Where would you move the water if you had the ability? In most places, it is illegal to channel water from your property onto another person's if it creates a nuisance to them. While it would clearly not be illegal to move water from one campsite to another, it would sure not be neighborly to flood the guy next to you because you want dry feet. I also wouldn't be digging ditches without permission from the park management. Most would not take kindly to that action.
Have you talked to the park and asked for help? The best option would be to level the low spot so the water doesn't pool. If there is common area adjacent to you site, the park may allow you to pump or channel the water onto it. It may also be that there is no cure due to an exceedingly wet spell and you may just have to either change sites or live with it. There just isn't a one size fits all answer.
