My symapthies - very frustrating! I'd be inclined to think it's woodchucks since both rabbits and deer typically are relatively neat. IME woodchucks leave pieces around and don't make really clean cuts. However, don't assume that deer would be deterred by this being a public park surrounded by roads and houses. They would come to feed probably around dawn (they feel fairly safe at 3:45 am) or dusk, and usually are fairly savvy about what people are threats IME.

Any repellents will need to be replaced after rain, and I don't know if they will work on woodchucks - we use a more permanent solution. Milorganite (which will fertilze as well), or any of the deer or rabbit repellents are worth trying such as Bobbex, Deer Away, etc., or there are lots of homemade repellent recipes that usually include some combination of garlic, hot pepper, old eggs, blood meal, etc. mixed well with a small amount of soap or some milk powder. Let the mix sit for several hours in a warm spot, strain through cheesecloth, and then spray. Regardless of what you use, commercial or homemade, spray from upwind and wear old clothes with good coverage since often they are something you don't want to be perfumed with. The scent dissipates in the garden after a relatively short time, but can cling to clothes and skin.

If it is woodchucks, I have yet to find a solution. We have them every year and I have just begun planting things that are toxic or that they won't eat. It's very frustrating! We have also set up a motion-sensor sprinkler by our veggie garden to deter them.

Woodchucks are jerks. They will take one bite of one thing and then one bite of the next. I have finally fenced my yard securely enough to keep them out....oh, and my two boxer dogs are great garden guards. Be aware that some of the pest repellents like coyote urine are manufactured via inhumane methods (coyotes bred and kept in cages that collect their urine).

A word to the wise, for human urine, pee in a cup (indoors) and pour it where you want it in the garden. I have no idea if it works as a repellent, but if you live in a populated area that is the safe means for application!

The damage done to your plants is very discouraging. :-( I have found that pinwheels planted in my vegetable garden will prevent birds from uprooting my new seedlings. I don't know if that would work with wood chucks, but it might be worth a try.

Woodchucks can climb trees and dig several feet underground. If they want to get in, they will. It just depends on how interested they are in what you're growing and if there are easier/better options elsewhere.