On some of the photos I've seen it looks like the river(s) have changed course in a couple areas. Either they will need to route the river bed back to its original flow or re-route the roads around the new river course. Given this was a natural event, they may be digging new road beds in a few spots to route the road around the new river paths. I'm not an engineer but once a river has decided to change path, getting it back to the original path not only takes a lot of work, it could mess with the spawning activity of native fish and other aquatic creatures.
Said differently, what a mess. We were thinking of heading out there again next year. We have been to Yellowstone I think 6 times. I want to see it again before I'm too old to go hiking and experience it on foot. I think we may change next summer plans and maybe head to the Southwest (Zion, Arches, Grand Canon) part of the country instead. It would be a totally different landscape with different wildlife and nature scenes to shoot.
Jeff