German insurers upgrading models to include flash floods

German insurers are working to take flash floods into account within their risk models.

“The July 2021 flood in particular showed that previous flood simulations do not depict flash floods accurately enough. In narrow mountain valleys where a lot of water falls from the mountain slopes, the river levels can rise significantly higher than with the same amount of rain in open areas,” said Anja Käfer-Rohrbach, deputy general manager of the German insurance association (GDV). “This means that the flow speed and destructive power of the water is many times greater,” she added.

The GDV successfully modelled flash flood risk for four test regions in 2023 – including the AR Valley, which was badly hit in 2021 – and will now expand this project on a larger scale.

“We concentrate on the relevant areas. These are the low and high mountain ranges,” explained Käfer-Rohrbach.

The modelling covers around a third of all addresses in Germany. However, not all of the sites are particularly at risk from flash floods, said the association.

The new information will then flow into the GDV’s ZÜRS geoinformation system, which calculates the risk of flood.

“The integration of the flash flood data is planned for 2025,” said Käfer-Rohrbach.

Insurers use ZÜRS to calculate premiums for natural hazard insurance. More than 22 million addresses are fed into the system. So far, ZÜRS has mapped the risk of flooding and heavy rain for four or three different risk classes.

By revising their risk models, German insurers are preparing for more frequent extreme weather events.

“With climate change, the intensity of heavy rain events is increasing,” said Käfer-Rohrbach.

With global warming, the temperature differences between the equator and the Arctic are decreasing. This changes the jet stream – the band of strong wind at a height of 10km that is driven by the temperature differences. The result is that the air masses will tend to move more slowly in the future. Low pressure areas no longer move away so quickly, but sometimes remain over a region for days,” said Käfer-Rohrbach.

“The more water falls from the sky, the more it collects in streams and rivers. Depending on the topography, dangerous flash floods can occur,” she added.

In view of the increased level of danger, the topic of prevention must come to the fore, said the deputy GDV managing director.

“The federal government, states and local authorities must promote prevention measures and adequately finance them. And we need a construction stop in risk areas,” demanded Käfer-Rohrbach.