A new study looks at the conditions that contribute to extreme flooding in Italy
In May of 2023, extreme floods devastated the Emilia-Romagna region of Italy. The floods killed seventeen people, displaced thousands, and caused an estimated €8.5 billion in damages. Since then, the region has also seen other devastating flooding events.
A new study, publishedin Scientific Reports, looks at the conditions that fuelled flooding in the Mediterranean, and what it means for future extreme events.
What causes floods?
Floods are often caused by extreme precipitation. And as the climate warms, heavy rainfall events are expected to increase, leading to more frequent and intense flooding.
In Europe, there are certain regions that are more susceptible to climate-induced flooding, such as the Mediterranean.
But flooding is influenced by multiple factors, including soil moisture, land use, and runoff sensitivity to sea level. And as the recent study shows, it can be a confluence of factors.
Researchers identified that the 2023 flooding in Italy extreme flooding was not the result of just one extreme precipitation event. Rather, it was fueled by the accumulation of rain over several days, fostered by the region’s topography.
What is the ‘cul-de sac’ effect?
The region experienced what the researchers call a “cul de sac” effect. Mountains blocked moisture from the Adriatic Sea, trapping the rain in the region. A stationary cyclone prolonged the downpour, causing the extreme (and rare) floods observed in 2023. The “cul de sac” effect likely also contributed to the 2024 floodingthat impacted the region.
Based on this, the researchers believe that similarly extreme floods could occur in similar geographic areas.
“Our analysis shows that the kind of persistent cyclone that caused the 2023 and 2024 Emilia-Romagna floods is not unique to this region,” says Enrico Scoccimarro, first author of the study and senior scientist at the Euro-Mediterranean Centre on Climate Change.
“Other Mediterranean areas with similar geography could face the same risks.”
Future models could better predict flooding
With climate change, these floods are likely to become more frequent. It’s important to be adequately prepared for such events, designing efficient and accurate early warning systems.
As such, the authors introduce a “cyclone density persistence” metric, which would help forecasters track cyclones that could lead to extreme weather events in vulnerable regions.
“This work represents the first step in a long-term plan to develop Early Warning Systems for flood events on a seasonal timescale at CMCC,” says Scoccimarro.
“Our goal is to go beyond current limitations of state-of-the-art numerical models, and aim at higher skills in directly forecasting extreme precipitation, and help communities better prepare for floods.”