NWS Decision Support Services for Riverside County Emergency Management Department: Onsite and Coordinated Warning and Public Notification

During the summer of 2018, several wildfires occurred across southern California. The largest fires scorched thousands of acres of steep high elevation terrain. The United States Forest Service Burn Area Emergency Response (BAER) Team, United States Geological Survey (USGS), CalFire Watershed Emergency Response Team (WERT) and California Geological Survey conducted field assessments and developed models that assessed the Holy and Cranston burn scars and determined there were high likelihood of debris flows following intense rainfall. The runoff volumes from the canyons were expected to increase 3 to 5 times in magnitude. Meetings between the National Weather Service, USGS, and the California Geological Survey developed specific thresholds that the lead warning agencies would use in the event of intense rainfall meeting or exceeding debris flow thresholds. These findings prompted about a dozen partner meetings led by Riverside County Emergency Management Department, City of Lake Elsinore, Fire and Police first responders, local school districts and Riverside County Flood Control District. These meetings led to the development of specific response and evacuation protocols for the burn areas. Once all partner agencies development strategic emergency plans and procedures there were several separate community outreach events to inform potentially impacted citizens. Attendees also included School District representatives, Home Owner Associations and other community leaders. The attendance at the meetings ranged from 50 to 150 persons. Communities within Lake Elsinore and Temescal Valley were identified as the greatest risk. Local agencies, including the Riverside Flood Control and Water Conservation District implemented canyon monitoring systems including rain gauges, remotely operated cameras, pressure sensors and other devices to be able to assess and detect potential debris flows. The National Weather Service developed special decision support services for Riverside County which included community outreach, a specific rainfall rate forecast template for the debris flow task force, internal guidance for issuing Flash Flood Warnings, and on-site deployment staffing for Emergency Operations Center activation. Information from the sensor networks and National Weather Service forecasts was shared freely between partner agencies to assist in response activities and refinement to protocols. Infrastructure to mitigate the impacts of potential debris flows, including levees, debris basins, channels and other devices were also implemented or enhanced to protect local communities. The winter of 2018-2019 offered several intense rain events that resulted in implementation of evacuation and response protocols. This presentation will cover the best practices and lessons learned from the 2018-2019 storm season.