Climate stressors and impacts

Wildfires have caused considerable damage in and around San Diego. In particular, fires ravaged the city and county in October 2007, burning nearly 200,000 acres across San Diego County and leading to the evacuation of over 500,000 people in the region.

The fires had a substantial impact on San Diego Gas & Electric (SDG&E), the utility that provides heat and electricity to many consumers in the region. In addition to direct physical damage to equipment and infrastructure, SDG&E paid out around $2 billion to the city and county of San Diego, insurers, individuals, and businesses that sustained damage. The reason? Some of SDG&E’s wires were blamed for sparking the fires during a period of strong, dry Santa Ana winds.

Key ingredients for fire

Along with high temperatures, dry conditions, and the availability of fuel, wind is a key ingredient in igniting and spreading fire. Strong winds can cause utility wires to come in contact with one another, or bring trees in contact with wires, creating the potential to start a fire. Once a fire has begun, wind can help spread it quickly. Since a Santa Ana wind typically involves warm, dry air moving down slope toward the California coast, it brings together several key ingredients for fire.

Fire crews set back-burn fires in an attempt to halt the advance of a Southern California fire in 2007.

The SDG&E Mesonet and the Wildfire Threat Index

Following the devastation of the 2007 fires, SDG&E made a number of investments and developed partnerships to help them better manage fire risks. First, they deployed one of the largest utility-owned networks of weather sensors—a “mesonet.” These sensors provide real-time information about weather conditions, including winds. Second, working with the University of California at Los Angeles and the U.S. Forest Service, SDG&E assisted with development of a forecasting system for fire weather—the Santa Ana Wildfire Threat Index (see sidebar). Based on observations recorded by the SDG&E mesonet, the Index provides forecasts of potential fire risk six days into the future. This advance information allows emergency responders and resource managers to proactively move firefighters and their equipment to high-risk areas in anticipation of fires, and to alert residents in these areas of potential danger. The index also helps the utility isolate trunk lines within zones that are at high risk for fire. By giving these zones additional fire-prevention attention, the utility can minimize the number of customers who experience outages and reduce the probability of spark-strike fires. Implementing the use of the wildfire index has helped SDG&E save money, reduce risk, and better serve their customers.

Managing fire in the future

Climate scientists project that future climate conditions will result in increased risk of wildfire across much of the Southwest. Although fires are a natural part of Southern California landscapes, efforts by SDG&E and their partners may help minimize the impacts of future fires.