Abstract
In this study, we analyze an evaluation of complex risks to diagnose a city's susceptibility to disaster. In particular, we take the stand that urban disaster risks are a composition of “human activity risks” and “field risks”. We then adopt the idea of niche, which is used in ecological community analysis. The nature of risk, which is evaluated based on overlap, is “symbiosis” of both activity and “aggregation” of activity and field risks. We propose that the indicies of niche overlap are suitable for expressing “symbiosis” and “aggregation”. Then we carry out case studies by applying niche analysis and examine its applicability.
