The hills are alive with the sound of your garden washing away
A sloped backyard may make an excellent sledding hill, but it's not ideal if you want to keep the nutrient-rich topsoil in place. Picking the proper method for landscape erosion often comes down to the angle of the hill—the more extreme the slope, the more support it needs to stay put.
In the end, preventing erosion on a sloped lawn is the best way to protect your drinking water from harmful runoff, the stability of your foundation, and, of course, the beauty of your landscape. Follow these tips to get started.
1. Determine Your Slope
The first step to choosing the correct erosion control methods is to determine the slope of your landscape.
The National Resources Conservation Service (NRCS) breaks down erosion-prone hills into three categories:
Less than 33% slope
Between 33% and 50% slope
Higher than 50% slope
These measurements can help guide which choices below are tough enough to fight erosion on each type of hill.
| Slope | Prevention Methods |
|---|---|
| Less than 33% | Mulch, Groundcover Plants |
| 33% to 50% | Drip Irrigation, Erosion-Control Blanket, Deep-Rooted Vegetation |
| Higher than 50% | Riprap, Terrace Gardening, Retaining Wall |
For additional support against erosion, you can also incorporate elements such as drainage, rain barrels, and professional landscape design.
2. Cover with Mulch
Low to moderate slopes—those with less than a 33% grade—will benefit from a layer of mulch made of wood chips, pine needles, bark, or small stones. You can even make your own mulch from composted leaves, ground-up branches, or straw.
Mulch pairs well if you plan to plant trees, shrubs, or deep-rooted plants. The layer of mulch will filter rainwater, retain moisture, and keep the most important soil in your garden from—literally—going down the drain.
3. Consider Native Groundcover Plants
While standard turfgrass can lower the rate of erosion on a low-to-moderate slope, go a step further by opting for deep-rooted grasses and plants that thrive on a slope. These may include:
Ornamental grasses and sedges
Fescue grasses
Ryegrass
Catmint
Groundcover roses
Creeping juniper
Wildflowers
A low-maintenance, native species of grass or plant is your best bet. Choose one that requires minimal watering, mowing, or fertilization to avoid exacerbating erosion. Also, be sure to pick a species that thrives in your climate and the level of sun exposure in that area of your lawn. For example, pick a cool or warm-season grass depending on your hardiness zone to encourage deep, tightly knit roots that hold soil in place.
4. Try Drip Irrigation
Watering the plants on a moderate-to-steep slope can be complicated if you want to save water and avoid runoff. Low-flow irrigation—also known as drip irrigation—sends water through the holes in a hose next to or under your garden. This system uses the gravity of your sloped landscape to evenly distribute water where it's needed.
5. Add an Erosion Control Blanket
Provide your soil and new plants with a little extra support by adding an erosion control blanket. The biodegradable layer often comes in jute, coconut, or straw netting to keep seeds, soil, and seedling in place as they take root.
The NRCS recommends erosion-control blankets in tandem with deep-rooted ground cover on slopes greater than 33%. An erosion blanket can also be helpful if you have particularly rocky soil where plants have a harder time taking root.
6. Plant Deep-Rooted Vegetation
Moving onto steeper slopes, consider planting larger, deeply rooted vegetation such as shrubs and trees. These will both hold soil in place and redirect rainwater.
For example, think of the branches and leaves or shrubs and trees like a sieve. The branches catch precipitation, redirect it, and keep it from causing a mini-mudslide in one concentrated area. If you plant a line of shrubs or trees, do so parallel to the hill. Planting them perpendicular will create an unwanted dam midway down the slope.
Some great shrub and tree options to prevent erosion include:
Forsythia
Boxwoods
Hydrangea
Red maples
Japanese maples
Bluepoint juniper
7. Redirect with Riprap
If you live along a shoreline or on lakefront property, riprap is a common option to filter and redirect floodwaters without building a wall. Riprap is a pile of large natural rocks that cover the extent of a moderately sloped area where vegetation is not possible.
8. Opt for Terrace Planting
Terrace planting is a time-tested method for both stopping erosion and broadening gardening opportunities on difficult land. You will likely need to use stabler installations like terraces and walls on slopes of more than 50%, but they will work well on smaller slopes as well.
Terrace gardening creates small, flat plateaus with walls of stone or treated wood between each layer. It's important to treat the wood against rot since these layers will play a large role in controlling the water flow. Call a local hardscaper for an estimate or recommendation on where to place your terrace.
9. Install a Retaining Wall
In the most extreme cases, you may need to add a retaining wall to break up the hill's steep slope. Retaining walls do exactly that—they retain the earth where it stands and prevents water from reshaping your landscape.
In addition to erosion prevention, you can use a retaining wall to break up the livable space in your yard, plant more flowers and shrubs, or even create a new seating area.
10. Add a French Drain
Our final two tips focus on controlling the direction of water coming off a slope. A French drain, for example, is a ditch lined with gravel and a perforated pipe to redirect water. While French drains are often used in foundations and basements, a qualified contractor can design a drain in your yard to prevent standing or deluges of water.
11. Place Rain Barrels
Flood-prone areas now encourage the use of rain barrels, rain chains, and proper gutters to keep stormwater from inundating a sloped landscape. Rain barrels, for example, collect water during a storm and then either hold water for later use or redirect it through a hose to a safe area.
12. Work with Local Experts
Whenever you plan to redirect groundwater, it's important to change local ordinances that protect your water systems. The NRCS recommends contacting your local public works or flooding prevention department for recommendations, available methods, and information about local permits.
A local landscaper specializing in erosion control will also have experience with the steepness of your slope and local climate patterns such as heavy rain. Ideally, you'll work together to combine several of the methods above to design a stunning lawn that stands up against the most intense weather.
