9.62 miles, took roughly 3 hours.
Launched from the canoe/kayak launch in the Avalon area of Patapsco Valley State Park. Paddled rest of the way down the river to its mouth with 1 canoe and 2 kayaks.
First mile had current and rocky bottom, until crossing the fall line (route 1 bridge) where current slowed (to a leisurely pace) and sandy bottom.
Occasional trees down across the river at beginning.
Several crossings under bridges, some of which had minor log jams at them, but there was always an easy and wide gap around these jams.
About 2/3 of the way in the current stops and river becomes wide and slow, trees disappear and grasses take prominence.
The "finale" where you hit the mouth of the river and can see the bridge, city line, and cruise ships across the channel is beautiful and well worth the trip. Somewhat open watery, but very sheltered. Might be choppy on windy days.
All in all it was just over 9 miles paddled (strava), and only became arduous at the very end.
Be aware of fishing lines coming off the bridges in the last few miles.