There are lots of methods to deter hawks.
Shiny CD's taped to the top of the run/coop
A decoy owl or hawk
Streamers that will flap in the wind (to make them get a plastic tablecloth like the ones used at kids' birthday parties and cut it)
Mirrors attached to the top of the run/coop (you don't have to cover the entire thing in mirrors, if you have an old one you can take it out of the frame and use it or break it up into largeish pieces and place them on the run/coop. The reflection when the hawk comes to land will frighten it).
Most likely the hawk will become used to these methods and figure out that they aren't real and can't hurt him. Hawks are quite smart. A dog is a great protector. I have a wonderful collie named Beau who has figured out that I don't like big birds. He keeps away foxes, raccoons, etc as well and alerts me if there is something out there. I trust him fully with the birds which is another nice thing (collies are considered one of the best dogs with chickens, if not the best).