Are there ever temporary flight corridors?
Flight corridors (airways) are just standard routes to simplify communication from controllers to pilots when describing where they should fly and between controllers when handing over flights. But the controllers can assign arbitrary vectors (headings and altitudes) to aircraft whenever they see fit. 

So there is no need to formally set up a temporary corridor. If the traffic for whatever reason does not fit the usual corridor, the controller will simply assign any free vector and explain the situation to the next controller. They do that all the time anyway.

However in non-radar environment (e.g. oceanic or in case of radar failure) airways become important tool for the air traffic control, because it would not be feasible to keep track of positions of all the aircraft on ad-hoc routes. With airways the controller knows which airways intersect so planes on them need to be separated vertically and only needs to track the aircraft progress in one dimension (along the airway) instead of two (on map).