Neural Network Models Of Soil Erosion And Runoff In Slope And System Dynamics Model Of Sediment Field In A Watershed

At present water and soil lose is a crisis threatening mankind. China is one of the most senous countries in the world in soil erosion and the ~vest of China is the most part in whole country. To protect the zoology in the upper reaches of Yangtze River, develop the west of China continuously, profound knowledge about the soil erosion is needed. The mechanism of soil erosion of slopes and watershed are studied in this paper and new meaningful results are obtained. Comparing with the research at present, works presented in this paper have characteristics of exploring and initiating.Based on the current results the necessary of researching on soil erosion of slopes and watershed by neural network and system dynamics is suggested.The abuse of fixed learning rate q in BP algorithm of artificial neural network is discussed. A new method in choosing of q is found out. Local minimum point of error function can be got out by this method and it can improve the precision of the algorithm. Using the new algorithm some research on soil erosion of slopes and watershed has conducted. Three neural network models are developed, including the model of annual average sediment concentration in a watershed, the model of sediment concentration and runoff on different gradient ploughing horizontally or vertically, and the model of sediment concentration and runoff on waste slopes using in six different ways.It is the first time to propose a model on the soil erosion in watershed by system dynamics in this paper. Following the view of system, we analyzed the dynamic and physical behavior of soil erosion in watershed, and constructed the system dynamicsmodel. An emulation experiment research is carried out on a small watershed.To avoid the difficulty of deciding the parameter of the model, we found out two ways. One is using neural network model, and the other by physical mechanism soil erosion. It can not only overcome blindness of parameters choice, but also improve the precision of dynamics model.Above all, some new theories and methods in the field if the soil erosion in watershed are obtained. A new research direction is found. It gives us more knowledge of soil erosion and provides an experiment at approach to establish police for controlling of soil and water erosion.