If your yard has a slope, especially if that slope is steep, you might notice that after each rainstorm, more soil continues to pile at the bottom of the hill, despite planted grass to help keep the topsoil in place. This is a sign that you need to design some type of erosion control, or your landscape will continue to change, eventually affecting your drainage and lawn quality. Here are some things you can do to slow the erosion of the slope.
Install a dry creek bed.
A dry creek bed is a shallow gully that directs water downslope-- water flows into it and moves easily to the bottom of the hill, leaving your soil intact. Dry creeks work because water takes the path of least resistance when it comes to flow. A dry creek is filled with rocks and the gully shape allows water from the hill to flow easily into it before it moves quickly downslope. Dry creeks can be a beautiful addition to a landscape. Typically, it just requires digging out a shallow channel and layering the channel with rocks of differing sizes. However, with very steep slopes, rocks may need to be fastened into place on top of a landscape fabric. In the case of steep inclines, it's better to hire a landscape design professional for maximum benefit.
When building your dry creek, be sure water is not directed into a neighbor's yard. Both these things can get you into a legal trouble. Instead, send the water in the direction of gutters or storm drains.
Terrace your hill.
This option is a little more labor intensive and involved than simply laying stones for a fry creek bed. However, terracing is necessary when a slope is too broad or steep for an effective dry creek. You can make small terraces out of a number of materials, and they don't have to be elaborate. The goal is simply to slow the water down on its decent. A row of rocks, treated timbers like railroad ties, or even a strategically placed boulder here and there on the hill will help to divert the flow of water. You can often grade your terraces to direct water to a dry stream, allowing both elements to work together.
Build level areas for long-term foliage.
One of the most traditional ways of dealing with erosion is to plant plants whose root systems prevent the soil from moving. In a residential setting, you still want to get some use out of your sloped yard, so traditional ground cover is not ideal. Instead, dig out level places into the hill and use these level spots as the planting sites for shrubs and small trees. The deep and aggressive root systems of the trees will make a natural terrace and help direct water to more predicable flow areas.
For more information on erosion control, talk to a landscape contractor in your area, such as Bill and Dave's Landscape.