Natural Hazards - Landslides

Landslides occur and can cause damage in all 50 States. Severe storms, earthquakes, volcanic activity, coastal wave attack, and wildfires can cause widespread slope instability. Landslide danger may be high even as emergency personnel are providing rescue and recovery services.

To address landslide hazards, several questions must be considered: Where and when will landslides occur? How big will the landslides be? How fast and how far will they move? What areas will the landslides affect or damage? How frequently do landslides occur in a given area?

Answers to these questions are needed to make accurate landslide hazard maps and forecasts of landslide occurrence, and to provide information on how to avoid or mitigate landslide impacts.

The U.S. Geological Survey develops methods to answer these questions to help protect U.S. communities from the dangers of landslides.

USGS Landslides Hazard Alerts

Flash Flood Warning for Western San Diego County and the Poomacha, Rice and Witch Burned Areas
On Friday, December 07, 2007, the National Weather Service issued a flash flood warning for western San Diego County in Southwest California. This includes the cities of Ramona, Poway, Escondido, El Cajon, Valley Center, Santee and Lakeside. In addition to flash flooding, rainfall is expected to cause debris flows in the Poomacha, Rice, and Witch fire burned areas.
National Weather Service Issues Landslide Advisory for Western Washington
...HEAVY RAINFALL WILL GIVE A RISK FOR LANDSLIDES TO WESTERN WASHINGTON THROUGH TONIGHT.. HEAVY RAINS OF 3 TO 6 INCHES OVER THE PAST 24 HOURS HAVE SATURATED SOILS AROUND WESTERN WASHINGTON. HEAVY RAINFALL RATES OF 0.25 TO TO 0.50 INCHES PER HOUR WILL CONTINUE THROUGH THE MID AFTERNOON HOURS. THIS WILL PUT EXTRA PRESSURE ON SOIL STABILITY. INDICES DEVELOPED BY THE U.S.G.S. SHOW THAT LANDSLIDES ARE POSSIBLE DURING INTENSE RAINFALL OR WHEN RAINFALL AMOUNTS EXCEED ONE INCH IN 24 HOURS. OBSERVED RAINFALLS HAVE ALREADY EXCEEDED THAT AMOUNT TODAY...INCLUDING THE SEATTLE AREA. WHILE THE U.S.G.S. RAINFALL THRESHOLDS APPLY TO THE SEATTLE AREA OF PUGET SOUND...MOST OF THE LOWLANDS OF WESTERN WASHINGTON ARE SUSCEPTIBLE TO LANDSLIDES DUE TO WET SOILS. AREAS MOST SUSCEPTIBLE TO LANDSLIDES UNDER THESE CONDITIONS ARE STEEP COASTAL BLUFFS AND OTHER STEEP HILLSIDES.