The Change Of River-Lake Relations And The Effect To Flood Control Of Dredging Up

Aiming at the severe condition of flood control that was caused by the phenomena of little discharge volume but higher water level in the middle reaches of Yangtze River, the dissertation analyzes the effect of the change between Jingjiang River and Dongting Lake relations, finds a main reason that caused this adverse state, and finally puts forward a solution.There are three diversion waterways (four, before 1958) in the south bank of Jingjiang River, In their floruit, about 43.1% of annual runoff and 52.7% of flood peak runoff volume of Jingjiang River may flowed through these diversion waterways. But along with the sediment deposition, especially after the project of river bend cut-off, the runoff volume and transporting sand of these distributaries decreased gradually. This change is benefit to slow down the filling up and to keep the flood storage ability of Dongting Lake. But this decrease increased the runoff of lower Jingjiang River and resulted in the rising of water lever. The most important is that the decrease of sediment transport was directly conveyed and deposited in the Chenglingji-luoshan reach. This variety not only makes the river raising but also affects the flood flow of Jingjiang and Dongting Lake, results in the flood storage ability of Dongting Lake to reduce. And this is the main reason that caused the severe situation of flood control in the middle Yangtze River. So the dredging up of Chenglingji-luoshan reach is one of the effective solutions to the flood control of middle Yangtze River.Using the one-dimension hydraulics model, this dissertation calculated and analyzed the change of water lever after dredging up. The result shows that the project of dredging would to reduce the water lever, to improve the flood flowing condition and also may let the benefit of the project of Dongting Lake dredging up to bring into full play.