Research On Mathematical Model And Risk Assessment Model Of Debris Flow

Debris flow is a kind of natural disaster that burst in a short time with powerful damage. It occurs frequently in mountain areas after heavy rain. Debris flow directly threatens the security of human's lives and properties and seriously impedes the sustainable development of the social economic. This article presents a mathematical model of debris flow based on the basic hydrodynamic theory and a risk assessment model of debris flow based on rough set theory. The mathematical model is used for forecasting the debris flow and the risk assessment model is adopted to predicate the danger degree of the debris flow,which are both have important theoretical significance and practical application value.The hydrodynamic mathematical model is established based on the basic hydrodynamic theory and the real time rainfall process. In this model, the theory of incipient motion of sediment is considered as the motion conditions of debris flow and five cities' administrative areas of Guangxi province are considered as the region boundary. Many factors such as geography, geology, climate and hydrology, vegetation and population are also considered in this mathematical model. Fortran programming generates the calculating meshes, GIS technique digitizes the geography information, various coding methods are applied to simulate the geology condition, and the river channels are combined together with the mesh channels. By comparing the simulated results with those obtained from geology disaster distribution chart, the mathematical model is proved to be credible.This article builds a risk assessment model of debris flow not only based on many concepts of the rough set theory such as knowledge and knowledge base, indiscernibility relation, upper and lower approximation, reduction, reduction of values, dependency graph of knowledge, importance of attribute, but also based on case based reasoning, similarity degree of similarity system. In this model, data comes from statistical data of thirty-seven debris flow ditch of Yunnan. The amount of debris flow, frequency of debris flow, valley covers, and other three impact factors are considered as the influencing factors of debris flow in this article. The paper calculates the weights of impact factors based on rough set theory. By comparing the simulated results with those obtained from the measured value, the risk assessment model is proved to be credible. Finally,the calculation method of synthesized weights is introduced to mathematical model to calculate the weight of impact factors,comparing calculated results and actual value to verify the correction weights.