CONNECTING LANDSLIDE EVENT RESPONSE DATA WITH EMERGENCY MANAGERS AND POLICY MAKERS USING THE CALIFORNIA GEOLOGICAL SURVEY’S REPORTED LANDSLIDES DATABASE DURING A SEQUENCE OF NINE ATMOSPHERIC RIVER EVENTS IN CALIFORNIA, DECEMBER 2022 - JANUARY 2023

From late December 2022 until mid-January 2023, nine atmospheric river (AR) events impacted California, resulting in year-to-date precipitation accumulations varying from more than 200 to 350% above average across a wide swath of the state. Historic flooding and multi-modal landslide activity occurred statewide, damaging transportation infrastructure, homes, property, and threatening life-safety and economic welfare. A state of emergency was declared by the Governor of California as well as by the President of the United States. The California Governor’s Office of Emergency Services (CalOES) mission tasked the California Geological Survey (CGS) to provide situational awareness of statewide landslide hazards, which CGS accomplished in partnership with the United States Geological Survey (USGS) as well as numerous state, county, and local agencies. CGS leveraged its Reported Landslides Database (RLD) mapping tools for desktop and field surveying to rapidly identify areas of observed landslide impacts. For three weeks, available reported landslide data was surveyed on a sub-daily basis from multiple sources including, but not limited to: photos and timing information from crowd-sourced reporting (e.g., Twitter, Facebook), local news media sources, state agency reporting, California Highway Patrol (CHP) data, and review of firsthand reports. The RLD mapping team identified more than 850 AR-induced landslides, resulting in deployment of field teams to provide further assistance to hardest hit areas. CGS utilized these data to update CalOES, and the state and federal Unified Command Group on a daily basis. In addition, the data were used to communicate to the public and media regularly via Twitter, which raised awareness of landslide activity to a national level, supporting the term “landslides” as a major component of a FEMA disaster declaration.