黄土坡地地表糙度特征及其对入渗、产流产沙的影响研究

发布时间：2018-05-08 09:25

本文选题：土壤侵蚀 + 地表糙度　；参考：《西北农林科技大学》2015年博士论文

【摘要】：在坡耕地上,地表糙度是由耕作及日常管理活动形成的地表起伏,由于它对土壤入渗、坡面产流与产沙具有一定的影响,故它是当前坡地水文学和土壤侵蚀学研究的热点问题之一。本研究在总结前人研究成果的基础上,选择人们在农业生产中普遍采用的掏挖(又称点种)、等高耕作等主要耕作措施在坡耕地上形成的地表糙度为研究对象,通过室内人工模拟降雨试验的研究方法,综合应用土壤侵蚀学、数学、土壤学、水文学和三维激光扫描技术、GIS技术等理论知识、技术和方法对地表糙度特征及其在水蚀过程中的作用进行了研究。研究内容包括:地表糙度的特征,地表糙度对坡面入渗过程的影响、地表糙度对坡面产流和产沙的影响、粗糙坡面产流曲线模拟等。主要结果如下:1.与整平坡面相比,耕作措施改变了地表土壤的空间结构,增加了地表糙度的空间异质性。锄耕、掏挖和等高耕作措施下地表糙度具有多分形特征,分形维数D分别为2.79、2.72和2.87,渡越长度L分别为1.09、1.03和1.01。地表糙度越大的坡面,分形维数和空间变异性也越大,渡越长度却越小。2.初始地表糙度特征对降雨侵蚀作用下地表糙度的变化方向(增大或减小)和变化幅度具有影响。在粗糙坡面,地表糙度随着累计降雨量的增加而降低,二者呈显著的幂函数关系(P0.05)。地表糙度在前20 mm累计降雨量内的累计变化量最大,约占总变化量的20%-40%。随着降雨历时的延长,后续降雨侵蚀作用对地表糙度大小的影响能力降低,但是对空间特征的影响仍然较大;其次,地表糙度具有空间变异性,故它的变化与其所在坡位密切相关。在不同坡位上,地表糙度的形态特征具有一定差异,这种差异会造成地表糙度对降雨和径流侵蚀作用的响应不同,从而导致它具有不同的变化特征和规律。3.地表糙度对入渗锋面变化的影响较大。在粗糙坡面上,垂直于坡面的方向上入渗呈现从非均匀到均匀过渡的变化特征。但是,随着入渗锋面深度的增加,影响减小,故与整平坡面相比,在粗糙坡面上入渗率随着深度的增加降低较明显。总体而言,粗糙坡面上降雨入渗率较整平坡面平均提高10%以上。4.地表糙度对坡面产流、产沙过程具有影响。与整平坡面相比,粗糙坡面上径流产生时间平均晚10 min左右。在产流初始阶段,粗糙坡面上径流量较整平坡面低。但是,随着降雨历时的延长,粗糙坡面与整平坡面之间、粗糙坡面之间径流量差异降低。对于坡面侵蚀产沙也具有与径流量相似的特征。可见,糙度大小对径流产沙的影响与降雨历时有关。此外,坡度和降雨强度对地表糙度影响坡面产流、产沙的能力具有消减作用。5.来自粗糙坡面上泥沙中粗颗粒(50μm)含量较整平坡面低。随着降雨历时的延长,粗糙坡面与整平坡面泥沙中粗颗粒含量都降低,细颗粒的含量增加。对比整平坡面与粗糙坡面泥沙颗粒分布的变化发现,在降雨过程中粗糙坡面泥沙中细颗粒的含量变化较整平坡面明显。此外,降雨强度,上方来水与来沙会降低地表糙度对泥沙颗粒分布的影响能力。6.在耕作条件下,凸地和洼地是地表糙度的基本构成元素。在产流过程中,洼地积水造成径流延缓,凸地通过分散径流,延长径流路径的方式延缓径流。本研究以洼地和凸地为例,建立了以降雨强度I,平均流速vm和洼地积水时间TPi等为主要参数建立坡面产流计算模型。对模拟结果与实测结果进行比较分析表明,该模型能够较好的反映糙度对坡面产流的影响,为人们深入理解地表糙度影响坡面产流机理提供了新的方法。
[Abstract]:On sloping land, surface roughness is a surface fluctuation formed by farming and daily management activities. Because it has a certain influence on soil infiltration, runoff production and sediment yield, it is one of the hot issues in the study of slope land hydrology and soil erosion. The surface roughness formed by high tillage and other major tillage measures, such as high tillage, is widely used in the production, and the research method of the surface roughness formed on the sloping land is the research method of soil erosion, mathematics, soil science, hydrology and three-dimensional laser scanning, GIS technology and other theoretical knowledge, technology and technology. The characteristics of surface roughness and its role in the process of water erosion are studied. The research contents include the characteristics of surface roughness, the influence of surface roughness on the infiltration process of slope surface, the influence of surface roughness on runoff yield and sediment yield, and the simulation of runoff yield curve of rough slope. The main results are as follows: 1. the improvement of tillage measures compared with the leveling slope surface The spatial structure of the surface soil has been changed, and the spatial heterogeneity of the surface roughness is increased. The surface roughness has multi fractal characteristics under the hoeing, excavating and high tillage measures. The fractal dimension D is 2.79,2.72 and 2.87 respectively, and the crossing length L is the greater the surface roughness of the surface roughness of 1.09,1.03 and 1.01., the larger the fractal dimension and the spatial variability, the crossing over. The smaller the.2. initial surface roughness has an effect on the change direction (increase or decrease) and the change amplitude of the surface roughness under rainfall erosion. In the rough slope, the surface roughness decreases with the increase of accumulated rainfall, and the two has a significant power function relationship (P0.05). The surface roughness is accumulated in the cumulative rainfall of the previous 20 mm. The amount of change is the largest, and the 20%-40%. of the total variation is decreased with the duration of rainfall. The influence of subsequent rainfall erosion on the roughness of the surface roughness is reduced, but the influence on the spatial characteristics is still larger. Secondly, the surface roughness has spatial variability, so its change is closely related to its slope position. The morphological characteristics of the degree are different. This difference will cause the response of the surface roughness to rainfall and runoff erosion, which leads to the different change characteristics and the regularity of the surface roughness of.3.. On the rough slope, the infiltration in the direction perpendicular to the slope is from the non uniform to the uniform. However, with the increase of the depth of the infiltration front, the influence decreases, so compared with the leveling slope, the infiltration rate on the rough slope decreases obviously with the increase of depth. In general, the rainfall infiltration rate on the rough slope is higher than that of the leveling slope by more than 10%.4. surface roughness on the slope surface production and sediment production process. Compared with the leveling slope surface, the average runoff generation time on the rough slope is about 10 min late. In the initial stage of the runoff production, the runoff on the rough slope is lower than that of the leveling slope. However, with the extension of the rainfall duration, the difference of runoff between rough slope and the leveling slope decreases. The influence of roughness on runoff and sediment is related to the duration of rainfall. In addition, the slope and rainfall intensity affect the surface roughness on the surface roughness, and the ability to produce sand is reduced by.5. from rough slopes (50 mu m), which is lower than that of the leveling slope. The content of coarse particles in the sediment in the slope is reduced and the content of fine particles is increased. The change of sediment particles in the surface and rough slope of the leveling slope shows that the content of fine particles in the sediment in the rough slope is more obvious than that in the leveling slope. The impact capacity of the cloth.6. is the basic element of the surface roughness under the condition of cultivation. During the process of production, the water accumulation in the depressions is delayed, and the runoff is delayed by dispersing runoff and prolonging the runoff path. In this study, the rainfall intensity, the average velocity of VM and the water accumulation in the depression were built in the case of depression and convex land. The flow calculation model of slope surface is established as the main parameter of TPi. The comparison and analysis of the simulation results and the measured results shows that the model can better reflect the influence of roughness on the runoff yield. It provides a new method for people to understand the influence of surface roughness on the mechanism of slope runoff.

【学位授予单位】：西北农林科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：S157.1

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