# Buildup index

# Description

The Buildup index (\(BUI\)) is one of the two intermediate indices required for calculating the Canadian fire weather index (\(FWI\)\)). The \(BUI\) represents the total amount of fuel available to the spreading fire. It is a combination of the \(DMC\) and the \(DC\) (Van Wagner 1987).

The \(BUI\) is affected mainly by the \(DMC\). The \(DC\) only has a limited and variable weight in the equation (Van Wagner 1987).

# Formula

For \(DMC\leqslant{0.4\cdot DC}\) the \(BUI\) is calculated as follows (Van Wagner and Pickett 1985):

\[BUI=0.8\cdot\dfrac{DMC\cdot{DC}}{DMC+0.4\cdot DC}, \mbox{ for DMC}\leqslant{0.4\cdot DC}\]

and for \(DMC>{0.4 \cdot DC}\) as follows:

\[BUI=DMC-\bigg(1-\dfrac{0.8\cdot DC}{DMC+0.4\cdot DC}\bigg)\cdot\big[0.92+(0.0114\cdot DMC)^{1.7}\big], \mbox{ for DMC}>{0.4\cdot DC}\]

where \(DMC\) is the Duff moisture code and \(DC\) the Drought code.

# References

Original publication:

Van Wagner and Pickett (1985)

Van Wagner (1987)