Cul-De-Sac Effect: Why Mediterranean Regions Are Becoming More Prone to Extreme Floods in a Changing Climate

By analyzing the devastating floods that affected Emilia-Romagna, Italy, in 2023 and 2024, a team of researchers from CMCC – the Euro-Mediterranean Center on Climate Change – describes for the first time how a particular orographic configuration makes certain regions particularly prone to extreme flooding. The “cul-de-sac” effect: where mountains act as a trap for moisture over a confined area for several days, while a stationary cyclone continues to channel humid air, leading to prolonged and intense precipitation. The research shows how these events, which affect other Mediterranean areas with similar orography, could become more frequent in a changing climate, paving the way for new forecasts and improved early warning systems that will help communities better prepare.

In May 2023, Italy’s Emilia-Romagna region experienced devastating, if not unprecedented, floods that caused widespread damage to infrastructure, homes, businesses, and farmland. Seventeen people lost their lives, and the disaster caused an estimated €8.5 billion in damages. The persistent rainfall and resulting landslides and flooding displaced tens of thousands of residents, leaving a deep mark on the region’s economy and communities.

New research from the Euro-Mediterranean Center on Climate Change (CMCC) sheds light on why this extreme event occurred, the role that climate change may have played, and what it could mean for the future of the Mediterranean region and beyond.

The study “A cul-de-sac effect makes Emilia-Romagna more prone to floods in a changing climate,” published in Scientific Reports, finds that the extreme flooding was not the result of a single extreme precipitation event, but was fueled by prolonged accumulation of rain over several days.

Read More: CMCC Foundation - Euro-Mediterranean Center on Climate Change

Photo Credit: Hans via Pixabay