Flash floods, characterized by rapid, short‐duration, and high‐velocity flows, are the major causes of property damage and casualties worldwide. Flash flood warning is one of the key measures to prevent flash floods. Relying upon rain gage data and official statistics of flash flood events with casualties, this study proposes a new rainfall triggering index, β, defined as the ratio of accumulated rainfall to intraday rainfall, which effectively divides floods into events triggered by heavy intraday rainfall (0 < β ≤ 5) and those triggered by high cumulative rainfall (β > 5). Then, historical disaster events were used to evaluate the performance of the proposed index. Results reveal that: (1) when 0 < β ≤ 5, the intensity–duration (I–D) curve method is more desirable, and the simulation result has a high correlation coefficient (r = 0.95) with the measured result; (2) when β > 5, the rainfall triggering index (RTI) method is more suitable (r = 0.8); (3) the cumulative critical rainfall using the RTI method ranges from 50 to 400 mm. This paper stretches the thought of flash flood warning method and provides the reference for flood‐prone regions.

中文翻译：

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云南省山洪暴发预警的新型降雨触发指标研究

洪水泛滥的特点是快速，短时和高速流动，是造成全球财产损失和人员伤亡的主要原因。暴雨警告是防止暴雨的关键措施之一。根据雨量计数据和山灾造成的人员伤亡的官方统计数据，本研究提出了一个新的降雨触发指数β，定义为累积降雨与日内降雨之比，该指数将洪水有效地划分为日内强降雨触发的事件（0 < β ≤5）和由高累计雨量（触发β  > 5）。然后，使用历史灾难事件来评估建议指标的性能。结果表明：（1）当0 < β≤5时，强度-持续时间（I - D）曲线法更可取，并且仿真结果与测量结果具有较高的相关系数（r = 0.95）；（2）当β  > 5时，采用降雨触发指数（RTI）方法更为合适（r = 0.8）；（3）使用RTI方法的累积临界降雨范围为50至400 mm。本文扩展了山洪预警方法的思想，为高洪灾地区提供参考。