Also in the novel, Obi-Wan is at the edge of a shallow cliff when he slices Anakin, who then falls down to the bank after losing grip with his mechanical hand. Not sure why George didn't do this. Makes a whole lot more sense.
btw, the novel is pretty good; I'd recommend it to any fan editors out there. Anakin's fall is so much more believable, with a lot of new insights and dialogue added. Some of the bad lines remain, but it's forgivable this time.