Whenever the U.K. is hit by major flooding, attention quickly turns to the performance of the nation’s flood defenses. Some defenses, such as London’s Thames Barrier, are regularly recognized for their vital role in protecting people and property. The value of other mitigation measures, however, has been frequently challenged, such as when defenses failed to prevent significant flooding in Cumbria during storm Desmond in 2015.
This week the final knockout rounds of Euro 2016 take place in France. Sadly, England has long since left the country and the tournament, largely due to some inept displays. But more miserable than England’s performance, was the weather at the start of the tournament, which caused concern in the capital as intense precipitation on top of an already saturated France, led to severe flooding.
Some areas of the country experienced the worst flooding they have seen in a century, with the floods across eastern and central France declared a natural disaster by French President François Hollande. River levels in the Seine were at their highest in nearly 35 years, impacting Paris, and leading to three of the capital’s best-known museums — the Louvre, the Grand Palais, and Orsay —closing their doors to the public, as staff moved priceless works of art to the safety of higher floors.
Source: The Guardian
There were also concerns surrounding how the flooding could impact the tournament. However, as you can see in the below image, which represents the RMS 1,000 year inland flood hazard extent, neither of the two stadia located in France’s capital (yellow markers) were really at any risk of flooding. The same can’t be said for the fan zone adjacent to the Eiffel Tower though (red marker). Continued intense rainfall, would have led to increased flood severity, meaning that 90,000 or so fans would have been in need of their waders.
Stade de France and Parc des Princes (yellow markers); Paris Fan Zone (red marker)
Paris wasn’t the only location in France to be impacted by the floods though; further south the town of Nemours observed severe flooding as the River Loing burst its banks. While devastating to the local community, this severity of flooding can be expected in the town. The RMS Europe Inland Flood maps demonstrate such flooding for events in excess of the 50 year return period, but as the below image of the 200 year flood extent demonstrates, the flooding could have been even more severe.
Rue de Paris, Nemours (yellow marker) and Château-Musée de Nemours (red marker)
The flooding in Nemours is a good example of why it is so important to understand the standard of protection offered by local flood defenses, in order to fully understand flood risk. The RMS Europe Inland Flood models and maps explicitly represent the impact of flood defenses and provide some noteworthy insights into the potential exposure at risk, if the standard of protection is not maintained or local flood defenses are overtopped.
Rue de Paris, Nemours. Source: The Guardian
If we removed all flood defenses and consider a 100 year return period level of flood hazard across France, the RMS analyses estimate that over €600 billion of insured exposure is at risk to flood damage. However, approximately 40 percent of this exposure at risk is protected against such levels of hazard by local flood defenses.
Source: Château-Musée de Nemours
And in the largest exposure concentrations, such as Paris and its surrounding area, the importance of local defenses is even more prominent. Looking at a similar 100 year return period level of flood hazard in this region, almost €60 billion of insured exposure would be at risk of flooding, but approximately 90 percent of that exposure is protected against this level of hazard.
Flood can be thought of as a polar peril; if you’re in the extent of a flood event, the costs are high but if you’re on the edge then you’re safe. And for this reason, an understanding of the impact of flood defenses is vital, because if they breach or become overtopped, the losses can be high. Knowing where exposure is protected allows you to write business smartly in higher risk zones. But understanding the hazard, should defenses fail, is also vital, enabling a more informed understanding of severe flood risk and its associated uncertainties.
This post was co-authored by Rachael Whitford and Adrian Mark.