Design Standard Of Rainfall And The Flood Mitigation Strategies For Nanhu Flood Diversion Project

In the Dongting Lake District, in order to avoid storm water from the mountain area flow directly to the lake and then become disaster of waterlog, one of the main engineering measures is to build flood diversion river along the bottom of mountain to mitigate the flood.Nanhu flood diversion project is one of the four main such projects in Hunan province. With total flood diversion area of 967.56 km2, it protected 16 townships with total cultivable land of 399,000 mu and population of 300,000 in Changde city and Hanshou country. Nanhu flood diversion project was built in order to divert the flood of 967.56 km2 directly to Yuanshui instead of coming to Yuannan district. The project has been implemented around 25 years since it was built and it has been done benefits in flood mitigation, flood diversion, irrigation and navigation. However, during the 25 years, there were also a lots of water related disaster in which 8 years were severely. During 90 century, there were 6 times severely waterlog with a loss around 2 billion Yuan. In July 3, 1995, Nanyangzui bank was broken and resulted in inundated area of 130,00.0 mu and a loss of 1.6 billion Yuan. It has become the bottleneck of flood mitigation in Hunan province of how to control the flood diversion river.Based on huge reference and data, this thesis investigated the water condition changes in Yuanshui, analyzed the storm water encounter conditions of four flood diversion projects in Hunan province, then the design standard of rainfall and the flood mitigation strategies were presented for Nanhu flood diversion project. Furthermore, main technical problems, which needed to pay attention and the tasks for further research, were also suggested.