变流量对浅沟侵蚀产沙和水动力参数的影响

Influence of variable flow on sediment yield and hydrodynamic parameters of shallow gully erosion

为了研究变流量对黄土丘陵区浅沟径流侵蚀产沙的影响,以延安燕儿沟流域26°坡面浅沟为研究对象,在变流量5~10、10~15、15~20和20~25 L/min的条件下,采用野外放水试验测定产沙率、含沙量、流速和阻力参数等产沙和水动力参数的变化。结果表明:变流量后较变流量前,浅沟径流平均产沙率、平均含沙量和平均流速分别减小8.8%~53.5%、31.9%~55.7%和6.8%~18.1%,最大产沙率和最大含沙量分别减少4.8%~66.5%和42.6%~69.0%;变流量后较变流量前阻力系数增加了1.55~2.55倍。变流量后产沙率、含沙量和流速均出现小幅度增大,阻力系数出现小幅度降低。产沙率和含沙量随时间变化在变流量前后存在先增大—到达最大值—减小—稳定的类似特点,整个试验时间内流速总趋势波动减小,阻力系数波动增大。

[Background]The runoff usually increases with the inflow of water and rainfall above in the shallow gully,and the runoff is usually a variable.Therefore,to study the influence of runoff variation in shallow gully on the erosion and sediment yield of shallow gully in loess hilly area is a great scientific significance for soil and water loss control on Loess Plateau slope.[Methods]The shallow gully on the 26°slope in Yan′ergou watershed of Yan′an were selected as the research object,and the field drainage erosion test was conducted under the conditions of variable flow of 5-10,10-15,15-20 and 20-25 L/min.[Results]The effect of variable flow on sediment yield is that the average sediment yield and maximum sediment yield decrease by 8.8%-53.5%and 4.8%-66.5%respectively after variable flow.The maximum value of sediment yield before variable flow is greater than that after variable flow.The sediment yield after variable flow is different,but the trend is similar,which shows the first increase and decrease the stable;after variable flow,the trend of sediment concentration is the same,It is manifested as:start to increase to reach the maximum The influence of variable flow on sediment concentration is that the sediment concentration before variable flow is greater than that after variable flow,and the average sediment concentration and maximum sediment concentration decrease by 31.9%-55.7%and 42.6%-69.0%respectively,compared with that before variable flow,the average velocity after variable flow decreases by 6.8%-18.1%,and the maximum velocity and average velocity after variable flow are smaller than that before variable flow The reduction of velocity before variable flow is greater than that after variable flow.The resistance coefficient increases by 1.55-2.55 times after variable flow rate compared with that before variable flow rate.[Conclusions]In the process of large runoff,the sediment yield,sediment concentration and runoff velocity increase with the increase of flow,and the resistance coefficient decreases with the increase of flow,but the overall trend increases.Therefore,in the process of prevention and control of runoff and soil loss in shallow gully measures should be taken to prevent the increase of runoff and reduce soil erosion.