Optimization of channel cross-sections based on water conveyance efficiency and anti-siltation performance

Sediment deposition in irrigation canals supplied by sediment-laden water can reduce conveyance capacity. To address this problem, this study develops a multi-objective optimization method for parabolic-bottomed trapezoidal composite channels that balances water conveyance efficiency and anti-siltation performance. The flow area A and the velocity non-uniformity coefficient Ψ are used as objective functions. The parabolic-section depth h 1 is taken as the decision variable, and the trapezoidal-section depth h 2 is solved iteratively from Manning’s equation using the bisection method, reducing the original multivariable problem to a one-dimensional continuous optimization problem. The weighted sum method combined with golden section search is then used to generate the complete Pareto front. Spacing is used as the convergence metric, and the knee-point method is used to select the recommended compromise scheme. The case study shows that, under the same roughness, bed slope, side-slope coefficient ( n = 0.015, i = 1/6 000, m = 0.577), and discharge ( Q = 12 m 3 /s), the recommended compromise section increases the flow area and wetted perimeter by only 1.06% and 2.64%, respectively, compared with the hydraulically optimal section. At the same time, it reduces velocity non-uniformity by 49.74%. The section therefore improves velocity uniformity and lowers sedimentation risk with little loss of conveyance efficiency. Because the optimization method matches the one-dimensional continuous structure of the problem, it is computationally efficient and has controllable accuracy. It provides technical support for channel cross-section design in irrigation districts supplied by sediment-rich water sources.