基于DEM的废弃矿山小流域地形特征分析

Landform Characters of a Small Abandoned Quarry Watershed Based on DEM

以北京市某废弃采石场的小流域地形为研究对象,对分辨率为0.3～7m的栅格DEM分别进行小流域参数和地形参数的提取和分析。结果发现,利用不同分辨率DEM提取的河网形态结构有显著差异,网格尺寸7,4和3m的河网结构与2,1,0.7,0.5,0.4和0.3m的河网结构有显著差异,二者主河道位置变化明显,但流域面积、河道长度及比降、平均坡度和高程参数相差不大,而河道总长度和河网密度参数相差较大。根据分析结果确定DEM的比较适宜的分辨率为0.5m,在此基础上利用主成分分析法得出高程和坡度为主成分。对研究区设置20°,25°,30°和35°的4个不同坡度的标准径流小区,观测日降雨量、坡度、径流量和土壤侵蚀量并分析和计算它们之间关系式,计算出整个流域在不同坡度分级及不同雨量级的平均径流量和土壤侵蚀量。研究成果对于废弃矿山修复和生态重建具有参考价值。

Taking an abandoned quarry watershed in Beijing City as the research object,the parameters of watershed and landform were extracted and analyzed using the raster DEM at the different resolutions from 0.3to 7 m.Results showed that the morphological structure of drainage networks extracted from the different resolution DEMs had significant differences.The structures of drainage networks had significant differences between the two sets of gird size：one was with 7,4and 3mand the other was with 2,1,0.7,0.5,0.4and 0.3m.Positions of the two main channels changed dramatically.But there was no marked qualitative difference among drainage area,channel length and gradient,average slope and elevation.The difference was obvious between the total channel length and drainage density.According to the results,the optimal resolution of DEM was estimated to be 0.5m.The main components,i.e.,elevation and slope,were obtained using the PCA（principal component analysis）.By setting four runoff plots of 20°,25°,30°and 35°in the research area,the relationships among rainfall,slope,runoff and soil erosion were analyzed and obtained.Then,the average runoff and soil erosion of the whole drainage basin were computed for different slope grades and rainfall levels.The research results can provide reference for the restoration and ecological reconstruction of abandoned quarry.