There's a really good book about a homesteader that did something similar to this in the 1930's in British Columbia, "Three Against The Wilderness". Basically he restored the dams that had been dynamited by the ranchers, and that restored all of the wetlands in the area.
Later on, the government brought him some beavers from elsewhere, and they flourished.
Later on, the government brought him some beavers from elsewhere, and they flourished.