Understanding the Potential Impact of the Next Catastrophic European Flood

Over the past year, Europe has intermittently but consistently suffered from significant flooding.

Most recently, the Balkans experienced widespread devastation in May due to some of the region’s heaviest precipitation on record. Three months worth of rain fell in just three days. The subsequent flooding was so severe that entire towns were submerged. While it is too soon to estimate the full impact, the economic and humanitarian costs will be high.

This event follows one of the stormiest and wettest winters on record for the U.K. Remote locations bore the worst of it, and for now, the U.K. government and insurance industry appear to have largely escaped a sizeable bill, at least on the scale of previous flood events.

The events come just one year after the costliest natural catastrophe of 2013 for the insurance industry, when flooding inundated Central and Eastern Europe in late May and early June. The event caused around $20 billion (€12 billion) in economic losses, of which it is estimated that approximately 20 percent was insured.

As with the more recent Balkans and U.K. events, the May 2013 flooding followed a period of extreme rainfall; consequently, groundwater and soil moisture levels were saturated. As more rain fell in late May and early June, the precipitation had nowhere to go except to flow through catchments into the river network as runoff. The Danube, Elbe, and other rivers overflowed, resulting in significant flooding across Germany and the Czech Republic, and, to lesser extents, Austria, Switzerland, Poland, Slovakia, Hungary, Croatia, and Serbia.

Each of these events highlighted the importance of understanding the impact of precipitation, whether from a short, intense period of rainfall, prolonged wet conditions, or a combination of these characteristics. In each case, to evaluate flood risk, it is vital to understand how antecedent wetness conditions influences subsequent flooding.

In 2002, Central Europe was similarly inundated by severe flooding, producing economic losses of over $28 billion (€17 billion). Both events were triggered by similar meteorological phenomena, Genoa type-lows. However, the antecedent conditions in 2002 were comparatively dry compared to those in 2013, and the precipitation that triggered the eventual flooding was more severe in 2002 compared to 2013.

Both events had significant impacts, but what would happen if we combined the worst features of both to create a “perfect storm” type of flood event?

Combining the antecedent wetness of spring 2013 with the extreme precipitation of the August 2002 event, RMS researchers estimated how severe this “perfect flood” could be. Results of this study show a substantial increase in peak flow (more than 50 percent on average) for both the Elbe and Danube rivers.

In certain locations, this scenario would be characterized by a flood extent (shown above for the area surrounding Riesa, Germany) of about 2.5 times that observed in 2002. But given the remarkable non-linearity between hazard and damage, RMS research estimates that the increased losses could aggregate to a total economic loss of approximately four times the 2002 losses. While this is a theoretical scenario, it is also an entirely realistic one.

The events that have occurred since May 2013 are a stark reminder that flood is a peril from which much can be lost.

After the 2002 flooding, flood defenses were improved in some locations, such as Prague, resulting in less severe flooding. However, because both the flood hazard itself and the physical environment change over time, Europe’s flood risk must be continually and holistically assessed to ensure that we are prepared for when, not if, a similar event occurs again.