Winter Landslide Warning Signs Around Your Property

The short version

• Learn your property's baseline before winter so you can spot what's new. One odd crack can be nothing; a cluster, or anything getting worse during a storm, is a warning.
• Watch for movement: new ground cracks or bulges, soil pulling away from foundations, tilting trees and fences, sticking doors, new seeps or saturated ground, a creek that suddenly runs muddy, and rumbling or cracking sounds.
• Active movement or an imminent slide: leave immediately and call 911. Don't stop to investigate or grab things.
• If an official alert names your area: follow it immediately. A Flash Flood Warning can include debris-flow danger and may arrive with little lead time.
• This is a homeowner's guide to noticing trouble early, not a substitute for a professional geologic assessment.

When heavy winter rain settles over a forested slope in the Santa Cruz Mountains, the ground can start to move, and risk can rise during and after the storm. Some landslides give warning signs; others happen suddenly with no warning at all. Knowing what to watch for can help, but it cannot predict a slide. This isn't a substitute for a professional geologic assessment. If the ground is actively moving or a slide looks imminent, don't investigate. Leave, if it is safe to do so, and call 911.

What to watch for

The U.S. Geological Survey and slope experts point to a consistent set of warning signs. Around your home and yard, watch for:

• New cracks or bulges in the ground, pavement, driveway, or the base of slopes.
• Soil or fill pulling away from foundations, decks, or stairs, or new gaps opening up.
• Tilting or leaning trees, fences, retaining walls, utility poles, or decks that were straight before.
• Doors or windows that suddenly stick or jam, or new cracks in walls, foundations, or tile, a sign the structure is shifting.
• Water showing up where it didn't before: new springs or seeps, unusually saturated ground, or water breaking out of a hillside.
• Changes in a creek or drainage: water that suddenly turns muddy, or flow that rises or drops sharply, can signal movement upstream.
• Sounds: faint rumbling, cracking, or trees popping, which can grow louder as movement increases, is a reason to get out now.
• Cracking or bulging retaining walls, or a wall that's begun to lean.

Any one of these can have an innocent explanation. A cluster of them, or any that are getting worse during a storm, deserves serious attention.

What to do if you see the signs

• If movement is active or a slide seems imminent (ground shifting, growing cracks, rumbling), get everyone out of the path immediately, if it is safe to do so, and call 911. Don't stop to gather things. If debris is already hitting the building you're in, the U.S. Geological Survey says not to go outside: get to the highest floor, or up onto something solid, and stay there.
• If you notice worrying but not active signs, keep people away from the area, document them with photos, and consult a geotechnical or geologic professional. On a county road or right-of-way, report it to the county.
• Reduce your exposure ahead of storms. Know which rooms and which side of the house are most exposed to an uphill slope. During a storm that could cause a slide, the National Weather Service's advice is to stay alert and awake rather than to sleep through it, because many landslide deaths happen while people are asleep. If you have real concerns about your slope, leave before the storm rather than waiting it out.

Burn scars need current, site-specific guidance

Postfire debris-flow danger was highest in the early rainy seasons after the 2020 CZU fire. The U.S. Geological Survey says that danger generally declines as vegetation recovers and that postfire debris flows after the second rainy season are unusual. Six years later, an old burn boundary by itself is not a current parcel-level risk assessment. Follow National Weather Service warnings and any current county guidance for your location, and act immediately if an alert includes your area.

Before and after storms

Before winter, walk your property and note the baseline so you can spot changes. Clear culverts and drainage so water doesn't saturate a slope unnecessarily. After a big storm, walk it again, and remember that ground can keep moving for days after the rain stops, part of what to do after a major storm.

Frequently asked questions

What are the warning signs of a landslide?

New ground cracks or bulges, soil pulling away from foundations, tilting trees or fences, sticking doors and new wall cracks, new seeps or saturated ground, sudden muddy or changed creek flow, and rumbling or cracking sounds. A cluster of these, or any worsening during a storm, is a warning. Some landslides occur without recognizable warning signs.

What should I do if I think a slide is starting?

If the ground is actively moving or a slide looks imminent, leave immediately, as long as leaving is safe, and call 911. If debris is already striking the building, don't go outside; get to the highest floor. For worrying but non-active signs, keep people away, document them, and consult a geologic professional.

Why is Boulder Creek at higher landslide risk?

Steep, forested slopes and heavy winter rain create the underlying risk. A property's current risk depends on its slope, drainage, soil, and recent conditions; the old CZU burn boundary alone does not establish a uniform 2026 risk.

This guide draws on official guidance from the U.S. Geological Survey and the National Weather Service. It is not a geologic assessment.

For active danger, call 911. For forecasts, watch the National Weather Service, and for local road and slope conditions before you travel, check Mountain Status. For context on how much rain the ground has already taken this season, see our rain tracker.