Chickadee,
I thought about that too. If you are making it as a permanent coop, and not moving around attached to a tractor coop, then yes you can make it very secured. Simply run a 1" X 4" treated board all the way down the coop and run near ground level, attaching them to the PVC with 1/2"...
Here's a good website for you. Look at the Greenhouse especially. If you build a coop or run like this example, you will simply bend the pipe.
Here ya go:
http://www.pvcplans.com/
Hope that helps.