Study On Risk Analysis And Assessment Of Hillslope Debris Flow

Hillslope debris flow is developed in hillslope, which is small-scale and without clear circulation area, and whose ditch slope and hillslope have nearly same slope. Debris flow's risk is decided by the hazard of debris flow and the vulnerability of affected object. Taking Beibei of Chongqing as example, the paper discusses problems about risk assessment of hillslope debris flow. The paper includes seven parts:Part One introduces simply general situation of Beibei of Chongqing, and expounds the conception of risk assessment of hillslope debris flow.Part Two analyses the condition (the source of material and water, terrain etc.) in the process of forming hillslope debris flow, and summaries the common regular of distribution of hillslope debris flow.In Part Three, according to the viewpoint of system, giving consideration to all kinds of condition of forming hillslope debris flow, taking five indexes as follow :the shape index of ditch, the mean value of greatest precipitation within 24 hours, the developing degree of unstable mass, the mean depth of loose 'accumulated clay and the rate of plant cover ,applying fuzzy mathematics, the paper designs a suit of scheme about judging hillslope data. The result indicates the scheme's rate of distinguish is 84.6%.Part Four is the hazard assessment of hillslope debris flow .Because the hazard of hillslope debris flow mainly is pounding, the former formula (Hazard = Magnitude X Probability)can't assess accurately the hazard of hillslope debris flow. Applying the law of conservation of energy, we improved the formula as : Hazard = Energy X Probability,and examined it on the basis of concrete example. The result indicates the relative value of hazard on the basis of improved formula can embody accurately the pound-destroy effect of hillslope debris flow. It conforms to reality.Part Five discusses preliminary vulnerability of hillslope debris flow. The vulnerability is composed by two parts. One part is the chance that affected object is destroyed .It is decided by affected object's place, terrace condition and the distribution of affected objects. The other part is the degree of difficulty that affected objects is destroyed by debris flow .It is related with affected objects' type, structure and condition. So we get the formula of vulnerability assessment.Part Six is the calculation of risk. Taking the results of Part Foul; and Part Five into the formula: Risk = Hazard X Vulnerability .It calculates the risk of every debris flow ditch.Part Seven is conclusion and discussion.