I will have to excavate my pond from flat ground, no dam, no runoff to speak of. And will line with vinyl or bentonite (mixed blanket with a foot of natural soil to cover.

I have read in numerous places that the slope of a pond should not exceed 3:1 to keep soil from sliding down the liner. I assumed this meant 3 inches per foot, is that correct? Or is it 1 foot drop in 3 foot of run? Doesn't sound like much, but a difference of 7.5 ft of depth or 10 ft in a 60 foot diameter pond is quite a bit.

Do I really need to pay that much attention:
1. with a vinyl liner?
2. with bentonite liner?

Will the topsoil slide down off of these, will the bentonite layer slide down leaving no seal at top?

etc. etc.

Greg