Jenna, this sounds difficult, and a long term project.
See this forum post for some great information on voles, and how to trap them/reduce their numbers.
They are difficult pests, far worse than moles.
Your sodden ground is another problem, voles like moisture, and it needs organic matter for mulch to encourage soil life and improve drainage.
Not sure how you find the organic matter!
Try a small area first.
Is it the only plot you might have access to? Are you planning to stay for a long time? You need to be clear on those questions.
