Why extreme floods are more common than you might think

Understanding spatial dependence is of the utmost importance when large areas, such as England and Wales, are considered. Flooding is unlikely to be extreme simultaneously at all gauges but can occur in more than one place at a time. Furthermore, historical flooding shows us that as events become more extreme they also become more localised.

The researchers simulated 10 000 years' worth of events, including events that are larger than those observed in the data for at least one site, but with the dependence structure of these events is consistent with the features of those observed in the historical record.

The analysis showed that statistical models can help to understand widespread flood risk and plan for future scenarios. The statistical modelling of measurements of extreme river flow allows providing robust answers to national-scale questions by capturing the complex dependence structure of river flows across a large number of measurement gauges.