Severe Storms Bring
Flooding to Italy

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

Figure 1: An extract of the JBA 1 in 20-year Italy 5m River Flood Map. The area illustrated is Treviso, located in the region of Veneto which experienced some of the worst damage. The Venetian Lagoon can be seen at the bottom right, with Venice experiencing widespread flooding. (JBA Risk Management Limited™).

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).

Table 1: Highest tide levels observed in Venice, based on records from 1872 - 2018 (Source: 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).

Figure 2: Tides greater than 140cm (above mean sea level) in Venice between 1872 – 2015 (orange dots). The highest tide recorded in the 2018 flooding was 164cm and is shown in red in this graph. (Source: City of Venice)

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.

Table 2: Economic and insured losses from recent flood events (NatCatSERVICE by Munich Re, Sigma explorer by Swiss Re)

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.

We've produced a regular flood report for major flood events around the world since August 2018. Read the full anniversary round-up here.

References

Andone, D., Waldrop, T., Borghese., L. and Bashir, N., 2018, '9 People from 2 Families Killed in Sicily Flooding as Italy Death Toll Rises to 29', CNN, viewed 29 October 2018 

Associazione Nazionale fre le Imprese Assicuratrici (Ania), 2017, 'Italian Insurance 2016 – 2017', viewed 30 October 2018

Donati, S., 2018, 'Storms in Italy's Dolomites Raze Centuries-Old Forests', Italy Magazine, viewed 29 October 2018

Giovannini R., 2017, 'Venice and MOSE: Story of a Failure', La Stampa (English Edition), viewed 29 October 2018

Henson, B., 2018, 'Flooding in Venice and Deadly Storms across Italy', Wunderground, viewed 31 October 2018

Horowitz, J., 2018, 'Venice Floods: Locals Fear for Italian City's Treasures as Historic Sites Submerged', The Independent, viewed 2 November 2018

Institution Centro Meree, 2015, 'Characteristic Values of the Tide in Venice from 1872 to 2015', City of Venice, viewed 30 October 2018

NatCatSERVICE, Munich Re, viewed 2 November 2018

Sigma Explorer, Swiss Re, viewed 2 November 2018

Povoledo, E., 2018, 'Venice Flooding is Worst in a Decade; Severe Weather in Italy Kills at Least 11', The New York Times, viewed 1 November 2018

Tondo, L., 2018, 'Death of Family in Italian Floods Shines Light on Illegal Builds', The Guardian, viewed 31 October 2018

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