I recently installed two neighboring privacy fences near the edge of a steep slope (appx 35 deg) in a new subdivision in central TX. I was lucky enough to get sod down prior to some heavy rains so I didn't have a wash out underneath, a house next door to this one lost a large amount of soil/yard. The owners have expressed concern about the posts washing out or the soil erroding beneath the fence. I quickly put some perferated pvc with crushed stone in places that look like the water naturally drains around under the fence/sod. I put this in the hardscape forum because I know those who work with high r-walls use special drainage and thought you might have a good answer. Any ideas? Oh, and by the way, the soil sucks here - anyone ever hear of calechae(sp?)?