Hi Kelly, Kimberly here from landscape solutions for you. Thank you for asking the question on your soil erosion problem underneath your wooden steps.
There are a couple things you can consider doing. One is to see where the water is flowing and if you have a drainage problem in that area. If you do, you will want to divert the water away from the steps. This can be done with a small trench and corrugated piping. You can buy the pipe at a local chain store.
Another option is to create a barrier by putting natural rocks to move any future water away. This can be done by doing a small dry rock bed. This will also divert the water. You can build up the eroded area with more dirt and level it out.
In the Outdoor feature section there is a page on dry rock beds, and in the simple solutions section there is a page on landscaping with corrugated pipes. These are two possible solutions you could do without hiring a landscaper if you have one or two other people to help you. My crew and I have done both of these to help clients with erosion problems. Let us know how you make out and if you need more help with solving your erosion problem, feel free to contact me here at the website. If anyone else has other options for Kelly, please feel free to share them with her. The best of luck to you and hope your day is going well.
Kimberly