Keetch-Byram Drought Index

The Keetch-Byram Drought Index (KBDI) is a cumulative drought severity index used in fire danger rating systems to track long-term soil moisture depletion and drying trends. Developed in 1968 by Keetch and Byram, KBDI integrates daily temperature, precipitation, and prior drought state to produce a continuous index ranging from 0 (no drought, moist soil) to 800 (severe drought, very dry soil). KBDI is widely used in fire danger prediction and fire behavior modeling because soil moisture is a major driver of fuel drying and flammability.