Yes, a heavy rain can overwhelm the pumps that clear the streets next to the river when it’s at flood stage. All that water has got to go somewhere and it sure won’t go into the river when the river is ‘uphill’ from it. I know there was a brief flood downtown maybe 10 days or so ago. There may well have been flooding yesterday, but I haven’t heard of it.
In any case CBS didn’t show that, but rather the much more serious and long-term flooding on the IL side of the river.
The video I saw didn’t show anything from the Illinois side; it showed the flood gate at Themis and N. Water.