Duane, what feeds (water) to your pond.....a creek, well, etc.?
The type of sediment trap design I am familiar with would be built on upstream side of pond to catch sediment from incoming water source, and keep sediment from getting into main body of pond.
I've never heard of having a perimeter ledge as a sediment trap.....suppose it could work, but you'd probably be better off mitigating the erosion to your pond above the water line, although the fish would probably love the ledge (and berm).
my little 2c.
