“TIMELINE” is a tool that supports people in disaster cases. After “TIMELINE” was used effectively in the United States at Hurricane Sandy, it was introduced in Japan to apply for river flood cases. In terms of Japan, “TIMELINE” is a developing method. Therefore, the objective of our research is to contribute for the effective application of “TIMELINE” in Japan. To achieve our objective, we tried two steps. First, to understand the reason of “TIMELINE” making, we found the primal concept of “TIMELINE” by case study in the United States. In this part, by using bibliographic survey, we researched the history of disaster prevention acts in the United States and tried to find the root of “TIMELINE”. Second, we extracted the difference of attitudes toward river floods between Japan and the United States with studying actual river flood cases. To catch issues with several aspects, we focused on geographical and societal backgrounds in both countries. About time scale of our research, we picked up from early 20th century to now. In this era, both Japan and the United States started to operate the modern approaches to river floods. As a result, we found that it might be important to recognize the difference of geographical and societal aspects between Japan and the United States for effective application of “TIMELINE”. Our research would also contribute for effective application of “TIMELINE” on flash floods.