【作者】 张翔；

【导师】 李占斌；

【作者基本信息】 西安理工大学 ， 水文学与水资源， 2016， 博士

【摘要】 土壤侵蚀会破坏生态环境,相比单一的侵蚀方式,复合侵蚀造成的土壤流失更为严重,其中风蚀与水蚀的复合是最为常见的一种复合方式。黄河上游的多沙粗沙区即为典型的风水复合侵蚀区。本论文以黄河上游十大孔兑地区东柳沟和西柳沟为研究对象,采用野外监测采样与室内模拟实验相结合的方法,系统地研究了区域侵蚀环境的变迁及水沙过程的变化,明确了复合外营力作用下流域沉积物的时空分布特征和输移过程;探讨了风水复合侵蚀规律,系统揭示了流域风力侵蚀和水力侵蚀的叠加作用;辨识了流域输入黄河泥沙的来源,量化了风力侵蚀和水力侵蚀对流域侵蚀产沙的贡献率。针对风蚀产沙和水蚀产沙的输移过程特征,开展了模拟降雨覆沙黄土坡面侵蚀产沙试验研究,辨识了覆沙黄土坡面和黄土坡面的侵蚀过程差异,揭示风蚀沉积对水蚀过程的影响和作用,推动了风水复合侵蚀过程的研究深化,为黄河多沙粗沙的治理提供了理论依据。本论文得到的主要结论如下:1)查明了风水复合侵蚀区下垫面的侵蚀特征。十大孔兑区域的主要土地利用特征为草地、沙地和耕地,2013年三种土地利用类型的面积分别占区域总面积的51.22%、21.42%和15.81%。自1980年以来,耕地、草地和建设用地的面积有增长趋势,林地和沙地有下降趋势,土地利用的变化主要发生在上游区域。伴随着土地利用的改变,区域的年际水沙关系也有较大变化,输沙的变幅大于径流。典型小流域西柳沟的径流量、输沙量和水沙关系均在1998年左右发生突变,变点前年径流量和年输沙量有较强的相关性,突变后年输沙量急剧减小。在这种侵蚀环境条件下,流域的土壤侵蚀强度的范围为2180.23 t/(km2·a)～17624.62 t/(km2·a),大部分属于强度和极强度土壤侵蚀,其中荒地(包括未利用地及沙地)和河道的侵蚀模数最高,耕地最低。从流域上游至下游,土壤侵蚀模数有减少的趋势。2)阐明了风水复合侵蚀区动力的时空分布。十大孔兑区域的侵蚀力在年内分布存在两个峰值,分别为3～5月的风季和7～9月的雨季,其中3～5月平均风速为5.4 m/s～6m/s,7～9月平均降雨量为31.67mm～74.06mm。通过有效侵蚀力的计算及叠加,十大孔兑区域的年均侵蚀力能量为:风蚀813.67 J·d/m2,水蚀1425.0 J·d/m2;其中3～5月侵蚀能量占全年总侵蚀能量的23.71%;7～9月侵蚀能量占全年总侵蚀能量的54.52%。在这种复合外营力的作用条件下,风季和雨季的主要侵蚀物质也有所差异。3月份径流中的悬移质则增加了极细沙和细沙,分别33.93%和28.56%,相应粉粒含量下降为36.36%。7、8月份流域出口站悬移质主要以粉粒为主,占有89.45%的构成;3)明确了风水复合侵蚀流域沉积物的分布特征、物质来源以及动力分配。东柳沟流域上游丘陵区的沉积物粒径范围为0.25mm～0.6mm,平均d50为0.47 mm;中游沙漠区和下游农田区的沉积物较细,粒径范围为在0.1mm～0.2mm,平均d50为0.18mm,而进入黄河的物质的主要构成为d50为0.093mm的丘陵区物质和d50为0.01mm沙漠区物质。基于物质守恒定律,通过Weibull函数对沉积物级配曲线的拟合,发现整个流域河道内的沉积物主要来自于丘陵区,在沉积物中比例约为78%,而来自沙漠区的物质约占22%;侵蚀这些物质的主要动力为风力,贡献约为72%,水蚀约为28%。但是在丘陵区,主要的侵蚀动力为水蚀,占该区域侵蚀能量的69.78%;而在沙漠区和农田区,主导侵蚀力为风蚀,分别占该区域侵蚀能量的74.54%和94.14%。由此可以得到风水复合侵蚀区土壤侵蚀的主要方式和区域为:丘陵区覆沙黄土坡面的降雨侵蚀过程。4)揭示了覆沙黄土坡面水蚀产沙过程的叠加作用机制。薄层风积覆沙格局显著的增加了黄土坡面的水蚀强度。随着覆沙质量的增加,覆沙黄土坡面会极大的延长初损历时。覆沙黄土坡面的主要侵蚀产沙物质为黄土,约占总侵蚀产沙量的83%;而所覆风沙的产沙量在产流3～5min出现峰值。坡面覆沙不仅增加了风沙作为侵蚀物质,还增强了对本底黄土的侵蚀:由于覆沙而额外增加的产沙量,是覆沙质量的64.15%～317.64%。相同降雨条件和覆沙质量条件下,覆沙格局从半坡覆沙变为全坡薄层覆沙,侵蚀产沙量增加了87.11%,其中黄土占的比重也从77.99%增加至92.37%。通过径流侵蚀功率与侵蚀风沙、黄土量的回归分析,发现侵蚀单位质量风沙所消耗的功率约为同质量黄土的1.19倍,这种差异会受到雨强、初始产流时间、覆沙质量、覆沙格局等因素的影响。相同的降雨和覆沙量条件下,薄层覆沙侵蚀能量增大,且侵蚀能耗较小的黄土的比例增加,因此薄层覆沙黄土坡面较黄土坡面的水蚀产沙更为严重。更多还原

【Abstract】 Soil erosion is an important factor that influences environmental change and ecological stability.Aeolian-fluvial interplay regions in northwestern China experience serious soil erosion,and are the main source of coarse sediments entering the Yellow River.Owing to the superposition of erosive power and erosion time in the aeolian-fluvial interplay regions,eroded material and erosion time are extended,resulting in greater ecological impact.Therefore,it is of important scientific significance to analyze the composition,distribution,and transport processes of eroded materials in these regions for the control of soil erosion.The study area are two typical aeolian-fluvial interplay erosion watersheds-the Dongliu Gully and the Xiliu Gully,both belong to the ten watershed of Inner Mongolia.Data were collected from hydrological station,filed sampling and monitoring,and laboratory rainfall simulation.The erosion situation of the study area were analyzed,the energy of erosive wind and precipitation were calculated,the distribution of deposited sediments were analyzed,the dynamic and physical source of deposited sediment in the stream channel were determined.The variations in composition of the eroded materials under different sand cover patterns and rainfall conditions were further analyzed through laboratory rainfall simulation of a sand-covered slope to reveal the influence of wind erosion on the water erosion.The results are conductive to provide scientific reference for control and management of soil erosion in aeolian-fluvial interplay erosion areas.1)The land use,annul runoff and annual sediment load characteristics and variation of the studied aeolian-fluvial interplay erosion watershed were analyzed.Grassland,desert and farmland are the main land use types in the ten watershed of Inner Mongolia,their area percentages are 51.22%,21.42,and 15.81%respectively.The areas of farmland,grassland and construction land have increasing trends,while forest land and desert have decreasing trends since 1980s,and the variation of land use mainly take place in the upper region.The statistics of annual runoff and sediment load also change greatly,and both the change points of annual runoff and sediment load take place around 1998.Annual sediment load is closely related to annual runoff before 1998,and annual sediment load decrease significantly.The soil erosion modulus range from 2180.23 t/(km2·a)～17624.62 t/(km2·a),and most regions belong to intense erosion and strongly intense erosion,while the soil erosion modules of the desert and stream channel are highest,and the farm land is lowest among different land use types.On the other hand,the soil erosion module have a decreasing trend from the upper region to the lower region.2)The energy of erosive wind and erosive precipitation in the study area were calculated.The intra-annual distribution of erosive energy showed that there are two peak points,i.e.,windy season from March to May,and rainy season from July to September.The average wind speed from March to May is 5.4 m/s～6m/s,and the average monthly precipitation from July to September is 31.67mm～74.06mm.Annual energy of erosive wind is 813.67 J·d/m2,and annual energy of erosive precipitation is 1425.0 J·d/m2.The erosive energy in the windy season accounts for 23.71%,and the erosive energy in the rainy season accounts for 54.52%.The composition of suspended load in the stream channel in the windy season is different from the rainy season.The main material of suspended load in the rainy season is silt,which takes up 89.45%.Powder sand and fine sand are included in the suspended load in the windy season,taking up 33.93%and 28.56%respectively,and the proportion of silt is 36.36%.3)The distribution of deposited sediment in the stream channel were analyzed and the sources of deposited sediment in the stream channel were determined based on the law of the conservation of matter.The sediment grain sizes in the watershed were concentrated within two ranges:relatively coarse deposited sediments(0.25 mm to 0.6 mm,mean median grain size(d50)of 0.47 mm)mainly distributed in the hilly zone in the upper watershed;and relatively fine deposited sediments(0.1 mm to 0.2 mm,mean d50 of 0.18 mm)mainly distributed in the desert zone located in the middle watershed and in the farmland zone located in the lower watershed.Sediment entering the Yellow River was dominated by hilly zone material with a d50 of 0.093 mm and desert zone material with a dso of 0.01 mm.The frequency distribution curves of sediments deposited in the stream channel were fitted using the Weibull function,the sources of deposited sediment in the stream channel showed that the hilly zone accounts for 78%of deposited sediments,and the desert zone accounted for 22%of deposited sediments.Wind erosion dynamics accounts for 72%of deposited sediments,while water erosion dynamics accounted for only 28%.However,the dominated erosion dynamic in the hilly zone is water erosion,which accounts foe 69.78%,and the dominated erosion dynamics in both the desert zone and farmland zone are wind erosion,which accounts for 74.54%and 94.14%respectively.Therefore,it can be concluded that the intense erosion in aeolian-fluvial interplay erosion take place in sand-coverd hilly during rainstorm.4)The sediment transport modes of the sand-covered slopes were explored through laboratory rainfall simulation.Water erosion is proved to be intensified under sand-covered slopes.The initial time producing runoff will be greatly delyed as the sand-coived mass increase.The prominent eroded material of sand cover slope is loess,and take up 83%in average.Sand erosion mainly take place in the initial stage of erosion.Sand-covered slopes aggravated loess erosion,not only added sand as additional erosion material,but also increased loess erosion amount,compared with the loess slopes.Both sand cover pattern and sand cover amount have influence on the erosion increment.Depending on the pattern,the increment of erosion material is 64.2%-317.6%of the sand cover amount.Under the same rainfall intensity and and-covered mass,the increment of eroded materials is 87.11%from the sand-covered half slope to thin but total sand-covered slope,and the proportion of loess increase from 77.99%to 92.37%.The relationship between runoff erosion power,erosion sand amount,and erosion loess amount were fitted by multiple linear regression,and it is indicated that the consumed erosion power of per erosion sand amount is 1.19 times per erosion loess amount generally,and the consumed erosion power is influenced by rainfall intensity,initial time producing runoff,sand cover mass,and sand cover pattern.The resluts indicate the thin sand cover induced the largest erosion amount compared with other sand cover patterns and explaine the cause of intense erosion for thin sand-covered slopes in the aeolian-fluvial interplay erosion regions.更多还原