黄土坡面细沟与细沟间侵蚀比率变化规律研究

发布时间：2018-06-18 12:40

本文选题：模拟降雨 + 细沟发育　；参考：《中国科学院研究生院（教育部水土保持与生态环境研究中心）》2015年硕士论文

【摘要】：坡面细沟侵蚀和细沟间侵蚀比率问题一直是坡面土壤侵蚀研究的难点问题,由于传统研究方法的局限性,制约了这一问题的深入研究,因此利用新方法新技术对这一问题进行深入研究,得到准确的坡面细沟侵蚀和细沟间侵蚀比率并分析其变化规律,对坡面土壤侵蚀理论的深化、构建土壤侵蚀预报模型及评价土壤侵蚀的环境效应(如农田非点源污染物的来源、估算与评价)有着重要科学意义。本研究分室内模拟降雨和室外模拟降雨两部分,室内模拟降雨采用三维激光扫描仪对坡面进行监测,研究了黄绵土坡面不同坡度(10°,15°,20°,25°)、降雨强度(90,120 mm.h-1)和坡长(5,7 m)下细沟发育过程、形态特征及细沟与细沟间侵蚀比率变化规律。室外模拟降雨利用7Be示踪法对坡面进行监测,研究了不同坡度(10°,15°,20°,25°,30°)、5 m坡长下细沟与细沟间侵蚀比率变化特征,同时较深入的研究了次降雨过程中细沟与细沟间侵蚀比率变化规律及其与径流、时间等的关系。主要结论如下:1.黄绵土坡面细沟侵蚀特征随着坡度、降雨强度增大,坡面产流时间、细沟出现时间有减小趋势,断面流速有增大趋势;随着降雨强度、坡度、坡长增大,坡面侵蚀率和产流速率明显增大,随坡度变化规律不明显;总侵蚀量和总径流量随降雨强度增大而明显增大,5 m坡长条件下,总侵蚀量和径流量随坡度变化规律不明显,而7 m坡长条件下,总侵蚀量随坡度增大而明显增大,径流量随坡度变化存在临界坡度;黄绵土坡面细沟形态变化受降雨强度影响较小,受坡度影响较大。以7 m坡长为例,在10°,15°坡度条件下,受溯源侵蚀及沟道下切作用较强,形成的细沟长、窄、深;在20°,25°条件下,受沟壁坍塌作用影响较大,形成的细沟短、宽、浅。2.次降雨过程中泥沙颗粒组成变化侵蚀泥沙分形维数与黏粒、粉粒含量呈极显著正相关,与砂粒含量呈极显著负相关;侵蚀泥沙分形维数随降雨强度增强有减小趋势,受坡度、坡长影响变化规律不明显,在5 m坡长条件下,侵蚀泥沙分形维数随着降雨历时的延长有先降低后升高趋势。7 m坡长条件下,10°、15°坡度情况下,侵蚀泥沙分形维数随降雨历时变化规律不明显,而在20°、25°坡度情况下,侵蚀泥沙分形维数有随降雨历时增大趋势;坡度为10°的条件下,细沟出现后侵蚀泥沙分形维数明显小于细沟出现前,在坡度为15°、20°、25°条件下,细沟出现后侵蚀泥沙分形维数明显高于细沟出现前。3.细沟与细沟间侵蚀比率变化规律研究对于室内模拟降雨,利用稀土元素示踪法研究坡面细沟与细沟间侵蚀比率试验结果与预想相差较大,具体原因还需进一步研究;对于室外模拟降雨,利用7Be示踪法计算次降雨过程中细沟间累计侵蚀量,发现细沟与细沟间侵蚀比率随降雨进行并不是持续增加,而是先逐渐增加,到达临界点然后逐渐降低;采用多元回归方法对细沟与细沟间侵蚀比率与坡度、降雨强度、径流的关系进行拟合,拟合函数为幂函数方程,室内模拟降雨和室外模拟降雨拟合方程分别为:,;利用RUSLE模型中计算细沟与细沟间侵蚀比率的方程进行计算,得出计算值与实测值差异较大,说明RUSLE模型中计算细沟与细沟间侵蚀比率的方程在黄土高原不适用。
[Abstract]:The rate of rill erosion and rill erosion is a difficult problem in the study of slope soil erosion. Because of the limitations of the traditional research methods, it restricts the deep research of this problem. Therefore, the new method and new technology are used to study this problem deeply to get the exact ratio of rill erosion and rill erosion. It has important scientific significance for the deepening of the slope soil erosion theory, the construction of soil erosion prediction model and the evaluation of the environmental effects of soil erosion, such as the source of non point source pollutants in farmland, estimation and evaluation. This study is divided into two parts of indoor simulated rainfall and outdoor simulated rainfall, and three-dimensional laser is used in indoor simulated rainfall. The scanner monitors the slope surface, and studies the development process of the rill under the different slopes (10, 15, 20, 25), the rainfall intensity (90120 mm.h-1) and the slope length (5,7 m), the morphological characteristics and the change law of the erosion ratio between the rill and the rill. The outdoor simulated rainfall is monitored by the 7Be tracer method, and the different slopes (10 degrees, 15) are studied. Degrees, 20 degrees, 25 degrees, 30 degrees), the change of erosion ratio between rill and rill under 5 m slope. At the same time, the relationship between the change of rill and rill erosion ratio and its runoff and time in the process of rainfall is studied. The main conclusions are as follows: 1. the characteristics of the rill erosion on the slope of 1. yellow soil slope, the increase of rainfall intensity, and the flow of the slope In the meantime, the occurrence time of the rill is decreasing and the velocity of the cross section increases. With the intensity of rainfall, the slope and the length of the slope increase, the erosion rate and flow rate of the slope increase obviously, and the law of the slope change is not obvious. The total erosion and total runoff increase obviously with the increase of rainfall intensity. Under the condition of 5 m slope length, the total erosion and runoff change with the slope. Under the condition of 7 m slope length, the total erosion amount increased obviously with the increase of slope and the critical slope of the runoff with the slope. The change of the rill shape of the yellow soil slope was less influenced by the rainfall intensity and influenced by the slope. The 7 m slope length was taken as an example, under the condition of 10 degrees and 15 degrees, the source erosion and the ditch cutting action was stronger. The formation of the trench is long, narrow and deep; under the condition of 20 degrees and 25 degrees, the effect of the collapse of the ditch wall is great, and the formation of the rill in short, wide and shallow.2. precipitation process, the fractal dimension of the sediment particles is very significant positive correlation with the content of the clay particles and the particle content, and has a very significant negative correlation with the content of the sand particles; the fractal dimension of the eroded sediment is with the rainfall intensity. In the condition of 5 m slope length, the fractal dimension of erosion sediment is not obvious under the condition of 10 degrees and 15 degrees under the condition of 10 degrees and 15 degrees, but the fractal dimension of the erosion sediment is not obvious, but at 20 degrees and 25 degrees, the fractal dimension of the sediment is not obvious under the condition of the slope length of rainfall. Under the condition of 10 degrees, the fractal dimension of the erosion sediment is obviously smaller than that before the emergence of the rill. Under the condition of the gradient of 15, 20, 25, the fractal dimension of the erosion sediment is obviously higher than that of the.3. rill and the rill erosion ratio before the appearance of the rill. In the study of indoor simulated rainfall, the results of the study on the ratio of erosion rate between rill and rill by rare-earth element tracing method are quite different from those in anticipation. The specific reasons are still needed to be further studied. For outdoor simulated rainfall, the 7Be tracing method is used to calculate the erosion amount of the rill among the rill in the secondary rainfall process, and the ratio of the erosion between the rill and the rill is found with the ratio of the rill and the rill. Rainfall does not continue to increase, but first gradually increase, reach the critical point and gradually reduce; using multiple regression method to fit the relationship between rill and rill erosion ratio and slope, rainfall intensity and runoff, fitting function is power function equation, indoor simulated rainfall and outdoor simulated rainfall fitting equation are respectively: using R The equation for calculating the erosion rate between rill and rill is calculated in the USLE model, and the difference between the calculated value and the measured value is obtained. It shows that the equation for calculating the erosion rate between the rill and the rill in the RUSLE model is not suitable for the Loess Plateau.
【学位授予单位】：中国科学院研究生院（教育部水土保持与生态环境研究中心）
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S157

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