【作者】 耿晓东；

【导师】 郑粉莉；

【作者基本信息】 中国科学院研究生院（教育部水土保持与生态环境研究中心） ， 土壤学， 2010， 博士

【摘要】 对比研究我国主要水蚀区坡面侵蚀产沙过程的差异性，不但深化对我国土壤侵蚀规律的认识，也为不同水蚀类型区坡面水土保持措施配置提供理论支持。本论文首次在国内采用统一的研究方法与试验技术，对比研究了我国三个水蚀类型区（西北黄土高原、南方红壤低山丘陵和西南紫色土丘陵）在不同降雨强度（50、75和100 mm/h）和坡度（5°~30°）条件下坡面土壤侵蚀过程与机理，揭示了降雨强度和坡度对坡面侵蚀产沙的影响，阐明了细沟侵蚀发育特征及侵蚀形态演变过程，分析了坡面侵蚀产沙的动力学机理，取得了新的研究进展，为针对性地建立我国侵蚀预报模型和水土保持措施布设提供了重要的理论依据。主要研究结论如下：1.研究了主要水蚀区坡面降雨入渗和产流过程。坡面降雨起始产流时间均随降雨强度和坡度的增大而趋于提前。坡面起始产流的先后顺序为：紫色土、红壤、黄土。坡面土壤入渗率随时间的变化服从幂函数规律，坡面径流率呈对数函数变化。紫色土和红壤坡面在降雨开始10 min左右进入稳定入渗和产流阶段，黄土坡面约在30 min后开始趋于稳定。三个水蚀区坡面径流量均随坡度增大而减小。入渗过程与坡面土壤结皮形成及坡面侵蚀方式演变过程紧密相关。紫色土坡面的径流系数变化于0.78~0.93，红壤坡面变化于0.61~0.88，黄土坡面则变化于0.3~0.67之间。2.对比分析了主要水蚀区坡面侵蚀产沙过程及降雨强度和坡度的影响。当降雨强度为50和75mm/h、坡度为5°~15°及降雨强度为100 mm/h、坡度为5°~10°时，红壤坡面侵蚀量最大，其次为紫色土坡面，而黄土坡面最小；其它试验条件下，三个水蚀区坡面土壤侵蚀量的排序为：紫色土坡面>黄土坡面>红壤坡面；其结果反映了在黄土区和紫色土区，坡度对坡面土壤侵蚀的重要影响。黄土和紫色土坡面侵蚀产沙速率最大值出现在降雨过程的后期，红壤坡面最大侵蚀产沙速率出现在降雨初期。三个水蚀区坡面土壤侵蚀量均随降雨强度和坡度的增加而增大。黄土坡面和紫色土坡面在25°左右出现侵蚀产沙的临界坡度，红壤坡面的临界坡度现象不明显。3.揭示了主要水蚀区坡面细沟侵蚀发展过程及其对坡面侵蚀产沙动态变化的影响。随降雨强度或坡度的增加，坡面更早发生细沟侵蚀，细沟溯源侵蚀速度也随之增大。黄土和紫色土坡面细沟溯源侵蚀速率与产沙速率具有较强的同步性，红壤坡面的这种同步性则较差。在50 mm/h降雨强度下，紫色土坡面在26 min内出现细沟，黄土在40 min内出现细沟，红壤坡面无明显的细沟侵蚀发生；75和100 mm/h降雨强度下，紫色土坡面出现细沟的时间亦早于黄土坡面和红壤坡面。发生细沟溯源侵蚀所需的汇水坡长在三个水蚀区的排序为：紫色土坡面＞黄土坡面＞红壤坡面。紫色土和黄土坡面最大溯源侵蚀速率达到18.5 cm/s，而红壤坡面仅10 cm/s。4.紫色土坡面细沟平均宽度和深度略大于黄土坡面，两者趋于形成宽且深的细沟，其细沟宽度分别介于5.0~15.5和2.5~18.5 cm之间，深度分别在1.5~15和1.5~10.5 cm之间；红壤坡面常形成宽度和深度都较小的平行细沟，其细沟宽度和深度分别介于3.1~7.6 cm和1.5~6.9 cm之间。试验条件下，三个水蚀区坡面的细沟侵蚀量皆随坡度或降雨强度的增加而增加，其占坡面总产沙量的比例：黄土坡面为10%~88.7%，紫色土和红壤坡面分别为37.1%~92.8%和14.7%~80.7%。随降雨强度和坡度的增加，坡面侵蚀方式由片蚀为主向以细沟侵蚀为主演变。黄土坡面在降雨强度为50和75 mm/h、坡度为25°~30°以及降雨强度为100 mm/h、坡度为15°~30°时，坡面侵蚀均以细沟侵蚀为主；紫色土坡面在降雨强度为50 mm/h、坡度为5°~10°以及降雨强度为75和100 mm/h、坡度为10°~30°时，坡面侵蚀以细沟侵蚀为主；红壤坡面当降雨强度为75和100 mm/h、坡度为20°~25°时，坡面土壤侵蚀以细沟侵蚀为主。5.对比分析了三个水蚀区坡面径流的流态和水力学参数特征。坡面细沟间水流流速受降雨强度、坡度和细沟发展过程的影响，三个水蚀区坡面的对比关系为：红壤坡面＞黄土坡面＞紫色土坡面。试验条件下，坡面细沟的出现，在增加坡面侵蚀产沙量的同时，也使坡面薄层水流横向溢流到细沟沟槽，从而加大了细沟水流流速，在紫色土坡面表现更为明显。紫色土坡面细沟水流流速是细沟间水流流速的2.1~4.7倍，黄土坡面和红壤坡面二者的比值分别是1.1~2.3和1.2~1.85倍。黄土和紫色土坡面在50和75 mm/h降雨强度下，当细沟水流雷诺数与薄层水流雷诺数的比值分别在10倍和15倍左右时，坡面侵蚀量出现剧增现象；100 mm/h降雨强度下，雷诺数的比值分别在8.2和10.0左右时，侵蚀量出现剧增。而对于红壤坡面，则没有明显的规律性。6.探讨了不同水蚀区坡面径流侵蚀的产沙动力机制。黄土坡面取平均断面单位能量E≥0.398 cm作为试验条件下坡面侵蚀发生的动力临界，径流剪切力J≥5.44 Pa作为其辅助的动力临界；紫色土坡面，取E≥0.351 cm作为试验条件下坡面侵蚀发生的动力临界，径流剪切力J≥8.98 Pa作为其辅助的动力临界；对于红壤坡面，取E≥0.883 cm作为试验条件下坡面侵蚀发生的动力临界，径流剪切力J≥3.87 Pa作为其辅助的动力临界。7.估算了三种侵蚀土壤可蚀性K（t·hm2·h·hm-2·MJ-1·mm-1）。由土壤侵蚀与生产力关系模型（EPIC）得到黄土的K值为0.053，紫色土和红壤K值分别为0.058和0.032。单位降雨引起的坡面侵蚀量或单位径流引起的坡面侵蚀量皆表现为：紫色土坡面>黄土坡面>红壤坡面。黄土坡面每mm降雨量所引起的土壤侵蚀量平均值为71.6 g/m2·mm-1，紫色土和红壤坡面分别为155.8和40.7 g/m2·mm-1；黄土坡面每mm径流深所引起的侵蚀量为161.5 g/m2·mm-1，紫色土和红壤坡面分别为171.75和64.1 g/m2·mm-1。更多还原

【Abstract】 Through the comparative study of the differences among the processes of hillslopeerosion and sediment yield in main water erosion regions in our country, will not only goodfor further understanding of the field of soil erosion laws, but also provide theoretical supportsfor the arrangement of hillslope soil and water conservation measurements in regions ofdifferent water erosion types. In this paper, the processes and mechanisms of hillslope soilerosion in three main water erosion regions (the Loess Plateau region, red soil low mountainhillyregion and purple soil hilly region), under different rainfall intensity (50, 75, and100mm/h) and slope gradients (5°-30°) was studied comparatively by adopting uniformresearching methodologies and experimental technologies, as well as the effects of rainfallintensity and slope gradient on the processes of hillslope erosion and sediment yield wereanalyzed. Besides, the developing features of rills and the evolution processes of erosion typeswere illustrated, and the dynamic mechanism of hillslope erosion and sediment yield were alsoanatomized. These were new developments in this field, and will provide theoreticalreferences for the establishment of soil erosion predicting model with pertinence and thearrangements of soil and water conservation measurements in our country. The mainconclusions are as follows:1. The hillslope rainfall and infiltration processes and runoff generation processes werestudied. The time of runoff generation tended to advance with the increasing of rainfallintensity and slope gradient. The order for the starting time of runoff generation was: purple,red soil and loess. The variation of slope infiltration rate along with time obey the law ofpower function, while the variation of slope runoff rate followed the law of logarithm function.The infiltration and runoff generation of purple soil hillslope and red soil hillslope entered tostable phases at about 10 minutes after the rainfall simulation began, while the loess hillslopeat about 30 minutes. The amount of runoff on the hillslopes of the three regions all decreasedwith the increase of slope gradient. It was found that the infiltration processes were closelyrelated to the crust formation and the evolution of erosion types on the hillslope. The runoffcoefficient of purple soil ranged from 0.78 to 0.93, red soil from 0.61 to 0.88, and loess from0.3 to 0.67.2. The sediment yielding processes of the main water erosion regions, and the effects ofrainfall intensity and hillslope gradient were comparatively analyzed. When the rainfallintensities were 50 mm/h and 75 mm/h and the hillslope gradients ranged from 5°-15°, or therainfall intensity was 100 mm/h and hillslope gradients ranged from 5°-10°, the red soilhillslope has the greatest sediment yield, and then the purple soil hillslope, loess hillslope was the least; under other experimental conditions, the order of sediment yield on the hillslopes ofthe three water erosion region was: purple soil hillslope>loess hillslope>red soil hillslope. Theresult indicated that hillslope gradients have important effects on soil erosion process in theloess and purple soil region. The sediment yield on loess and purple soil hillslopes reached themaximum value at the later period of the rainfall process, and the red soil hillslope at the initialstage. The sediment yield on the hillslopes of the three regions all increased with the increaseof rainfall intensity and hillslope gradient. The crucial slope gradient value of sediment yieldon the loess and purple soil hillslope appeared at 25°, but that of the red soil hillslope was notclear.3. The process of rill erosion developing in main water erosion regions and its influences onthe dynamic variation of sediment yielding were also illustrated. The time of rills formed wereshorten with the increase of rainfall intensity and hillslope gradient, as well as the rates ofheadward erosion. The headward erosion rates and sediment yielding rates of both loess andpurple soil were strong synchronism, which was weak for red soil. When the rainfall intensitywas 50 mm/h, rills on purple soil hillslopes appeared at the 26th min, and loess hillslopes at the40th min, while there was no clear rill appeared on the red soil hillslopes. When the rainfallintensity was 75 mm/h and 100 mm/h, rill on the red soil hillslopes appeared earlier than loesshillslopes and red soil hillslopes. The order of the slope length which were needed for theoccurring of headward erosion in the three water erosion regions was: purple hillslope>loesshillslope>red soil hillslope. The maximum value for the headward erosion on purple soilhillslopes and loess hillslopes were both18.5 cm/s, while red soil slopes was 10 cm/s.4. The average width and depth for rills on purple soil hillslopes were slightly wider anddeeper than that on loess hillslopes, and the rills on both soil hillslopes tended to form widerand deeper rills, the ranges of width were from 5.0 cm to 15.5 and 2.5 cm to 18.5 cm, and theranges of depth from 1.5 cm to 15 cm and 1.5 cm to 10.5 cm; while the rills formed on the redsoil hillslopes were always paralleled ones with smaller width and depth, which the width anddepth changed between 3.1 cm to 7.6 cm. Under the conditions in this study, the amount of rillerosion in the three water erosion regions all inceased with the increase of rainfall intensity orhillslope gradient. The proportion of rill erosion to total hillslope sediment yielding of was:10%-88.7% for loess, 37.1%-92.8% for purple and 14.7% - 80.7% for red soil, respectively.With the increase of rainfall intensity and hillslope gradient, the dominant erosion typeevoluted from sheet erosion to rill erosion. When the rainfall intenstiy were 50 and 75 mm/h,hillslope gradientwas 25°~30°, and rainfall intensity was 100 mm/h and hillslope gradient was15°~30°, the dominant erosion type on the loess hillslope was rill erosion; when the rainfallintenstiy was 50 mm/h, hillslope gradient was 5°~10°and rainfall intensity was 75 and 100mm/h, hillslope gradient was 10°~30°, rill erosion was the dominant erosion type on the purplesoil hillslopes ; when the rainfall intensity was 75 and 100 mm/h, hillslope gradient was20°~25°, the dominant erosion type on the red soil hillslopes was rill erosion.5. The flow types and characteristics of hydraulic parameter of the flows in the three watererosion regions were analyzed. The runoff rates in rills were influenced by rainfall intensity, hillslope gradient and the processes of generation and development of rills. And the runoffrates on hillslope followed the order: red soil>loess>purple soil. Under the conditions in thisstudy, the generation of rills, not only increased the amount of sediment yielding on thehillslope, but also caused the lateral overflowing of thin flow into the rills, which increased therunoff rate in rill , and this was more obvious on the purple soil hillslope. The runoff rateswithin the rills were 2.1 to 4.7 times greater than those of interrill on the purple soil hillslope,and were 1.1 to 2.3 on the loess hillslope, and 1.2 to 1.85 on the red soil hillslope.When therainfall intensity were 50 and 75 mm/h, the erosion amount increased sharply on both loesshillslopes and purple soil hillslopes, as the ratio of Reynolds of runoff within rills to that ofthin flow were 10 to 15; when the rainfall intensity was 100 mm/h, the sharp increase oferosion amount appeared as the ratio of Reynolds was 8.2 to 10.0. However, there was noobvious law on the red soil hillslope.6. The study discussed dynamics mechanism of sediment yielding driven by runoff erosionThe average specific energy in a cross section(E),was taken as the crutial dynamics for theoccurrence of hillslope erosion , the E value on the loess hillslopes.purple soil hillslope and red soil hillslope were E≥0.398 cm, E≥0.351 cm, and E≥0.883cm ,respectively. Moreover ,the sheer stress J was taken as the assitant crutial dynamics. The Jvalue on the loess hillslopes, purple soil hillslope and red soil hillslope were J≥5.44 Pa., J≥8.98 Pa and J≥3.87 Pa, respectively.7. this paper also estimated the soil erodibility K (t·hm2·h·hm-2·MJ-1·mm-1) The K value wasobtained by the Erosion and Productivity impact EPIC . The K for loess was 0.053, 0.058 forpurple soil and 0.032 for red soil, respectively. The amount of erosion caused by unit rainfall orby unit runoff followed order: purple soil hillslope>loess hillslope>red soil hillslope. Theaverage amount of loess eroded by per milimeter precipitation was 71.6 g/m2·mm-1, and that ofpurple soil and red soil was 155.8 and 40.7 g/m2·mm-1, respectively. While the average amountof loess eroded by per milimeter runoff was 161.5 g/m2·mm-1, and that of purple soil and redsoil was 171.75 and 64.1 g/m2·mm-1, respectively.更多还原