In reply to no_more_scotch_eggs:
Dunno - I always seem to cross the Geldie in the dark, making it more awkward than it needs to be. For the Tarf at least, you could cross the Bedford Memorial bridge at the Falls of Tarf and work your way back up to the track on the south side of the river.
Geldie is quite wide - probably does get rather deep in the sort of weather we're having just now. I've never had to cross it, but I've waded the upper reaches of the Feshie not far to the west, and that could certainly get pretty uncrossable with a bit of rain. Again, you could approach from Linn of Dee on the south side of the Dee/Geldie to avoid the crossing, although the going would be a bit harder.
Sorry, that's a very inconclusive response!
Post edited at 22:54