Abstract: Integrated risk assessment is one of the important parts of integrated risk management, which can help governments to take maeasures on preventing and mitigating the losses of disasters. What's more, multi-hazards integrated risk assessment is currently very important and difficult in the field of disaster reduction at home and abroad, with the systematic theory and methodology not yet obtained. Based on the system theory of disaster risk, this study has introduced the methods of fuzzy information granulation and fuzzy transformation function, and built a soft hierarchical model of integrated risk assessment for multi-hazards, which is characterized by the following aspects. 1) Not only the certainty of disaster risk, but also the random uncertainty and fuzzy uncertainty are considered. 2) The approach of fuzzy information granulation can reduce the uncertainty of data, and it includes some subjective information so as to make the results of assessment more realistic, theory and practice more tightly combined, and thus, it is more conducive to risk managers and decision makers to provide the basis of loss reduction and risk aversion. 3) Fuzzy transformation function transforms different types of quantity into the same type of quantity in order to comprehensively analyze and obtain the assessment result of multi-hazards integrated risk. Using earthquake-flood disaster risk as a case study, the demonstration analysis of soft hierarchical model of integrated risk assessment for earthquake-flood disaster illustrates that this soft hierarchical model suggested in this study holds the ability of synthetically assessing multiple disasters.

Key words: earthquake risk, flood risk, fuzzy information granulation, fuzzy transformation function