Tufted hair grass (Deschampsia caespitosa)? I may be a little obsessed with the grass but it really has excellent characteristics. It's native; it stabilizes soil with deep roots; it likes shade to part-shade.

The grass usually grows around vernal pools where there is a lot of water in a small pond that slowly dries over the summer. Then it is fine with drought the rest of the dry season. It would work well for a stream bank too, I think. You can get seed from Larner Seeds (see link). The holciformis cultivar has thinner, brighter green but less drought hardy leaves.

Here is a link that might be useful: Larner Seeds