What barriers can I put up to ward off woodchucks?
I'm sorry you have a wood chuck hanging around! There are a couple of options to keep wood chucks out of your garden. This article may help you: https://www.gardeningknowhow.com/plant-problems/pests/animals/get-rid-groundhogs.htm
I've personally used buried chicken wire and so far (knock on wood) it's working. Good luck!