GCCM-KNN驱动的宁夏南部未来强降雨滑坡易发性评价

Landslide Susceptibility Evaluation in Southern Ningxia Under Future Heavy Rainfall Scenarios Based on GCCM-KNN

  • 摘要: 针对现有滑坡易发性评估方法在因子因果识别、动态响应及未来情景融合方面的局限性,本文以宁夏南部为研究区,提出了“因果筛选-静态建模-动态评价”的一体化评估框架。首先,改进地理收敛交叉映射(Geographical Convergent Cross Mapping, GCCM),引入K最近邻(k-Nearest Neighbor,KNN)自适应邻域构建机制,形成GCCM-KNN因子筛选方法,从17个候选因子中筛选出9个具有因果意义的核心环境因子。基于该因子集,利用支持向量机(Support Vector Machine, SVM)、随机森林(Random Forest, RF)和极端梯度提升(eXtreme Gradient Boosting, XGBoost)构建静态易发性模型,确定最优方案。随后在动态层面,构建由支持向量回归(Support Vector Regression, SVR)、XGBoost与图神经网络(Graph Neural Network, GNN)集成的滚动预测模型,对未来十年(2025-2034年)的强降雨指标(R95P, 降水量超过历史同期95%分位值的极端降雨事件)进行年尺度预测。结果表明:(1)基于GCCM-KNN筛选构建的XGBoost模型(GCCM?XGB?9)在总体精度与灾害点识别指标上优于对比模型,极高易发区对滑坡点覆盖更高,具有较强的识别与空间聚集能力;(2)在强降雨情景下,部分区域易发性等级有所上升,2025年新增滑坡点落入高、极高易发区的比例由静态评价的35%提高至动态评价的48%,验证了该框架的可靠性。本文证实了GCCM-KNN方法在提升因子筛选合理性方面的有效性,所构建的框架能够科学刻画未来气候情景下滑坡风险的时空动态演变规律,可为区域地质灾害风险防控提供决策支持。

     

    Abstract: Objectives: This study proposes an integrated framework combining causal factor screening, machine-learning susceptibility modeling, and R95P-driven dynamic evaluation to assess landslide susceptibility in southern Ningxia, China, under predicted heavy-rainfall conditions from 2025 to 2034. Methods: Based on 777 historical landslides and 17 conditioning factors, a Geographical Convergent Cross Mapping method coupled with k-Nearest Neighbors, termed GCCM-KNN, was developed to identify causally relevant factors through adaptive neighborhood selection and local weighted fitting. The selected factors were compared with those obtained using original GCCM, Principal Component Analysis, ReliefF, and the full-factor scheme. Support Vector Machine, Random Forest, and XGBoost models were constructed for static susceptibility assessment, with SHAP used for interpretation. For dynamic evaluation, annual R95P from 1960 to 2024 was predicted using an ensemble model integrating Support Vector Regression, XGBoost, and Graph Neural Networks with ridge-regression weighting. Predicted R95P layers for 2025–2034 were then incorporated into the optimal susceptibility model while other factors remained unchanged. Results: GCCM-KNN identified nine key factors: gully density, elevation, relief degree, lithology, distance to fault, precipitation, distance to river, population density, and distance to road. Compared with other factor-selection schemes, GCCM-KNN improved the balance between model simplicity, causal interpretability, and spatial discrimination. The GCCM-KNN-XGBoost model achieved the best static performance, with an Accuracy of 0.881, F1-Score of 0.878, and Precision of 0.900. The R95P prediction model performed well during 2015–2024, with an average RMSE of 24.77 mm, MAE of 20.37 mm, and R² of 0.88. From 2025 to 2034, predicted R95P showed moderate interannual fluctuation, and dynamic susceptibility remained generally stable with local upgrading in transition zones. By 2034, medium and high susceptibility areas increased to 10.7% and 13.6%, respectively. In addition, 48% of newly identified 2025 landslides fell within dynamically predicted high or very high susceptibility zones. Conclusions: GCCM-KNN improves landslide factor selection by integrating causal constraints and adaptive spatial neighborhoods. The GCCM-KNN-XGBoost model provides accurate and interpretable susceptibility assessment for southern Ningxia. Coupling predicted annual R95P with the optimal model enables dynamic evaluation of rainfall-driven susceptibility changes. Future heavy rainfall may not reshape the overall susceptibility pattern, but it can promote local upgrading in valley margins, piedmont zones, and transition belts. However, annual R95P cannot fully represent short-duration rainstorms, rainfall peak intensity, or fine-scale precipitation heterogeneity, which should be further addressed in future studies.

     

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