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2021 Multijurisdictional Local Hazard Mitigation Plan 16.2.5 Severity The most recent deadly fire in San Mateo County was the CZU Lightning Complex fires, which burned in San Mateo and Santa Cruz County starting on August 16, 2020. This fire destroyed 1,490 structures, damaged 140 others, and caused 1 injury and 1 fatality. Fires burned in both Butano and Big Basin Redwoods state parks, where a number of historic buildings were destroyed, including the visitor’s center at Big Basin. The total acreage burned was 86,509. CAL FIRE tracks the deadliest, largest, and most destructive wildfires that have occurred in the state, with the lists last updated in late April 2021. The CZU Lightning Complex fire is listed as the 12th most destructive California wildfire. Although San Mateo County has not had many major wildfire events, nearby Alameda County has demonstrated some worst-case scenario fires that could occur in other Bay Area counties. The October 1991 Oakland/Berkeley Hills “Tunnel Fire” was the most damaging fire and the second most deadly fire in California at the time it occurred. This WUI fire resulted in 25 lives lost, including a fire battalion chief and an Oakland police officer, 148 people injured, and 2,900 structures destroyed. The blaze started from a grass fire in the Berkeley Hills and burned 1,600 acres. The estimated private property loss was $1.7 billion at the time, according to the Insurance Information Institute. 16.2.6 Warning Time Wildfires are mostly caused by humans, intentionally or accidentally. There is no way to predict when one might break out. Since fireworks often cause brush fires, extra diligence is warranted around the Fourth of July when the use of fireworks is highest. Dry seasons and droughts are factors that greatly increase fire likelihood. Dry lightning may trigger wildfires. Severe weather can be predicted, so special attention can be paid during weather events that may include lightning. Reliable National Weather Service lightning warnings are available on average 24 to 48 hours prior to a significant electrical storm. If a fire does break out and spread rapidly, community members may need to evacuate within days or hours. A fire’s peak burning period generally is between 1 p.m. and 6 p.m. Once a fire has started, fire alerting is reasonably rapid in most cases. The rapid spread of cellular and two-way radio communications in recent years has further contributed to a significant improvement in warning time. 16.3 EXPOSURE A quantitative assessment of exposure to the wildfire hazard was conducted using the hazard mapping shown in Figure 16-3 and the asset inventory developed for this plan. Population exposure was estimated by calculating the number of buildings in the mapped hazard areas as a percent of total planning area buildings, and then applying this percentage to the estimated planning area population. Detailed results by municipality are provided in Appendix E; results for the total planning area are presented below. 16.3.1 Population and Property Table 16-1 summarizes the estimated population living in the moderate-high and high wildfire hazard zones and the estimated property exposure. In addition to the populations living in wildfire risk areas, people working or recreating in resource lands, such as hikers, are exposed to the wildfire risk. Firefighting crews are exposed as they work to combat fires and to protect property. All county community members are potentially exposed to the health-related impacts of reduced air quality from wildland fires. 16-8