ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    黄土地质灾害评价因子地形起伏度提取最佳尺度研究:以榆林市米脂县为例

    Research on Optimal Scale for Extraction of Relief Amplitude in Loess Geological Hazards Assessment Factors: a Case Study of Mizhi County, Yulin City

    • 摘要: 目前地质灾害相关评价工作中,部分研究人员对于“地形起伏度”(也称相对坡高)选取最佳窗口单元进行提取存在着一定程度的随意性和主观性,致使取得的地形起伏度参数与研究区实际情况相比存在一定的误差。后续地灾评价中,无论采用以栅格为基础的信息量模型还是现今普遍流行的各类机器学习方法,其评价因子本身的误差甚至错误会导致评价结果可靠性降低。笔者基于ArcGIS平台,利用陕西省榆林市米脂县分辨率为2 m的DEM数据,采用均值变点分析法,通过两轮分析,数量分别为10×10和1×1的矩形窗口逐渐逼近研究区地形起伏度的最佳统计单元,计算出该县地形起伏度为0~256.60 m,最佳统计单元为59×59的窗格,栅格单元边长为2 m,提取窗格边长为118 m,对应提取面积为13924 m2。随后依据陕北黄土地区历史滑坡及崩塌的易发坡高统计将米脂县地形起伏度等分为<20 m、20~40 m、40~60 m、60~80 m、>80 m等5个区间,受原始地形条件及削坡建房、建厂等综合影响,40~80 m为灾害隐患发育的主要区间,灾害隐患点占比为88.60%。结合米脂县地质灾害隐患点信息量值和灾害点密度对比曲线,结果显示二者有很好的相关性,体现了地形起伏度统计单元选取和区间划分的合理性。本研究所采用的高精度DEM数据的计算及分析结果,首先避免了目视寻找拐点的弊端,其次在黄土高原地区千沟万壑的地貌条件中能够满足数字地形分析与精细化地质灾害调查的需求,可为黄土高原区地质灾害评价防治及黄河中上游流域的水土流失治理与生态环境保护提供一定的技术支撑。

       

      Abstract: In the current evaluation of geological hazards, there is a certain degree of arbitrariness and subjectivity in selecting the best window unit scale for the extraction of relief amplitude (also named relative slope height). The certain error exists as compared the obtained relief amplitude parameters with the actual situation in the study area. During the disaster assessment, using grid-based information models or various popular machine learning methods can lead to a reduction in the reliability of the evaluation results due to the errors of the evaluation factors. In the current study, we use DEM data (2 m resolution) of Mizhi County, adopt 10×10, 1×1 rectangular windows for the relief amplitude extraction based on ArcGIS platform, and use the mean change-point analysis to calculate the relief amplitude of Mizhi County from 0–256.60 m, and the best statistical cell is 59×59 with the grid length of 2 m, and the side length of the extraction window is 118m and square is 13924 m2. Afterwards, according to the statistics on the slope height easily inducing historical landslides and collapses in the loess region of northern Shaanxi Province, the relief amplitude in Mizhi County is divided into five intervals: <20 m, 20–40 m, 40–60 m, 60–80 m and >80 m. Due to the comprehensive influence of the original terrain conditions, slope cutting and building of houses, factories, etc., 40–80 m is the main interval for the development of disaster hazards, with a proportion of 88.60% of disaster hazard points.The comparison curves of information value and hazard point density of each interval were made, which demonstrates the reasonableness of the selection of the statistical unit and the division of the interval of the relief amplitude. The calculation and analysis results of high-precision DEM data adopted first avoid the drawbacks of visually searching for inflection points, and secondly meet the needs of digital terrain analysis and refined geological hazard investigation in the mountainous terrains of the Loess Plateau region. The method and the results can provide technical support for the evaluation and prevention of geological hazards in the Loess Plateau area and the management of soil erosion and ecological environment protection in the middle and upper reaches of the Yellow River basin.

       

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