t is said that the urban drainage work began in thousands of years ago. By the 1980’s, application of computational technique for simulation of drainage network had been improved economic benefit and more technical transparent. However, statistical reports shows still rapidly flood damages in the world . Annual flood damage estimate is at 100 millions USD in the first half of the XX century and it reaches 1 billions USD in the second half, especially about 10 billions in the latest 10 years.