Study On The Effect Of Seasonal Channel Leakage On Flood Evolution

Flood disaster is one of the most frequent and most serious natural disasters in China and even the world.The mathematical model of flood control is the key component and important analysis method of flood control system.At present,the influence of river seepage loss is less considered in the study of flood routing model.Due to the northern arid or semi-arid regions of the rivers are seasonal rivers.The floods in the pre-flood season are often in the dry state,and in the flood season have the characteristics of skyrocketing and flooding.The leakage of the rivers in the flood period is relatively large,and the loss of water along the river is basically the loss of the river channel.The river channel leakage directly affects the flood discharge with the flood process.Therefore,it is the key to study the seasonal seepage law and its influence on flood evolution.The research results will be of great scientific significance and application value for river flood forecasting,flood control and disaster reduction and comprehensive utilization of water resources in arid or semi arid areas.First of all,based on the data of the three vertical river infiltration tests on the upper,middle and lower reaches of the Dagu river basin in seasonal rivers,three infiltration models of Horton model?Kostiakov model and Philip model are fitted by Matlab software,the infiltration parameters are obtained,and the suitability of the infiltration model is evaluated.Secondly,based on the basic principle of fluid mechanics,a mathematical model of flood routing considering the channel seepage is established by analyzing the basic equations of river channel flood motion.The numerical discrete solution is also given and the definite solution condition is given.Thirdly,using FORTRAN language to develop a set of computing equations for flood routing equations with seepage term.Finally,using the example data to verify the reliability and the finite value of the leakage model.Through the above experimental data fitting analysis,model construction and program research and development and verification,the following conclusions are obtained:(1)the porosity,particle size and dry bulk density of sand samples decreased asthe upper,middle and lower reaches,and the steady infiltration rate decreased,which was about 0.0066cm/s,0.0041cm/s,0.0025cm/s;The fitting results of the curves of the three representative river bed tests show that,the Isqcurvefit function in Matlab software is applied to obtain infiltration parameters of infiltration model;Horton model and Kostiakov model have better fitting effect on the infiltration process of upper,middle and lower riverbed,and the fitting effect of Philip model is poor.Among them,the fitting coefficient of Horton model is the highest,and the model parameters have physical meaning,which is suitable for describing the seasonal riverbed infiltration process.(2)Based on the principle of hydrodynamics,the mathematical model of flood evolution considering the flood leakage is established from the basic equations of river flood movement.The Preissmann four-point eccentric implicit scheme is introduced in detail.The numerical method is used to solve the computational process,and the initial conditions and the internal and external boundary conditions are discussed respectively.The numerical solution and the method of boundary are effective from the whole results.(3)Based on the study of the vertical leakage test in the field and the process of the discrete solution of the flooding equation,a FORTRAN language and the compiler are used to develop a calculation program considering the flooding evolution equation.From the operation results point of view,running faster,the output of a higher degree of credibility.(4)The Dagu river the actual data verification results show that the coupling results of the coupled flooding model are in good agreement with the measured data,which indicates that the selection of the relevant parameters of the coupling model is basically in line with the actual situation.It is reasonable and effective to apply the model system to simulate the seasonal evolution of seasonal river flooding by coupling the channel leakage loss into the Saint-Venant equations.