The Flood Control Technology Of The Lower Yellow River Which Based On Deposition On The Floodplain, Scour In The Main Channel

The Lower Yellow River is varied quickly between erosion and deposition. The main channel is always silted in recent years, and the suspended river appeared at the control of levee. After that the overbank flood became less and less because of continuous low flow year, hydropower complex projects, control works and production dykes in the Lower Yellow River. The water and sediment exchange between main channel and old beach areas weakened. The main channel and the new beach areas became the main place that sediment deposit. That made the elevation of main channel and the new beach areas raise year by year, the secondary suspended river appeared. After the secondary suspended river appeared, the main channel sostenuto shrank and the cross slope increased. That was really dangerous to the river flood control.In this article the characters of overbank flood and water-sediment exchange between main channel and beach were analyzed first. Then the representative reach was selected and the physical model was made. The model tests were done with different boundary and flow-sediment, in order to find out the flood control technology of the Lower Yellow River which based on Deposition on the floodplain. Scour in the main channel. Based on the flood control technology, the different operation plan of beach and new beach deposition were studied. At the end the inundation loss of representative old beach was surveyed. The main conclusions are as flowing:(1) Sediment deposition ratio and floodplain degree of the Overbank flood is closely related in the Lower Yellow River. The11overbank floods measured data show that the erosion amount of main channel accounted for about0.65-0.99times than the sedimentation amount of beach. When the incoming sediment coefficient of the overbank floods is less than0.015, the sedimentation amount of beach is directly proportional to the erosion amount of main channel. That indicate the effect of deposition on the floodplain, scour in the main channel is better.(2) In the condition of big overbank floods, the exchange mode of main channel and beach can be divided into two. One is triangular beach which is8-10km. Another is longandnarrow beach which is about20km.(3) At the status quo of the boundary condition, the ovcrbank floods randomly enter old beach. The deposition mainly concentrates on nearby the import. Also the inundation area is large, flooding time is long and the flow velocity closed to the levee is high. All those problems were improved at control boundary condition. The flood of8000m3/s is the best one at the two boundary condition.(4) As the test results of different operational mode of the beaches show that the effect is better when Changyuancr beach and Dongming beach arc used for flood detention and settling at Jiahetan Gaocun. In addition keeping the discharge of the main channel4000m3/s is better to improve the deposition of new beach in the rise period of flood peak.(5) The inundation loss mainly depends on inundated area and inundated times. In the talc qualc condition of bankfull discharge is4000m3/s, it is better that the discharge controlled by Xiaolangdi Reservoir is less than8000m3/s. In addition if the sediment concentration is more than30kg/m3, the control discharge can be not more than4000m3/s in the rise period of flood peak when the beaches are used for flood detention and settling. At Jiahetan-Gaocun reach Dongming beach and b Changyuancr each is an better choice.