American Rivers has some new (as of a month ago) videos of the Copco 1 and J.C. Boyle dams being breached. I’m really excited to see how the Klamath river responds to these dams being removed.
Copco 1: https://www.youtube.com/watch?v=SEAuGu6zp-0&t=106s
J.C. Boyle: https://www.youtube.com/watch?v=RDD8lYV_GRQ
Also, someone made a post-breach video of the river with their drone: https://www.youtube.com/watch?v=WIJcOaSBsOg
(Sorry for not including alternate Piped links. That site isn’t working for me right now for some reason.)
Most likely, worse water quality and the death of a lot of fish/aquatic life.
Why would you think that? A planned dam breach is a pretty controlled thing and not something done lightly.