Abstract: Scientific risk analysis of emergency is helpful to make correct contingency plans for Emergency Management Agency and to reduce event loss. However, most emergency risk analyses are under restrictions of multi factors, high dimensional data, small samples and incomplete information, and cannot fully recognize the risk of an emergency. In emergency system viewpoint and under the assistance of knowledge element model, projection pursuit method and information diffusion theory, a method of emergency risk analysis is developed in this paper based on knowledge element. By making use of the knowledge element model, the common ontological characteristics are described. Reducing dimensionality of the observed data on the input elements through searching for the optimum projection direction of the standard data on emergency risk grade, risk information contained in the observed data of the input elements is diffused into the points of the risk index universe on the output elements, and the emergency risk probability is carried out. Taking a lake as an example, risk of the water pollution is graded according to the national standard of environmental quality for surface water, with the data collected from 8 real-time monitoring sites of the lake. The results show that the emergency risk analysis based on knowledge element could analyze and evaluate potential risk of an emergency according to the risk standard grade and the observed data on site. The model of emergency risk analysis based on knowledge element expands the study of risk analysis and provides a scientific basis for the emergency management.Further, the results will provide references to emergency risk analysis in the dangerous areas where real-time monitoring system has been established.

Key words: knowledge element, emergency, risk analysis