黄土坡面细沟侵蚀发育过程与模拟

以坡面细沟侵蚀过程为研究对象,利用人工模拟降雨试验和三维激光扫描技术,研究了同一坡面三场间歇性降雨下细沟侵蚀发生、发展和演化的图形化过程;同时,采用已有细沟侵蚀过程模型(CARill),结合Net Logo软件,将试验结果与模型模拟结果进行对比分析。结果表明:(1)扫描三场降雨图形化过程显示:侵蚀阶段呈现出溅蚀—片蚀—跌坑—断续细沟—连续细沟—细沟崩塌过程,沟长发育迅速,沟宽和沟深发育相对缓慢,细沟沟网形成迅速,降雨结束后侵蚀强度达到22.11 kg m-2,较初期降雨侵蚀增加了22.04倍。(2)CA-Rill模型模拟结果显示,在细沟侵蚀演化图形化过程方面,该模型可较完整地模拟细沟形态发育过程,实现细沟侵蚀的发生、发展以及演化过程中细沟形态的可视化模拟;(3)模型模拟三场降雨细沟侵蚀参数t检验结果发现:最长平均沟深、最大沟深、最长沟平均沟宽模拟效果不好;而细沟平面密度、最长沟长、侵蚀强度模拟效果较好。

Development of rill erosion on loess slope and its simulation

It is of great significance to dynamically simulate development and evolution of soil erosion for the purpose of erosion forecast. Traditionally, most soil erosion models are basically steady-state models that have limitations in real-time simulation of initiation and development of soil erosion. Cellular Automata (CA), with a "from bottom to top" dynamic modeling framework, is capable of simulating spatial-temporal evolutionary processes of the complex geographical system. So, in this paper, rill erosion on loess slope was studied. By means of artificial simulated rainfall and three dimensional laser scanning, how rill erosion started, developed and evolved on a loess slope,15o in gradient, under three intermittent artificial rainfall events were investigated and visualized in graphics. At the same time, the CA-Rill model, already available for simulation of rill erosion process, was used in couple with the NetLogo software, to analyze and compare results of the experiment and the results of model simulation. Results show: (1) The scanning images of the rill erosion processes under the three events of rainfall reveal that the entire course of rill erosion consisted of the following phases in sequence, splash erosion, sheet erosion, drop pit, intermittent rill, continuous rill and rill collapse. Rills developed very rapidly in length, and relatively slowly in width and depth, and soon connected with each other to form a rill network. At the end of the third rainfall event, erosion intensity reached as high as 22.107 kg m^-2, 22.04 times that at the initial stage of rainfall. (2) Results of the CA-Rill simulation indicate that in visualizing evolution of the rill erosion, the model could quite perfectly simulate the entire morphological development of rills and realize visualization of the simulation. (3) Validation of parameter t of the simulated rill erosion under three artificial rainfall events demonstrates that the simulation of mean rill depth of the longest rill, depth of the deepest rill and mean width of the longest rill is not so ideal. However, the effect of the simulation of horizontal rill intensity, length of the longest rill and erosion intensity is quite good.