Abstract: Wenchuan Earthquake brought about great amount of secondary geological disaster. To recognize the risk levels of this disaster in different areas of Wenchuan, this paper used post-disaster density of area weighted (HCA) as the index, and analyzed the corresponding relationships between various geological disaster-induced factors and disaster degree, taking Chongzhou City as an example. By using factor analysis to achieve the comprehensive hazard assessment, the study area was divided into five risk levels. The basic security area accounted for 53.61% of the total, most of which distributed in eastern plain region. Low risk area distributed in hilly region. Moderate and sub-high risk areas accounted for 19.58 % and 16.22%, respectively, and distributed in the mountainous and high rift zone density regions. High dangerous area was 37.82 km², accounting for 3.5% of the total, where the secondary geological disaster was easily occurred, and thereby, most concern should be paid. Comparing with the traditional method based on disaster density (HC), the method based on HCA had an obviously higher accuracy.

Key words: Phytoplankton, Toxin, Zooplankton