The mud and debris around the river will take months to both dry and be cleaned up, and teh lakes/swamps created/refilled by the flood will be a problem for a while.That's...not really a given. It'll take a week or so for the waters to level out. Then they can cross with pretty much the same difficulty as before. It also has the possibility of making the crossings easier as the higher waters may open up add'l crossing sites.
Only place to actually effectively cross is above the lake that drained, I don't expect more than arty duels or SoF raids/recovery down stream of it for the foreseeable future.