Study on Regulation Indexes of Flood in the Lower Reaches of Yellow River

According to the grade of floodplain, the flow sediment concentration, the features of discharge process line, and the difference between flood peak and sediment peak, the flood is classified based on the data of more than 200 floods using statistical methods. The simulation experiments and mathematical models, and the key factors related with main channels formed by flood are discussed, and the key regulation indexes of flood in the lower reaches of Yellow River are studied. Results show that the flat beach discharge, which has an important effect on transport sediment and on the formation of main channels, is about 4 000 m3/s, the critical amount of transport sandiness is 50 kg/m3; the non floodplain flood or common floodplain flood should be controlled according to the flat floodplain discharge of the main channel first, and the flood discharge process would be better to take a form close to rectangular wave, and the water quantity before flood peak would be better to take a value greater than 25 % of the total water quantity, and the flood time would be better to last more than 7 d; the floodplain flood peak discharge should be controlled to be bigger than 1.5 times of flat floodplain flood peak discharge and bigger than 1.2 times of average flood discharge, and at the same time, the ratio between water quantity in swelling period and total flood should be more than 0.5, and the flood peak should be kept in step with the sandiness peak, and the flood time would be better to last more than 7 d; the content of sediment in different regulation floods is determined by the ratio of suspended sand and bed sand; the regulation indexes of flood incoming sediments should be changed according to the flood type, non floodplain flood sediment coefficient is 0.012 kg·s/m6, the common floodplain flood sediment coefficient is 0.015 kg·s/m6, and the incoming sediments of grouping sandiness should be controlled, too.