Roofing help over run

We have a small pre-fab coop for our five hens. My husband built a fenced in run area for them to spend time in when they can't free-range (I usually only let them out if I can keep an eye on them--we live in a varmint paradise!) Anyway, we used some tarps for roofing and that is not going to cut it for winter rains here. My main concern is maintaining an area that can be kept dry when our rains start in November (and last through May!) Trying not to break the bank so hoping there are some creative people who have workable ideas. The coop is just not large enough for them to spend their days in and certainly can't hold their feeders, etc. Thanks for any help you can give.