融合Transformer与CNN的正样本缓冲滑坡易发性评价模型—以宝鸡市为例

A landslide susceptibility assessment model based on positive sample buffering, integrating Transformer and CNN—A case study of Baoji City

  • 摘要: 宝鸡市滑坡灾害频发,但历史样本稀少,空间代表性不足,从而制约了对该区域滑坡风险性评估精度。针对此,结合卷积神经网络模型(Convolutional Neural Network,CNN )的局部特征提取优势和注意力机制Transformer的全局建模能力,提出了一种融合Transformer与CNN的正样本缓冲滑坡易发性评价模型。依据滑坡规模设置90-130 m动态缓冲区扩展正样本,并综合考虑地形地貌、地质条件、水文气象和人类工程等选取13类滑坡影响因子,通过多重共线性分析后构建了滑坡评价体系。研究结果显示:采用缓冲区将随机森林、CNN、Transformer、CNN-Transformer模型四者AUC从0.834、0.852、0.847、0.875分别提升至0.883、0.913、0.926、0.959;此外,CNN-Transformer相较于CNN、Transformer,未缓冲时AUC (Area Under the Curve)从0.852、0.847提升至0.875,进行缓冲时从0.913、0.926提升至0.959;基于SHAP(Shapley Additive Explanations)算法可解释性分析进一步揭示出,岩性、年降雨、坡向三类因子对滑坡易发性预测贡献度最大,贡献度分别达0.55、0.47、0.43,且三者交互效应显著,为锁定区域滑坡高风险区提供了可量化依据。

     

    Abstract: Objectives: Landslide susceptibility mapping (LSM) serves as a fundamental tool for geohazard prevention and regional planning. However, the accuracy of LSM in complex geological environments, such as Baoji City, is often constrained by two primary challenges: the scarcity of historical landslide samples leading to poor spatial representation, and the limitation of traditional convolutional neural networks (CNN) in capturing long-range spatial dependencies. To address these issues, this study proposes a novel framework that integrates a positive sample buffering strategy with a hybrid CNN-Transformer model. The primary objective is to enhance the spatial representation of landslide samples and effectively fuse local and global features to improve the predictive performance and interpretability of LSM. Methods: First, to overcome the limitations of point-based sampling which fails to reflect the actual spatial extent of landslides, a dynamic buffering strategy was implemented. Based on the scale of historical landslides, variable buffer radii ranging from 90 m to 130 m were applied to expand positive samples from isolated points into spatial polygons. Second, a total of 13 conditioning factors were selected, including topography (elevation, slope, aspect, plan curvature, profile curvature), geology (lithology, distance to faults), hydrology (distance to rivers, TWI, rainfall), ecological environment (NDVI) and human activities (land use, distance to roads). Multicollinearity analysis, utilizing both Pearson correlation coefficients and Variance Inflation Factor (VIF), was conducted to ensure the statistical independence of these factors. Third, a CNN-Transformer coupled model was constructed. The architecture utilizes a CNN backbone with a 15×15 input window to extract high-dimensional local features, which are then serialized and fed into a Transformer encoder. The Transformer employs a multi-head self-attention mechanism to dynamically weigh the importance of different spatial positions, thereby capturing global non-linear interactions among factors. To rigorously evaluate the proposed framework, a total of eight experimental scenarios were designed, comparing the performance of Random Forest (RF), standalone CNN, standalone Transformer, and the coupled CNN-Transformer model under both buffered and unbuffered sample conditions. Furthermore, the SHAP (Shapley Additive Explanations) algorithm was integrated to interpret the "black-box" decision process of the optimal CNN-Transformer model, quantifying the contribution of each factor to landslide susceptibility. Results: Experimental validation demonstrated significant improvements in both model robustness and prediction accuracy. (1) Effectiveness of Buffering Strategy: The application of the buffering strategy universally enhanced the performance of all tested models. Specifically, the AUC values for RF, CNN, Transformer, and CNN-Transformer increased from 0.834, 0.852, 0.847, and 0.875 (unbuffered) to 0.883, 0.913, 0.926, and 0.959 (buffered), respectively. (2) Superiority of the Hybrid Model: The proposed CNN-Transformer model consistently outperformed single-structure models in both experimental settings. In the unbuffered scenario, it improved the AUC from 0.852 (CNN) and 0.847 (Transformer) to 0.875; in the buffered scenario, it further elevated the AUC from 0.913 (CNN) and 0.926 (Transformer) to 0.959. (3) Interpretability Analysis: Based on Shapley Additive Explanations (SHAP) interpretability analysis, it was further revealed that lithology, annual precipitation, and slope aspect contributed most significantly to predicting landslide susceptibility in Baoji City, with contributions of 0.55, 0.47, and 0.43 respectively. the interaction effects among these three factors were significant. Conclusions: The positive sample buffering strategy effectively mitigates the issue of insufficient spatial representation in historical inventories. The CNN-Transformer coupled architecture successfully overcomes the intrinsic limitations of singlestructure models, offering a state-of-the-art solution for complex non-linear geological modeling. This study establishes a robust framework for landslide susceptibility assessment in data-scarce regions.These findings provide actionable scientific insights for local disaster mitigation and land-use planning.

     

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