Debris flow initiation in postglacial terrain: Insights from shallow landslide initiation models and geomorphic mapping in Southeast Alaska
Debris flow initiation in postglacial terrain: Insights from shallow landslide initiation models and geomorphic mapping in Southeast Alaska
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冰后地形中的泥石流引发：来自阿拉斯加东南部浅层滑坡引发模型和地貌测绘的见解
DOI：
10.1002/esp.5336
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发表时间：
2022
影响因子：
3.3
通讯作者：
Orland, Elijah
中科院分区：
文献类型：
--
作者：
Patton, Annette I.;Roering, Joshua J.;Orland, Elijah
泥石流造成持续的危害，并在不同的自然地理环境中形成高浮雕景观，但预测冰川后地形中泥石流的时空发生仍然具有挑战性。为了评估高海拔冰后期地形中的泥石流过程，我们进行了地貌调查，以表征地质，冰川，火山和土地利用对阿拉斯加东南部滑坡发生的贡献。为了评估锡特卡滑坡（特别是泥石流）发生的控制，我们使用了实地观察，地貌测绘，滑坡特征记录在汤加斯国家森林资源清单，和一个新的应用程序的浅层滑坡模型SHALSTAB冰后期地形。冰川作用和火山活动的复杂地貌历史为空间异质性滑坡的发生提供了模板。整个地区的滑坡密度变化很大，但在南部或东南面的山坡上，泥石流密度很高，那里存在火山灰土壤和/或自1900年以来发生了木材采伐。巴拉诺夫岛和克鲁佐夫岛西海岸沿着高滑坡密度与冰川沉积物和厚火山灰的沉积相吻合，并暴露于南向大气河流的极端降雨，但这些控制的相对贡献尚不清楚。木材采伐也被确定为控制该区域滑坡发生的重要手段。针对锡特卡附近的一部分地质参考滑坡，我们使用了SHALSTAB浅层滑坡启动模型（该模型经常应用于非冰川地形）来识别陡峭收敛地形中的高滑坡潜力区域。在对绘制的滑坡多边形的验证中，该模型的表现明显优于随机猜测，在真阳性与假阳性的性能分类曲线上，曲线下面积（AUC）= 0.709。SHALSTAB的这一成功应用展示了冰后期景观灾害分析的实用性，以减轻对人类和基础设施的风险。
Debris flows pose persistent hazards and shape high‐relief landscapes in diverse physiographic settings, but predicting the spatiotemporal occurrence of debris flows in postglacial topography remains challenging. To evaluate the debris flow process in high‐relief postglacial terrain, we conducted a geomorphic investigation to characterize geologic, glacial, volcanic, and land use contributions to landslide initiation across Southeast Alaska. To evaluate controls on landslide (esp. debris flow) occurrence in Sitka, we used field observation, geomorphic mapping, landslide characteristics as documented in the Tongass National Forest inventory, and a novel application of the shallow landslide model SHALSTAB to postglacial terrain. A complex geomorphic history of glaciation and volcanic activity provides a template for spatially heterogeneous landslide occurrence. Landslide density across the region is highly variable, but debris flow density is high on south‐ or southeast‐facing hillslopes where volcanic tephra soils are present and/or where timber harvest has occurred since 1900. High landslide density along the western coast of Baranof and Kruzof islands coincides with deposition of glacial sediment and thick tephra and exposure to extreme rainfall from atmospheric rivers on south‐facing aspects but the relative contributions of these controls are unclear. Timber harvest has also been identified as an important control on landslide occurrence in the region. Focusing on a subset of geo‐referenced landslides near Sitka, we used the SHALSTAB shallow landslide initiation model, which has been frequently applied in non‐glacial terrain, to identify areas of high landslide potential in steep, convergent terrain. In a validation against mapped landslide polygons, the model significantly outperformed random guessing, with area under the curve (AUC) = 0.709 on a performance classification curve of true positives vs. false positives. This successful application of SHALSTAB demonstrates practical utility for hazards analysis in postglacial landscapes to mitigate risk to people and infrastructure.
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