Debris Flow Hazard Maps for Southern California Released

PASADENA, Calif. - Maps showing the potential for destructive mudflows in the wake of recent Southern California wildfires were made available to the public and emergency responders today by the U.S. Geological Survey (USGS).

The maps estimate the size of potential debris flows, commonly known as mudflows, and the areas that could be affected when rainfall begins on recently-burned areas.

“Fast-moving, highly destructive debris flows triggered by rainfall are one of the most dangerous post-fire hazards,” said Dr. Sue Cannon, the USGS scientist who led a team of experts that developed the hazard maps.

USGS today unveiled 10 maps that show potential volumes of debris flows from basins burned by the Buckweed, Santiago, Canyon, Poomacha, Ranch, Harris, Witch, Rice, Ammo, Slide, and Grass Valley Fires in October and November. The maps will be used by the National Weather Service to provide debris-flow warnings to the public, by the Federal Emergency Management Agency (FEMA) to use in conjunction with their flood-inundation maps, and by local and state emergency managers.

“These maps are designed to provide emergency managers with tools to implement protective measures to preserve values at risk, including life and property,” said Lee Rosenberg of the Multi-Agency Support Group (MASG) that represents federal and state agencies.

“Knowing the areas most vulnerable to a particular hazard is critical in preparing to meet the needs of that community when an emergency strikes,” said Henry Renteria, Director of the Governor’s Office of Emergency Services (OES). “The new maps are a brand new tool emergency managers and first responders can use in their planning and response efforts.”

More information about debris-flow and landslide hazards can be accessed at http://landslides.usgs.gov/research/wildfire/07sca/.