In some places there may be restrictions during flooding of the Ruhr. For some areas there are therefore map sections with simple bypasses available. You can find them here subdivided by the cities where floods are expected.
You can check the current water level of different parts of the Ruhr online at http://www.talsperrenleitzentrale-ruhr.de/online-daten/gewaesserpegel/. There is also an electronic water level indicator on site, which you can find at the railroad bridge in the Hattingen Ruhraue.
Only for the flooding of the cycle path in the area Bochum/Dahlhausen - Essen/Horst are certain empirical values available. Here, first obstructions are to be expected from a water level of about 250 cm (gauge Hattingen).
With the help of the webcams of the Ruhrverband you can also always get an up-to-date picture of some places in the Ruhrgebiet: https: //ruhrverband.de/fluesse-seen/webcams/