When they built the Dam in the Grand Canyon it prevented the natural flow of water through the canyon causing multiple species of fish to become extinct and endangered. By flooding some water back in it restores the sand bars and habitats of some of the animals that live in the Grand Canyon.
Humans should never do anything to nature to change it. The flooding of the Grand Canyon in 2008 was a bad decision and ruined a history of nature that had been in existence for thousands of years. It was not a wise decision and now many aspects, beauty, and archaeological evidence may have been washed away or eroded.