What is Erosion?
Erosion is the breaking down and/or wearing away of soil, rock, sediment and other land surface materials that's then carried away by water, wind or ice. It's a natural geological process that, over time, alters the landscape by reshaping the Earth's surface and creating new landforms like coastlines, canyons, deltas, etc. Erosion can occur in deserts, hillsides, riverbanks and mountains, but it can also occur in residential areas, farms, etc.
Causes of Erosion
We've all seen erosion occur where major excavation is underway, but construction sites aren't the only areas where erosion takes place. Without proper erosion control solutions, such as erosion control wattles, our home landscapes are also susceptible to runoff and topsoil erosion.
Just because you don't see gullies or mudslides in your yard doesn't mean that erosion isn't occurring. The process can be very subtle. Look for symptoms such as exposed roots, or signs of splashing of soil or mud on pavement. You may not see it on your own property, but runoff from your yard may be more evident farther down the street or in a neighbor's property.
Not only is erosion unsightly, but it can also be dangerous. Rainfall or excess irrigation causes runoff from our lawns, roads, parking lots and farm fields. Topsoil — with its organic matter, beneficial microorganisms and nutrients — washes away, along with contaminants such as fertilizer, pesticides and petroleum products, all of which ends up downstream and eventually in our water supply. This is why it's important to utilize the proper erosion control products on your slope. While controlling erosion can be challenging, it can be achieved with the right products and methods.
Slopes that adjoin wetlands, stream sides, lakesides, shorelines and other waterfronts are another issue. These areas serve as buffer zones between land and water. If your slope affects a watershed, get advice from a water mitigation expert or conservation agency.
Erosion Control Methods
The best erosion control solutions work by stabilizing the soil on the slope. There are several common methods and erosion control products to control a slope.
Add Physical Barriers
Baffles or barriers are obstruction devices that slow down or divert water from flowing directly downhill. They consist of partially buried stone or timbers (laid parallel to the slope). These barriers work best for lesser slopes.
Erosion control wattles are manmade fiber tubes, usually filled with compressed straw, that trap sediment, control water runoff and prevent erosion.
Riprap is rough, loose stone (at least 6-8 inches wide each). The stone, usually granite, is embedded into or spread loosely onto the slope. Riprap slows and diverts flowing water. It is effective but can appear stark or harsh in some landscape designs. To soften the impact, you can plant the areas between the stones with a variety of ground covers or rock garden plants.
Temporary erosion control solutions include plastic sheets, straw bales, mesh, silt fences and mulch. These are short-lived, as most will biodegrade or wash away over extended periods of time.
Build Terraces
Terraces stair-step up the slope. The flat surfaces allow you to plant on the terraced levels. Terraces allow water to soak in instead of running off. Use timber, stone, concrete or precast concrete block to build the retaining walls. Start at the bottom and fill in the level above with soil from the area just leveled (a technique called "cut and fill"). Terraces should slope a bit (about 2% is recommended) to prevent water from collecting at the back of the terraced portion. For more information, check out our guide on How to Build a Retaining Wall.
Mortarless retaining walls can only reach a certain height — usually around 2 feet. Check the specifications of the product you are using for height restrictions. Also, remember to backfill the area behind the wall with crushed rock to ensure drainage. If you build a terrace around existing trees, make sure the soil level is not raised. Covering the roots too deeply can damage the tree.
Plant Ground Cover
Plants can help control slopes. You can plant in any of the slope control methods above or you can use plants alone. When plants are established, the roots help anchor the soil. However, getting them established on a slope can be difficult. Seeds and mulch wash away and planting holes erode before the plant gets established. Wildflowers, clump-forming ornamental grasses or other perennial native plants usually adapt quickly to slopes and unimproved soil. You can also adapt rocky soil for a rock garden.
If you choose to provide irrigation for a planted slope, make sure that the system's water pressure is adequate to water the entire area. Some recommended landscape plants for slopes include ajuga, barberry, cotoneaster, daylilies, forsythia, ivy, juniper, liriope, pachysandra, sedum and vinca.
Plant Grass
Turfgrass can control erosion on minor slopes if the grass is healthy. A grass such as annual rye can germinate quickly and help stabilize soil while perennial grasses get established. Compacted soil is a major contributor to runoff. Aerate, if possible, and add organic matter such as compost to promote a healthy strand of grass. A covering of straw can help secure the seed and reduce water runoff. An excellent method of starting turfgrass on slopes (or anywhere) is by using a seed germination blanket. The blanket is a combination of biodegradable material and wood fiber that holds seed and fertilizer in place until grass seedlings can take root.
Getting grass seed to stay in place until it germinates can be tough on steeper slopes. On some slopes, you may need to resort to hydroseeding by a landscape contractor. Severe slopes, especially those that lead downhill toward a structure, require the attention of an engineer or landscape architect. Check local building codes before starting a major project.
Frequently Asked Questions
Here are answers to some common questions about erosion in the landscape.
What Is Landscape Erosion?
Landscape erosion is the movement of soil by water, wind, or gravity. While landscape erosion is a natural process, it can be exacerbated by landscaping or construction. Effective erosion control solutions include baffles, riprap, terraces, erosion control wattles, barriers and plants, among others.
What Is the Best Plant for Erosion Control?
The best plant for erosion control is one that holds the soil in place. Many cover crops, such as rye and clover, create nets of roots that hold soil together and help reduce weeds. Ornamental ground cover, including ivy, creeping juniper and periwinkle, are also proven erosion control solutions. Many native grasses (depending on your zone and region) can also help.
How Do You Keep Soil from Washing Away on a Slope?
There are many effective erosion control solutions to keep soil from washing away on a slope. These include riprap, baffles, barriers, terraces, plants and erosion control wattles.
How Do You Stabilize Soil on a Slope?
One easy way to stabilize soil on a slope is through the use of plants like ground covers and native grasses. At Lowe's, we offer a variety of additional erosion control products designed to stabilize soil on a slope.