The Study Of The Joint Operation Alternatives And Mathematical Modeling Flow And Sediment For Yongding River Flood-Retention Reservoir

Yongding River is one of the four main national flood-control rivers and the key of flood control river for the capital city, Beijing, China. Yongding river flood-retention reservoir (YDFRR) is being built at the right bank of the downstream after Sanjiadian Sluice gate of Yongding River. With introducing the flood water into the YDFRR, the flood control standard of Beijing city can be increased from flood occurancy of 2% to 1% in Beijing. And with the YDFRR, the flood loss at the right bank will be controlled. In this paper a 2-dimensional mathematic model is established for water and sediment evolution of Yongding River Flood-Retention Reservoir. And alternatives for the design of YDFRR and the joint operation of the three reservoirs were analyzed. The objective is to ensure the security of the project with smooth river flow and without damage on the middle and left banks by the flood. The research result provides solid foundation for the hydraulic constructions' design and operation of YDFRR.The model was calibrated and verified with measured data, investigated flood track data and physical model test results. Results indicated that the calculated flood level agrees well with the investigated flood track, the mainstream direction in the river basically accords with the surveyed river figure, measured topographical data in the river bed is mostly the same with calculated data. Therefore, the established model can simulate water and sediment flow , and the erosion-deposition process in the river bed with moderate accuracy. This then indicated that the model is reliable and capable of being used.The erosion-deposition evolution and water surface level of the YDFRR are calculated with two flood occurancies of 2% and 1% for the present river and the river after the implementation of YDFRR. The flood routing process, flow pattern and the change pattern of erosion-deposition in the riverbed are simulated for two flood occurancy of 2% and 1% with pre-assigned reservoirs' operationalternatives. Results indicated that the mainstream in the YDFRR and its planned main riverway will be within the planned guide leads, water flow will not produce intensive damage on the middle and left banks. So it is demonstrated that the design of the Flood-Retention Reservoir and the recommended three reservoirs' joint operation alternatives are reasonable. In addition, it must be mentioned that the mainstream is much closer to some parts of the right bank, flow speed is higher and some protection measures should be taken.