For hillside households, the rain path isn’t always visible from the front door. A drain, wall or cut slope can look familiar for years before a new seep or crack appears. The first safe task is to record change, not to diagnose a landslide or start digging.
A weather forecast tells you when rainfall may occur. This page concerns visible changes on or below the property. USGS signs of landslide development make clear that some slopes fail suddenly with no warning, so lack of observed change does not guarantee stability.
Compare against the last safe baseline
From a safe location, note when the observation is new and how it changed. Do not step onto a slope, cross an active slide, climb retaining walls, or walk close to the edge of a cut or excavation.
| Observation | Why it matters | Safe handoff |
|---|---|---|
| New ground crack or soil pulling away from paving | Could reflect movement; also has other causes | Local public works or qualified geotechnical professional |
| New water spring or seep on a slope | May indicate altered water movement | Property owner and geotechnical/drainage professional |
| Leaning fence, tree, pole or retaining wall | A changed position can be a warning | Relevant utility/authority and qualified expert |
| Mud or water entering a previously dry channel | Drainage conditions may be changing | Local NWS alert and emergency agency |
| Ponding beside a foundation or downhill retaining wall | Requires assessment of site drainage | Qualified building and drainage professional |
| Cracking sounds, rushing muddy water, visible movement | Possible imminent hazard | Leave area if safe and contact emergency services |
Never treat this table as a personal stability test. Many harmless-looking changes need professional interpretation; serious movement may happen without any of these visible clues.
Roof and gutter water is not the whole hillside system
The gutter/downspout rain-path checklist is useful for safe exterior observations. It does not authorize changing the discharge of a hillside pipe. An improvised extension or excavation could send water toward an unstable slope, neighbor’s property, foundation or utility line.
Request an appropriate site assessment before changing grading, trench drains, retaining walls, infiltration, discharge points or buried drainage. For shared land, slopes near roads, public creeks or easements, ask the local authority who has jurisdiction.
After wildfire, use a different threshold for concern
Recent burn scars can have much faster sediment-laden runoff. USGS postfire work documents this risk. Read the separate post-wildfire debris-flow decision guide when a recent fire affects an upslope watershed. Do not assume that sandbags or a backyard barrier can contain a debris flow.
Hillside change record
| Location / safe photo | What is different from before? | Date and weather context | Authority / professional notified | Immediate access restriction |
|---|---|---|---|---|
For a changing slope, keep people out of the area until a qualified assessment or local authority provides appropriate direction. Follow all current warnings and evacuation instructions. The single next action is to report the clearest new observation to the responsible authority, not to alter the drainage yourself.