The one thing I wonder is that if it really was premeditated, what did he expect to happen when he landed? Wouldn't you pack some water? He mentions there being water in the plane, perhaps he forgot to bring it with him? I wondered when watching it whether he took his parachute with him to make a little tent with if he ended up needing to spending a night out there.
I also wonder if he severely underestimated how long it would take to get to the riverbed. He claims it took him five hours, and the distance of the riverbed from the crash site is only about 1.5 miles.