Green beans under assault

I'm new to the forum, and relatively new to gardening. I live in an urban setting, so I have to maximize the space I have available.

Among other things, I planted a dozen bush green beans, and they've done very well. They've been producing a handful of harvestable beans every couple of days for a week now. The last couple of nights, they've been under assault by a family of groundhogs. The entire yard is well-fenced, and I thought it was secure from rodent assault. I came face-to-face with one of the little critters, so I was able to see where he went when I scared him off. I've sealed up the holes and the weak spots. Now, 2 questions.

1. Will sprinkling a bit of used cat litter around the likely entry points help deter them. I'm not squeamish, so I have no problem doing it if it will work.

2. The rodents ate about half the leaves on several plants, leaving them not quite bare, and knocked them over in the process. Assuming the rascals don't come back, are green beans strong enough to bounce back from such an attack?

Thanks for any help.