人工掏挖坡面侵蚀微地貌演化及其水力学特性分析
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摘要
人工掏挖是黄土高原地区夏闲地翻耕时广为应用的耕作方式,为探明其坡面侵蚀过程,利用三维激光扫描仪及Arc GIS软件,阐明其在人工模拟间歇降雨下坡面微地貌、侵蚀产沙及水力学参数演变规律。结果表明:(1)坡面侵蚀历经溅蚀—片蚀、断续细沟、连续细沟3个阶段;降雨截止时细沟平面密度、平均沟深、最大沟长和最大沟深分别增至初始的1.42倍、2.24倍、15.5倍和2.43倍。(2)地表糙度随降雨历时推移从1.706呈近似线性趋势减小至1.488;累积降雨量达80 mm之前,径流量、含沙量随地表糙度的减小增加缓慢,但之后随地表糙度减小增加剧烈。(3)降雨过程中流速呈现波动增加趋势,水流由层流快速过渡至紊流,但始终保持为缓流,水流阻力呈波动下降,且形态阻力一直居于主导地位。人工掏挖耕作坡面在雨强1.5 mm/min、降雨量80 mm以内可起到蓄水保土作用,但在连续强降雨下也更易引起细沟侵蚀。
Artificial digging was accomplished comprehensively in the Loess Plateau region during summer fallow tillage period. In order to elucidate the evolution processes on erosion as well as the flow hydraulic characteristics of its complicated slope surface under the condition of continuous rainfall,this study utilizes 3-D Laser Scanner and Arc GIS.They were employed to investigate the microtopography evolution process and hydraulic characteristics under intermittent simulated rainfall,following which it offers theoretical basis for tillage practices. The results demonstrate the following:(1) There are three processes which are splash erosion and sheet erosion stage,the formation of rill stage and the developing of rill stage. The rill density,average depth,maximum rill length and depth increased by 1. 42,1. 72,15. 57 and 3. 18 times as against initial rill forming stage with rainfall.(2) The initial surface roughness of artificial digging is 1. 706 which decreased linearly to 1. 488 with the rainfall. In the process of accumulated rainfall reaching 81 mm,the runoff and sediment yield increased slowly with the decline of roughness,but increased dramatically later.(3) The flow velocity with fluctuation increased after the rill shaping,and the flow advanced from laminar to turbulent flow speedily,but keeping the subcritical flow all the way. Under the effect of surface roughness,the flow resistance comprised of grain resistance,rain resistance and form resistance which decreased with the rainfall duration,where the form resistance took the most significant position during the entire process. The slope surface of artificial digging might have a positive impact on soil and water conservation under the rainfall intensity of 1. 5 mm/min when the rainfall is within 80 mm,but it may prone to suffer rill erosion under continuous extreme rainfall.
Artificial digging was accomplished comprehensively in the Loess Plateau region during summer fallow tillage period. In order to elucidate the evolution processes on erosion as well as the flow hydraulic characteristics of its complicated slope surface under the condition of continuous rainfall,this study utilizes 3-D Laser Scanner and Arc GIS.They were employed to investigate the microtopography evolution process and hydraulic characteristics under intermittent simulated rainfall,following which it offers theoretical basis for tillage practices. The results demonstrate the following:(1) There are three processes which are splash erosion and sheet erosion stage,the formation of rill stage and the developing of rill stage. The rill density,average depth,maximum rill length and depth increased by 1. 42,1. 72,15. 57 and 3. 18 times as against initial rill forming stage with rainfall.(2) The initial surface roughness of artificial digging is 1. 706 which decreased linearly to 1. 488 with the rainfall. In the process of accumulated rainfall reaching 81 mm,the runoff and sediment yield increased slowly with the decline of roughness,but increased dramatically later.(3) The flow velocity with fluctuation increased after the rill shaping,and the flow advanced from laminar to turbulent flow speedily,but keeping the subcritical flow all the way. Under the effect of surface roughness,the flow resistance comprised of grain resistance,rain resistance and form resistance which decreased with the rainfall duration,where the form resistance took the most significant position during the entire process. The slope surface of artificial digging might have a positive impact on soil and water conservation under the rainfall intensity of 1. 5 mm/min when the rainfall is within 80 mm,but it may prone to suffer rill erosion under continuous extreme rainfall.
引文
[1]刘国彬,李敏,上官周平,等.西北黄土区水土流失现状与综合治理对策[J].中国水土保持科学,2008,6(1):16-21.(LIU G B,LI M,SHANGGUAN Z P,et al.Current status and comprehensive control strategies of soil erosion for loess region in the Northwestern China[J].Science of Soil and Water Conservation,2008,6(1):16-21.(in Chinese))
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[3]SHI H,SHAO M A.Soil and water loss from the Loess Plateau in China[J].Journal of Arid Environments,2000,45(1):9-20.
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[5]孙正宝,陈治谏,廖晓勇,等.侵蚀性降雨识别的模糊隶属度模型建立及应用[J].水科学进展,2011,22(6):801-806.(SUN Z B,CHEN Z J,LIAO X Y,et al.Development and application of a fuzzy membership model for identifying erosive rainfall events[J].Advances in Water Science,2011,22(6):801-806.(in Chinese))
[6]赵龙山,张青峰,梁心蓝,等.基于GIS的坡耕地数字高程模型的建立与应用[J].农业工程学报,2010,26(11):317-322.(ZHAO L S,ZHANG Q F,LIANG X L,et al.Establishment and application of DEM for loess slope land based on GIS[J].Transactions of the CSAE,2010,26(11):317-322.(in Chinese))
[7]郑子成,吴发启,何淑勤,等.地表糙度对径流和产沙影响的室内试验研究[J].农业工程学报,2007,23(10):19-24.(ZHENG Z C,WU F Q,HE S Q,et al.Effects of soil surface roughness on runoff and sediment discharges with laboratory experiments[J].Transactions of the CSAE,2007,23(10):19-24.(in Chinese))
[8]王健,吴发启,孟秦倩.农业耕作措施蓄水保土效益试验研究[J].水土保持通报,2004,24(5):39-41.(WANG J,WU F Q,MENG Q Q.Benefits of tillage measures for soil and water conservation[J].Bulletin of Soil and Water Conservation,2004,24(5):39-41.(in Chinese))
[9]FU B J,LIU Y,LYU Y H,et al.Assessing the soil erosion control service of ecosystems change in the Loess Plateau of China[J].Ecological Complexity,2011,8(4):284-293.
[10]李鹏,李占斌,郑良勇.黄土坡面径流侵蚀产沙动力过程模拟与研究[J].水科学进展,2006,17(4):444-449.(LI P,LI Z B,ZHENG L Y.Hydrodynamics process of soil erosion and sediment yield by runoff on Loess Slope[J].Advances in Water Science,2006,17(4):444-449.(in Chinese))
[11]梁心蓝,赵龙山,吴佳,等.地表糙度与径流水力学参数响应规律模拟[J].农业工程学报,2014,30(19):123-131.(LIANG X L,ZHAO L S,WU J,et al.Simulation of response law for soil surface roughness and hydraulics parameters of runoff[J].Transactions of the CSAE,2014,30(19):123-131.(in Chinese))
[12]LINDEN D R,DOREN D.Parameters for characterizing tillage-induced soil surface roughness[J].Soil Science Society of America Journal,1986,50:1561-1565.
[13]吴普特,周佩华,武春龙,等.坡面细沟侵蚀垂直分布特征研究[J].水土保持研究,1997,4(2):47-56.(WU P T,ZHOU P H,WU C L,et al.Research on the spatial distribution characteristics of slope rill erosion[J].Research of Soil and Water Conservation,1997,4(2):47-56.(in Chinese))
[14]ABRAHAMS A D,PARSONS A J,HIRSCH P J.Field and laboratory studies of resistance to interrill overland flow on semi-arid hillslopes,southern Arizona[C]//PARSONS A J,ABRAHAMS A D.Overland flow:hydraulics and erosion mechanics.London:UCL Press,1992:1-23.
[15]HU S X,ABRAHAMS A D.Partitioning resistance to overland flow on rough mobile beds[J].Earth Surface Processes and Landforms,2006,31:1280-1291.
[16]吴淑芳,张永东,卜崇峰.黄土细沟侵蚀演化过程及其水力学特性试验研究[J].泥沙研究,2015(6):72-80.(WU S F,ZHANG Y D,BU C F.Experimental study on rill erosion processes and flow hydraulic characteristics on loess gentle slope[J].Journal of Sediment Research,2015(6):72-80.(in Chinese))
[17]HE J J,LI X J,JIA L J,et al.Experimental study of rill evolution processes and relationships between experimental study of rill evolution processes and relationships between runoff and erosion on clay loam and loess[J].Soil Science Society of America Jour-nal,2014,78(5):1716-1725.
[18]张攀,唐洪武,姚文艺,等.细沟形态演变对坡面水沙过程的影响[J].水科学进展,2016,27(4):535-541.(ZHANG P,TANG H W,YAO W Y,et al.Evolution and quantization methods of rill morphology on the slope under rainfall simulation[J].Advances in Water Science,2016,27(4):535-541.(in Chinese))
[19]MAGUNDA M K,LARSON W E,LINDEN D R,et al.Changes in microrelief and their effects on infiltration and erosion during simulated rainfall[J].Soil Technology,1997,10(1):57-67.
[20]NEARING M A,POLYAKOV V O,NICHOLS M H,et al.Slope-velocity-equilibrium and evolution of surface roughness on a stony hillslope[J].Hydrology and Earth System Sciences,2017,21(6):3221-3229.
[21]王龙生,蔡强国,蔡崇法,等.黄土坡面细沟形态变化及其与流速之间的关系[J].农业工程学报,2014,30(11):110-117.(WANG L S,CAI Q G,CAI C F,et al.Morphological changes of rill on loess slope and its relationship with flow velocity[J].Transactions of the CSAE,2014,30(11):110-117.(in Chinese))
[22]PENG W Y,ZHANG Z D,ZHANG K L.Hydrodynamic characteristics of rill flow on steep slopes[J].Hydrological Processes,2015,29(17):3677-3686.
[2]ZHANG Q F,WANG J,ZHAO L S,et al.Spatial heterogeneity of surface roughness during different erosive stages of tilled loess slopes under a rainfall intensity of 1.5 mm·min-1[J].Soil and Tillage Research,2015,153:95-103.
[3]SHI H,SHAO M A.Soil and water loss from the Loess Plateau in China[J].Journal of Arid Environments,2000,45(1):9-20.
[4]张宽地,王光谦,吕宏兴,等.模拟降雨条件下坡面流水动力学特性研究[J].水科学进展,2012,23(2):229-235.(ZHANG K D,WANG G Q,LYU H X,et al.Experimental study of shallow flow hydraulics on a hillslope under artificial rainfall conditions[J].Advances in Water Science,2012,23(2):229-235.(in Chinese))
[5]孙正宝,陈治谏,廖晓勇,等.侵蚀性降雨识别的模糊隶属度模型建立及应用[J].水科学进展,2011,22(6):801-806.(SUN Z B,CHEN Z J,LIAO X Y,et al.Development and application of a fuzzy membership model for identifying erosive rainfall events[J].Advances in Water Science,2011,22(6):801-806.(in Chinese))
[6]赵龙山,张青峰,梁心蓝,等.基于GIS的坡耕地数字高程模型的建立与应用[J].农业工程学报,2010,26(11):317-322.(ZHAO L S,ZHANG Q F,LIANG X L,et al.Establishment and application of DEM for loess slope land based on GIS[J].Transactions of the CSAE,2010,26(11):317-322.(in Chinese))
[7]郑子成,吴发启,何淑勤,等.地表糙度对径流和产沙影响的室内试验研究[J].农业工程学报,2007,23(10):19-24.(ZHENG Z C,WU F Q,HE S Q,et al.Effects of soil surface roughness on runoff and sediment discharges with laboratory experiments[J].Transactions of the CSAE,2007,23(10):19-24.(in Chinese))
[8]王健,吴发启,孟秦倩.农业耕作措施蓄水保土效益试验研究[J].水土保持通报,2004,24(5):39-41.(WANG J,WU F Q,MENG Q Q.Benefits of tillage measures for soil and water conservation[J].Bulletin of Soil and Water Conservation,2004,24(5):39-41.(in Chinese))
[9]FU B J,LIU Y,LYU Y H,et al.Assessing the soil erosion control service of ecosystems change in the Loess Plateau of China[J].Ecological Complexity,2011,8(4):284-293.
[10]李鹏,李占斌,郑良勇.黄土坡面径流侵蚀产沙动力过程模拟与研究[J].水科学进展,2006,17(4):444-449.(LI P,LI Z B,ZHENG L Y.Hydrodynamics process of soil erosion and sediment yield by runoff on Loess Slope[J].Advances in Water Science,2006,17(4):444-449.(in Chinese))
[11]梁心蓝,赵龙山,吴佳,等.地表糙度与径流水力学参数响应规律模拟[J].农业工程学报,2014,30(19):123-131.(LIANG X L,ZHAO L S,WU J,et al.Simulation of response law for soil surface roughness and hydraulics parameters of runoff[J].Transactions of the CSAE,2014,30(19):123-131.(in Chinese))
[12]LINDEN D R,DOREN D.Parameters for characterizing tillage-induced soil surface roughness[J].Soil Science Society of America Journal,1986,50:1561-1565.
[13]吴普特,周佩华,武春龙,等.坡面细沟侵蚀垂直分布特征研究[J].水土保持研究,1997,4(2):47-56.(WU P T,ZHOU P H,WU C L,et al.Research on the spatial distribution characteristics of slope rill erosion[J].Research of Soil and Water Conservation,1997,4(2):47-56.(in Chinese))
[14]ABRAHAMS A D,PARSONS A J,HIRSCH P J.Field and laboratory studies of resistance to interrill overland flow on semi-arid hillslopes,southern Arizona[C]//PARSONS A J,ABRAHAMS A D.Overland flow:hydraulics and erosion mechanics.London:UCL Press,1992:1-23.
[15]HU S X,ABRAHAMS A D.Partitioning resistance to overland flow on rough mobile beds[J].Earth Surface Processes and Landforms,2006,31:1280-1291.
[16]吴淑芳,张永东,卜崇峰.黄土细沟侵蚀演化过程及其水力学特性试验研究[J].泥沙研究,2015(6):72-80.(WU S F,ZHANG Y D,BU C F.Experimental study on rill erosion processes and flow hydraulic characteristics on loess gentle slope[J].Journal of Sediment Research,2015(6):72-80.(in Chinese))
[17]HE J J,LI X J,JIA L J,et al.Experimental study of rill evolution processes and relationships between experimental study of rill evolution processes and relationships between runoff and erosion on clay loam and loess[J].Soil Science Society of America Jour-nal,2014,78(5):1716-1725.
[18]张攀,唐洪武,姚文艺,等.细沟形态演变对坡面水沙过程的影响[J].水科学进展,2016,27(4):535-541.(ZHANG P,TANG H W,YAO W Y,et al.Evolution and quantization methods of rill morphology on the slope under rainfall simulation[J].Advances in Water Science,2016,27(4):535-541.(in Chinese))
[19]MAGUNDA M K,LARSON W E,LINDEN D R,et al.Changes in microrelief and their effects on infiltration and erosion during simulated rainfall[J].Soil Technology,1997,10(1):57-67.
[20]NEARING M A,POLYAKOV V O,NICHOLS M H,et al.Slope-velocity-equilibrium and evolution of surface roughness on a stony hillslope[J].Hydrology and Earth System Sciences,2017,21(6):3221-3229.
[21]王龙生,蔡强国,蔡崇法,等.黄土坡面细沟形态变化及其与流速之间的关系[J].农业工程学报,2014,30(11):110-117.(WANG L S,CAI Q G,CAI C F,et al.Morphological changes of rill on loess slope and its relationship with flow velocity[J].Transactions of the CSAE,2014,30(11):110-117.(in Chinese))
[22]PENG W Y,ZHANG Z D,ZHANG K L.Hydrodynamic characteristics of rill flow on steep slopes[J].Hydrological Processes,2015,29(17):3677-3686.