泥石流平面形态的统计分析

泥石流扇的平面形态可用规划的几何图形来模拟。在研究了中国西南地区小江流域和意大利东北部阿尔卑斯山区的５２个泥石流扇的基础上，本文提出了两种泥石流扇的平面形态：中国西南地区的“等腰三角形＋半圆形”泥石流扇和意大利东北部的“几何扇”。用统计分析建立了两组泥石流扇和泥石流流域之间的形态度量关系。通过两个研究区域的对比，两个流域参数：流域面积和主沟比降确定为影响泥石流扇平面形态和面积的最重要的因素。

STATISTICAL ANALYSIS ON THE PLANE SHAPES OF DEBRIS FLOW FAN

The plane shapes of debris flow fan can be simulated with the combinations of one or two regular geometric figures. After detailed researches on 52 debris flow fans in Xi-aojiang Valley of southwestern China and in Alps of northeastern Italy,the plane shapes of debris flow fan in SW China can be generally represented as a combination of an isosceles triangle with a semicircle,and the agreeableness of this simulation is averagely 84. 74%. The plane shapes of debris flow fan in NE Italy can be generally represented as a circular sector,and the agreeableness of this simulation is averagely 91. 08%. Supposedly, in other regions of the world,other combinations of regular geometric figures may be found for debris flow fan. Thus a basic frame to forecast the potential maximum extent of debris flow fan may be provided. Only considering the single-factor morphometric relationship between debris flow fan area and debris flow basin area,the power function,Af = CAdb is acceptable. However, not only C but also b varies from location to location. Moreover,the research demonstrates that the approach of multiple-factor has a better precision than that of single-factor on the subject. Based on comparison of plane shape modes of debris flow fans in SW China and in NE Italy, drainage basin area and main channel gradient are the two most important parameters commonly affecting the development of debris flow fan. Theoretically, using the plane shape modes of debris flow fan plus standard deviation , the potential maximum extent of debris flow fan could be forecasted from the drainage basin parameters,but the forecasts still have some errors,and the actual situations are complicated. The two modes of debris flow fan plane shape are not strongly recommended for prediction nowadays,but anyway,this kind of researches are strongly encouraged.