Living or building in Los Angeles? Then, no doubt, you are likely to be no stranger to hills, canyons, and steep backyards. 

Such hillside vistas are breathtaking, but the terrain is not there to look at. It also comes with a significant risk, which is the potential for slope failure.

In LA, landslides, debris flows, and hillside failures are not uncommon. One deluge, one earthquake or one poorly done grading and a slope can degrade. That’s why slope stability isn’t just a technical term. It’s your safety net.

To ensure the safety of people and property, engineers will perform two kinds of analyses. One is surficial, and the other is global slope stability checks. They seem technical, and they are. 

This article will guide you on when to grade and construct a plot in the Southern California area. Let’s have a brief look at it.

Slope stability is fundamental enough to be concerned with the stability of a hillside not fail. It is the science of determining whether or not it is possible to have soil on a slope to hold itself up or even slide.

Slope stability refers to the capacity of a hill or embankment to remain in place without any form of collapse or sliding down. It is a geotechnical terminology which means: Are these slopes going to hold up or collapse when they are put under some pressure?

Or, to put it simple–then you start cutting into a hill or construct upon the edge of a slope, will the earth remain where it is, or will it slide downward all by itself?

All this is not mere theorizing. Unstable slopes in LA can–and many a time do–turn out:

• Landslides
• Mudflows
• Breaks in buildings
• Collapsed retaining walls
• Roads or driveways in the state of disrepair

Slop stability is of particular concern to you on, or around a hillside and that is every where in Beverly Hills, Topanga Canyon, Hollywood Hills, Pasadena, or Hollywood.

We deal with two kinds of slopes here:

• Natural slopes: These slopes include the Hollywood Hills, canyon sides, or Malibu cliffs. 
• Artificial slopes: The ones that we dig, fill in, or recontour so that we can have roads, houses, and gardens.

And what makes slopes unstable? In LA, we’ve got a perfect storm:

• Loose soils, especially clay-rich ones
• Seasonal rains, which soak and weaken the ground
• Vegetation loss, from wildfires or over-clearing
• Seismic activity, because yes—we live in earthquake country

All these ingredients can mix and cause slopes to fail. So, before a single shovel hits the dirt, we need to understand the slope’s behavior. That’s where geotechnical analysis comes in.

Surficial slope failures are shallow. They are usually only to the upper 3 to 6 feet of land. However, such depth is not to be mistaken with these slides have the potential to cause havoc.

Imagine it rains for two days. Your backyard slope, made of loose clay and stripped of vegetation, starts to slump. 

Mud, rocks, and water rush downhill into your neighbor’s yard, or worse, into a house. It is called superficial failure. 

What Causes It?

The following can be the causes for this failure.

• Clayey or silty soils that will soak up the water
• Slopes steeper than 2:1 (H: V)
• Poor drainage
• Landscaping changes or over-irrigation

How Engineers Analyze It

The infinite slope method is typically used here. It calculates the Factor of Safety (FoS), a simple number that tells us if the slope is safe.

A value above 1.5 is generally stable. Below that, it is a red flag.

How We Prevent It?

We can prevent superficial failure by taking the following steps:

• Surface drainage: swales, culverts, or slope grades, etc. 
• Vegetation: Land dwellers that are born to live many years are plants.
• Lightweight retaining walls
• Avoiding overwatering or planting thirsty trees

Surficial analysis is often part of regular grading plans. Especially in hillside neighborhoods like Echo Park, Silver Lake, or Beverly Hills.

The right inspections prevent project delays and the risky projects or the budgets. Properly framed inspections safeguard schedules, jobs and project budgets.

Global slope failures happen when the entire slope mass shifts. It is probably the slides that go from 10 to 50 feet underground. 

These aren’t your backyard mudslides. These are the big ones. It is the type that shut down highways or take out multiple homes.

What Causes It?

Most probable causes for global slope failures are:

• Poor fill placement or over-steepened cuts
• Weak, layered soils with low shear strength
• Seismic shaking (especially near fault zones)
• Water infiltration at deeper levels

How Engineers Analyze It?

This isn’t surface-level math. Engineers use:

• Bishop’s and Janbu’s methods (for circular failure)
• Rigid-block analysis
• Finite Element Modeling using PLAXIS, SLOPE/W, or Slide2

But first, we need subsurface data:

• Boreholes and soil samples
• Lab testing (shear strength, moisture content)
• Groundwater measurements

Global analysis is critical for bigger projects. For example, the case of retaining walls, highway slopes, subdivisions on hillside or deep excavations. 

This analysis is required in case you are constructing in Mulholland Drive or Pacific Palisades, or Pasadena Hill, etc.

We can differentiate superficial and global analysis for different aspects. Here is a summary. 

When to use what?

Here are some tips on when to use what.

• If you’re re-landscaping your front slope or regrading for a patio, surficial is enough.
• If you’re cutting into a steep hillside for a new home or road, global analysis is the only safe option.

If you are building in LA? Then the Los Angeles Department of Building and Safety (LADBS) is your boss.

They’ve laid down clear rules in their Grading Code and Bulletin P/BC 2017-101. Here’s what you need to know:

• Geotechnical reports are required for slopes higher than 10 feet or steeper than 2:1.
• You must analyze for both surficial and global stability if the site conditions demand it.
• Reports must be stamped by a licensed geotechnical engineer or engineering geologist.
• These rules apply across the county—from downtown LA to Thousand Oaks.

LADBS Slope Stability Bulletin – P/BC 2017-101 can provide detailed guidance. Ignoring these rules can delay your permit, cost you thousands—or worse, get someone hurt.

Slope analysis isn’t guesswork. Slope analysis uses both boots on the ground and cutting-edge tech. The following are the methods that are used for slope analysis.

Site Work:

For assessing the slope on the ground, we use:

• Reconnaissance: The engineers review the site by walking and verifying. If they can find any signs of prior breakdown. 
• Aerial photos: Aerial photos are used to construct the terrain of the drone. Satellite images and LIDAR are also good sources.

Soil Investigation:

For experimental tools, we carry out tests on the soil of the terrain to ascertain the slope stability. Below are the common tests for soil analysis. 

• Test borings
• SPTs (Standard Penetration Tests), CPT (Cone Penetration Test)
• Lab testing: Shear strength, Atterberg limits, moisture content

Analysis Software:

Not only on-ground, but the software is another handful of tools to assess the slope. Here is some useful software for soil stability analysis.

• GeoStudio SLOPE/W
• Rocscience Slide2
• PLAXIS 2D/3D
• FLAC

These tools simulate slope movement and predict failure zones. But remember—they’re only as good as the data and engineer behind them.

Still thinking slope stability is “just paperwork”? Think again. Because it has a wide scope in construction and grading. The following are some associated risks.

• That nice home addition? Useless if the slope below fails.
• That $5,000 retaining wall? Gone if it wasn’t properly designed.
• That hillside pool? Could crack, leak, or worse—slip downhill.

Legal & Financial Risks:

• Code violations can halt construction or trigger fines.
• Lawsuits from neighbors if your slope fails onto their property.
• Insurance claims might get denied without proper reports.

In short, skimping on geotechnical work is a false economy.

Do It Right:

• Hire a local geotechnical engineer who knows LA soils.
• Submit proper stability reports to LADBS before grading.
• Design with drainage, retaining structures, and vegetation in mind.

Remember: building on a slope isn’t the problem. Building without planning is.

LA’s hills and canyons offer prime real estate—but they come with real responsibility.

Before you grade, dig, or build, make sure your slope can handle it. Know the difference between surficial and global stability. Get the right experts involved.

Whether it’s a minor grading job in Highland Park or a deep hillside cut in Bel Air, slope analysis isn’t optional. It’s your defence against nature, code violations, and expensive mistakes.

Need help? We provide geotechnical slope evaluations tailored for LA County, including LADBS -compliant reports, expert soil analysis, and custom grading plans.

Contact us today to protect your project from the ground up.

Q: My hillside is only 8 feet tall. Do I still need a report? If the slope is steeper than 2:1, yes. LADBS requires analysis for steep slopes regardless of height.

Q: Can I build a retaining wall myself? Nope—retaining walls over 4 feet tall require engineering design and city permits.

Q: What if my property already had a landslide? You’ll need a full geotechnical investigation and probably global slope analysis before any rebuild.

Q: What agencies regulate slope safety in California?

• LADBS  (City of Los Angeles)
• California Geological Survey 
• LA County Public Works 
• Caltrans