In November 2009 and December 2015, two record‐breaking 24‐hr rainfalls occurred in Cumbria, UK, significantly changing the perception of flood risk for local communities. FEH13, the current UK rainfall depth‐duration‐frequency (DDF) model, estimated return periods of around 1,000 years for both events. The previous model, FEH99, received criticism from panel engineers responsible for making technical safety decisions relating to reservoirs for appearing to estimate relatively short return periods for extreme events. Although FEH13 is more consistent with current probable maximum precipitation (PMP) estimates, there is high uncertainty in both models due to the limited number of extremes captured by UK rain gauges. Furthermore, neither model included the 2009 or 2015 event in its calibration. Here, we re‐calibrate FEH13 using additional gauged rainfall data collected in Cumbria during 2006–2016, including the record‐breaking 2009 and 2015 storms. Using the updated calibration data set reduces the estimated return periods of the 2009 and 2015 events to approximately 140 years each. This case study illustrates the considerable uncertainty in short‐sample records, demonstrates the importance of maximising the quantity of relevant calibration data, shows that perception of risk depends upon the method and data used, and illustrates the difficulty of separating trends and natural variability.

中文翻译：

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深度-持续时间-频率模型的重新校准对降雨返回期估算的影响

2009年11月和2015年12月，英国坎布里亚郡发生了两次破纪录的24小时降雨，这极大地改变了当地社区对洪灾风险的认识。FEH13是当前的英国降雨深度持续时间频率（DDF）模型，估计这两个事件的回归期约为1000年。先前的模型FEH99受到小组工程师的批评，该小组负责做出与储层有关的技术安全决策，因为它们似乎估计出极端事件的返回时间相对较短。尽管FEH13与当前可能的最大降水量（PMP）估计值更加一致，但由于英国雨量器捕获的极端事件数量有限，两种模型的不确定性都很高。此外，两个模型均未在其校准中包含2009年或2015年的事件。这里，我们使用2006-2016年期间在坎布里亚郡收集的更多经测量的降雨数据（包括创纪录的2009年和2015年的暴风雨）对FEH13进行了重新校准。使用更新后的校准数据集可将2009年和2015年事件的估计返回周期减少到每个大约140年。本案例研究说明了短样本记录中的巨大不确定性，说明了最大化相关校准数据的重要性，表明对风险的感知取决于所使用的方法和数据，并说明了区分趋势和自然变异性的难度。