Study On Regulation Of Check Dam On Channel Flow

Check dam is an important measure of channel governing in the Loess Plateau,it changes the water and sediment transport in watershed significantly,reduces the flood peak and retains the sediment,meanwhile,the Check dam alters hydrodynamic characteristics of original channel.The present study selected 2#check dam in Wangmaogou catchment,in the Suide county,Shaanxi province,as research subject.Based on original river channel recovery and numerical simulation,we researched the adjustment effect of check dam on flood extension in watershed,analyzed the hydrodynamic process of river channel with or without check dam in watershed.The main conclusions were as follows:(1)The present study used improved QHSP(Quartic Hermite Spline with Parameter)recover the river channel without check dam,the accuracy and stability of the interpolated river bed terrain is improved by 15%and 16%respectively using the QHSP,and the hydrodynamic simulations on the constructed river bed terrains of Wangmaogou catchment by using CHS and QHSP,the latter can improve the computation accuracy of the discharges by at least 18.5%in all cross sections,indicating the QHSP is more proper for reconstructing river terrain providing for shallow water flow models than the CHS.The proposed approach perforams satisfactorily to construct river terrain used for hydrodynamic modelling.It provides a more reliable tool to investigate hydrologic and hydrodynamic process in the regions without sufficient topography data.(2)The hydrodynamic model GAST(GPU Accelerated Surface-water and Transport Model)was used in the present study to simulate the flood extension under the conditions of the 2#check dam was filled with deposition arnd not constructed with the "715" rainfall process,the results indicate that 2#check dam reduces the flood peak and total flow.At downstream section,compared with that 2#check dam was not constructed in Wangmaogou catchment,the flood peak is reduced by 42%,the total flow is decreased by 28%,the appearance of flood peak is also postponed when 2#check dam was filled with deposition.At the front and back sections nearby 2#check dam,the flows passing these two sections are all decreased.At the front section of 2#check dam in Wangmaogou catchment,because of the reservoir effect of 2#check dam in Wangmaogou catchment,the runoff is baonked-up at the front of 2#check dam,compared with that 2#check dam was not constructed in Wangmaogou catchment,the flood peak is reduced by 46%when 2#check dam was filled with deposition;At the back section of 2#check dam,because of the runoff is banked-up at the upstream,the flow discharging to downstream is reduced,compared with that 2#check dam was not constructed in Wangmaogou catchment,the flood peak is reduced by 48%,meanwhile,the appearance of flood peak is delayed when 2#check dam was filled with deposition.(3)The gradient of river channel was raised and the local terrain was transformed when 2#check dam was filled with deposition in Wangmaogou catchment,the hydrodynamic process is changed apparently at the front and back of 2#check dam,the velocity,shear force,power of runoff were decreased sharply.But at the downstream section,the difference between that 2#check dam was filled with deposition or not constructed in Wangmaogou catchment is not obvious.The runoff erosion power is decreasing along the river channel,but at the sections where tributary river channel exists,due to the collection of tributary flow,the runoff erosion power would raise abruptly,compared with that 2#check dam not exists in Wangmaogou catchment,the runoff erosion power of midstream and downstream is reduced by 50%-70%;when 2#check dam was filled with deposition in Wangmaogou catchment,the flood peak and total flow passing the front of 2#check dam is reduced,and because of the reservoir effect of 2#check dam,the flood peak and total flow of downstream is decreased,the runoff erosion power is changed apparently.(4)Compared with that 2#check dam was not constructed in Wangmaogou catchment,the kinetic energy of runoff is decreased 60%-80%when 2#check dam exists,the kinetic energy of runoff is reduced sharply at the location where 2#check dam exists,the retardant effect of 2#check dam on runoff is remarkable;the kinetic energy peak of runoff is corresponding to the raining process,the kinetic energy of runoff is reduced when the rainfall capacity is decreased,the kinetic energy peak is almost 9.2×107J when 2#check dam was filled with deposition,it is 3.23 times than the kinetic energy peak with that 2#check dam was not constructed,the total kinetic energy is 1.86 times than the total kinetic energy with that 2#check dam was not constructed.This demonstrates that 2#check dam in Wangmaogou catchment has conspicuous effect on the kinetic energy reduction of runoff.