While residents of Southern California enjoy about ~300 sunny days per year… California is also one of the most at-risk states for landslides. In fact, the Vice President of International Consortium on Landslides at the USGS, Peter Lyttle shared that while landslides can occur in all 50 states, “regions like the Appalachian Mountains, the Rocky Mountains and the Pacific Coastal Ranges have ‘severe landslide problems,’” listing California, Oregon, Washington, Alaska and Hawaii as especially prone.
Why? In general, landslides are more common where slopes are steep and surrounding rocks, soil and supporting natural structures are weak…. And unfortunately,these conditions are very common here in our native SoCal. Add in the fact the San Andreas fault runs the length of California and this tectonic boundary pushes up rocks that are too weak to support these slopes, and BAM — you’ve got all the makings of a landslide.
Common Causes of Landslides
Some of the leading factors that can cause residential landslides include:
- Heavy rainfall or recurrent storm systems
- Erosion from foot traffic or construction
- Poor construction practices
- Rapid temperature flux (e.g. freezing and thawing)
- Natural disasters (e.g. earthquake shaking, and volcanic eruptions)
- Brush/topsoil that’s been removed or lost to forest fire
How to Prevent Landslides At Home
There are lots of preventative measures you can take that can decrease your risks of property damage due to landslides. One of the most effective is to have a retaining wall installed. If you already have a retaining wall, you’re not off the hook. Older retaining walls can be the cause of landslides as well. Without proper upkeep they can cause drainage issues which can cause weight and pressure to build up and overflow.
The good news is, there are some relatively easy things you can do yourself to help prevent landslide damage:
- Minimize foot traffic. Human use is typically the largest contributor to erosion and landslides. Over time, home projects and other routine activities can really wear down the natural slopes of your property. Make sure to regularly assess and shore up areas which may be prone to weakening.
- Repurpose yard waste. Leaves or loose gravel can be used to create drainage on any slopes or earthen support structures.
- Reroute stormwater. If you notice stormwater pooling or puddling, make sure to redirect this away from sloping areas or hillsides
- Irrigate/install vegetation. While irrigation is good, make sure to avoid installing any irrigation systems, water sources, or pools near hillsides or sloped areas. Plant vegetation or use gravel on slopes or earthen structures that need extra support.
Use temporary landslide protection. Sandbags, plastic sheeting, tarps, and even burlap can be used to divert water from uncontrolled spilling and protect unstable areas.
When it's Time to Call in the Professionals
While all of the above can be incredibly helpful in preventing damage, often to really protect yourself from landslide damage you’ll need the help of a professional — especially if your property is situated around deeply graded areas or is prone to drainage or runoff. In this case, a landscaping professional (preferably one well versed in landslide prevention) will need to assess your property and help you determine the best type of retaining wall to use.
There are several different types of retaining walls, including:
- Concrete Retaining Walls. Concrete blocks lock together without requiring mortar. Soil is then tightly packed behind it to prevent weakening and collapse. Concrete retaining walls easily form curves, which is typically a requirement of this stabilization approach.
- Steel Beam/Pipe Pile Retaining Walls. These are often used on extreme slopes where a concrete wall is too expensive. The steel beams are usually placed in a pre-drilled hole and encased in concrete.
Or, a landslide expert may suggest one of these other options:
- GeoGrid Systems. A cost-effective approach to rebuilding slopes that have previously failed due to a landslide or mudslide.
- Drainage Systems. Stormwater management is a very important component of landslide control services, and poor drainage or water management is often the main culprit in landslide events.
- Silt Fence. These are constructed using a long fabric barrier which can be used in any area where there’s runoff or loose soil. These function as a good intermediary option for areas which need support while vegetation or other topsoil methods are put in place.
- Erosion control matting. The matting remains in this location until native vegetation can begin to grow through, and does no harm to the environment. Erosion control mats provide the strength and surface area needed to protect an area from erosion or runoff.
Man-made terraces. The subsoil is levelled, followed by installing a solid top soil and side supports. Natural terraces using elements such as grasses can also produce the same effect.
About Unilited Drilling
Unlimited Drilling & Foundations Inc. was founded in 1993. Over the past 28 years, the company has completed thousands of foundation repair, slope stabilization and drainage systems projects in Southern California.