W.B. The concept of entropy in landscape evolution", U.S. Geol. Survey. Prof. Paper 500-A (1962). 4. Pickup, G. Adjustment of stream channel shape to hydrologic regime". Journal of Hydrology, 30, pp. 365- 373 (1976). 5. Kirkby, M.J. Maximum sediment e_ciency as a criterion for alluvial channels", In River Channel Changes, K.J. Gregory, Ed., Wiley: Chichester, pp. 429-442 (1977). 6. Yang, C.T. Potential energy and stream morphology", Water Resources Research, 7, pp. 311-322 (1971a). 7. Yang, C.T., Song, C.C.S., and Woldenberg, M.J. Hydraulic geometry and minimum rate of energy dissipation", Water Resources Research, 17, pp. 1014- 1018 (1981). 8. Song, C.S.S. and Yang, C.T. Minimum stream power: theory", J. Hydraul. Eng. ASCE, 106(9), pp. 1477- 1488 (1980). 9. Huang, H.Q. and Nanson, G.C. A stability criterion inherent in laws governing alluvial channel ow", Earth Surface Processes and Landforms, 27(9), pp. 929-944 (2002). 10. Eaton, B.C. and Millar, R.G. Optimal alluvial channel width under a bank stability constraint", Geomorphology, 62, pp. 35-45 (2004). 11. Parker, G. Surface-based bedload transport relation for gravel rivers", Journal of Hydraulic Research, 28, pp. 417-436 (1990a). 12. Manning, R. On the ow of water in open channels and pipes", Transactions of the Institution of Civil Engineers of Ireland, 20, pp. 161-207 (1891). 13. Huang, H.Q., Deng, C., Nanson, G.C., Fan, B., Liu, X., Liu, T., and Ma, Y. A test of equilibrium theory and a demonstration of its practical application for predicting the morphodynamics of the Yangtze River", Earth Surface Processes and Landforms, 39, pp. 669- 675 (2014). 14. Knighton, A.D., Fluvial Forms and Processes, Edward Arnold, London (1998). 15. Lane, E.W. The design of stable channels", Trans, ASCE, 120(2776), pp. 1234-1279 (1955b). 16. Millar, R.G. and Quick, M.C. Stable width and depth of gravel-bed rivers with cohesive banks", J. Hydr. Div. ASCE, 124(10), pp. 1005-1013 (1993). 17. Parker, G. Hydraulic geometry of active gravel rivers", Journal of the Hydraulics Division, ASCE, 105, pp. 1185-1201 (1979). 18. Lacey, G. Flow in alluvial channels with sandy mobile beds", Proceedings of the Institute of Civil Engineers, London, 9; and Discussion, 11, pp. 145-164 (1958). 19. Brownlie, W.R. Flow depth in sand-bed channels", Journal of Hydraulic Engineering, ASCE, 109, pp. 959-990 (1983). 20. Einstein, H.A. The bed-load function for sediment transportation in open channel ows", U.S. Department of Agriculture, Soil Conservation Service, Technical Bulletin, No. 1026 (1950). 21. Yang, C.T., Sediment Transport: Theory and Practice, McGraw-Hill (1996). 22. Meyer-Peter, E. and Muller, R. Formulas for bed load transport", In Proceedings of the 3rd Meeting of IAHR, Stockholm, pp. 39-46 (1948). 23. Du Boys, P. The Rhone and streams with movable beds", Annales des Ponts et Chaussees, Section 5, 18, pp. 141-195 (1879). 24. Parker, G. Hydraulic geometry of active gravel rivers", Journal of the Hydraulics Division, ASCE, 105, pp. 1185-1201 (1979). 25. Flintham, T.P. and Carling, P.A. The prediction of mean bed and wall boundary shear in uniform and compositely rough channels", In River Regime, John Wiley and Sons, White, W.P. Ed., pp. 267- 287 (1988). 26. Knight, D.W. Boundary shear in smooth and rough channel", Journal of the Hydraulics Division, ASCE, 107(7), pp. 839-851 (1981). 27. Knight, D.W., Demetriou, J.D., and Hamed, M.E. Boundary shear in smooth rectangular channels", Journal of the Hydraulic Engineering, ASCE, 101(4), pp. 405-422 (1984). 28. Henderson, F.M., Open Channel Flow, Macmillan Pub. Co., New York, p. 522 (1966). 29. Hey, R.D. and Thorne, C.R. Stable channels with mobile gravel beds", Journal of the Hydraulic Engineering, ASCE, 112(8), pp. 671- 689 (1986). 30. Darby, S.E. Re_ned hydraulic geometry data for British Gravel-Bed Rivers", Journal of Hydraulic Engineering, 131(1), pp. 60-64 (2005). M. Mahmoudi et al./Scientia Iranica, Transactions A: Civil Engineering 26 (2019) 1169{1181 1181 31. Andrews, E.D. Bed material entrainment and the hydraulic geometry of gravel bed rivers in Colorado", Bulletin of the Geological Society of America, 95, pp. 371-378 (1984). 32. Mahmoodi, M., Tabatabai, M.R.M., and Mousavi Nadoushani, S. Role of extermal hypotheses in rivers hydraulic geometry relationships derivation", Sharif Civil Engineering Journal, 33.2(2.1), pp. 49-60 (2017). 33. Huang, H.Q. Reformulation of the bed load equation of Meyer-Peter and Muller in light of the linearity theory for alluvial channel ow", Water Resources Research, 46(9), pp. 1-11 (2010).