I'm not sure what's happening everywhere, but I live in what was a closed off town, surrounded by the remains of roads, bridges, and rivers on all sides. What I have seen by me is that the path of the big rivers during the flooding gouged wide swaths.
The sides are pretty sandy in some cases. They are now much, much wider than they had been in the past. Even as of yesterday, Thursday night's rain caused more sliding off the hill sides from the ground that remains unstable. There are piles of boulders and dirt where there never were before and voids where there used to be boulders and dirt. What I see is the road crews moving this type of stuff around and bringing in fill from local gravel pits. There's just so much rock they will never clear it all. I see them doing what they need to to get some infrastructure back, but not complete dredge outs. Again this is the big rivers I drive by daily.
On the smaller streams its harder to say. There were so many affected. I've seen streams and brooks with what is probably dredging in sections as they cleared the debris. They didn't put back deep channels though, just cleaned out the bed. One of the things that amazed me in the first days after was how many people actually own their own backhoe's and bulldozers in this area. Must of the effort immediately after was by locals with there own equipment. Right, wrong or indifferent, these guys cleared stuff and moved stuff to make passage ways in and out. Probably not to anybody's code.
As peakbagger said, the insects and the terrain that are both necessary for the fish. There's one picture from the flood of a beaver in the road down from me. He was out on 100 trying to escape the raging flood on it's brook. The flood cleaned house on most water based critters in general.
I'm going to pay closer attention to what they are doing around here now though just in case. We do need to keep a balance between safe passable roadways and what we're doing to the envirnoment all around us as a result.