During flooding, the suspended sediment transport usually experiences a wide-range of dilute to hyper-concentrated suspended sediment transport depending on the local flow and ground conditions. This paper assesses the distribution of sediment for a variety of hyper-concentrated and dilute flows. Due to the differences between hyper-concentrated and dilute flows, a linear-power coupled model is proposed to integrate these considerations. A parameterised method combining the sediment size, Rouse number, mean concentration, and flow depth parameters has been used for modelling the sediment profile. The accuracy of the proposed model has been verified against the reported laboratory measurements and comparison with other published analytical methods. The proposed method has been shown to effectively compute the concentration profile for a wide range of suspended sediment conditions from hyper-concentrated to dilute flows. Detailed comparisons reveal that the proposed model calculates the dilute profile with good correspondence to the measured data and other modelling results from literature. For the hyper-concentrated profile, a clear division of lower (bed-load) to upper layer (suspended-load) transport can be observed in the measured data. Using the proposed model, the transitional point from this lower to upper layer transport can be calculated precisely.

Scour is the main cause of failure for spur dike. The accurate prediction of scour around spur dike is essential to design a spur dike. The present study focuses on the maximum scour depth in equilibrium condition and parameters, which influence it in a sand–gravel mixture bed. Outcomes of the present experimental study showed that the non-dimensional maximum equilibrium scour depth increases with critical velocity ratio (U/Uca), water depth-armour particle ratio (h/da), Froude number for sediment mixture (Frsm), water depth-spur dike length ratio (h/l), and decreases with increase in armour particle-spur dike length ratio (da/l). The maximum scour depth is proportional to dimensionless parameters of U/Uca, h/da, Frsm, h/l, but the scour depth is inverse proportional to da/l. Scour around spur dike in a sand–gravel mixture is mainly influenced by the property of the sediment mixture. The scour increases with decrease in non-uniformity of the sediment mixture. A non-linear empirical equation is proposed to estimate the maximum scour depth at an upstream nose of rectangular spur dike with a maximum error of 15%. The sensitivity analysis indicates that the maximum non-dimensional equilibrium scour depth depends on Frsm, followed by the secondary sensible parameters da/l, h/l, and h/da.

This paper deals with generalized scour estimation to investigate maximum scour depth at equilibrium scour condition using experimental data obtained from experiments conducted by the authors along with data of previous researchers. 300 experimental data were used to derive the generalized clear water scour relationship around circular bridge pier by using GA (Genetic Algorithm) and MLR (Multiple Linear Regression) technique. GA based maximum scour depth relationship showed more precise results than MLR. In addition, present GA and MLR relationships were compared with some equations developed by earlier researchers. Graphically and statistically, it was observed that the GA and MLR relationships provide better agreement with experimental data as compared to earlier relationships. Present study highlights that the GA approach could be effectively used for estimation of maximum scour depth prediction around bridge pier.

The CCHE2D model, a depth-averaged, two-dimensional, unsteady-flow model, developed at the National Center for Computational Hydroscience and Engineering, has been verified for channel confluence and bifurcation applications. The computational efficiency for natural-river applications was the governing factor in the selection of the mixing-length model for turbulence closure. In the absence of field data, flume data for channel bifurcation and confluence collected in the laboratory were used to verify the simulated results. The simulated depth-averaged velocity and water surface profiles in the main and branch channels of a bifurcating channel compare well with the experimental data. In addition, the ratio of the discharge in the branch channel to the upstream discharge in the main channel, which is the most commonly sought value in the case of bifurcation, is in good agreement with the experimental data. The width and length of the recirculation zone in the branch channel are satisfactorily predicted by the model. The simulation results for the water surface profile near a channel confluence agree well with the measured data.

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