GBBUDD,
The bottom gradually slopes from north to south (right to left in most images) about 6 inches in about 24 feet of bottom. Waste removal is not a significant issue nor a design constraint in this or my previous build. With the few goldfish and mosquito fish I have, not a lot of waste or plant material waste is created in terms of solids. What is created can be netted off the bottom once every year or three. The stock tank you see in the background of most of the images is a gravity up-flow filter and works quite well. The stream bed at 25 feet long with many small rocks functions as a horizontal trickle tower and does a great job of maintaining water clarity. I'm more concerned about being able to get in and out of the pond without risking life and limb to do clean up and maintenance on plantings, pumps and plumbing. With 3 pumps (just got an additional one last night), one feeding the stock tank and the other two feeding the top of the stream bed, I've got right around 7,000 gph going down the stream for a pond that is probably 4,500 gallons.
Time will tell regarding the new design and I will report back as time goes on. The problems I've had in the past was with string algae in the stream bed. The ratio of sun to shade is significantly favoring the sun in this build versus last time, so water clarity will be a concern.
Bottom drains are more common in large koi ponds but they don't seem so common here on this forum. I've noticed that people here often place their submersible pumps up off the bottom to prevent a pond being pumped dry by a plumbing or stream bed fault and that's what I have done. There's far fewer ponds on this forum with external pumps than I saw on various koi forum that I frequented earlier. Likewise UV filters and pressure filters. Not saying there aren't any here, just less frequently here than on koi oriented forums.
It's like many others have said - build what amuses you/makes you happy. For me, I like the simplicity (and low cost) of my set up.
I love watching your build - it's great! That's a big reason I come here is to see the huge variety of takes on pond design and how so many are wonderful regardless of their design.
John