Thanks for writing. There are a number of quick-growing groundcovers you can consider for covering the bank --- though you may need to check for permission before planting anything to ensure the State will allow it. See a nice selection of groundcovers here or check with the staff at your local garden center or nursery.
You might also check with your state's Department of Natural Resources to find out if there are restrictions about planting around banks like that.
---Justin, Senior Garden Editor, BHG.com