【作者】 樊登星；

【导师】 余新晓；

【作者基本信息】 北京林业大学 ， 水土保持与荒漠化防治， 2014， 博士

【摘要】 坡面是地表过程发生发展的基础单元,是流域最基本的组成单元,同时也是土壤侵蚀的主要发生地和沟道泥沙的主要来源区。本文基于北京山区坡面径流场以及首都圈森林生态站的定位观测资料,采用径流小区定位观测和野外及室内人工模拟降雨试验的方法,系统分析了降雨雨型、地形、植被覆盖和水土保持措施等多要素影响下的坡面土壤侵蚀响应机制。从侵蚀性降雨事件入手,基于改进的前期降雨指数模型(API)、改进的径流曲线模型(SCS-CN-MS)和改进的坡面土壤侵蚀模型(RUSLE-MM),构建了次降雨条件下坡面降雨-径流-侵蚀模型。应用构建的模型开展坡面土壤侵蚀定量化研究与模拟,揭示北京山区坡面降雨径流侵蚀过程及其机制。本研究结果为北京山区坡面水土流失规律提供理论基础,为北京山区坡面土壤侵蚀模型预报提供理论依据。主要研究结论如下：(1)研究区内的降雨事件可以划分为3种降雨雨型。降雨雨型Ⅰ为降雨历时短,降雨量小,降雨强度高、高频率的一类降雨事件；降雨雨型Ⅲ为降雨历时长,降雨量大,降雨强度低、低频率的一类降雨事件；而降雨雨型Ⅱ是介于降雨雨型Ⅰ和降雨雨型Ⅲ之间的一类降雨事件。通过分析不同降雨雨型的季节分布特征以及不同降雨雨型下的土壤侵蚀特征可知,在研究区内以降雨雨型Ⅰ占主导地位,即在短历时、高雨强、高频率的降雨雨型下,坡面土壤侵蚀剧烈。(2)不同坡度径流小区的径流量和侵蚀量的变化规律(多年平均、年际变化)存在一定的差异,但总体上表现出随着坡度的增而增大的趋势。不同坡长径流小区的径流量和侵蚀量的变化规律(多年平均、年际变化)存在一定的差异,坡面径流量表现出随着坡度的增加而减小的趋势,而土壤侵蚀量则随着坡长的增加呈现出先增加然后减小的趋势。在不同坡度、坡长条件下,坡面径流量和侵蚀量与降雨量和最大30min雨强I30的关系密切,表现为降雨量P和最大30min雨强I30越大,坡面土壤侵蚀越强烈。(3)植被覆盖对于控制坡面土壤侵蚀具有明显的作用。首先,植被覆盖能够显著的延缓坡面产流时间；其次,植被覆盖可以有效地调控坡面入渗过程；第三,植被覆盖可以有效调控坡面产流、产沙过程,随着植被覆盖的增加,坡面产流、产沙强度减小。(4)不同土地利用方式及水土保持措施的坡面土壤侵蚀特征分析表明：1)5种土地利用方式的土壤侵蚀量差异明显,与裸地相比较,耕地、人工草地、封禁荒草地和林地的减沙率达63.88%-99.63%；2)梯田比坡耕地措施小区的土壤侵蚀量减少了95.62%；3)采用水平条和鱼鳞坑措施林地小区的减沙率分别为83.56%和96.53%；4)与人工草地相比较,封禁荒草地的侵蚀产沙量减少了98.25%。(5)改进前期降雨指数模型(API)。分析了不同季节和不同土壤深度的土壤水分消退系数K的变化规律,并根据北京山区侵蚀性降雨特征对土壤水分消退系数K值进行优化取值(K=0.95)。应用次降雨事件的前期降雨指数Pa来表征土壤水分状况,定量分析了受前期土壤水分条件影响下的坡面降雨-径流过程。研究结果表明：应用前期降雨指数模型(API)能够较好的反映受前期土壤水分条件影响下的坡面降雨-径流过程。(6)改进径流曲线模型(SCS-CN-MS)。利用反算法对典型降雨事件下不同土地利用的初损系数λ进行计算,并确定不同土地利用的初损系数λi。在模型中引入前期土壤含水量M,并应用前期降雨指数模型(API)计算前5天降雨量,以确定前期土壤含水量M。应用4种径流曲线模型对不同土地利用类型的坡面径流量进行模拟研究。研究结果表明,改进后的径流曲线模型(SCS-CN-MS)在北京山区具有较理想的适用性。(7)改进坡面土壤侵蚀模型(RUSLE-MM)。直接考虑地表径流对土壤侵蚀的影响,在RUSLE模型中引入降雨径流侵蚀力指数(QREI30);考虑不同土地利用／覆被对土壤侵蚀的影响,构建不同土地利用类型的模型结构表达式。基于改进的径流曲线模型(SCS-CN-MS)和改进的坡面土壤侵蚀模型(RUSLE-MM),对次降雨条件下,北京山区不同土地利用类型坡面径流小区的土壤侵蚀量进行模拟研究。研究结果表明RUSLE-MM模型在北京山区具有较好的适用性。更多还原

【Abstract】 Slope is the basis unit of the surface process development, also one of fundamental units of river basin, as well as the source areas of soil erosion and channelsediment. We conducted the study by runoff plots location observation and the artificial rainfall simulation test in field and indoor, our object is:to analyzethe response of slope soil erosion to the effects of multi-factors including rainfall pattern, topography, vegetation cover, soil and water conservation measures and so on; to build the runoff-erosion model in slope scale under the condition of rainfall runoff through improving the antecedent precipitation index model, runoff curve model and slope soil erosion model, then conducted the quantified study and modeling of slope soil erosion process by these models, and indicated the process and mechanism of slope rainfall erosion. The study provide theoretical basis for slope soil erosion and related model in Beijing mountain areas.The main conclusions are as follows:(1)The rainfall events in study areas were divided into three different rainfall patterns. The first rainfall pattern is short-term, small-amount, high-intensity and high-frequence rainfall event; third rainfall pattern is long-term, large-amount, low-intensity and low-frequence rainfall event; and the second pattern is between these two rainfall patterns. We analyzed the seasonal distributions of different rainfall patterns, and the characteristics of soil erosion under these patterns, the results indicated that the first rainfall pattern play a dominant role in slope soil erosion.(2)Some differences existed in the change discipline of runoff and erosion in runoff plots with different gradient, which showed the increased trends with increased gradients. The variations of runoff and erosion were different in runoff plots with different slope length, runoff decreased with the increase of slope gradient, while soil erosion showed increase firstly and then reduction. Slope runoff and erosion were closely correlated with rainfall amount and maximum30min rainfall intensity in different slope gradients and lengths, which showed positive relationships.(3)The analysis of soil erosion characteristics under different land use pattern and soil and water conservation measures indicated that:the differences of soil erosion were significant in five land use patterns, the sediment reduction rate of farmland, artificial grassland, banning wild grassland and forest reached63.88%-99.63%contrasting with bare land;2.soil erosion of terrace were95.2%smaller than slope cropland, which demonstrated remarkable effect of soil and water conservation;3. soil erosion of horizontal bar and scale-hole measures were83.56%and96.53%smaller respectively, indicated significant effects of decreasing erosion.4. soil erosion of banning wild grassland were98.25%smaller than artificial grassland, that could effectively control soil erosion. So the engineering measures of soil and water conservation were very usefully through increasing aboveground vegetation cover, reducing human interference and the proper configuration of terraces.(4)The variation of soil water fading coefficient were analyzed in different seasons and soil depths based on the study of soil moisture dynamics, and optimized depending on the characteristics of erosive rainfall. The rainfall index model were improved by soil water fading coefficient. The processes of rainfall-runoff, which was affected by antecedent soil moisture, were analyzed quantitatively using the antecedent rainfall index of rainfall events,which is the representation of soil water condition. The results indicated that:the antecedent rainfall index model could perfectly reflect the processes of slope rainfall-runoff under the effect of antecedent soil water, suggested antecedent rainfall index model has good applicability in Beijing mountain areas.(5)Modeling slope runoff by improved runoff curve model. Firstly, the key model parameter was optimized, the optimal values of early damage coefficient (λi) on different land use types were determined using anti-inference method; then the model structure was improved by introducing the antecedent soil moisture(M), and the revised antecedent rainfall index model was used to calculate the effective rainfall in early stage (P5). Lastly, the modeling results of slope runoff, by the model of improved runoff curve, indicated that there was the validity of model simulation due to the very closed value between slope runoff simulation and measured runoff.(6)Improved the model of Revised Universal Soil Loss equation (RUSLE). Rainfall-runoff erosivity index was added in the model structure, determined by the parameter of slope runoff simulation calculated by the model of improved runoff curve. The results of soil erosion, which was determined by developed slope erosion model, indicated that the validity of model simulationwas very obvious, the soil erosion were very closed between simulation and actual measurement.更多还原