Honestly I think the rain skirt/poncho/umbrella/cagoule people may have this right, as seems to limit contact with the legs and doesn't drip all the water onto the feet (only some of it). But then, I only have experience with a poncho, from many years ago.
I do recall seeing many first efforts by Scouts and especially adult leaders in tarp-pitching, enough to recognize that water is surprisingly easy to collect in a gutter, albeit by accident. The problem, as you stated, is in getting rid of it without a catastrophic spill over the edge (in this case, off a jacket and onto one's crotch). Again, I think oversized rain gear may be a simpler fix.
Or a waterproof hoop skirt? ;)
Edited to give credit to those smart umbrella folks. I imagine some of them may come across this thread and think, "that's why I use an umbrella."