Since I move to the west coast almost 20 years ago, I haven't had a problem with ground water. I have always been able to find a spot that had an good combination ground material and drainage.

But there are places I have been (midwest comes to mind) where we were limited to fixed campsites that were less than ideal. I have certainly had the experience of a stream running under (or through) my shelter (in spite of some trenching). If I had to go back to one of those places I would certainly bring a shelter with bathtubs floor and a highly hydraulic head than provided by the floors of most ultralight shelters.

--mark