6 November 2018
Strong storms brought severe rainfall and high winds to much of Europe last week, resulting in flooding in Italy and Croatia.
Torrential rainfall, combined with strong winds, claimed at least 30 lives across Italy and extensively damaged properties (CNN). In addition, a part of the Red Fir forest in the Dolomites was wiped out by the extreme winds, uprooting approximately 14 million trees (Italy Magazine). The worst damage, however, was observed in the northern regions of Trentino and Veneto; it is estimated that losses in Veneto alone will exceed €1 billion (CNN).
Risk of illegal housing in Italy
In the town of Casteldaccia in Sicily, a family of nine lost their lives as their house was engulfed by the Milicia River when the river burst its banks (Guardian). These fatalities highlighted the issue of unauthorised housing. In this instance, the villa was ordered to be demolished two years ago as it was located close to the river and thereby considered as a high flood risk (Guardian). However, the family appealed against the order and remained in the property (Guardian).
Approximately 1.2 million houses are estimated to have been built illegally in Italy and these houses are typically built close to foothills or river banks, exposing them to landslides and high flood risk (Guardian). In 2012, 46,700 properties were ordered to be demolished but only 10% of these orders were implemented (Guardian). Furthermore, 80% of demolition orders issued between 2004 and 2018 have not been carried out (Guardian).
High tide flooding in Venice – the worst seen in the past decade
Last week, Venice experienced flooding as strong winds combined with high tides during a series of storms (Independent).
A strong low-pressure system in southern Europe enhanced southerly high winds, pushing water towards Venice from the Adriatic Sea (Wunderground). The winds coincided with the seasonal high tides bringing a maximum water level of 156cm (61 inches) above sea level on 29 October 2018 (Wunderground). Based on historical records dating back to 1872, there have been only three occasions where water levels have surpassed this height, with this being the worst flooding observed in the last decade (Table 1) (Wunderground).
Venice continually struggles to remain above sea water levels due to land subsidence and sea level rise (Wunderground). Since 1897, the average water level in Venice has increased by 23cm (9 inches), with approximately 60% of this rise due to land subsidence caused by water extraction from the underlying aquifer during the 1920s and early 1970s (Wunderground). The remaining 40% is likely due to the increase in sea level (Wunderground). Exceptional tides (defined as being greater than 140cm in Venice) are occurring more frequently in Venice; in the late 20th century, tides greater than 140cm happened once every 5 to 10 years (Wunderground). In the past two decades, exceptional tides have occurred 10 times (Figure 2) (Wunderground).
The flooding in Venice may have been avoided had the planned flood gates of the MOSES project been implemented. Originally scheduled to finish in 2011, the MOSES project remains unfinished with the project in turmoil due to corruption and poor management (La Stampa). The original estimated cost for the flood gates was €1.6 billion which rose to €5.5 billion due to further investment needed for construction and future maintenance (La Stampa).
However, the flood gate will only be effective against tidal flooding that exceeds 110cm in Venice which means prolonged rainfall may still result in flooding, as witnessed at the Piazza San Marco (La Stampa; New York Times; Wunderground).
Flood risk in Italy
Flood remains a severe peril in Italy and, in particular, the valleys through which the Po and Arno rivers flow. Heavy rainfall in the north of Italy makes many areas highly vulnerable to flash floods. 70% of Italy is exposed to flood risk and landslides, with previous severe floods costing an estimated €0.37 billion– €3.5 billion (USD $0.50 billion– USD $6.46 billion) (Table 2) (NatCatSERVICE by Munich Re; Sigma explorer by Swiss Re).
Italy is behind other developed European countries in insurance penetration. The insurance penetration for non-life insurance in 2016 is approximately 1.9% of GDP for Italy, lower than both France (3.4%), Germany (3.3%) and Belgium (2.8%) (Ania). The majority of insurance for natural hazard covers industrial and commercial properties, with less than 0.5% of households having any form of insurance to protect themselves against natural catastrophe.
This event is a timely reminder of the need for more adequate flood defences and the dangers of living in high-risk flood areas.
JBA Risk Management has just released nationwide return period flood maps for Italy at 5m resolution. Please get in touch for further information.
