Copperheads seem to like moist areas, but not too moist. I would bet that you see them after a good rain and if you see one, there is bound to be more. They are quite common in this area.
My cul-de-sac is adjacent to the Occoquan Reservoir and several kids in my neighborhood got bit when they were running around in the woods with flip flops.
My advice to you is to not go running around in your yard without shoes on; better still would be to wear ankle high boots especially after a good rain.
I don't usually bother them unless they get too close to the house. It seems to happen at least once a year.
I have two creeks going through my yard (This is the burb house) and ten acres of woods so yes I have a lot of them.
They aren't normally aggressive except during mating season (spring) but this one has a bad temper. I never had one actually move up on me and try to bite me before.
I'll get him sometime today or tonight. This time of year, they are out more after dark. I was surprised I didn't find more last night when I was turning over logs looking for him.
He also stood up higher than most. If I hadn't moved, he'd have gotten me in mid calf. He was up a full third of his body length. That's unusual. Even when I step on one they just bite at my boot.