Hillside Erosion Control in Palos Verdes: Slope Planting, Drains, and Winter Protection

On the Palos Verdes Peninsula, a lot of the yard is slope. Canyon edges in Rancho Palos Verdes, terraced lots in Palos Verdes Estates, and large hillside parcels in Rolling Hills and Rolling Hills Estates all have the same weak point: bare or poorly planted soil that rain can move.

Erosion control isn't one product. It's plants that hold soil, protection while they establish, drains that carry water off the slope instead of down its face, and irrigation that doesn't overload it.

Start With Water, Then Plants

Most slope erosion starts at the top. Water from a roof, patio, or driveway runs over the edge and cuts a channel. Before you plant anything, figure out where water enters the slope and stop it:

• Send downspouts and area drains through solid pipe to the street or an approved outlet, not over the slope.
• Keep a berm or swale at the top of the slope so pad runoff doesn't spill over the edge. LA County's Homeowner's Guide shows this detail.
• Clear concrete slope (bench) drains and V-ditches. According to the County, keeping these clear is usually the homeowner's job, and a blocked drain can undermine itself and erode the hillside.

Slope Planting That Actually Holds Soil

The County's planting guidance for erosion control favors a mix of species, smaller plants that establish well, and rapid-growing ground cover with burlap mat or mulch around it. It specifically warns against large-leafed ice plant (Carpobrotus) on slopes, because when it's saturated it tends to drag surface soil down.

For Peninsula hillsides, native coastal sage scrub plants are a good place to start. The Palos Verdes Peninsula Land Conservancy's habitat restoration plans for local reserves call for species such as California sagebrush, coyote brush, buckwheats, lemonadeberry, and native sages. An LA Times storm prep guide this fall suggested ground covers like buckwheat and coyote brush for sloped yards that struggle with runoff.

Two cautions:

1. Timing. Plants that go in this fall won't be established enough to provide meaningful erosion control this winter, as arborist Alison Lancaster told the Times. Plant anyway for the long term, but protect the soil in the meantime.
2. Fire. The County's guide calls for low-fuel-volume, non-invasive plants with proper spacing, and lists species to avoid, including pampas grass, juniper, eucalyptus, and acacia. Check your city and fire department requirements.

Temporary Protection While Plants Establish

LA County lists these measures for erosion-prone soils, each matched to slope steepness:

• Mulch (bark or wood chips): for slopes flatter than 3:1 (33%). Work it into the top few inches and keep the cover layer about an inch or less.
• Burlap, jute, or coconut-fiber (coir) netting: for slopes flatter than 2:1 (50%), installed with planting. Roll it with the direction of flow and staple it down. Burlap and jute last about a year. Coir lasts several years.
• Hydroseed: for slopes flatter than 2:1 and areas larger than half an acre. Hand seeding works for smaller areas.
• Terraces: for slopes steeper than 2:1. These may need city approval because they change drainage and can affect stability. Talk to your building official first.
• Plastic sheeting: only for short-term protection through one storm, on small areas. It sends 100% of the water downhill, so it has to be at least 6 mil, keyed in at the top, overlapped 12–24 inches like shingles, weighted no more than 10 feet apart, and replaced with mulch, netting, or terraces as soon as possible.

Irrigation on Slopes: Less, and Slower

Overwatering is a quiet cause of slope problems. The County notes that drip irrigation puts water where it's needed, while conventional overhead spray often causes erosion on steep slopes. The soil conditions vary by property. A geotechnical report can help determine how moisture affects your particular slope and foundations. In Rancho Palos Verdes' landslide area, irrigation is tightly limited and has to be part of a water management system approved by the city.

Warning Signs That Need More Than Planting

• Cracks running along the slope, especially near the top.
• Soil bulging at the bottom of a slope or behind a wall.
• Water seeping out of the slope face well after rain stops.
• Fences, walls, or trees that start to tilt.
• A slope drain that cracks or separates.

The County's guide is clear here: if unusual cracks, settling, or earth slippage start, consult a state-licensed civil engineer with geotechnical experience or a licensed geologist right away, and don't change your slopes or drainage without expert advice.

Contractor or Engineer?

A landscape contractor is the right call for slope planting, drip conversion, netting and mulch, and drain repairs. An engineer is the right call when the ground may be moving, when a repair involves regrading or new retaining walls, or when the city requires a soils report. Structural slope repairs in hillside and landslide areas usually need engineering and permits. Rosewood coordinates with the engineer and handles the city process.

Frequently Asked Questions

What Are the Best Plants for Erosion Control on a Palos Verdes Slope?

Native coastal sage scrub species such as coyote brush, buckwheats, California sagebrush, and lemonadeberry are used in local restoration. Plant a mix, plant small, and pair with mulch or netting.

Does Ice Plant Stop Erosion on Hillsides?

LA County advises against large-leafed ice plant on slopes because it tends to drag surface soil down when saturated.

Should I Cover My Slope With Plastic Before It Rains?

Only as a short-term fix for a single storm on a small area. Plastic sheds all the water onto the soil below it, so install it carefully (6 mil minimum, keyed in, overlapped, weighted) and replace it with mulch or netting as soon as you can.

Is It Too Late to Plant a Slope Before El Niño?

Fall planting won't be established enough to control erosion this winter, but it will help next year. For this season, protect bare soil with netting or mulch and get drainage working. Then plant for the long term.

Do I Need a Permit to Regrade or Terrace My Slope?

Often, yes. LA County notes that terracing may need agency approval. Peninsula cities have grading thresholds, and RPV, PVE, Rolling Hills, and Rolling Hills Estates each have their own rules. Check with your city before moving soil.

Let's Look at Your Slope Together

If you have a slope that's bare or eroding, call Rosewood Landscape at (424) 533-3600. Our office is in Palos Verdes Estates, and most of our work is right here on the Peninsula. We'll look at where water enters the slope and tell you whether the fix is landscape work or something an engineer should see first.

Contact Rosewood Landscape to discuss your hillside project →