ISSN 1000-3665 CN 11-2202/P

    基于精细化调查的乡镇尺度岩质滑坡易发性评价

    Evaluation of township-scale rocky landslide susceptibility based on refined surveys

    • 摘要: 地质灾害精细化调查是目前乡镇及其同等尺度地质灾害风险防控的基础性工作,需建立与之相适应的同尺度同精度的评价模型与方法。以万州区熊家镇地质灾害精细化调查为基础,将岩质滑坡灾害根据斜坡结构细分为顺向坡和非顺向坡,分别建立相应的评价指标体系,针对乡镇尺度历史滑坡数据少的特点,采用启发式的层次分析模型(AHP)和适于小样本计算的随机森林模型(RF)进行评价,并将精细化调查研判为欠稳定斜坡点纳入滑坡样本、稳定斜坡点纳入非滑坡样本,用于模型建立及检验。结果表明:(1)基于两种模型的易发性评价分区大体一致,顺向岩质滑坡高和极高易发区主要在中南部,与软弱地层、临空条件和人类过程活动有关,非顺向岩质滑坡高和极高易发区主要在北部,与斜坡坡度、冲沟密度和可动块体数量有关。(2)基于AHP评价的AUC值分别为0.803和0.798,基于RF评价的AUC值分别为0.849和0.876,整体上RF的准确度高于AHP,其中AHP对非顺向坡评价的准确度高于顺向坡,RF则相反。本研究可为当地地质灾害风险管控提供支撑,对我国正在开展的区域地质灾害精细化调查评价具有参考价值。

       

      Abstract: Fine investigation of geological disasters forms the foundation for effective disaster risk mitigation in township-level regions. However, appropriate evaluation models and methodologies that match the scale and required resolution of township-level assessments remain limited. Based on the geological disaster refinement survey in Xiongjia Township, Wanzhou District, rocky landslide hazards were subdivided into dip slopes and non-dip slopes according to the slope structure, and then evaluation index system was established separately. Given the limited availability of historical landslide data at the township scale, an Analytic Hierarchy Process (AHP) and a Random Forest (RF) suitable for small-sample calculations were used for evaluation. The points of unstable slopes judged by the refined survey were included in the landslide samples, and the points of stable slopes were included in the non-landslide samples, which were used for the establishment and testing of the RF model. The results show that the susceptibility evaluation zones based on the two models are generally consistent. The high and very high susceptibility zones of compliant rocky landslides are mainly in the south-central part of the country, related to the soft strata, the proximity conditions, and the human process activities, while the high and very high susceptibility zones of non-compliant rocky landslides are mainly in the northern part of the country, related to the slope gradient, the density of the gully, and the number of movable blocks. The AUC values for AHP-based evaluations were 0.803 (dip slopes) and 0.798 (non-dip slopes), while RF-based evaluations achieved AUCs of 0.849 and 0.876, respectively. Overall, the accuracy of RF was higher than that of AHP, in which the accuracy of AHP evaluation of nonconformal slopes was higher than that of conformal slopes, and the opposite was true for RF. This study provides a basis for local disaster prevention and mitigation and for the ongoing regional geohazard refinement investigation and evaluation in China.

       

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