A Drought Index for Forest Fire Control
The moisture content of the upper soil, as well as that of the covering layer of duff, has an important effect on the fire suppression effort in forest and wildland areas. In certain forested areas of the United States, fires in deep duff fuels are of particular concern to the fire control manager. When these fuels are dry, fires burn deeply, dam-age is excessive, and fire extinguishment unduly expensive. Even rela-tively small fires are costly; the larger fires may be disastrous. As an example, in 1955 and 1956, four fires in the Southeast each burned more than 100,000 acres. During these years, normally moist areas which usually served as good fire barriers, such as branch heads and bays, became so dry that the fires accelerated through the heavy fuel instead of slowing down.