Study on evaluation models of severity degree of dam failure impact

Dam risk assessment technique has already been used in the field of dam safety management abroad especially in Canada, Australia and USA in recent twenty years. There are more than 85 000 dams in China and about one-third of them are with severe deficiency and in high risks. Therefore it is real necessary to use this kind of technique to assist prioritizing dam maintenance or rehabilitation, reducing risks caused by dam failure. The technique consists of two important research objectives, dam-break probability analysis and dam failure impact evaluation. Dam failure impact includes three main factors: loss of life, financial loss, society and environment. How to evaluate the severity degree by means of these three factors comprehensively is a challenge of dam rehabilitation decision-making. The paper is to present a comprehensive evaluation coefficient for dam-break severity degree. The study introduces integrative assessment function L which considered weights S_i respectively of life loss, financial loss, society and environment, and their severity coefficients F_i, formed as linear weighted sum method. In order to integrate loss of life, financial loss, society and environment in accordance with existing laws and regulations in China, logarithm non-linear or linear models of data normalization are established to deal with their different units. A series of quantitative values of L which divide disaster event into deferent degree are suggested according to Chinese situation. The method and evaluation model is practically applied at 5 reservoir dams to appraise their severity degree of failure impact respectively and the comparison of these results are made to decide which one is more severe. The analyzed result shows that hazard of all these 5 dams would be extreme severe and should report to State Council as soon as the event of dam break occur.