That's pretty nuts.
The first time we went camping at Zion, we were probably 50 feet from the Virgin River and maybe 10 feet above it. The river during the day was barely moving and maybe a foot deep and 4-5 feet across. Tons of rain north of it one day, and we got woken up in the middle of the night telling us we needed to move because of the river. It was so fucking loud, I have no idea how we didn't hear it. Was probably moving 30+ mph and had come over the 10 foot bank that we were camping on top of.