According to a concept discussed in a previous study, vulnerability consists both of the so-called inner factor and the outer factor. Inner factor pertains to the community conditions in a hazardous area, whereas the outer factors are those outside of the community that affect the loss. In this study, we focused on how the effects outside the community affect disasters. The disaster risk reduction plans led by governments were considered to be an important factor and we intend to connect this idea with the concept of vulnerability in this paper. As a first step, we examined the disaster risk reduction plans in Taiwan, Japan, and the USA. Second, insufficiency in the Taiwanese disaster risk reduction plan was listed according to a comparison between disaster risk reduction plans, which were listed as whole disaster risk reduction plans through all stages: before the disaster occurs – mitigation resource, during the disaster – emergency response, and after the disaster – recovery. Then, the vulnerability assessment was carried out through the measurements provided from 1999 to 2009. The result shows that the resource for debris flow disaster prevention is increasing each year. Finally, some suggested improvements were made and conclusions were drawn on the basis of the results. Copyright © 2012 John Wiley & Sons, Ltd.