The development of urbanization not only brought about the problem of water resources shortage, but also the speed expedition of rainwater runoff, the flux augmentation of flood peak, the time shortening of flood's duration due to the speedy change of landform and geomorphy in city area, the intense density of building, the increasing proportion of staunch area, which resulted in the addition of flood venture. In order to solve the two problems that had close correlation with rainfall, the resourcing of cit...