安达木河流域坡面糙率及其影响因素分析

发布时间：2018-04-04 03:01

本文选题：植物边坡　切入点：曼宁糙率系数　出处：《北京林业大学》2015年硕士论文

【摘要】：曼宁糙率系数是采用水动力学方法研究和模拟地表径流最为重要的参数之一。研究曼宁糙率系数对改善坡面侵蚀状况、研究坡面水流冲刷、泥沙输移运动规律以及采取正确的坡面水土保持措施有着重要的现实意义。本实验选取北京市密云县安达木河流域,研究对象为裸地、狼尾草、野豌豆、黄花蒿、苔藓、枯落物覆盖面、砾石压盖面,7种坡面类型,通过野外放水冲刷实验,研究不同植物坡面径流流速、曼宁糙率系数、流水动力学参数和产流产沙的变化特征以及各坡面糙率系数和各影响因素的相关性分析。实验结果显示：1、当坡度固定的情况下,改变入流量的大小,狼尾草坡面流速始终最小,裸地始终最大,苔藓地表的径流流速增长趋势最为明显；当流量固定为5rnl/s时,枯落物地表糙率系数最大,裸地最小；对裸露地表坡面加之砾石覆盖,对坡面糙率系数的影响甚微；7种坡面雷诺数均处于32.33-33.90之间,弗劳德数处于0.85-6.50之间,Darcy-Weisbach阻力系数f数值在6.48-376.17之间,其中枯落物地表阻力系数最大,裸地地表阻力系数最小。2、曼宁糙率系数和土壤侵蚀量呈反相关关系,曼宁糙率系数与稳定入渗率在一定程度上呈正相关关系,狼尾草坡面对土壤侵蚀的抑制作用效果最好,因此坡面地表的曼宁系数可以用来间接表示此地表的土壤抗蚀性强度。3、当坡度为15°和35°时,糙率系数随着径流量的增加而减小,坡度接近25°时,糙率系数随着径流量的增加而上升；当流量逐步增加时,随着坡度的增加,狼尾草边坡径流流速的变化过程为“先增加后减小”；野豌豆边坡为‘逐渐增加”；黄花蒿边坡为“先减小后增加”。4、狼尾草对坡面土壤的改良作用效果最明显,野豌豆坡面次之,黄花蒿对土壤的改良作用较差；地表糙率系数n值与植被覆盖度、土壤有机质含量、毛管持水量、毛管孔隙度、Darcy-Weisbach阻力系数f呈正相关关系,与坡度、土壤容重、流量、土壤侵蚀率、雷诺数呈负相关关系；曼宁系数与Darcy-Weisbach阻力系数f呈高度正相关。
[Abstract]:Manning roughness coefficient is one of the most important parameters to study and simulate surface runoff by hydrodynamic method.It is of great practical significance to study the roughness coefficient of Manning for improving the condition of slope erosion, studying the law of flow erosion, sediment transport and movement, and taking correct measures of soil and water conservation on slope.In this experiment, the Anamu River Basin of Miyun County, Beijing, was selected. The subjects of the study were bare land, Wrangling grass, wild pea, Artemisia annua, moss, litter coverage and gravel cover surface.The variation characteristics of runoff velocity, Manning roughness coefficient, income dynamic parameters and sediment yield on different plant slopes were studied.The experimental results show that when the slope is fixed, the flow velocity on the slope is the smallest, the maximum on the bare land, and the increase trend of the runoff velocity on the moss surface is the most obvious when the flow rate is fixed to 5rnl/s.The surface roughness coefficient of litter is the largest and the bare land is the smallest, and the Reynolds numbers of 7 kinds of slope are between 32.33-33.90, which have little effect on the roughness coefficient of the slope surface with gravel covering.The Froude number is between 0.85-6.50 and the resistance coefficient f of Darcy-Weisbach is between 6.48-376.17, in which the surface resistance coefficient of litter is the largest, the surface resistance coefficient of bare land is the smallest, and the roughness coefficient of Manning is inversely correlated with soil erosion.Manning roughness coefficient and steady infiltration rate were positively correlated to some extent.Therefore, the Manning coefficient of the slope surface can be used to express indirectly the erosion resistance strength of the soil surface. When the slope is 15 掳and 35 掳, the roughness coefficient decreases with the increase of runoff, and the slope is close to 25 掳.The roughness coefficient increases with the increase of runoff flow, and with the increase of slope, the variation process of runoff velocity is "increase first and then decrease", and that of wild pea slope is' increasing gradually'.The slope of Artemisia annua is "decrease first and then increase" .4.The effect of improving soil on slope is the most obvious by Wolfgrass, second by wild pea slope, and worse by Artemisia annua, surface roughness n and vegetation coverage.Soil organic matter content, capillary water holding capacity, capillary porosity and Darcy-Weisbach resistance coefficient f were positively correlated, but negatively correlated with slope, soil bulk density, flow rate, soil erosion rate and Reynolds number.The Manning coefficient was positively correlated with the Darcy-Weisbach resistance coefficient f.
【学位授予单位】：北京林业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S157

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