The little Carson River runs right through Dayton going east. It is oxbowed high plains river and there are detention ponds. I imagine that the river is full and no drainage is possible and all the streets and residential lots are flooding.
The key to your observation is high plains. It has somewhere to go. The most curious thing is the Dayton name and the WHIO station. I’m going to look at the USGS maps because something really bothers me about the details.
Tere is no dam anywhere close to the town to validate a specific evacuate order that would bot apply to other towns along the same stream.