Abstract Debris flows caused by channel bed erosion present major hazards affecting life, livelihoods, and the built environment in mountainous regions. An efficient way to decrease hazard impact is through reliable hazard forecasts and appropriate early-warning strategies. Rainfall thresholds are fundamental in achieving reliable hazard forecasts. However, a lack of rainfall records often impedes the empirical establishment of such thresholds. This paper constructs rainfall intensity-duration thresholds based on process-based critical runoff discharge for the initiation of debris flows and a mathematical approximation among peak discharge, rainfall intensity and duration. Simulations of conditions that triggered debris flow and non-debris flow events allowed determination of the lower and upper limits of critical discharge for debris flow initiation. In turn, these critical discharge limits are compared with four estimates derived from process-based approaches to test which approach best delimit the critical conditions. Hydrological simulations derive S-hydrographs for recorded rainfall events. Further analysis of the S-hydrographs results in a mathematical approximation of peak discharge as a function of rainfall intensity and duration and the establishment of the minimum rainfall required to produce a particular peak discharge. The minimum rainfall threshold to trigger an event can be calculated by setting the process-based critical discharge as the peak dis charge. In turn, this enables the establishment of a conventional rainfall I-D threshold for debris flow initiation. This process-based approach enables the construction of valley-specific I-D thresholds in data-poor areas and provides a promising pathway to improve the reliability of debris flow hazard forecasts and early warnings.

中文翻译：

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基于临界流量和S-水位线的泥石流起始降雨阈值构建

摘要 河床侵蚀造成的泥石流是影响山区生活、生计和建筑环境的主要危害。减少灾害影响的有效方法是通过可靠的灾害预测和适当的预警策略。降雨阈值是实现可靠灾害预报的基础。然而，缺乏降雨记录通常会阻碍此类阈值的实证建立。本文基于基于过程的临界径流排放来构建降雨强度 - 持续时间阈值，用于引发泥石流，以及峰值流量、降雨强度和持续时间之间的数学近似。触发泥石流和非泥石流事件的条件模拟允许确定泥石流启动的临界排放的下限和上限。反过来，这些临界排放限值与源自基于过程的方法的四个估计值进行比较，以测试哪种方法最好地界定临界条件。水文模拟为记录的降雨事件导出 S 水文图。对 S 水文过程线的进一步分析得出峰值流量的数学近似值，作为降雨强度和持续时间的函数，并确定产生特定峰值流量所需的最小降雨量。触发事件的最小降雨阈值可以通过将基于过程的临界流量设置为峰值流量来计算。反过来，这使得能够为泥石流启动建立常规的降雨 ID 阈值。这种基于过程的方法能够在数据贫乏地区构建特定于山谷的 ID 阈值，并为提高泥石流灾害预报和早期预警的可靠性提供了一条有希望的途径。