That Hill Behind Your House Is Eroding. What Can You Do? How to read the damage, what a homeowner can fix with a rake and some straw, and the signs that mean you call an engineer instead of us

Disclosure. We rent excavators, loaders and tractors for a living. Most hillside erosion control does not need any of them, and the worst thing you can do to a soft slope is drive a machine across its face. We will say that a few more times.

Short answer: Hillside erosion control starts with water, not dirt. Move roof and irrigation water off the slope, cover bare soil with plants, jute or coir netting and straw wattles laid along the contour, and fill small rills by hand. Cracks in the ground, slumping, bulging soil or a slope above or below a house mean you stop and call a civil or geotechnical engineer.

A hill does not erode because it is a hill. It erodes because water found a bare path down it.

Most backyard slopes we see in LA County, Riverside County and San Diego County were cut or filled when the tract was built, planted once, and then left to fend for themselves through heat, drought, gophers and the occasional wildfire. Then one wet winter shows you every weakness at once.

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Read the Damage Before You Fix Anything

Erosion comes in stages. Each one tells you how far along the problem is and who should be fixing it. Walk it after a rain and take photos from the same spots every time.

Sheet erosion

A thin layer of soil washes off evenly. You see it as exposed roots, small stones sitting on little pedestals of dirt, and a fan of silt at the bottom of the slope or on your patio. Minor, and the cheapest stage to fix.

Rills

Small channels, a few inches deep, that run straight downhill. Water has started to concentrate. They grow every storm. A homeowner can still handle them.

Gullies

Channels deep enough that you cannot step over them casually, often a foot or more. Gullies usually point straight back to a water source: a downspout, a broken sprinkler line, a driveway edge.

Slumps and slides

This is a different problem. Instead of soil washing off the surface, a chunk of slope moves as a block. Look for a curved crack or step near the top, soil bulging out near the bottom, leaning trees or fence posts, and new cracks in walls, paths or pool decking. This is not erosion you fix with straw. This is a stop sign.

Move the Water Off the Slope First

Every erosion fix fails if water keeps arriving in the same place. Netting slows water down. It does not stop a downspout.

Walk it in the rain

During light rain, from a safe spot off the slope, watch where water enters it. Lawn edge, driveway, a roof corner. The rill usually lines up with it.

Deal with the downspouts

Extend downspouts so they do not empty onto the top of the slope. Where the water goes next matters. A solid pipe that carries roof water to the bottom of the slope, or to a street or approved outlet, is a common approach. Ask a contractor or your city what outlet is allowed. Never point it at a neighbor's property.

Turn the sprinklers down

Shut slope irrigation off or way down in the rainy season. A wet spot on a slope in July is a leak, not a spring.

Look at the top edge

The flat ground above a slope should not dump water over the edge. A small berm (a low ridge of soil) or a shallow swale (a gentle, wide ditch) along the top can catch sheet flow and carry it to a controlled outlet. Anything that changes how water leaves your property needs a contractor or engineer to sign off.

Cover the Soil: What a Homeowner Can Actually Do

Once the water is under control, keep rain off bare dirt and slow down whatever runs across it. None of this needs a machine. It needs gloves, stakes and a free Saturday.

Plants, the long-term answer

Roots hold soil. Deep-rooted, drought-tolerant ground covers and shrubs suited to your area do more for a slope over time than anything else on this list. Ask a local nursery what works on slopes in your area. Plant in fall so winter rain does the watering. Expect a season or two before they fill in.

Jute or coir netting

Erosion control blankets are open-weave mats made of jute (plant fiber) or coir (coconut husk fiber). You roll them down the slope, overlap the edges, and pin them with landscape staples. They break raindrop impact, hold seed in place, and rot away as plants take over. Coir lasts longer. Jute is cheaper. Skip plastic netting, which tangles snakes and birds.

Straw wattles and fiber rolls

Wattles are long tubes of straw or fiber, about the diameter of a fence post. Lay them across the slope along the contour (level lines across the hill, like the rings on a topo map), set them in a shallow trench, and stake them. Each one slows water and catches soil above it. Running them downhill or leaving gaps at the ends turns them into gutters.

Filling rills

Small rills can be filled by hand with soil, lightly tamped, then covered with netting. Fill them after you fix the water source, not before, or you will be doing it again next storm.

If you are working through a whole property list before winter, our El Nino property checklist puts this alongside gutters, culverts and the rest.

When to Stop and Call an Engineer

Here is the part where a rental company tells you to hire somebody else.

And one rule that has no exceptions. Nobody works on a saturated slope, in moving water, or during a storm warning. If the hill is actively moving during a storm, leave and call your local emergency number.

If water from the slope is crossing a property line, document it with photos and dates and read our guide on what to do when a neighbor's yard drains into yours. Talk first. Lawyers later, if at all.

Straight Answers