Changing storm surge patterns compound the issue of sea level rise

A research team led by the University of Central Florida (UCF) has recently developed a new method to determine where storm surges are most likely to occur, whether the likelihood of such extreme weather events is changing over time, and why. Clarifying these issues could help cities better prepare for storm surge events by investing in flood-protecting resources such as larger sea walls or pump stations.

“We don’t want to over design and waste money to build things bigger than they need to be, which is very expensive,” said study co-author Thomas Wahl, an assistant professor of Coastal Engineering at UCF. “On the other hand, we don’t want to build things too small to just find out 20 years down the road that we underestimated the design and now we need to pay more money to further adapt our infrastructure.”

Dr. Wahl and his colleagues incorporated historical tide gauge data from 79 locations along the coasts of Europe (spanning a time period from 1960 to 2018) into a novel statistical approach that they developed. Their analyses revealed that – in addition to sea level rise – changes in storm surges have been significantly affecting the magnitude of extreme flooding events on European coastlines.

However, while some places such as the northern coasts of Scotland saw an additional increase in extreme flooding events because of changes in storm surges, others – including the coasts of Spain, Denmark, the Netherlands, France, Belgium, or Germany – witnessed a decrease in such events.

“What used to be a 50-year event, is now a 30-year event in some areas,” explained Professor Wahl. “So, there is an almost a 40 percent increase in the probability that certain extreme events could occur. But in other areas, what used to be a 50-year event with a two percent chance of occurrence in a given year in the 1960s is now closer to a 100-year event with only a one percent chance of occurrence.” 

“Those changes take place on top of sea level rise. So, while some places see a compounding effect of sea level rise and increase in storm surges, these two cancel each other out in other places,” he added.

While previous studies argued that changes in the likelihood of extreme sea-level events were mainly due to sea-level rises, these new findings suggest that changes in storm surges may also play a significant role in the frequency and severity of such events. 

“Our results demonstrate that both external and internal influences can considerably affect the likelihood of surge extremes over periods as long as 60 years, suggesting that the current coastal planning practice of assuming stationary surge extremes might be inadequate,” the authors concluded.

The study is published in the journal Nature. 

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By Andrei Ionescu, Earth.com Staff Writer