Taiwan has an unfortunate tendency to suffer disasters due to its mountainous geography and its location in a typhoon-prone area. To make matters worse, Taiwan’s rivers tend to have steep bed slopes and short length, and thus overland runoff occurs rapidly and can cause dangerous flooding in this population dense country, In order to protect both its citizens and extremely valuable high density urban developments in regions downstream it is thus critical and urgent to upgrading potential inundation maps for the programming of disaster prevention and protection. The purpose of this study is to upgrading potential inundation maps using the SOBEK model for Taichung City. There are 64 scenarios in this study, including 24 conditions of rainfall-frequency-situation and 40 conditions of quantitative rainfall. The result of this study is expected to provide more useful evaluations for decision makers who need to devise strategies for urban inundation prevention and protection.