Simulation Study On Influence Of Sedimentation Process Of Check Dam On Hydrodynamic Process

As the most important channel treatment measure on the Loess Plateau,the check dam plays an important role in the ecological construction of soil and water conservation on the Loess Plateau.It scientifically understands the influence of check dams on the water and sediment processes in the basin during different siltation stages,and has the ecological safety of maintaining the Loess Plateau.Significance.This study takes the Wangmaogou watershed in Suide County of Shaanxi Province as the research object,and uses terrain restoration and hydrological simulation to simulate different sedimentation stages of the check dam(including:no dam construction,no dam construction,siltation 4m,siltation 8 m)The runoff process of the basin,the influence of the siltation process of the check dam on the hydrodynamic process of the channel is analyzed,and the generalization of the effect of the check dam system is studied.The study aims to quantify the benefits of water and sediment reduction of the check dam on the Loess Plateau.for reference.The main conclusions obtained are as follows:(1)The check dam with the siltation stage has different peak-cutting effects on the flood process in the basin.Among them,when the dam is not silted,it is reduced by 57.34%compared with the un-dam flood peak flow,and the peak cutting effect is the most obvious:the peak flo,w of the dam is 4 m.The decrease was 30.82%;the peak flow of 8m of dam deposition decreased by 28.94%.The check dam will not only reduce the total amount of floods significantly,but also increase the flood duration of the basin and delay the occurrence of flood peaks.The dams are not deposited and the floods are most obvious.The increase is 263 min,the flood peak lags 77 min;the siltation is 4 m.Under the circumstance,the flood time of the basin increased by 53 min,and the flood peak lags 15 min;the flood of 8 m is increased by 90 min and the flood peak is 27 min.(2)The construction of the check dam significantly changed the hydrodynamic process behind the dam and reduced the erosion of the channel runoff.The check dams with different siltation degrees reduce the flow velocity,runoff shear force and unit water flow power in front of the dam.Moreover,the lifting height of the dam is different,and the influence of the flow velocity on the channel along the section is also different.The check dam is the highest when the sedimentation is 8 m,and the distance between the dams with the specific drop of 0 is the longest.The impact range is the largest;the second is dam deposition 4 m,the dam construction is the smallest,the runoff shear force and runoff power also show the same change law.The check dam system can still greatly reduce the runoff velocity along the channel in the full state,and reduce the maximum flow velocity along the channel by more than 50%.The decrease of the flow rate leads to a decrease in the sand carrying capacity of the rmnoff,which will directly reduce the runoff erosion intensity of the basin and still have a good regulation effect on the channel erosion process.(3)The construction of the check dam significantly reduced the runoff energy in the main channel of the Wangmaogou basin.The flow energy along the path of the dam with no siltation,4 m of dam construction and 8 m of dam deposition decreased by 55.93%,27.44%and 38.09%,respectively,compared with the condition of unbuilt dam.The check dam not only reduces the runoff energy,but also reduces the runoff erosion power.The runoff erosion power of different silt thickness increases with the degree of siltation,and the degree of runoff erosion power decreases.A method for quantifying the effect of the check dam system is proposed,and the role of the basin dam group is quantified by setting an equivalent single dam.The equivalent single dam can well reflect the hydrological process of the check dam group at the river basin exit.By setting the equivalent single dam generalized dam group effect,the effect of simplifying the model can be achieved,and the hydrological model simulation of the large-scale basin can be realized.