Assessing the element of surprise of record-breaking flood events

The occurrence of record-breaking flood events continuous to cause damage and disruption despite significant investments in flood defences, suggesting that these events are in some sense surprising. This study develops a new... [ view full abstract ]

The occurrence of record-breaking flood events continuous to cause damage and disruption despite significant investments in flood defences, suggesting that these events are in some sense surprising. This study develops a new statistical test to help assess if a flood event can be considered surprising or not. The test statistic is derived from annual maximum series (AMS) of extreme events, and Monte Carlo simulations were used to derive critical values for a range of significance levels based on a Generalized Logistic distribution. The method is tested on a national dataset of past events from the United Kingdom, and is found to identify recent large event that have been identified elsewhere as causing a significant change in UK flood management policy. Finally, it is discussed if the record-breaking floods experienced in northern England during Christmas 2015 can be considered a surprise.