How to prepare for a landslide
The ground warns before it moves, but with signs almost nobody reads. What to check at your house, why a slope fails after the rain stops and what to do.
A landslide is one of the few disasters you prepare for by looking at your own house. No gauge or bulletin is required: the signs that a slope has started to move show up in the ground, in the walls and in the yard, weeks before anything comes down.
The trouble is that those signs look a lot like a house settling. A door that rubs, a new crack in the patio, a slightly crooked post. Most people put it down to construction, call a builder and get on with their lives.
Before: look at the ground, not just the house
Are you on a slope, at the foot of one, or at the mouth of a ravine? Landslides travel downhill and debris flows channel along drainages. Living at the base of a steep slope is the single heaviest factor.
Has ground moved here before? Slopes that have failed tend to fail again. Neighbours with years in the area know more than most maps.
Was there a wildfire nearby in recent years? It is the factor that multiplies short-term risk the most, and the one most often ignored.
Has the terrain been altered? Cuts for building, fill, diverted water and blocked drainage change the behaviour of a slope that had been stable for centuries.
The signs that ground is moving
Geological agencies describe a fairly specific set of signs. None is conclusive on its own; several together are.
| Where | What to look for |
|---|---|
| Ground and yard | New cracks, bulges, steps where it used to be flat |
| House | Doors and windows that stop closing, cracks in floors or foundations |
| Attachments | Decks, porches or walls tilting or pulling away from the house |
| Utilities | Repeated breaks in buried pipes or cables |
| Verticals | Poles, trees, fences or retaining walls leaning |
| Roads | Sunken or stepped pavement |
| Water | New springs, saturated ground where it was never wet |
| Channels | Water rising fast and turning muddy, or dropping suddenly while rain continues |
| Sound | A rumble that grows, cracking trees, knocking rocks |
During: seconds, not minutes
If it is already moving, the response is short because the time is too.
- Get out sideways if you can, perpendicular to the direction of movement, not downhill ahead of the material.
- If you are inside and cannot get out, go to the highest floor and get under sturdy furniture.
- If there is no exit and no upper floor, curl into a ball protecting head and neck.
- Stay away from channels and ravines. Debris flows follow drainages and travel further than people expect.
After: the second one does not wait
The area stays unstable after the first movement, and often there is more.
- Do not return until it has been cleared.
- Do not approach the toe of the slide: material keeps settling and more can come down.
- Check for trapped people without going in yourself: notify rescue teams.
- Watch the channels downstream. A slide can dam a river and cause a sudden flood when that plug gives way.
- Have foundations and utilities inspected before living in the house again.
The ZonaProtec monitor shows official landslide and debris-flow warnings where the local agency issues them, alongside the rest of the threats near you.
Guides
- Why a burned hillside floods and slides for years A burn scar turns ordinary rain into a debris flow, and the risk lasts years. How to tell if you are below one and what the rainfall thresholds mean.
- How to tell if the ground under your house is moving Slopes usually warn for weeks, but the signs look like an ordinary settling house. What to walk out and check, and which combinations mean leave now.
- What to do in the seconds a landslide gives you A slide leaves seconds, and the instinct to run downhill is the wrong one. Where to move indoors, outdoors and in a car, and why the return is also dangerous.
Gear that covers this
Products that match what the guide above recommends.
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Battery or hand-crank radio
Heavy-rain warnings for hillside areas are often issued overnight, and power usually fails before the ground does.
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Go bag kept by the door
A landslide leaves seconds, not minutes. Whatever is not already packed does not get packed.
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A headlamp for each person
Leaving a hillside at night needs both hands free, and outages are routine during the storms that trigger slides.
Frequently asked questions
Do landslides give any warning?
Many do, days or weeks ahead, but with signs that look like ordinary house problems: doors that stop closing, new cracks in a patio, a leaning fence post. The problem is not the absence of warning, it is that the warning gets blamed on the building instead of the ground.
Why do they happen after the rain rather than during it?
Because water takes time to infiltrate. Rain saturates the soil, adds weight and reduces friction between layers, and that process continues once the sky has cleared. That is why slopes fail in bright sunshine a day or two after a storm.
Does a wildfire increase the risk?
Enormously, and for years. A burned hillside loses the vegetation that held the soil together and much of its ability to absorb water, so rainfall that used to be harmless can produce debris flows. The risk peaks in the first rainy seasons after the fire.
What do I do if it catches me indoors?
Go to the highest floor if you can do it in seconds and get under sturdy furniture. If you cannot get out or up, curl into a tight ball protecting your head and neck: it is the position that best protects against debris impact.