Nonlinear Analysis In Water Level Process Of Erodible-bed Channel

There are a lot of factors that work on the water level of erodible-bed channel together, each of them varies no role, but is correlative. In the adjacent years or the adjacent flood peak of a floodwater, the conditions of the factors that influence water level are always very different. So, There is a nonlinear relation between water level and the factors influencing it. Substantively, the complexity that water level is influenced by all of the factors and their strong nonlinear random disturbance. For controlling the variance of model error to reduce the errors, we need to separate the market random disturbances from the random error.For the characteristic of the river course and the conditions of water-sand are different in adjacent year. It follows the thinking that respectively build approximate model by the data of water-sand in different years, then finds out the forecasting model by recurring the approximate parameter array of each year.By using the yearly data of water-sand that is gotten by a couple of adjacent hydrologic station in yellow river lower reaches, this paper makes use of kinds of math methods looking for the nonlinear disturbance among all of the factors, and introduces the thinking of analysis, logic, conclusion, inference, and random to nonlinear hydrologic forecasting. It realizes the valid approximation of the water level process in erodible-bed channel.Mainly by mathematics analysis, this paper explains that why just selects these parts in the model, and if these parts are added, reduced or changed, why the precision will be dropped. All of the conclusions are gotten from the strict analysis of mathematics, not gotten by comparing with the data obtained from the experiential or trial way.At first, this paper analyzes the factors of water-sand influencing water level of yellow river and the feasibility just using the factors of water-sand to study water level, and collects the corresponding data; Secondly, because there are strong nonlinear relation in the corresponding data, by meticulous theory analysis, this paper integrates basic nonlinear analysis method, theory of random analysis, method of least squares and so on. It puts forward a method which can get the high accuracy simulation of the data, perfects the multi-factor analysis of variable (over three factors) of the statistic; Thirdly, it applies the method to the approximation of corresponding water level process which belong to the capacity of sand of middle-high and middle-low, and get the high-accuracy simulation about the typical nonlinear relation; at last, this paper definitudes the main influence mode that the capacity of sand. It mainly unite with other factors to work on the water level in the yellow river lower reaches; Moreover, this paper analyzes the difficult point and the direction of improvement to realize the accuracy forecasting of the flood level of erodible-bed channel.