SIMULATING CHANNEL BIFURCATION FLOWS WITH WEIRS FOR FLOOD RISK REDUCTION

K.J. NG, C.Y. TAN, A. SELVARAJOO, M.R.M. HANIFFAH, E.H. KASIMAN, S.H. LAI, D. YUAN, F.Y. TEO

Abstract


Weir is widely used for controlling the flow discharges and water levels of a bifurcated river for flood risk reduction. The effects of weir on the bifurcation flow properties and hydrodynamic processes were not systematically studied by previous research, some of these have limitations and only showed that the discharge ratios were varied by the changes of weir height. Thus, there is a need to further explore on the effect of overall weir geometry and weir location on flow properties. In this study, an one-dimensional (1D) numerical model of Hydrological Engineering Centre - River Analysis System (HEC-RAS) has been applied to simulate an idealised channel with the applications of a variety of weir geometries at various locations. The model has been set to simulate a U-shaped main channel with two identical U-shaped bifurcated channels. Simulations have been undertaken for the weirs with cross-sectional shapes of rectangular, Cipolletti (trapezoidal), and V-notch (triangular). Comparisons of velocity profiles and water elevations with different Froude numbers have been undertaken. The results present the relationships of the outlet discharge ratio and velocity ratio to weir height, crest length, and crest angle ratio with different cross-sectional shapes and locations of weir. The findings show that flood risks could be potentially reduced by understanding the flow behaviours of channel bifurcation with presence of weirs as controlled structure.


Keywords


Bifurcation channel, flood risk, HEC-RAS, numerical model, Froude number

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References


BERTOLDI W. (2004). River Bifurcations. PhD Thesis, s.l.: University of Trento, Italy, pp. 8

BIJANKHAN M., FERRO V. (2017). Dimensional Analysis and Stage Discharge Relationship for Weirs: A Review. Journal of Agricultural Engineering, Vol. 48, Issue 1, pp. 1-11.

BOLLA PITTALUGA M., REPETTO R., TUBINO M. (2003). Channel bifurcation in braided rivers: Equilibrium configurations and stability. Water Resources Research, Vol. 39, Issue 3, pp. 1-13.

BRUNNER G. (2010). HEC-RAS version 4.1, River Analysis System Hydraulic Reference Manual. Davis, CA: Hydrologic Engineering Center.

CADDIS B., NIIELSEN C., HONG W., TAHIR P.A., TEO F.Y. (2012). Guidelines for floodplain development - A Malaysian case study. International Journal of River Basin Management. Vol. 10, Issue 2, pp. 161-170.

CHEAH R., BILLA L., CHAN A., TEO F.Y., PRADHAN B., ALAMRI A.M. (2019). Geospatial modelling of watershed peak flood discharge in Selangor, Malaysia. Water, Vol. 11, Issue 12, pp. 2490.

HAGER W.H., SCHWALT M. (1994). Broad-crested weir. Journal of Irrigation and Drainage Engineering, Vol. 120, Issue 1, p. 13.

HARDY R.J., LANE S.N., YU D. (2011). Flow Structures at an idealized bifurcaion: A numerical experiment. earth surface processes and landforms, Vol. 36, Issue 15, pp. 2083-2096.

HOEY T. (1992). Temporal variations in bedload transport rates and sediment storage in gravel-bed rivers. Progress in Physical Geography: Earth and Environment, Vol. 16, Issue 3, pp. 319-338.

HYDROLOGIC ENGINERING CENTER (2016). HEC-RAS River Analayis System User Manual. 5.0 ed. s.l.:s.n.

JOSEPH N. (1978). Hydraulics of Bridge Waterways, Hydraulic Design Series No. 1, Washington D.C.: Federal Highway Adminstration, U.S. Department of Transportation.

KLEINHANS M., FERGUSON R. I., LANE S. N., HARDY R.J. (2013). Splitting rivers at their seams: bifurcations and avulsion. Earth Surface Process and Landforms, Vol. 38, Issue 1, pp. 47-61.

KULKARNI K.H., HINGE G.A. (2021). Performance enhancement in discharge measurement by compound broad crested weir with additive manufacturing, Issue 48, pp 169-188.

KUMAR S., AHMAD Z., MANSOOR T., HIMANSHU S.K. (2012). Discharge Characteristics of Sharp Crested Weir of Curved Plan-form. Research Journal of Engineering Sciences, Vol. 1, Issue 4, pp. 16-20.

MIORI S., HARDY R.J., LANE S.N. (2012). Topographic Forcing of Flow partition and Flow Strcutures at River Bifurcation. Earth Surface Processes and Landforms, Vol. 37, Issue 6, pp. 666-679.

RAHMAN R.A. (2019). Anual Report 2019, s.l.: Jabatan Meteorologi Malaysia.

SAYED, T. (2019). An Experimental Study of Branching Flow in Open Channels. Limnol Revision, Vol. 19, Issue 2, pp. 93-101.

SCHIELEN R.M.J., BLOM A. (2018). A reduced complexity model of gravel sand river bifurcation: Equilibrium states and their stability. Advances in Water Resources, Vol. 121, pp. 9-21.

SHAH S.M.H., MUSTAFFA Z., TEO F.Y., IMAN M.A.H., YUSOF K.W., AL-QADAMI E.H.H. (2020). A review of the flood hazard and risk management in the South Asian region, particularly Pakistan. Scientific African, Vol. 10.

THOMAS R.E, PARSON D.R., SANDBACH S.D., KEEVIL G.M., MARRA W.A., HARDY R.J., BEST J.L., LANE S.N., ROSS J.A.. (2011). An experiment study of discharge partitioning and flow structure at symmetrical bifurcations. Earth Surface Processes and Landforms, Vol. 36, pp. 2069-2082.

UNITED STATES DEPARTMENT OF AGRICULTURE (2001). Water Measurement Manual. Washington: s.n.

WANG, Z. B., VRIES, M. D., FOKKINK, R. J., LANGERAK, A. (1995). Stability of river bifurcations in 1D morphodynamic models. Journal of Hydraulic Research, Vol. 33, Issue 6, pp. 739-750.

ZANICHELLI, G., CARONI, E. & FIOROTTO, V. (2004). River Bifurcation Analysis by Physical and Numerical Modeling. Journal of Hydraulic Engineering, Vol. 130, Issue 3, pp. 237-242.

ZAWAWI, I. S. M. ET AL. (2019). Mathematical Modeling for Flood Mitigation: Effect of bifurcatioin Angles in River Flowrates. Civil Engineering and Architecture, Vol. 7, Issue 6A, pp. 50-57.


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