It has been a long time for me, but that looks like the castle in Heidelberg.
So I had a look to find out how much rain actually fell ... the source is meteociel.fr which has excellent weather information for Europe.
The heaviest rainfalls were in the range of 4 to 5 inches a day or 6 inches for two days over the past 48 hours. Those were measured in the Rhineland region of Germany. Amounts in Bavaria were generally 2 to 4 inches.
Those are not excessive by North American rainfall standards but I suppose the climate there does not go to such extremes as often. Still I was surprised not to find higher amounts on the maps (which go up to 0600 GMT or 0800 CET today).
Rainfall records in the UK extend to values as high as 10 to 12 inches a day in extreme cases. However these rainfalls in Germany and northeast France were widespread and probably added a lot of runoff on a regional basis. It has been quite wet for several months so the water tables would have been high before this started.
That’s exactly what it is.
You are correct, Sir!