Effect of developed rill formation accompanied with the variation of slope length on soil loss

倾斜裸地土壤颗粒的冲刷形成细沟侵蚀是造成土壤侵蚀的因素之一。在产生细沟侵蚀的情况下，即使降雨强度和径流比相同，也可能产生土壤总流失量的差异。由此推断，倾斜裸地降雨形成的复杂细沟影响着土壤流失量。本文通过室内试验，在不同坡长（100cm、150cm、200cm）条件下，考虑了坡长对细沟发育形态的影响，对细沟发育形态进行了把握和分类。室内试验证明，通过建立本研究的条件，细沟可分为I、Y、RY三种类型，在每种类型中，坡长对土壤流失的影响有不同的趋势。1）利用新旧两种降雨模拟器对地表径流的土壤流失和细沟形成进行了调查。定性和定量地分析了在土层干密度不变的条件下，地表水流在土箱上运行所形成的细沟。3）通过收集资料，阐明了降雨、地表水流与土壤流失的基本关系，4）根据人工模拟降雨试验和田间试验小区的观测结果，建立了与降雨类型有关的土壤流失方程，并对该方程进行了验证，结果表明，该方程具有较好的实用性。

It is one of the factors for soil erosion that the washing out of soil particles from inclined bare fields is rill erosion. In the case of producing rill erosion, even if the intensity of rainfall and runoff ratio are the same, it is possible to produce a difference in total soil loss. It is inferred that complicated rill owing to rainfall in inclined bare fields influences the quantity of soil loss. The present stuby is aimed at grasping and classifying the form of developed rill by an indoor experiment in the changing length of slope (100cm, 150cm, 200cm) which considers the influence of the length of a alope in case of each form of developed rill. The indoor experiment proved that the rills are classified in types (I,Y,RY) by establishing a condition of the present study, the effects of the length of a slope involved in soil loss have a different tendency in each type.Results are as follows ;1) Soil loss and rill formations for surface water flow were surveyed using old and new type rainfall simulators.2) Rill formations occurred by surface water flow running dawn on the soil box under the dry density of the soil layler set constant condition were analyzed qualitatively and quantitatively.3) Basic relationship of rainfall, surface water flow and soil loss was clarified by collecting, arranging and analyzing the data of the experiment under same soil condition in the soil box.4) A Soil loss equation with regard to rainfall types was developed using results of experiment and observations of the rainfall simulator and the field test plots, and it was found that the equation showed good application to actual fields.