@appassionato interesting detail here is that this is all intentional: the area is a floodplain that gets flooded naturally in periods of heavy rain or melting snow. When the rail line was constructed, the rails were built on top of a dam. Apparently that was in 1880!

Source (in German): https://www.bz-berlin.de/deutschland/hochwasser-bahn-faehrt-nidderau

(Maybe you already know all this, but I was curious so I did a quick search for an explanation.)