Hey Slip, I'm not as old as "D" but I have fished and seen the Spillway silt in over the years. Big Pigeon at Little Pigeon would be one example.

Technically everything within the two guide levees paralleling the Atchafalaya River 15 or so miles apart is the Atchafalaya Spillway.
On the other hand, all of the low lands between the Mississippi River and Bayou Teche can be considered part of the Atchafalaya Basin.

I haven't heard of any dredging. There is pipeline and rig activity on going.