Past European floods may not be the best guide for what the claims bill will be from heavy flooding that swept western and central Europe earlier in July.

Milan Simic, senior vice president of global business development at data company Verisk, said some analysts have used losses from the 2002 and 2013 flooding in central Europe as benchmarks when sizing up losses from this summer's flooding. Each of those past events would cost insurers between €3 billion and €4 billion if they hit today, but they impacted different parts of the continent, Simic said.

That leaves modelers without a "like-for-like comparison" in the last 30 to 40 years, Simic said.

Germany is expected to bear the brunt of the insured losses from the flooding, according to a July 19 report from Aon's Impact Forecasting division. Simic noted that the Rhine valley is the "one of the richest and most industrialized" parts of Germany and accounts for much more economic output than the parts of the country affected in 2002 and 2013.

This summer's events were "almost flash-flood-like" as water rose rapidly, sweeping away bridges and destroying some buildings entirely, Simic said, and debris acted "like bullets" to cause even more damage. Rating agency Moody's said that while the regions worst hit by the flooding are smaller and less densely populated than those most severely impacted by the 2013 flooding, the damage is more severe.

The take-up rate for all-weather insurance coverage is 37% and 47%, respectively, in the worst-affected German states of Rheinland-Pfalz and Nordrhein-Westfalen. Across the country, the take-up rate for such coverage is 46%.

Germany's non-life insurance association has estimated that the country's insurers face claims of between €4 billion and €5 billion. Verisk owns risk modeling company AIR Worldwide, which, like its peers, has yet to produce an insured loss estimate for the flooding.

Business interruption could also feed into the total claims bill. Rob Kleinveld, executive general adjuster at loss-adjusting firm Crawford & Co., in an interview said that, based on what his company was seeing so far, commercial claims were mainly coming from retail chains, where business interruption is a concern.

A further complicating factor, according to Kleinveld, is the effect of material shortages on the cost and time of repairs. Even before the flooding, many contractors were not willing to provide quotes for certain types of work because of the skyrocketing costs of building materials, Kleinveld noted.