2D Numerical Modeling For Flow And Sediment Transport In Gaocun-Aishan Reach Of The Lower Yellow River

The Gaocun-Aishan reach of the lower Yellow River is a typical transitional reach.The meandering channel and the complex relationship between water and sediment bring difficulties to the simulation of water and sediment transport and channel erosion and deposition.Because there are many villages and towns and large population in the reach,flood will cause great losses.The two-dimensional model can simultaneously simulate the changes of flow and sediment in the longitudinal and transverse directions of the channel.Therefore,it is necessary to establish a two-dimensional mathematical model to simulate the flow and sediment movement and the changes of scour and siltation in the reach,so as to ensure the flood control safety of the lower Yellow River.Based on the measured data of daily runoff and sediment from Gaocun,Sunkou and Aishan hydrological stations in the lower Yellow River from 1964 to 2016 and the existing research results,this paper analyzes the runoff and sediment changes and the characteristics of beach and channel erosion and deposition in different periods of Gaocun-Aishan reach,and then establishes a two-dimensional flow and sediment model of Gaocun-Aishan reach in the lower Yellow River by using CCHE-2D software,Finally,three typical flood processes of "82.8","93.8" and "96.8" were selected for simulation calculation to simulate the flood evolution and changes of shoal and channel erosion and deposition in Gaocun-Aishan river section under different sand peak and flood peak phase difference conditions.The results show that the calculated runoff and sediment series are in good agreement with the measured runoff and sediment series,and the calculated results of the model are reliable;During the whole flood process,the main channel of "93.8" type flood with synchronous sand peak and flood peak silts continuously,and the siltation degree is close to that in flood period and flood period;When the flood peak is in the front and the sand peak is in the back,"96.8" type flood,the overall siltation degree of the river reach in the falling period is significantly higher than that in the rising period;The "82.8" type flood reach with sand peak in the front and flood peak in the back shows the characteristics of channel scouring and beach silting in flood period and flood period.In conclusion,the two-dimensional flow and sediment model based on CCHE-2D software can well simulate the flood routing process and sediment transport characteristics of Gaocun-Aishan River in the lower Yellow River,and the simulation results can provide decision-making basis for water and sediment regulation and planning in the transition section of the lower Yellow River.