Zero is the point of no moisture deficiency and 800 is the maximum drought that is possible. At 8 inches of water, the KBDI assumes saturation. It is a closed system ranging from 0 to 800 units and represents a moisture regime from 0 to 8 inches of water through the soil layer. The KBDI attempts to measure the amount of precipitation necessary to return the soil to full field capacity.
It is a continuous index, relating to the flammability of organic material in the ground. It is a number representing the net effect of evapotranspiration and precipitation in producing cumulative moisture deficiency in deep duff and upper soil layers. Keetch and Byram (1968) designed a drought index specifically for fire potential assessment.
