I have done this river run in my Cessna 182 many times, there are wires on this river , so one has to know where they are before doing this kind of flight.
In the Cessna I do this river run at about 60kts, in the CJ6 was about 130kts, what a different experience, lots of fun.
I usually do energy turns with the Cessna on this river but at 60kts you just go above the trees and make the turn, I tried the same with the CJ 6 and at 130kts it would take me way to high, so I opted to stay low and do some G turns instead.
In the Cessna was doing this river one time (first time) always do it very slow 60kts 20 degrees of flaps, after a sharp left turn saw the powerlines, was too low and slow to climb, and below the trees so couldnt do a 180, so I put full flaps and slowed it down to 50kts so I could see better and be slower in case I hit.
I decided to go under the powerlines,(no other option really) just before going under the powerlines I saw another wire under them, I ended up going between the powerlines and the other cable.
Lesson learned, was very lucky , very stupid, I admit it.
And the faster the plane the least things you will see and least amount of reaction time.