Early Warning Systems for the Management of Forest / Bush FireThe Keech-Byram Drought Index

Teddy AllenPostdoctoral Research Scientisttallen@iri.columbia.edu

Keech-Byram Drought Index (KBDI)The KDBI drought index is defined as a number representing the net effect of evapotranspiration and precipitation in producing cumulative moisture deficiency in deep duff or upper soil layers.

• Developed by John Keetch and George Byram in 1968 for the United States Department of Agriculture’s Forest Service.

Keech-Byram Drought Index (KBDI)The KDBI drought index is defined as a number representing the net effect of evapotranspiration and precipitation in producing cumulative moisture deficiency in deep duff or upper soil layers.

An INDEX is a number that represents an indicator, sign, or measure of something.

examples include:

• tornado classification• hurricane classification• El Nino / La Nina phases• HAPPINESS!

Keech-Byram Drought Index (KBDI)The KDBI drought index is defined as a number representing the net effect of evapotranspiration and precipitation in producing cumulative moisture deficiency in deep duff or upper soil layers. An INDEX is a number that represents an indicator, sign, or measure of something.

Keech-Byram Drought Index (KBDI)The KDBI drought index is defined as a number representing the net effect of evapotranspiration and precipitation in producing cumulative moisture deficiency in deep duff or upper soil layers.

evapotranspiration = evaporation + transpiration

movement of water into the air from a moisture source

movement of water within a plant and the subsequent loss of water as vapor through leaves

The purpose of the drought index is to provide fire control managers with a continuous scale of reference for estimating deep-drying conditions in areas where such information may be useful in planning fire control operations.

KBDI is, thus, a quantity that relates to the flammability of organic material in the ground.

𝒅𝑸=[𝟖𝟎𝟎−𝑸 ] [𝟎 .𝟗𝟔𝟖𝒆(𝟎 .𝟎𝟒𝟖𝟔𝑻 )−𝟖 .𝟑 ]𝒅𝒕

𝟏+𝟏𝟎 .𝟖𝟖𝒆(−𝟎 .𝟒𝟒𝟏𝑹) ×𝟏𝟎−𝟒 (English units)

.

Step 1 – Calculate the daily change in KBDI (dQ, also known as the drought factor)

Step 2 - Reduce the drought index by the amount of net rain, if any.

Step 3 --Increase the drought index by the amount found in the drought factor.

At any point along the scale, the index number indicates the amount of net rainfall that is required to reduce the index to zero, or saturation.

Q = KBDI = 0 at initialization due to saturation

Keech-Byram Drought Index (KBDI)The KDBI drought index is defined as a number representing the net effect of evapotranspiration and precipitation in producing cumulative moisture deficiency in deep duff or upper soil layers.

R = mean annual rainfall T = daily temperature

mid-summer vegetation (NDVI)precipitation

KBDI

1 18 35 52 69 86 1031201371541711882052222392562732903073243413580

100200300400500600700800

0.000.250.500.751.001.251.501.752.00

sample KBDI and rainfall (Manley 2010)

Jan 1 Dec 31June 1 18 35 52 69 86 1031201371541711882052222392562732903073243413580

100200300400500600700800

0.000.250.500.751.001.251.501.752.00

sample KBDI and rainfall (Manley 2014)

Jan 1 Dec 31June

Keech-Byram Drought Index (KBDI) requested by JMS and supported by UWI

55 station locationsstation based KBDI mapping for a specific day

station based point or interpolated gridded maps

nearest neighbor

Inverse distance weighting

kriging

1234567

KBDI

Sta

ges

CUSTOMIZE DISPLAY

OPTIONS

KBDI Category Distribution

1 March –31 Dec 2010, Manley

1 March – 31 Dec 2014, Manley

Category1 Category2 Category3 Category4 Category5 Category6 Category7 Category8

low fire risk high fire risk

82%(249 days)

9%26 days

10%4%

21%

18% 18%11%7%

4%

12%

KBDI anomalies (historical context)

Conclusions and Future Work

• 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 (200 mm) 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 and reflects water gain or loss within the soil.

Conclusions and Future Work

• 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 (200 mm) 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 and reflects water gain or loss within the soil.

• OPERATIONS: Meteorological Service of Jamaica is leading a collaborative effort to make KBDI an operationalproduct specific to Jamaica

• RESEARCH: Seek Caribbean wide KBDI relationshipto drought / fire outbreak