基于投影覆盖法的小流域模型地貌分形特征

针对流域地貌所具有的明显各向异性和三维立体特征,将投影覆盖法引入其三维表面分形特征的直接量化,结合投影覆盖法计算三维表面分形维数基本原理和GIS技术,提出了基于投影覆盖法的计算流域地貌三维表面分形维数的GIS实现过程,并对9次摄影测量所得小流域模型地貌三维表面分形维数进行了计算。结果表明,投影覆盖法可实现流域地貌三维表面分形特征的直接量化,计算出的地貌三维表面分形维数准确反映了模拟降雨驱动下小流域模型地貌总体特征的动态变化过程;与计盒维数法相比,投影覆盖法更有利于揭示小流域模型不同发育阶段地貌特征的差异性,对于流域水土流失预报模型中地貌因子量化参数的选择具有重要意义。

Study of Quantization of Topographic Fractal Feature of Small Watershed Model Based on Projective Covering Method

In view of the obvious anisotropy and three-dimensional characteristics of watershed topographic possess,the projective covering method is introduced to quantize fractal feature of three-dimensional surface.Combining the basic theory of fractal dimension of three-dimensional surface calculated by projective covering method and GIS technology,this paper presents the actualization process of GIS on the basis of fractal dimension calculation of three-dimensional surface of watershed geomorphy.And it calculates the fractal dimension of three-dimensional surface of small watershed geomorphy with nine times photogrammetry.The result shows that the projective covering method can realize the quantization of fractal feature of three-dimensional surface of small watershed geomorphy;the calculated fractal dimension can exactly reflect the dynamical characteristics of small watershed geomorphy drived by simulated rainfall;comparing with box-dimension method,the projective covering method can be more favorable in finding out the difference of topographic characteristics under different phases of small watershed.Therefore,it has important meaning in choosing quantization parameters of topographic factors in forecasting model of soil and water conservation.