紫色土坡耕地细沟发育的形态演变

Configuration Evolvement of Rill Development on Purple Slopeland

研究细沟发育的形态演变规律是认识细沟发生机理的前提,本研究通过人工降雨与微地貌扫描相结合的方法,调查了紫色土坡耕地细沟发生过程的形态演变特征。采用三维激光扫描仪扫描不同降雨时段坡面,生成高精度坡面DEM图像,统计各时段不同坡段等高线偏离度,量算坡面凹陷区的表面积、周长、直径以及沟头下切深度;结果表明,等高线偏离度越大细沟发育越完全,有细沟发生坡面等高线偏离度是无细沟坡面的1倍以上;凹陷区的表面积、周长、直径相对于单位降雨量的扩展速率均在细沟贯穿时段出现最大值;跌坑位置与坡面水平起伏关系不明显,统计的3条沟头分别发育于水平方向起伏的最高点、中间点和低点;跌坑下切深度及其单位降雨量的扩展速率在跌坑贯穿形成细沟时段出现最大值,之后逐渐降低,说明跌坑的形成是细沟造床的关键。

The investigation on the configuration evolvement of rill is the precondition of rill development mechanism research.This study adopted the methods of artificial rainfall and macro-morphology scan to investigate the configuration evolvement of rill development on purple soil slopeland.The results displayed that some indexes were effective to express configuration evolvement of rill,such as the degree of contour line departure,enlarge rate of surface area,perimeter,diameter and rill deepness with unit precipitation.The higher the degree of contour line departure,the more entireness of rill development,and the degree of contour line departure in the rill development region was more than one time to the no rill development area.The maximum of enlarge rate about surface area and diameter,was taken place when the drop-pit was rush through.And the position of drop-pit was not directness relation with the undulation of surface level,because the positions of three drop-pit we surveyed were taken place on the vertex,middle and low.The enlarge rate of rill deepness was augment firstly,then played down gradually,and the maximum took place at the drop-pit rush through period,so it implies that the forming of drop-pit was the key of rill cutting channel.