| 其他摘要 | Ephemeral gully erosion is an important erosion type in hilly area of Loess Plateau. With the generation and development of ephemeral gully, the catchment of ephemeral gully become bigger, the conflux of slope become more quickly and more easily, and so the power of erosion current become stronger. This force the development of gully erosion and move forward of gully head. Based on field investigation and theoretical analysis, the main factors of ephemeral gully erosion be determined. And then the simulating experiments were carried on in the simulating rainfall hall of State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau. The main experimental equipment is an alterable gradient trough. The evolvement characters of topography, hydrodynamics parameters of erosion flow and soil erosion and sediment yield in ephemeral gully erosion were studied by soil erosion science, hydrology, hydraulics, mathematical statistics. This study can provide with theoretical support for understanding characteristic of ephemeral gully erosion deeply, developing the mechanism of soil erosion and sediment yield and building ephemeral gully erosion model. And the results can service for agriculture, planning of soil and water conservation and ecological environment sustainable development. Main conclusions as follow:(1)Soil type, slope gradient, rainfall intensity, the area of upper catchment, the Distance between ephemeral gully, tilth were main influencing factors of ephemeral gully erosion in hilly area of Loess Plateau.There was a positive correlation between intensity of ephemeral gully erosion and slope gradient, rainfall intensity, the area of upper catchment. Tilth was the mainly impact factor, and rainfall intensity secondly.(2) Response relation is not obvious between width depth ratio of ephemeral gully and rainfall intensity, slope gradient, the area of upper catchment. In the beginning stage, width depth ratio under no-tilth much less than it under tilth. In the end, width depth ratio was about 1 under the both conditions.(3)The change of velocity of ephemeral gully flow with time was closely related to slope gradient and rainfall intensity. And the change of velocity of ephemeral gully flow with slope length was closely related to tilth.Re was bigger than 1000,and ephemeral gully erosion flow is turbulent flow. Fr number fluctuated with time and space nearby 1, and ephemeral gully erosion flow altered between supercritical flow and subcritical flow。Re and Fr number were obvious effected by rainfall intensity, the area of upper catchment, slope gradient, the conflux of the area between gullies and tilth.The fluctuation range of shear stress of ephemeral gully erosion flow was large. And the shear stress became bigger with increase of slope gradient, rainfall intensity and the area of upper catchment, and tilth broke this relationship.(4)Because of bank landslip and the change of soil characters by Tillage remarkable influence the process of ephemeral gully erosion，the contribution rate of soil erosion and sediment yield and the influence of hydrodynamics characteristic by the conflux of the area between gullies, bank landslip, headcut must be fully considered. |
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