If you are going to do Riverside or the Bearcreek run (the two top drifts before the closed water)you should make arrangements to follow someone that knows the drifts. Both are very challenging, and shouldn't be attempted unless you are extremely good on the sticks. If you are familiar with the middle/lower end of the 'Duc the upper stuff makes the "double rapid" and the drops above Luyendekers look like a cake walk....but, I have to admit Riverside and Bearcreek are my favorite floats as long as I'm with a guide.....otherwise they are too much work/stress.
Riverside - put in off the ledge up the road on the opposite side of the river from Klahowya campground (float under the bridge before you fish) take out at the paved road (I forget the name) a few miles above Bear Creek Cafe. That is also the put-in for the Bearcreek float. The take-out for the Bearcreek float is the salmon hatchery.
Good Luck.