唐古拉山东段冰川与河流作用谷地的特征分析

Analysis of the Characteristics of Glacier and Fluvial Interaction Valley in the Eastern Section of Tanggula Mountains

对山谷横截面形态进行分析是区分冰川和河流作用的首要工作。以往常用的数学方法包括形态比率法、二次项式法和幂函数模型法,近年来提出了一种新方法——V指数法。为了验证这些方法在区分冰川区和非冰川区(即河流作用区)方面的有效性,应用ArcGIS 10.6软件从唐古拉山东段布加岗日地区提取了5448个山谷地的横剖面,并通过Matlab软件对全谷和截谷的横剖面形态进行了分析。结果表明:①就V指数和幂函数模型中的b值而言,全谷和截谷在冰川区的平均值均大于非冰川区的;对于二次多项式模型中的c值和形态比率,全谷和截谷在冰川区的平均值均小于非冰川区的。这些统计结果都表明,在山谷横剖面形态上,冰川区更接近“U”形,非冰川区则更接近“V”形。②逻辑回归分析结果显示,截谷的V指数是判断冰川区与非冰川区最准确的指标,其预测精度可达62.0%。

The analysis of valley cross section morphology is an important method to distinguish the effects of glaciers and rivers.The mathematical methods commonly used in the past include morphological ratio,quadratic term expression and power function model.A new method has emerged in recent years,which is the V-index method.In order to verify the effectiveness of these methods in distinguishing glacial and non-glacial areas(i.e.,areas of fluvial action),the ArcGIS 10.6 software is applied to extract 5448 cross-sections from Bujiagangri area in the eastern part of Tanggula Mountains,and the cross-section morphology of whole valley and truncated valley is analyzed by Matlab software.The results are as follows.Firstly,in terms of V-index and b value in the power function model,the average value of whole valley and truncated valley in the glacial region is greater than that in the non-glacial region.For the c value and shape ratio in the quadratic polynomial model,the average values of whole valley and truncated valley in the glacial region are smaller than those in the non-glacial region.These statistical results show that the glacier area is closer to″U″shape in the transverse section of the valley,while the non-glacier area is closer to″V″shape.Secondly,the results of logistic regression analysis show that the V-index of truncated valley is the most accurate index to judge glacial and non-glacial areas,with a prediction accuracy of 62.0%.