How to shore up part of a hill?
I've been struggling with (and learning about) my steeply-sloping, ghetto-terraced (ancient wood planks held up by stakes made of machete-chopped tree branches in earthquake country, anyone?), clay-soiled, ivy and tree-of-heaven overrun "garden" since we moved in a year and a half ago, and my question is this -- I have some cement stairs that go almost all the way up to the flat area at the top of the garden, but at the top of the stairs there's this weird sloping depression where the soil must have washed away a zillion years ago and you sort of have to pick your way up to the flat area (climbing back down is sorta scary, especially if the clay soil is wet).
My question is this: how can I fill in that depression? Will bagged soil/mulch/gravel be OK if it's tamped down hard enough, or will it just wash away in our rainy season (it won't rain here for another 4-5 months)? Should I ... I don't know, pour concrete there, or something? Grow some sort of wicked-sturdy groundcover over it? Just ignore it?
Any advice would be greatly appreciated,