Quantifying spatial distribution of interrill and rill erosion in a loess at different slopes using structure from motion (SfM) photogrammetry

The spatial distribution of interrill and rill erosion is essential for unravelling soil erosion principles and the application of soil and water conservation practices. To quantify interrill and rill erosion and their spatial development, four 30-min rainfalls at 90 mm h^?1 intensity were consecutively simulated on runoff plots packed with a loess at six slopes of 10°, 15°, 20°, 25°, 30° and 35°. The soil surface was measured using the structure from motion (SfM) photogrammetry upon each simulation run, and the runoff and sediment samples were collected and measured at every 10 min. Rills did not develop until the third simulation run. During the initial two runs, the lower third section was more severely eroded than the upper and middle thirds along the slope direction, yet the interrill erosion was statistically uniform from left to right. Rills tended to emerge by both sidewalls and in the lower portion in the third run. The corresponding rill erosion increased with slope from 10° to 20° and then decreased for the slopes steeper, which was consistent with the slope trend of the sediment yield directly measured. The rills expanded substantially primarily via head retreat and to a lesser extent via sideward erosion after receiving another 30-min rainfall. Rill erosion contributed 69.3% of the total erosion loss, and shifted the critical slope corresponding to the maximum loss from 20° to 25°. These findings demonstrate the significance of rill erosion not only in total soil loss but also in its relation to slope, as well as the effectiveness of SfM photogrammetry in quantifying interrill and rill erosion.     

黄土坡面细沟侵蚀强度的空间分布及形态分异特征

为探索细沟侵蚀的空间分异特性,通过人工模拟降雨试验的方法,分析不同降雨强度和坡度下的坡面细沟侵蚀过程,探讨细沟侵蚀强度及形态在坡面尺度的沿程变化特征.结果 表明:随着坡度和雨强增加,细沟侵蚀量不断增大;在特定处理下,细沟侵蚀强度沿坡长方向均呈现出先增后减的规律;沟宽、沟深和细沟割裂度等细沟形态参数也表现为先增加后减小,...     

基于立体摄影技术的细沟与细沟水流参数测量

细沟和细沟水流参数的准确测量可为深化坡面土壤侵蚀过程研究提供重要理论依据。基于立体摄影测量技术,以坡度为15°和20°的黄土坡面为研究对象,采用人工模拟径流冲刷的方法,对比不同时刻坡面的高精度数字高程模型DEM,提出了动床条件下坡面细沟宽度、深度以及细沟水流宽度、深度的测量和计算方法,分析了2个坡度处理下坡面细沟形态、细沟水流特征及其变化规律,探讨了立体摄影测量技术与其他测量技术在细沟形态及径流特征参数测量方面的异同。结果表明:经过比例尺的校正,可以在垂直拍摄的立体摄影照片上直接准确测量细沟宽度和细沟水流宽度;运用内插法,立体摄影测量技术能较准确地测量细沟深度和细沟水流深度的实时动态变化。随坡长的增加,细沟深度逐渐增大,而细沟水流深度则无明显变化趋势;细沟宽度随坡长的增加呈先增大后减小的变化趋势,而细沟水流宽度逐渐减小;20°坡度下细沟宽度和深度的增加速率分别是15°坡度下的1.7倍和1.3倍;同20°坡度相比,15°坡度条件下的细沟水流的宽度增加了1.7%~13.1%,而2个试验坡度下的细沟水流深度无明显差异。     

Evaluation of an erosion-sediment transport model for a hillslope using laboratory flume data

Climate change can escalate rainfall intensity and cause further increase in sediment transport in arid lands which in turn can adversely affect water quality. Hence, there is a strong need to predict the fate of sediments in order to provide measures for sound erosion control and water quality management. The presence of microtopography on hillslopes influences processes of runoff generation and erosion, which should be taken into account to achieve more accurate modelling results. This study presents a physically based mathematical model for erosion and sediment transport coupled to one-dimensional overland flow equations that simulate rainfall-runoff generation on the rill and interrill areas of a bare hillslope. Modelling effort at such a fine resolution considering the flow connection between interrill areas and rills is rarely verified. The developed model was applied on a set of data gathered from an experimental setup where a 650 cm×136 cm erosion flume was pre-formed with a longitudinal rill and interrill having a plane geometry and was equipped with a rainfall simulator that reproduces natural rainfall characteristics. The flume can be given both longitudinal and lateral slope directions. For calibration and validation, the model was applied on the experimental results obtained from the setup of the flume having 5% lateral and 10% longitudinal slope directions under rainfall intensities of 105 and 45 mm/h, respectively. Calibration showed that the model was able to produce good results based on the R2(0.84) and NSE(0.80) values. The model performance was further tested through validation which also produced good statistics(R2=0.83, NSE=0.72). Results in terms of the sedigraphs, cumulative mass curves and performance statistics suggest that the model can be a useful and an important step towards verifying and improving mathematical models of erosion and sediment transport.     

水力梯度影响下WEPP模型估计细沟侵蚀参数的可行性分析

为分析近地表水文条件影响下WEPP(Water Erosion Prediction Project)模型估计细沟可蚀性和临界剪切力的可行性,该研究选取长江中上游地区典型黄壤为研究对象,采用不同水力梯度值模拟饱和/渗流(水力梯度为0、0.71和1.43 m/m)和排水(水力梯度为?0.71和?1.43 m/m)2种近地表水文条件,并设置3个放水流量(0.55、1.58、2.51 L/min),利用"V"形试验土槽测定不同条件下细沟产流产沙,以WEPP模型估算的土壤可蚀性和临界剪切力为计算值。测定增大流量直到侵蚀开始并出现连续不断的土壤颗粒分离时所对应的流量,将基于此流量计算获得的临界剪切力作为实测值。比较临界剪切力计算值与实测值验证WEPP模型估算的可靠性。结果表明,在饱和/渗流条件下,土壤剥蚀率随着冲刷历时的增加逐渐减小;在排水条件下,放水流量为0.55 L/min的土壤剥蚀率随冲刷历时的增加快速减少并逐步稳定,而随着放水流量增大土壤剥蚀率波动的更为剧烈。5个水力梯度平均细沟可蚀性为2.51×10?2 s/m。饱和/渗流条件下细沟可蚀性为3.07×10?2 s/m,是排水条件的1.78倍。除水力梯度为?1.43 m/m时临界剪切力在WEPP模型中的计算值与实测值相符外,在?0.71~1.43 m/m范围内,临界剪切力的计算值均高估了实测值,平均高估了36.85%。临界剪切力实测值与计算值呈指数函数关系(R2=0.77,P0.01)。该研究可为黄壤的侵蚀防治及WEPP细沟侵蚀模型临界剪切力修正提供理论支持和科学指导。     

Effects of atmospheric circulation on summertime precipitation variability and glacier mass balance over the Tuyuksu Glacier in Tianshan Mountains,Kazakhstan

The amount and the form of precipitation have significant effects on glacier mass balances in high altitude mountain areas by controlling the accumulation, the ablation and the energy balance of a glacier through impact on the surface albedo. The liquid precipitation has negative effects on glacier accumulation and may increase the ablation of surface ice through the heat input for melting. The timing and the forms of precipitation over glacierized regions depend on the weather processes both locally and regionally. Early studies showed that regional to large-scale atmospheric circulation processes play a key role in affecting the precipitation events over glaciers. This paper analyzed the relationship between the inter-annual variability of the summertime precipitation over the Tuyuksu Glacier and the atmospheric circulation types, which related to various atmospheric circulation types in the Northern Hemisphere. Results indicated that the decrease in the duration of zonal processes and the increase in the meridional northern processes were observed in the last decade. The total summer precipitation associated with these processes also increased along with an increase of summertime solid precipitation. Although the decadal fluctuation of glaciological parameters were found in dependent of the above large-scale atmospheric circulation processes, global warming was a dominant factor leading to the mass loss in the recent decades under the background of the increase in precipitation over the Tuyuksu Glacier.     

(土娄)土堆积体坡面细沟形态及其沿程分布特征

采用人工野外放水冲刷试验,以(土娄)土地质为下垫面的工程堆积体坡面为研究对象,研究了不同坡长、坡度的(土娄)土堆积体坡面细沟形态特征及其沿程分布。结果表明:沟宽随时间延续呈现先递增后倾于稳定的趋势,沟宽与坡长存在二次函数关系,沟深随时间延续不断递增,表现为线性函数关系,沟深与细沟断面面积均对坡长变化存在响应,但并不存在显著函数关系,细沟宽深比随径流的持续呈现先骤减后倾于稳定的趋势,细沟断面面积随时间延续呈现逐渐递增的走势,可以用线性函数来描述断面面积与时间二者的关系,沟宽的沿程分布规律不一,呈现迥异,整体上来看,沟深的分布特性表现为先骤减后保持稳定的规律,就堆积体渣面汇集径流冲刷坡面的情况而言,对堆积体上半坡面布设合理的防治措施是重中之重。     

降雨条件下风速对迎风坡坡面细沟侵蚀特征的影响

[目的] 为明确风力作用下迎风坡坡面细沟侵蚀特征。[方法] 采用人工模拟风驱雨试验,研究在不同风速条件(0,3,5,7 m/s)下迎风坡坡面水沙过程变化规律及细沟形态特征。[结果] 与无风坡面相比,迎风坡面产流时间和跌坎出现时间分别增加20.59%~47.06%和33.10%~137.78%,坡面平均流速减小12.86%~22.53%;产流率和产沙率随风速的增加而显著减少(p＜0.05),不同风速条件下,迎风坡面产流率变化趋势相近,随着降雨进行产流率逐渐增加,一段时间后保持稳定,不同风速下的阶段性无明显差异。产沙率随降雨历时的延长整体呈先迅速增加后缓慢下降并趋于稳定趋势,产沙率发生变化的节点与跌坎出现时间基本一致。细沟宽度、深度及其波动程度随着风速的增加而减小;细沟宽度、深度及其波动程度随着风速增加而减小;细沟宽深比和细沟倾斜度分别为1.40~1.69和13.47°~14.76°,均随着风速的增加而增大;不同风速条件下,细沟体积、细沟割裂度和细沟密度分别为4.39×10³~10.27×10³ cm³,0.024~0.042,2.03~2.92 m/m²,三者均随风速的增加而减小。[结论] 细沟体积、细沟密度和割裂度与坡面侵蚀量均呈极显著正相关关系,是表征迎风坡坡面细沟形态的优选指标。     

细沟股流剥蚀率与载沙量以及沟长的耦合关系

土壤剥蚀是指由侵蚀动力引起的土壤颗粒从土壤母质移动的过程。细沟剥蚀土粒随着细沟股流中含沙量的增加而减少 ,已有的一些侵蚀模型 (如 WEPP)均提到了这一点。用黄土高原一种典型的粉壤土 ,在 5种坡度、3种流量下进行了细沟侵蚀模拟试验。对试验结果进行了回归 ,分析了黄土高原斜坡及陡坡地、细沟股流剥蚀率随含沙量以及沟长变化的函数关系。这对细沟侵蚀动力过程的研究深入 ,以及对侵蚀过程的预测预报提供了有力的参考依据     

黄土坡面细沟流速随细沟发育的特征

研究细沟流速特征是对细沟侵蚀发育机理探讨的必要方面,通过不同雨强(1.5,2.0,1.0mm/min)连续室内纯净水人工模拟降雨试验,分析不同坡度(10°,15°,20°,25°)、不同坡长(5,10m)条件下细沟流速随细沟发育的变化特征。结果表明,坡面发生细沟侵蚀且再降雨小于前降雨强度的条件下,细沟流速随时间变化的差异极小,可以利用坡面平均细沟流速进行此阶段的相关研究分析;相同降雨条件下,坡长对细沟流速的影响不显著,细沟流速与细沟流路之间的关系应作为进一步研究对象;细沟流速与坡度呈负相关关系,随着降雨进行,细沟的发育,相关程度逐渐增大。