Appendix E. The 1932 Matilija Fire perimeter and prior 20th-century fire history.
Between 1911 to 1932 only a single lightning fire was suppressed within the 89,100 ha fire perimeter area (it occurred in 1931 and is indicated with a star) and another (in 1925) was suppressed on the northern perimeter (Fig. E1).
|FIG. E1. Fire perimeter map for the 1932 Matilija Fire. Point of origin for prior anthropogenic fires that were ignited within the fire perimeter and suppressed is indicated with closed circles (based on individual fire records from USFS Los Padres National Forest ) and for those that were larger than 40 ha the fire perimeters are indicated with shading (CalFire FRAP database). Lightning ignited fires suppressed are indicated with stars.|
The extraordinary size of this fire (main text, Table 1) is due to a number of factors. This fire was initially fanned by a strong offshore flow of northwest winds, but the erratic winds changed direction multiple times (Los Angeles Times, 9 Sept 1932). Winds created a firestorm that carried firebrands far ahead of the fire front and were a major factor in the rapid spread, which covered 8,000 ha in 12 hrs. Over the subsequent 10 days there were repeated blowups from northern Santa Ana winds (Cermak 2005). These winds, coupled with the rugged terrain, pushed the fire in three directions and it rapidly developed a large fire front. It then burned eastward into remote chaparral covered backcountry, described as “the wildest and least known portion of California … never tred by a white man, and probably seldom by an Indian” (Los Angeles Times, 13 Sept 1932). The inaccessibility of this area is illustrated by the fact that during fire suppression activities, 12 of the 17 fire camps had to be supplied by mule (Brown 1945). The primary factors that contributed to the size of this fire are the inaccessibility of the area and a particularly severe drought leading up to the fire; for each of the 23 months prior to this fire the central coast had negative Palmer Drought Severity Indices, with an average of -2.22 (main text, Table 1). According to the Los Angeles Times (17 Sept 1932), very dry fuels, along with the high winds, contributed to the proliferation of long distance spotting and the rapid development of the 160 km fire front.
In 2007 the Matilija Fire was surpassed in size by the Zaca Fire (main text, Table 1), further west on the Los Padres National Forest , but also in very remote chaparral dominated landscapes; 68% of the area was roadless. Although reports referred to this as a “fuel-driven” fire it could also appropriately have been described as a “topography-driven” fire (Dave Sapsis, Cal Fire, personal communication 10 April 2008) since the steep topography largely replaced severe winds as a primary driver of this fire; both enhance the rate of fire spread by heating fuels ahead of the fire front. As with the Matilija Fire, inaccessibility was an important limitation in direct aggressive suppression tactics. The remoteness of this landscape also meant that it had not been subjected to excessive anthropogenic burning during the 20th century (see Safford and Schmidt 2008) and thus older fuels, although well within their historical range, were a contributor as well. These factors coupled with a prior drought (main text, Table 1), high temperatures, low humidity and significant westerly onshore winds all contributed to the large size of this fire (USFS 2007).
Brown, W. S. 1945. History of the Los Padres National Forest, 1898-1945. USDA Forest Service, Los Padres National Forest, Goleta, California, USA.
Cermak, R. W. 2005. Fire in the forest. A history of forest fire control on the national forests in California, 1898–1956. USDA Forest Service, Pacific Southwest Region, R5-FR-003, Albany, California, USA.
Safford, H. D., and D. Schmidt. 2008. Fire departure maps for southern California national forests. USDA Forest Service and The Nature Conservancy.
USFS. 2007. Zaca Fire --- Chronology of events July 4 through September 4, 2007 . Unpublished report at http://www.fs.fed.us/r5/lospadres/documents/zaca-final-chronology.pdf. USDA Forest Service, Goleta , California, USA.