Try your local South Platte in town
I would try running the South Platte here in town. You can run from Chatfield (C-470 & Santa Fe South Platte River Park) to Confluence. There are 48 or so drop structures and rapids on the way down. Some of them will challenge you. But it is perhaps some of the most underrated urban paddling on the Front Range.
Right now the flow is at 1,050 CFS out of Chatfield and tops up to almost 1,400 CFS at Confluence.
And the Lord said, let there be whitewater. So on Friday, the 13th day of the month....