基于M-DEM的黄土人工锄耕坡面水系分维特征研究

M-DEM-based Stream Fractal Dimension of Artificial Backhoe Cultivated Loess Slope

该文旨在微观尺度上对地表微地形水系形成过程及其几何分形特征进行研究与分析,为研究坡面流水侵蚀过程及其防治提供科学依据。通过构建90mm/h雨强、15°坡度下不同水蚀阶段(雨前—溅蚀—片蚀—细沟侵蚀)黄土人工锄耕坡面微地形数字高程模型,设置不同集水面积阈值提取微地形水系,并基于格网法计算相应的水系分维值。结果表明:(1)分形理论用于研究微地形水系及其形成过程具有可行性;(2)降雨前、溅蚀、片蚀和细沟侵蚀阶段的最适集水面积阈值分别为15,20,25,30cm2,对应的最佳分维值分别为1.067,1.088,1.068,1.079;(3)人工锄耕坡面在各侵蚀阶段均处于侵蚀发育的幼年期。该研究不仅为微观层面研究黄土耕作坡面水系分维提供方法指导,也可为进一步揭示土壤侵蚀机理提供数据支持。

This paper aims to explore a way to illustrate the stream network forming process with its fractal geometry characteristic of micro-topography in the micro scale, and provide the scientific basis for further re- search about slope surface water erosion process and prevention. In this paper, 4 M-DEMs for artificial back- hoe cultivated loess slope with the slope gradient of 15~ and the rainfall intensity of 90 mm/h were built dur- ing the evolution of soil erosion from before rainfall （BR）-,-splash erosion （SpE）--~ sheet erosion （SHE）-＋ rill erosion （RE） based on laboratory experiment. Then stream networks for different catchments thresholds were extracted with the support of ArcGIS 9.3 soft package. Correspondingly, fractal dimensions were cal- culated based on the grid method. The results showed that： （1） fractal theory could be safely adopted to the study of river network with its forming process of micro-topography; （2） the optimal catchments thresholds of each rainfall stage were 15, 20, 25, 30 cm2, and the optimal fractal dimensions were 1. 067, 1. 088, 1. 068 and 1. 079, respectively~ （3） Artificial backhoe slope erosion was still in the primary stage. In general, a methodology on a micro-topographic stream with its fractal dimension is illustrated, and it should be safe to be adopted for further research for surface micro-topographic.