Question
I live in Zone 6, Oklahoma.
What groundcover can sustain foot traffic? From full sun to shade?
What groundcover will grow under Western Red Cedars, from full sun to full shade?
What groundcover will grow in ditches or "wet weather creeks"? Normally dry all the time, but when it rains it washes out my grass, wildflowers, etc.
Thanks for you help, Jerry

Answer
Sorry, I've been madly getting my yard in shape...

Groundcovers that you can walk on that I have used are:
 Irish Moss-Low-growing Irish moss is ideal for filling in crevices between bricks or stepping-stones.
Zone 4 to 7
 
  Sedum-very short groundcover only about 1" tall and spreads nicely year to year and you can take pieces and transplant them anytime!

Pachysandra, Lush
Grows under trees where even grass won't do well - only plant that thrives under pines.

 Vinca Minor, or Myrtle, is one that will grow under a cedar tree.  Try to find someone that wants to thin out their vinca bed and get lots of little starts from them.
It takes a lot to get a patch started and it does take time to spread.  I would start planting from the outside inward.

All above can be in shade or sun.

Sijka