Keetch-Byram Drought Index
Encyclopedia
The Keetch-Byram Drought Index (KBDI), created by John Keetch and George Byram in 1968 for the United States
Department of Agriculture's Forest Service
, outlines mathematical models for predicting the likelihood of wildfire
based on soil
moisture
and other conditions related to drought
.
KBDI is a soil/duff drought
index that ranges from 0 (no drought
) to 800 (extreme drought
) and is based on the soil capacity in 8 inches (20.3 cm) of water. The depth of soil
required to hold 8 inches of moisture varies. A prolonged drought
(high KBDI) influences fire
intensity largely because fuels have a lower moisture content.
The KBDI is a measure of meteorological drought; it reflects water gain or loss within the soil. It does not measure fuel moisture levels in the 1 to 10 hour fuel classes, which must be measured by other means for an accurate assessment of fuel moisture, regardless of the drought index readings.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
Department of Agriculture's Forest Service
United States Forest Service
The United States Forest Service is an agency of the United States Department of Agriculture that administers the nation's 155 national forests and 20 national grasslands, which encompass...
, outlines mathematical models for predicting the likelihood of wildfire
Wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...
based on soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
moisture
Moisture
Humidity is the amount of moisture the air can hold before it rains. Moisture refers to the presence of a liquid, especially water, often in trace amounts...
and other conditions related to drought
Drought
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
.
KBDI is a soil/duff drought
Drought
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
index that ranges from 0 (no drought
Drought
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
) to 800 (extreme drought
Drought
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
) and is based on the soil capacity in 8 inches (20.3 cm) of water. The depth of soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
required to hold 8 inches of moisture varies. A prolonged drought
Drought
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
(high KBDI) influences fire
Fire
Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....
intensity largely because fuels have a lower moisture content.
The KBDI is a measure of meteorological drought; it reflects water gain or loss within the soil. It does not measure fuel moisture levels in the 1 to 10 hour fuel classes, which must be measured by other means for an accurate assessment of fuel moisture, regardless of the drought index readings.
