Recognize Landslide Warning Signs


•Changes occur in your landscape such as patterns of storm-water drainage on slopes (especially the places where runoff water converges) land movement, small slides, flows, or progressively leaning trees.

•Doors or windows stick or jam for the first time.

•New cracks appear in plaster, tile, brick, or foundations.

•Outside walls, walks, or stairs begin pulling away from the building.

•Slowly developing, widening cracks appear on the ground or on paved areas such as streets or driveways.

•Underground utility lines break.

•Bulging ground appears at the base of a slope.

•Water breaks through the ground surface in new locations.

•Fences, retaining walls, utility poles, or trees tilt or move.

•A faint rumbling sound that increases in volume is noticeable as the landslide nears.

•The ground slopes downward in one direction and may begin shifting in that direction under your feet.

•Unusual sounds, such as trees cracking or boulders knocking together, might indicate moving debris.

•Collapsed pavement, mud, fallen rocks, and other indications of possible debris flow can be seen when driving (embankments along roadsides are particularly susceptible to landslides).

Landslides DO happen, and MANY have occurred in Mill Valley.  Mill Valley has lost roads, vehicles and homes to landslides.  Sadly, Mill Valley has experienced landslide-caused fatalities too, including one resident killed in 2006. Landslides have caused creek overflows, street closures and other problems in our town.

If you live in a slide-prone area (i.e. near steep hillsides in Mill Valley) you would be well advised to hire a geologist who specializes in slide risk assessment to complete a ground study of your property. 

What to do if you see signs of an potential landslide

A mudslide(“debris flow” in GeoJargon) in Cascade Canyon damaged this home and several vehicles and caused flooding downstream and damage to bridges over Cascade Creek.

This slide undermined Molino Avenue during the dark of the night.  Fortunately no vehicles crossed over before it was noticed!  Even then some residents tried to drive around safety barriers so as not to be “inconvenienced”!  Go figure.

Red areas on this map indicate high landslide risk area.  Click on the map to link to the full map.

 To watch a short mudslide video click herehttp://landslides.usgs.gov/recent/images/laconchita/LaConchita0105_sm.movhttp://landslides.usgs.gov/recent/images/laconchita/LaConchita0105_sm.movhttp://www.google.com/shapeimage_2_link_0shapeimage_2_link_1

If your home is threatened - leave!

Contact City officials to alert them to the potential danger.

Contact your neighbors, especially any and all down-slope.