U.S. Geological
Survey
Geologic mapping and El Niño in southern California:
Landslide and debris-flow susceptibility maps
Southern California historically has received extreme precipitation during nearly every El Niño event, suggesting that the upcoming event of 1997-1998 will impact this area more than other parts of the western United States. The El Niño is expected to bring unusual amounts of rainfall and snowfall to the Los Angeles basin and nearby coasts and mountains. Heavy precipitation may cause damage from debris flows and landslides in the hilly areas and may lead to floods along rivers in populated areas.
The U.S. Geological Survey's Southern California project and its partner project in California Division of Mines and Geology are using past studies of damage from El Niño events to predict and describe areas prone to possible future damage. Information on the danger is given below.
Daily landslide activity reports:
Find out what is happening and where. Updated daily during storm
activity.
Hot! Update on Laguna Canyon Landslide with Photos
Update on the Laguna Niguel
Landslide 3/19/98
NEW! Maps of burned areas from 1997 fires. Data for the wildfire areas, from the California Division of Forestry, California Office of Emergency Services, USDA Forest Service, and Orange, Los Angeles and Ventura Counties are compiled by USGS Landslide Team.
Debris flow hazards: Why El Niño events trigger
debris flows, and what can happen
Area under study: Where USGS is mapping debris flow
hazards
Maps describing debris flow hazard: What the maps
show and how to get them
The Hazard: Fast moving flows of mud and rock, called debris flows or mudslides, are among the most numerous and dangerous types of landslides in the Los Angeles - San Diego region. When prolonged, intense rain falls on steep hill slopes, the saturated soils can become unstable and move rapidly downhill as debris flows. These catastrophic flows are capable of destroying homes, washing out roads and bridges, sweeping away cars, knocking down trees, and obstructing streams and roadways with thick deposits of mud and rocks. Numerous past storms have triggered damaging debris flows in southern California, especially after large fires have destroyed the vegetation that helps hold soil in place.
Photographs of
debris flows and landslides
Geologic mapping in southern California
For further information, contact David Miller
USGS El Niño Home page
http://geology.wr.usgs.gov/wgmt/elnino/scampen/, 09 March 1998,, Contact: El Niño Web Team