Downstream from a Kansas City flood would be in Missouri, not Oklahoma.
Downstream includes Oklahoma. Ever hear of Grand River Dam? Water generally runs down hill unless something stops it.
I was in the far North East Corner of Oklahoma and remember the flood well because Grand River Damn Authority held the water back. We had rivers on both sides of our town and farm land was flooded for miles, in fact one of my school mates drowned on his farm.
You might recall Kansas City put several Railroad Engines on one of their bridges to try and save it and lost the Engines when the Trestle went down. In our town, being just dumb Okies, they loaded several cars of gravel on our trestle and saved it without risking Engines.