Wildfire alters the hydrologic and geomorphic responses of burned areas relative to nearby unburned areas, making them more prone to runoff, erosion, and debris flow. In post-wildfire settings, debris flows often initiate when runoff concentrates on steep slopes and rapidly mobilizes sediment. Rainfall intensity-duration (ID) thresholds have been proven useful for assessing post-fire debris-flow potential but can vary substantially from one location to another as a result of hydrologic factors that control rainfall-runoff partitioning. Debris-flow initiation thresholds based on a slope-dependent dimensionless discharge criterion, which have the theoretical benefit of being consistent from site to site, have also been proposed but not extensively tested. We monitored debris-flow activity in 12 small (< 1 km2) watersheds burned by the 2018 Buzzard Fire in New Mexico, USA, documenting 24 debris flows during the first several months following the wildfire. We use a recently proposed dimensionless-discharge threshold in combination with rainfall-runoff modeling to estimate basin-specific rainfall ID thresholds for debris-flow initiation. These model-derived thresholds compare well with observations. Areas burned at low severity are characterized by higher infiltration capacity, rainfall interception, and hydraulic roughness relative to areas burned at moderate or high severity, but differences in rainfall ID thresholds between these two areas can be predominantly attributed to wildfire-induced changes in hydraulic roughness. Results highlight the utility of thresholds based on dimensionless discharge relative to those based on rainfall intensity and also provide additional data that will help constrain general models for the prediction of rainfall ID thresholds.

中文翻译：

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是什么驱动了野火后泥石流降雨强度-持续时间阈值的空间变异性？来自美国新墨西哥州 2018 年 Buzzard Fire 的见解

野火改变了燃烧区域相对于附近未燃烧区域的水文和地貌响应，使它们更容易发生径流、侵蚀和泥石流。在野火后的环境中，当径流集中在陡坡上并迅速移动沉积物时，泥石流通常会开始。降雨强度持续时间 (ID) 阈值已被证明可用于评估火灾后泥石流的潜力，但由于控制降雨-径流划分的水文因素，可能会因地点而异。还提出了基于斜率无因次排放标准的碎屑流启动阈值，该阈值具有从站点到站点一致的理论优势，但尚未进行广泛测试。我们监测了 12 个小型（< 1 平方公里) 流域被 2018 年美国新墨西哥州的秃鹰大火烧毁，记录了野火后最初几个月内发生的 24 次泥石流。我们使用最近提出的无量纲排放阈值与降雨径流模型相结合来估计泥石流引发的特定盆地降雨 ID 阈值。这些模型派生的阈值与观察结果很好地比较。与中等或高度烧毁的区域相比，低严重程度燃烧的区域具有更高的渗透能力、降雨截留和水力粗糙度，但这两个区域之间降雨 ID 阈值的差异主要归因于野火引起的水力粗糙度变化.