| Quantitative simulation and analysis of water and sediment process in a high resolution numerical simulation is of great significance to reveal water-sediment process under combined influences of climate change and human activities.Due to the dual effects of climate change and human activities,the water and sediment process is still a hot research topic in China and abroad.In recent years,with the implementation of water conservation engineering measures year by year,the underlying surface of the water and sediment process has changed greatly.The establishment of high-efficiency and high-resolution water and sediment mathematical model is the basis for accurate simulation and prediction of water and sediment processes.The higher the DEM resolution of the input terrain is,the higher the accuracy of the numerical algorithm is.The simulation results can reflect the real physical process and detailed flow structure of the water and sediment process.However,the higher the DEM resolution is,the larger the number of grids calculated by the model is,and the greater the timeliness challenge of the model calculation efficiency is.There fore,this paper uses GPU acceleration technology to improve the computational efficiency of solving sediment equation and riverbed deformation equation,which can meet the requirements of high precision and high efficiency simulation of water and sediment process.Therefore,it is of great practical significance to establish a set of high-efficiency and high-resolution numerical models for water and sediment process simulation and prediction and water and sediment management under the action of extreme rainstorm in the future.In summary,the following main conclusions are drawn:(1)A high-efficiency and high-resolution numerical model of river sediment process is established,and the numerical stability and simulation accuracy of the model are verified by classical experiments and existing literature data.The verification results show that the model has good simulation performance and can be used for efficient and high resolution simulation of river water and sediment process.Different Manning values are selected to simulate the ideal river channel.It is found that when Manning value is 0.02,the model can better predict the erosion and deposition process and the change of riverbed morphology.When Manning value is 0.03,the model has good simulation effect on the water level change at all time points of the ideal river.It is extended to the actual river simulation application,and the law similar to the ideal river simulation results is obtained.The scour caused by water and sediment movement is greater than that caused by siltation.The scour depth of different sections is about 1.7m,and the elevation change range of the upper and lower reaches of the river is about 118m～128m.(2)The influence of DEM resolution of river water and sediment process simulation on calculation efficiency is explored.Select the same example 1m～30m DEM resolution terrain,input the same flow conditions,simulate the response of water and sediment movement to different DEM resolution.The results show that the higher the resolution of DEM,the higher the accuracy of the simulation results of water-sediment scouring and silting process and flood inundation range.With the improvement of DEM resolution,especially when the DEM resolution is increased from 30m to 5m,the difference of simulation results is reduced,and the increase of simulation accuracy is also reduced.The accuracy of submerged range and water depth is increased by 3.1%and 4%respectively.Considering the simulation accuracy and simulation time,5 m resolution DEM is more suitable for river water and sediment process simulation,assessment and prediction.It can be seen from the graph that the higher the resolution of DEM and the larger the number of grids,the higher the acceleration efficiency of GPU shows a trend of continuous improvement.The acceleration ratio of GTX 1080 and GTX 2080 is 2～12 times on the whole.In contrast,the acceleration effect of GTX 2080 is better than that of GTX 1080,especially when the number of grids exceeds 5 × 105.(3)The high-efficiency and high-resolution numerical model of river basin water and sediment process is constructed.By improving the coupled slope sediment transport formula and combining with the channel sediment transport equation,the water and sediment process simulation integrating slope,channel and basin is realized.The experimental data in the existing literature are selected to verify the constructed model,and the results show that the model has high accuracy and stability.There was a linear positive correlation between the cumulative sediment yield on the slope surface and the rill width without vegetation cover,and there was a negative correlation between the runoff velocity and the rill width,which can be expressed by an exponential function.When the vegetation coverage reached 35%,the runoff velocity decreased significantly;for every 5%increase in vegetation cover,the flow velocity decreases by about 5%～10%.The slope runoff resistance coefficient increases with the increase of vegetation coverage,which shows exponential function relationship.(4)The cumulative erosion under vegetation cover patterns A,B and C was significantly less than that under vegetation cover patterns D and E.Compared with the non-vegetation cover model A(2636.27L),the sediment erosion amounts under vegetation cover models B,C,D and E were 217.65L,643.42L,75L and 1929.368L,respectively,and the cumulative total erosion amount reached 5874.128 L,indicating that vegetation cover can properly adjust the erosion and sediment transport process in the whole slope range.A typical Wangmaogou watershed with DEM resolution of 2m was selected for simulation.14 monitoring sections representing the whole basin were selected,and the flow velocity,flow rate and sediment concentration of the section were extracted.It was found that the law of each parameter was consistent with the actual physical sediment production process. |
