Mudslides in California: Facts, Risks, and How to Prepare

Mudslides can cause great destruction, particularly when they happen close to inhabited places. Extreme rainfall combined with steep topography makes areas vulnerable to mudslides because the surplus water presses against the soil. Although mudslides can happen anywhere, they are particularly dangerous in states like California, Oregon, Washington, Alaska, and Hawaii. Here are some details and advice on how to get ready for mudslides in California if you live there.

What Is a Mudslide?

A mudslide occurs when a significant amount of silt, clay, or wet soil slides rapidly and unexpectedly down a steep incline. There are times when the surge is so strong that it sweeps up people, automobiles, and trees. Mudslides usually occur after heavy rains in regions that have been destroyed by wildfires or have little vegetation.

Mudslide vs. Landslide

Any pile of soil or rock moving down a mountain or cliff is referred to as a landslide. Water doesn’t always have to be present for the movement to occur, and it might happen quickly or slowly.

One kind of landslide known as a mudslide is characterized by large volumes of moist soil flowing quickly down a slope. It is brought on by prolonged, intense rain or flooding, and its liquid-like substance frequently runs down channels.

Why Is California Prone to Mudslides?

Loose soil deposits and sediments found in California’s steep terrain and mountains are prone to sloughing off in wet weather. In addition, the state’s droughts have hardened the earth, which has reduced the soil’s absorbency. The water gathers more pace as it flows over the hardened ground, collecting dirt and debris.

Devastating wildfires are another issue. The lack of vegetation on hillsides prevents the soil from being retained. Without obstructions, the mudslide plunges farther and faster.

Most Vulnerable Areas in California to Mudslides

The most vulnerable areas are those with steep inclines that have seen wildfires within the last three years. This covers the counties of Napa, Mariposa, and Monterey. The deadly mudslide that engulfed Montecito in 2018 occurred shortly after one of the biggest wildfires in the region destroyed 280,000 acres.

Mudslides are most common in Southern California and the San Francisco Bay Area.

How Many Mudslides Have Been Recorded in California?

The U.S. Geological Survey and the California Geological Survey counted seven hundred mudslides and landslides in California in only the month of January 2023. The state received 150 percent of its normal amount of precipitation by April 2023, with certain regions receiving 200 percent of the usual amount. That much precipitation increases the risk of mudslides.

What Is the Worst Mudslide to Ever Happen in California?

Big Sur saw one of the worst mudslides in California history in February 2017. According to scientists, one of the contributing factors was the prolonged, intense drought that Big Sur endured. Then, strong storms slammed through the region in February 2017. Six million cubic yards of debris from the combined mudslide and landslide blocked the Pacific Coast Highway. The Big Sur Landslide caused damages that required $54 million to fix, making it the largest in state history. It took more than a year to finish the repairs. The destructive power of landslides is demonstrated by other large ones in California’s past.

Steps to Take to Prepare for Mudslides in California

There are numerous safety measures you may take to be ready even before a mudslide happens. The following are wise preparations to make:

Keep a disaster supply kit in your house. This contains provisions for several days’ worth of food and drink, a first aid kit, a flashlight, a local map, a manual food can opener, extra batteries, a tent or plastic sheeting for shelter, hand sanitizer, and wipes for personal hygiene.

Establish a family plan so that in the event of a mudslide, everyone is aware of what to do and where to meet.

Sign up for local emergency alerts.

Find out if you live in a region that is prone to landslides and what your coverage options are for flood insurance by speaking with your insurance agent.

During a Mudslide Warning:

Keep abreast of any recent advisories or orders from the local emergency managers regarding evacuation.

If you observe water or mud streaming on a road, do not cross it. It’s possible for the mudslide to accelerate before you reach safety.

As soon as you can, get uphill and steer clear of river valleys and the mudslide trail.

The same weather patterns that create floods and mudslides can also cause flash floods.

To ensure that those areas are redirected and utilities are switched off, report any damage to roads, utility lines, or other risks to the appropriate authorities.

Have a professional assess the damage to your home or foundation following a mudslide. In the future, if your home needs corrective measures, speak with a geotechnical specialist.