Rivers change with the seasons. Floods, falling trees or rocks and other detritus can change the river in many ways. From a tree temporarily blocking a rapid until it washed away to a complete remodeling of the river such as that inflicted on the River Sanna in Austria in the floods of 2005.
This is why no matter how familiar we may be with a river we shouldn’t make any assumptions, just because a drop was clear yesterday doesn’t mean it will be today.
High water levels just before Christmas seem to of moved the rocks at the top of Surprise Surprise on the Upper Dart. Consequently the centre line seems to have been made a slightly easier path down it.
How long it will stay this way is anyone’s guess.