黄土区土质道路径流水动力学参数的灰色关联度分析

黄土区土质道路路面侵蚀是该地区土壤侵蚀中的重要形式之一,为了探讨其土壤剥蚀率与径流水动力学参数的相关关系,以便为该地区道路土壤侵蚀预报模型的建立提供帮助,采用室内人工降雨及放水冲刷实验、灰色关联度分析方法研究了裸露土质路和植草土质路的径流水动力学参数与土壤剥蚀率间的关系,结果表明:1)在15°坡度、不同雨强条件下,可根据径流量或水流功率计算土壤剥蚀率;2)在2mm.min-1雨强、不同坡度条件下,可根据水流功率或坡度计算土壤剥蚀率;3)在降雨加放水冲刷试验条件下,裸露土质路的土壤剥蚀率可通过径流水深或径流流速计算得出,而植草土质路的土壤剥蚀率可通过过水断面单位能量或径流量计算得出。因此,在无汇水条件时,根据径流水流功率计算土壤剥蚀率较为合理;在有汇水条件时,采用径流量计算土壤剥蚀率较为合理。     

黄土坡面侵蚀方式演变过程中汇水坡长的侵蚀产沙作用分析

利用由位于坡面上部的供水装置和坡面下部的试验土槽组成的试验装置系统,通过模拟降雨试验,研究了不同降雨强度(50、75和100 mm/h)和不同坡度(15°、20°和25°)条件下坡面侵蚀方式演变过程中汇水坡长对侵蚀产沙的作用.结果表明,黄土坡面片蚀-细沟侵蚀-切沟侵蚀方式演变过程中汇水坡长对侵蚀产沙具有重要作用,且受降雨强度、坡度和侵蚀方式演变过程的综合影响.汇水坡长增加,使坡面片蚀-细沟侵蚀-切沟侵蚀发育速度明显加快,侵蚀产沙量明显增加.在坡面侵蚀不同发育阶段,汇水坡长对坡面侵蚀的产沙作用也不尽相同.当坡面以切沟侵蚀为主时,汇水坡长对坡面侵蚀产沙的作用最大,其次是以细沟侵蚀为主时.而以坡面片蚀为主时,汇水坡长对坡面侵蚀产沙的作用最小.通过对坡面侵蚀产沙量与汇水坡长的相关分析表明,它们呈正线性关系.     

黄土丘陵地区沟谷系统的平面结构及其对土壤侵蚀的影响

黄土丘陵地区的最突出的地貌景观特征是梁峁起伏、沟壑纵横、支离破碎,即沟谷系统的发育最为典型。沟谷既是流水侵蚀的产物,又是黄土丘陵沟壑系统中物质和能量传输的通道。流域的地貌发育正是流域内地面物质的被侵蚀和搬运过程中的产物。沟谷系统的增大,进一步增大了侵蚀的潜在条件。侵蚀类型中,沟蚀既是最重要的类型之一,同时对面蚀、重力侵蚀等也有着直接的影响。因此,沟谷系统发育的研究在土壤侵蚀规律的研究中一直占有重要地位。本文以黄土丘陵沟壑发育之现状最为典型的无定河流域的调查为例,试图     

细沟侵蚀临界坡度研究

根据细沟泥沙运动特点,考虑细颗粒泥沙的粘着力作用和非均匀沙的暴露度,建立了细沟泥沙起动公式。结合细沟泥沙起动公式和细沟稳定条件得到坡面侵蚀临界坡度的计算方法。通过计算得到如下的结论:(1)坡面细沟侵蚀临界坡度是土壤性质的函数,在反映土壤性质的容重等参数一定的情况下,仅是粒径的函数。(2)黄土坡面细沟侵蚀临界坡度在21.3°~50.4°之间。对于中值粒径为0.0185mm的黄土坡面,临界坡度为39.9°。(3)对应细沟侵蚀临界坡度存在一临界粒径,当粒径大于该粒径时,不存在细沟侵蚀临界坡度。当临界粒径为0.0198mm,对应的最大临界坡度为50.4°。     

黄土丘陵沟壑区典型治理小流域水沙输移的尺度效应

近年来,水土流失的尺度特征及尺度效应一直是土壤侵蚀研究的前沿。文中通过对黄土丘陵沟壑区第一副区不同空间尺度互为嵌套的小流域(5.97km~2的王茂沟小流域和70.1km~2韭园沟小流域)监测数据的分析,比较了流域治理措施实施后不同空间尺度小流域产流产沙过程及其对降雨事件的响应,揭示该流域淤地坝建设等措施对小流域泥沙输移特征的影响及其尺度效应。研究结果表明:两个尺度小流域径流对降雨响应过程均十分迅速,且退水后几乎没有基流,这同南方丘陵区小流域不同;王茂沟和韭园沟小流域径流量迅速增大,达到峰值后逐渐回退,大致在降雨停止6小时后完全消退;源头小流域(王茂沟)地表径流系数相较更大尺度小流域(韭园沟)略低,土壤流失量则相反;治理后的韭园沟小流域高含沙水流现象减少。重力侵蚀仍是源头区域发生高含沙径流的潜在影响因素,小流域尺度水土流失防治应重点治理源头区域。     

黄土耕作坡面微地形面积高程积分计算及特征研究

面积高程积分(Hypsometric Integral,HI)是定量表征地形发育阶段及侵蚀趋势的重要指标。通过90mm/h雨强下4个典型坡度的人工模拟分段降雨试验,在三维激光扫描的基础上,利用点云数据生成DEM,对微地形坡面HI值的3种计算方法及其变化特征进行了分析,并根据细沟河网格网的HI值进行了验证。结果表明:1)HI方法可用于微地形坡面侵蚀发育的定量表征,HI值介于0.50-0.59之间。在不同坡度条件下,细沟出现之前坡面侵蚀量逐渐增加且HI总体呈现递减趋势,而细沟出现后侵蚀量在细沟中有所堆积且HI值有一定回增。2)河网格网HI值介于0.45±0.11之间。随着坡度的增加,HI值总体上表现出增加的趋势,潜在侵蚀能力有增大的趋势且侵蚀量和坡度之间存在一定的转折关系。3)对比3种不同HI计算精度来看,坡面HI与格网HI之间的RMSE和SAE值差别并不明显,但总体均表现为积分曲线法的计算精度要略优于体积比例法和起伏比法。研究结果对于丰富微地形尺度下HI的计算,深入认识坡面侵蚀发育过程及其机理具有重要的参考价值。     

不同密度膜侧沟播油菜的植株性状表现及产量效应

为进一步完善油菜膜侧沟播栽培技术体系,本试验研究了不同密度膜侧沟播油菜的植株性状表现及产量效应。结果表明:稀植虽有利于改善油菜部分性状指标的增加,并最终表现出单株产量优势,但随着油菜生长期的延长,不同密度处理间差异逐渐缩小。适宜密度种植油菜的分枝数、叶面积以及部分生理指标等均优于低密度或高密度种植。种植密度与单位面积产量的灰色关联度高于单株产量。我国西北沿山干旱区膜侧沟播种植油菜的适宜密度以4.5万株/667m2最为适宜,可比当前生产上推行的密度(3.0万株/667m2)增产39%以上。     

小流域人类活动的时空分异的景观格局特征——以纸坊沟流域为例

纸坊沟流域位于黄土高原典型的丘陵沟壑区,是黄土高原小流域综合治理的示范区。从上世纪30年代以来,纸坊沟流域经历了从急剧破坏到缓慢恢复、基本保持和快速恢复的四个阶段,其中每一个阶段的人类活动都有其鲜明的特色。为了量化人类活动的程度和人类活动对土壤侵蚀的影响,本文将纸坊沟流域的土地利用类型归并为两类:加剧侵蚀的斑块和减缓侵蚀的斑块,并根据流域的海拔高度,给流域内每个土地利用斑块分别赋予位置属性。然后根据人类活动与土壤侵蚀的关系提取了5个景观格局指标,分别计算各指标自上世纪30年代以来的变化情况,并划分变化阶段,分析各阶段的景观格局变化情况后,本文得出以下结论:1)人类活动变化最剧烈最频繁的区域在坡下(即流域内海拔高度介于1100—1150m之间的区域);2)流域破坏性开发体现在斑块破碎化,而流域治理体现在斑块连通度增加;3)在流域治理过程中,流域景观格局变化特征体现在:减缓侵蚀的斑块被合并,加剧侵蚀的斑块部分被合并,部分被转化为减缓侵蚀的斑块。     

黄土丘陵沟壑区不同侵蚀微环境对植物更新的影响

微生境对于脆弱生态系统的植被更新与恢复至关重要。为了探明侵蚀微环境对植物更新的影响,以黄土丘陵沟壑区裸坡为对照,选取细沟、浅沟沟坡、浅沟沟底3种侵蚀微环境,结合7种主要物种种子补播试验,通过2 a的萌发出苗、幼苗存活与生长监测,结果表明:除铁杆蒿幼苗存活率在裸坡高于各侵蚀微环境外,其他供试物种的种子萌发出苗率和存活率在细沟或浅沟环境明显高于裸坡,而且大部分植物种子萌发出苗率和幼苗存活率在细沟内最高;供试的7种物种幼苗的高度在裸坡不同程度地低于细沟、或浅沟沟底、或浅沟沟坡下,尤其在浅沟沟底的白羊草、长芒草和杠柳高度显著高于其他环境(P0.05)。各侵蚀微环境下,不同坡位对供试物种的种子萌发出苗率、幼苗存活率与高度的影响没有一致性规律。在黄土丘陵沟壑区,土壤侵蚀塑造的侵蚀微环境对大部分植物种子萌发出苗、幼苗存活和生长等更新关键过程具有一定的优势,其中,细沟更有利于植物种子萌发出苗及幼苗存活,而浅沟更有利于植物幼苗生长。然而,土壤侵蚀微地形对植物更新也存在一定的种间差异性,细沟和浅沟不利于种子极小的铁杆蒿种子萌发出苗及幼苗存活。合理管理与利用侵蚀微环境,对该区恶劣生境的植被恢复具有实际意义。     

不同地表覆盖方式油菜花后干物质积累与分配规律研究

为探索春油菜在西北沿山旱作区的最佳地表覆盖栽培方式,采用田间试验法,以常规露地平播为对照,研究了双垄面全膜覆盖沟播、全地面覆盖平播、膜侧沟播、半地面覆盖平播、麦秸覆盖平播等5种地表覆盖方式下春油菜的干物质积累及分配规律。结果表明,不同地表覆盖栽培方式对油菜植株各器官的干物质分配比率产生不同程度的影响,双垄面全膜覆盖沟播和全地面覆盖平播栽培方式与对照差异最大;各种地膜覆盖栽培方式均有利于油菜单株干物质积累,但不同覆膜方式效果不同。双垄面全膜覆盖沟播和全地面覆盖平播栽培方式油菜单株干物重、单位面积产量最高,秸秆覆盖未能显著提高油菜的单株产量及单位面积产量;油菜单位面积产量同油菜单株干物重呈现正相关关系,并获得最优线性回归方程;采用地膜覆盖栽培技术能有效地加快油菜植株茎秆、叶片同化物向角果的转移速度,提高油菜地上部干物质积累量和单位面积产量。其中,双垄面全膜覆盖沟播和全地面覆盖平播栽培方式比常规露地栽培增产达到30%以上,应在生产上大面积推广应用。     

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.     

Interactions between wind and water erosion change sediment yield and particle distribution under simulated conditions

Wind and water erosion are among the most important causes of soil loss, and understanding their interactions is important for estimating soil quality and environmental impacts in regions where both types of erosion occur. We used a wind tunnel and simulated rainfall to study sediment yield, particle-size distribution and the fractal dimension of the sediment particles under wind and water erosion. The experiment was conducted with wind erosion firstly and water erosion thereafter, under three wind speeds(0, 11 and 14 m/s) and three rainfall intensities(60, 80 and 100 mm/h). The results showed that the sediment yield was positively correlated with wind speed and rainfall intensity(P<0.01). Wind erosion exacerbated water erosion and increased sediment yield by 7.25%–38.97% relative to the absence of wind erosion. Wind erosion changed the sediment particle distribution by influencing the micro-topography of the sloping land surface. The clay, silt and sand contents of eroded sediment were also positively correlated with wind speed and rainfall intensity(P<0.01). Wind erosion increased clay and silt contents by 0.35%–19.60% and 5.80%–21.10%, respectively, and decreased sand content by 2.40%–8.33%, relative to the absence of wind erosion. The effect of wind erosion on sediment particles became weaker with increasing rainfall intensities, which was consistent with the variation in sediment yield. However, particle-size distribution was not closely correlated with sediment yield(P>0.05). The fractal dimension of the sediment particles was significantly different under different intensities of water erosion(P<0.05), but no significant difference was found under wind and water erosion. The findings reported in this study implicated that both water and wind erosion should be controlled to reduce their intensifying effects, and the controlling of wind erosion could significantly reduce water erosion in this wind-water erosion crisscross region.     

Influences of sand cover on erosion processes of loess slopes based on rainfall simulation experiments

Aeolian-fluvial interplay erosion regions are subject to intense soil erosion and are of particular concern in loess areas of northwestern China.Understanding the composition,distribution,and transport processes of eroded sediments in these regions is of considerable scientific significance for controlling soil erosion.In this study,based on laboratory rainfall simulation experiments,we analyzed rainfall-induced erosion processes on sand-covered loess slopes(SS)with different sand cover patterns(including length and thickness)and uncovered loess slopes(LS)to investigate the influences of sand cover on erosion processes of loess slopes in case regions of aeolian-fluvial erosion.The grain-size curves of eroded sediments were fitted using the Weibull function.Compositions of eroded sediments under different sand cover patterns and rainfall intensities were analyzed to explore sediment transport modes of SS.The influences of sand cover amount and pattern on erosion processes of loess slopes were also discussed.The results show that sand cover on loess slopes influences the proportion of loess erosion and that the compositions of eroded sediments vary between SS and LS.Sand cover on loess slopes transforms silt erosion into sand erosion by reducing splash erosion and changing the rainfall-induced erosion processes.The percentage of eroded sand from SS in the early stage of runoff and sediment generation is always higher than that in the late stage.Sand cover on loess slopes aggravates loess erosion,not only by adding sand as additional eroded sediments but also by increasing the amount of eroded loess,compared with the loess slopes without sand cover.The influence of sand cover pattern on runoff yield and the amount of eroded sediments is larger than that of sand cover amount.Furthermore,given the same sand cover pattern,a thicker sand cover could increase sand erosion while a thinner sand cover could aggravate loess erosion.This difference explains the existence of intense erosion on slopes that are thinly covered with sand in regions where aeolian erosion and fluvial erosion interact.     

Sediment yield and erosion–deposition distribution characteristics in ephemeral gullies in black soil areas under geocell protection

Investigating the effect of geocells on the erosion and deposition distribution of ephemeral gullies in the black soil area of Northeast China can provide a scientific basis for the allocation of soil and water conservation measures in ephemeral gullies. In this study, an artificial simulated confluence test and stereoscopic photogrammetry were used to analyze the distribution characteristics of erosion and deposition in ephemeral gullies protected by geocells and the effect of different conflue...     

Two-dimensional hydrodynamic robust numerical model of soil erosion based on slopes and river basins

Erosion is an important issue in soil science and is related to many environmental problems, such as soil erosion and sediment transport. Establishing a simulation model suitable for soil erosion prediction is of great significance not only to accurately predict the process of soil separation by runoff, but also improve the physical model of soil erosion. In this study, we develop a graphic processing unit (GPU)-based numerical model that combines two-dimensional (2D) hydrodynamic and Green-Ampt (G-A) infiltration modelling to simulate soil erosion. A Godunov-type scheme on a uniform and structured square grid is then generated to solve the relevant shallow water equations (SWEs). The highlight of this study is the use of GPU-based acceleration technology to enable numerical models to simulate slope and watershed erosion in an efficient and high-resolution manner. The results show that the hydrodynamic model performs well in simulating soil erosion process. Soil erosion is studied by conducting calculation verification at the slope and basin scales. The first case involves simulating soil erosion process of a slope surface under indoor artificial rainfall conditions from 0 to 1000 s, and there is a good agreement between the simulated values and the measured values for the runoff velocity. The second case is a river basin experiment (Coquet River Basin) that involves watershed erosion. Simulations of the erosion depth change and erosion cumulative amount of the basin during a period of 1-40 h show an elevation difference of erosion at 0.5-3.0 m, especially during the period of 20-30 h. Nine cross sections in the basin are selected for simulation and the results reveal that the depth of erosion change value ranges from -0.86 to -2.79 m and the depth of deposition change value varies from 0.38 to 1.02 m. The findings indicate that the developed GPU-based hydrogeomorphological model can reproduce soil erosion processes. These results are valuable for rainfall runoff and soil erosion predictions on rilled hillslopes and river basins.     

Freeze-thaw effects on erosion process in loess slope under simulated rainfall

Seasonal freeze-thaw processes have led to severe soil erosion in the middle and high latitudes. The area affected by freeze-thaw erosion in China exceeds 13% of the national territory. So understanding the effect of freeze-thaw on erosion process is of great significance for soil and water conservation as well as for ecological engineering. In this study, we designed simulated rainfall experiments to investigate soil erosion processes under two soil conditions, unfrozen slope (UFS) and frozen slope (FS), and three rainfall intensities of 0.6, 0.9 and 1.2 mm/min. The results showed that the initial runoff time of FS occurred much earlier than that of the UFS. Under the same rainfall intensity, the runoff of FS is 1.17-1.26 times that of UFS; and the sediment yield of FS is 6.48-10.49 times that of UFS. With increasing rainfall time, rills were produced on the slope. After the appearance of the rills, the sediment yield on the FS accounts for 74%-86% of the total sediment yield. Rill erosion was the main reason for the increase in soil erosion rate on FS, and the reduction in water percolation resulting from frozen layers was one of the important factors leading to the advancement of rills on slope. A linear relationship existed between the cumulative runoff and the sediment yield of UFS and FS (R²>0.97, P<0.01). The average mean weight diameter (MWD) on the slope erosion particles was as follows: UFS0.9 (73.84 μm)>FS0.6 (72.30 μm)>UFS1.2 (72.23 μm)>substrate (71.23 μm)>FS1.2 (71.06 μm)>FS0.9 (70.72 μm). During the early stage of the rainfall, the MWD of the FS was relatively large. However, during the middle to late rainfall, the particle composition gradually approached that of the soil substrate. Under different rainfall intensities, the mean soil erodibility (MK) of the FS was 7.22 times that of the UFS. The ratio of the mean regression coefficient C₂ (MC₂) between FS and UFS was roughly correspondent with MK. Therefore, the parameter C₂ can be used to evaluate soil erodibility after the appearance of the rills. This article explored the influence mechanism of freeze-thaw effects on loess soil erosion and provided a theoretical basis for further studies on soil erosion in the loess hilly regions.     

Soil surface roughness change and its effect on runoff and erosion on the Loess Plateau of China

As an important parameter in the soil erosion model, soil surface roughness（SSR） is used to quantitatively describe the micro-relief on agricultural land. SSR has been extensively studied both experimentally and theoretically; however, no studies have focused on understanding SSR on the Loess Plateau of China. This study investigated changes in SSR for three different tillage practices on the Loess Plateau of China and the effects of SSR on runoff and erosion yield during simulated rainfall. The tillage practices used were zero tillage（ZT）, shallow hoeing（SH） and contour ploughing（CP）. Two rainfall intensities were applied, and three stages of water erosion processes（splash erosion（I）, sheet erosion（II） and rill erosion（III）） were analyzed for each rainfall intensity. The chain method was used to measure changes in SSR both initially and after each stage of rainfall. A splash board was used to measure the splash erosion at stage I. Runoff and sediment data were collected continuously at 2-min intervals during rainfall erosion stages II and III. We found that SSR of the tilled surfaces ranged from 1.0% to 21.9% under the three tillage practices, and the order of the initial SSR for the three treatments was ZT〈SH〈CP. For the ZT treatment, SSR increased slightly from stage I to III, whereas for the SH and CP treatments, SSR decreased by 44.5% and 61.5% after the three water erosion stages, respectively, and the greatest reduction in SSR occurred in stage I. Regression analysis showed that the changes in SSR with increasing cumulative rainfall could be described by a power function（R2〉0.49） for the ZT, SH and CP treatments. The runoff initiation time was longer in the SH and CP treatments than in the ZT treatment. There were no significant differences in the total runoff yields among the ZT, SH and CP treatments. Sediment loss was significantly smaller（P〈0.05） in the SH and CP treatments than in the ZT treatment.