We have a large sunny yard that slopes down to a lake. The slope is gentle enough that I don't think we need to terrace it. There are no erosion problems. The slope descends (or ascends, depending on were you stand) 52 inches in height over 79 linear feet. It's a little steeper at the bottom of the slope right by the lake, but I believe those additional ~8 feet should be left just how they are for the sake of the lake (as well as the bathroom habits of the Canada Geese, in accordance with a suggestion from nandina a few years ago). The measurements here do not include the area sacrificed to the geese, nor do they include the area under the deck, which is also well-sloped away from the house.

At present, this slope is all in grass, weeds, and crabgrass. I would like to create a ~20' deep flat grassy area at the top of the slope, just forward of the deck, and let the rest of the slope remain, to be planted in something that looks gorgeous, loves sun, and does not need mowing.

At present, the first 18 feet just forward of the deck are already kinda sorta pretty flat, although it's bumpy and irregular. Here are my questions:

Am I correct that at 52 inches in height over 79 linear feet I don't have big engineering concerns? Can I create a flat area up top without worrying about the impact on the slope below? How would I secure the slat area to keep it from becoming part of the slope again--Rocks? Timbers? Retaining wall blocks? Do I need to dig down to a frost line?

Also, I think the whole arrangement would look a lot better if I also created a flat area near the bottom, so that from the lake looking up to the house it's goose sacrifice, then a small tier that's flat, then the large slope to be planted in the future, then the new flat grassy area. To my eye, a flat leading to a slope leading to a flat makes a house look wonderfully rooted to the site. But if I do create a flat area at the bottom of the slope, am I inviting new engineering concerns?

The yard is about 120 feet in width, by the way. Also, I have another thread going about how to treat the line of arborvitae along one edge of the property; these topics are only minimally related. Finally, there is a gorgeous set of photos posted by thyme2dig a couple of years ago in another thread. My slope isn't nearly as steep as thyme2digs, and I dont' need a set of stairs, but his/her photos show how wonderful a large planted slope can look with flat areas at the top and bottom. I've linked that thread below.

Thanks for looking and thinking about this!

Here is a link that might be useful: look for thyme2dig's gorgeous photos here!