Sounds very challenging! Someone more expert than I can give greater details and comments about the engineering but I do have some thoughts.
Are you doing all of this work by hand or will you have heavy machinery (or at least some helpers)? Sun from 9-4 sounds o.k. just off the top of my head but check with experienced vegetable gardeners about that.
How is the drainage? The soil? What is the sunlight like during the seasons when you are most likely to be in the terrace garden? If the walls will be dry-stacked stone then excess moisture will be able to escape. A mortar wall requires more thought about how to relieve moisture build up. Landscape fabric between the walls and the soil should help to retain dirt but let moisture out.
Vegetable gardening is labor intensive so my first thought for after the terraces are built is to make things more comfortable and more practical for the time that you will be in the terraces.
Some sort of hard suface (planks, flat stones, whatever) to walk on and roll carts on in each terrace would probably reduce the amout of slipping, sliding, compaction and sinking in when you are in the beds. I'd like to see photos. A ten foot drop over 50 feet does not sound ultra-horrible but a picture would give more perspective.

Bob64:

Thanks for the reply.

Well, I have a small tractor with a backhoe and front end loader, and I have more rounded granite rocks (from potato to potato sack size) than I know what to do with. The soil is 6" topsoil over sandy loam over gravel: pretty much perfect drainage. I have a friend who is a master wall builder and excavator, so I'll get some good advice on design and construction. And I'm learning not to be in a hurry.

We'll probably raise the beds on each terrace using rocks. In past gardens its been pine bark mulch in the paths, but here we are near a cheap source for crushed clamshells, which might look nice and make for easy rolling (and weeding). I'll lay 4" of gravel under the shells of course. I am currently building materials bays on a flat spot nearby (hopefully in place by the middle of October) to work with the gravel and shells, and then will be able to get deliveries of compost and mulch for the beds later on.

Wish I could post a picture.

RK

Here's a link to the photo I was able to upolad to the Gallery. Taken last spring on burn day.

Here is a link that might be useful: Northeast Facing Hillside

I saw the photo. You have a nice property. I am jealous.
Clamshells sounds good and interesting (you'll hear a little bit of crunching whenever you walk over the shells). There might be some good trace minerals in the shells also. Having friends in the right trades is always a bonus. Wish I had more of those.
I use woodchips for most paths although we used gravel or crushed stone on some of the steeper areas. When tree work is done, I have the arborist leave the woodchips - we don't have to pay for disposal and we use the woodchips. I have also had tree services drop off woodchips for paths and mulch. We used treated wood for a small terrace system in a steep area. We installed an erosion control blanket on another steep area. We wanted to go with stone but the budget did not allow for it. You already have the stone, the backhoe and the knowledgeable friend so I think you're in business.

arcane - where is the hill??

the picture shows quite a flat area, which should be fine for a garden.

Clam shells are a great source of slow release calcium and were used by many of the first people's in our area which is/was predominately conifer needle covered.

Quicker to decompose and more readily available are egg shells. We use them in our "veggie pitting" (digging the kitchen scraps into holes in the garden). Crumpling/crushing the egg shells makes them "dissappear" all the faster. I'm not sure just what makes them decompose or dissappear but, I think that the worms actually eat on them as well as the soil microbes.