According to catastrophe modeling firm AIR Worldwide, heavy rains have caused widespread flooding in France and Italy during the first week of November after a low pressure system that developed over the Mediterranean Sea moved northwards, bringing high levels of precipitation. The system responsible for the recent flooding in Italy and France began as an extratropical storm named “Rolf” and subsequently developed tropical characteristics over the warm waters of the Mediterranean.
According to AIR, the flooding in Italy and France has been caused by a specific form of low-pressure system that occasionally forms over the Mediterranean Sea. The relatively warm waters of the Mediterranean can facilitate the formation of such storms, which are hurricane-like with well-defined central regions and roughly symmetrical cloud-structures. Opinion is divided as to how to classify these events since they exhibit properties of both hurricanes and polar-low systems (sometimes called “artic hurricanes”).
In the last 20 years, studies have reported approximately 15 instances of these storms, which have the potential to generate hurricane-force winds and heavy precipitation. According to AIR, Europe’s commercial building stock displays a wide variety of construction materials. Smaller commercial structures are usually masonry construction, while large commercial buildings are more likely to be of reinforced concrete or steel; they also tend to be well engineered. Because concrete and steel have lower porosity and higher strength than masonry and wood construction, commercial buildings typically have lower vulnerability to flooding than do residential structures.
During its development, the storm generated sustained winds of tropical storm strength and gusts up to 95 mph at Porquerolles Island, France, south of Toulon. Although these hybrid events tend to be short-lived due to the proximity of land in any direction, they can still cause significant damage from both wind and flooding. The recent event-more damaging from a flood perspective- brought rainfall in excess of 400 mm over a period of 4 days in the Var region of France.
In France last week, flood warnings were issued throughout the Riviera and westward along regions near the Pyrenees Mountains. As of yesterday, 12 French regions remained on high alert amid reports that the flooding has affected approximately 2,300 people in the Var and Alpes-Maritimes Départements of France-where at least 750 people have reportedly been evacuated.
In northern Italy, meanwhile, the city of Genoa was on high alert last week after local rivers burst their banks. More than 350 millimetres of rain fell in six hours. The flooding compounded problems from flooding that had inundated the area just a week earlier. Alerts were also issued across the north of Italy, particularly along the Po and Tanaro rivers, and westward as far as Venice. Thousands of people were evacuated from low-lying areas in and near Turin after the Po River was raised by as much as 4 meters.
According to AIR, in the south of France, this storm has caused widespread damage to property and infrastructure. As of November 10, 36 municipalities in France, mainly in the southeastern Var region, had applied for recognition of this event by the insurance industry as a “natural disaster.”
In Italy, the city of Genoa was particularly hard hit. Flash floods throughout the city caused major damage to infrastructure. Residential building stock in this part of Europe is typically of non-engineered masonry construction. When subject to flooding, damage to such structures is typically limited to the basement, which are present in many single-family homes. The presence of a basement increases the risk of damage to contents, particularly in the case of heavily-used basement areas (i.e., those that enclose recreational rooms, bedrooms, or home offices).
The storm that triggered the flooding in parts of southeastern France and northern and central Italy has now dissipated; no further flooding is expected to occur as a result of this event.
AIR continues to monitor the situation and will provide information if changes occur