Study On The Water System Morphology And Hazards Of Debris Flows Along Panxi Area Chin-Sha River Based On Nonlinear System

Debris flow is a kind of very common geological disaster which often happens in mountain area. Its universality is reflected not only on the frequency of occurrence in the debris flow, but also in the geographical distribution of debris flow. Around the world, as long as there are mountainous areas, there are basically more or less debris flow disaster phenomena. In our country, about 66.7% of our land is mountains, complicated geological conditions; relatively sparse vegetation; thick and broken Quaternary cover in the surface; frequent earthquakes in some regions make China become one of the most effected countries by debris flow in the world. Therefore, the research on debris flow has great academic value and practical significance.In this thesis, "Rough Set Theory", "AHP" and "entropy" are taken as the guiding ideology. The risks of 239 debris flows in Chin-sha River are evaluated through optimal combination of weights of factors. Based on the specification, the activity intensity of debris flow in the study area are quantified. According to the above work, based on fractal theory, the three-dimensional water system morphology of debris flow in the study area is analyzed quantitatively. The relationship between factors including fractal dimension of water system and risk index of debris flow is analyzed. From the kinematics and morphological point of view, the results are deeply discussed which obtained the fowling inclusions.1. In the study area, there are 35 debris flows belonging to severe risk,187 debris flows belonging to moderate risk,17 debris flows belonging to mild risk. There are 3 debris flows belonging to very strong activity intensity,105 debris flows belonging to strong activity intensity,112 debris flows belonging to relatively strong activity intensity,19 debris flows belonging to weak activity intensity.2. A new idea of improving AHP by rough set theory is proposed. The comparison matrix of AHP is established using the data extraction ability of rough sets. This new method eliminates undue subjective interference by forming the matrix according to the important degree of factors.3. The mathematical model of debris flow risk is established by information entropy theory. The infection to the debris flow risk model by factors has been expressed in the most extent because of the good ability to deal with the chaotic system.4. The concept of distance model is firstly proposed to calculate the distribution index of the optimal combination weighting method which is good at showing the factors'real contribution to the debris flows and excluding unnecessary interference.5. Through the calculation of the risk of 239 debris flows in the study area, it can be conclude that the results calculated by the new method is basically same as the results calculated by the traditional method which confirm that the new method is scientific and reasonable.6. The water morphology can be expressed by fractal dimension which is a kind of irregular fractal phenomenon in the nature having its own self-similar interval. Any judgment and analysis must be related to self-similar interval without which the research on water system fractal will lose its significance.7. The three-dimensional structure of water system is firstly studied based on fractal dimension using Matlab to calculate the water system fractal dimension.8. According to above re'search, we can see that the development and changes of water system can influence the occurrence of debris flow here very deeply.9. From the research, it can be seen that as the amount of loose material, length ratio of sediment supply segment and fractal dimension increases, the risk and activity intensity of debris flows increases. It is necessary to study the amount of loose material, length ratio of sediment supply segment and fractal dimension together.10. The amount of loose material, length ratio of sediment supply segment and fractal dimension interact with each other. It is unreliable to just study some single factor.