| River flood routing is an important part of hydrological forecasting,which is used to analyze the propagation law of flood wave in river channels.The results of river flood routing have important practical significance for flood control,disaster reduction and the comprehensive utilization of water resources.The simulation of flood routing in open channels based on the Saint-Venant equations plays a considerable role in the forecast of runoff concentration and river floods.Yet,the traditional Saint-Venant equations do not incorporate infiltration loss of river channels and thus bear uncertainty if applied to scenarios with severe infiltration in arid and semi-arid areas.Therefore,the purpose of this paper is to do some research on numerical simulation of flood movement and river bed deformation in river channels with severe infiltration.First,here a one-dimensional flow-sediment mathematical modelling for open channel flows considering infiltration is established based upon the flow-sediment mathematical modelling and the soil infiltration model,with the soil infiltration described by the Green-Ampt equation.The governing equations are discretized by the finite volume method and numerical fluxes are estimated by the total-variation-diminishing(TVD)version of the slope limiter centered(SLIC)scheme,which can automatically capture shock waves and discontinuities featured by hyperbolic equations.Next,the proposed model is first validated against three experimental test cases:experiment of runoff generation,experiment of flash floods in ephemeral channels and experiment of bore-driven swash on permeable rough slopes.The numerical results show that the results obtained by the proposed mathematical model agree well with the observed datasets of runoff generation process.The flood routing process computed results simulated by the mathematical model proposed is in good agreement with the previous computed results.The simulation results of bore-driven swash on permeable rough slopes are also in good agreement with the measured results.Finally,the model is applied to resolve two observed flash floods in the Zhuozhang River in Shanxi Province,China.The results obtained by the present model agree well with the field observed datasets,compared to those when infiltration is ignored.It shows that the influence of infiltration should be taken into account in numerical simulation of rivers floods with severe infiltration.By comparing the simulation results of the two methods,it can be seen that the peak discharge is smaller,the flood duration is shorter,the flood volume is smaller,and the sediment deposition is more obvious when considering the infiltration of river channels.Sensitivity analyses of the model parameters demonstrate that the discharge hydrographs are sensitive to the Manning roughness,correction coefficient of sediment entrainment fluxes,coefficient of saturation recovery and the parameters in the Green-Ampt equation.The proposed model incorporating infiltration is shown to be essential for the correct prediction of rivers floods with severe infiltration,which dictates the value of the present model in practical applications. |
