The serious flood disaster occurred at the river basin of Kinu-river in September of 2015. The disaster was called “Kanto-Tohoku heavy rain fall in September 2015”. In this disaster, the levee of Kinu-river was breached, and the flood flow had spread over the urban area of Joso city in Ibaraki prefecture. In this study, research on flood resistant architectures was reviewed. Also, the numerical simulation on the flood flow was performed. And, the reason why the houses had been swept away was discussed on the basis of the result of simulation. Furthermore, a necessity of hazard maps considering an inundation depth and a flood velocity was pointed out.