You can try a larger fence.

Also if you have a cat, putting cat hair around the garden can sometimes scare them off. Maybe a fake owl decoy as well.

You can also buy fox urine and apply around the base of the bed.

Groundhogs are one of the very worst pests because they are hard to deter or catch and they will consume just about everything in short order.

If you can't shoot it, maybe you can trap it. A medium-sized live catch trap may work if your woodchuck is not too savvy. They are pretty smart, but if you disguise the trap by covering it with branches and leaves and put something particularly yummy (I used okra--their favorite) inside it may go in.

Look around your yard for the hole--they will have another so you can't really trap them in there but you can at least discourage them by plugging it up. Some people have put rodent poison in the holes or flooded them.

The only fence that works is a metal one that is buried and turned out underground so they will not dig under it. I highly doubt cat hair, an owl decoy or fox urine will frighten it now that it knows where the banquet is set up. A live dog will, but must be on guard constantly.

Oh, btw, if you do trap it, please do not bring it out to the country to eat our gardens out here! A large park with no homes nearby is a better choice.