I have kayaked from the Whitney dam to Cameron Park on a couple of occasions. The first time they were letting out a ton of water, and it was 30+ miles of essentially a giant lazy river ride, and it was absolutely awesome. It was first clear day after 2-3 days of major rain, and I went with a couple of buddies and more fun could not have been had.

That said, on another trip, same circumstances following rain, we checked all the gauges, called into the Whitney folks and got assurances that they'd be releasing, and they did for only about 90 minutes. And the next 25 miles that followed back down to Waco, over the course of about 15-16 hours, was the most grueling experience of my life. Into the wind, having to portage several times over sandbars, not having adequate nav lights for the darkness we thought we'd have no business seeing, dodging fan boats that run the Brazos at night (also with no nav lights and leaving SERIOUS wakes) and hearing the sounds of angry beavers smacking their tails on the water when you get close in the pitch blackness and it sounds like you're taking on Confederate cannon fire from the Merrimack.

So...all that to say, can be pretty hit or miss.