Abstract
Recently, we often experience a localized torrential rain whose intensity exceeds much beyond the designed magnitude for both a drainage system and an urban river in Tokyo. On September 4-5, 2005, such an extremely heavy rainfall caused the inundation damage in the Myosyoji River basin. And also on August 5, 2008,five workers who worked in a trunk drainage pipe drowned because of the sudden concentration of rainwater in it in Zoshigaya area, Toshima Ward. In this study, numerical simulation model was developed in order to investigate how the rainwater can be removed by both a drainage system and an urban river in these areas during such a rainfall event.The validity of the model was verified by comparing the numerical results and the observed data. As a result of this study, the expanding process of inundation in each region explained above was made clear for some extent hydraulically.
