1. INTRODUCTION: South Africa passed a new national fire Act in 1998; the act requested the development of national
fire danger rating system (FDRS) which will be suitable for the country. FDRS are systems which are developed to assist
in fire management of veld and forest fires. These systems assess the possibilities of occurrence, spread and difficulties
of fire suppression. The effectiveness of the entirely rely on combination factors to be calculated in which influence
fire occurrence, rate of spread and fire behaviour. The Fire danger index (FDI) is for declaring burning index. The
importance of determining the FDI has influenced the development of different FDRS which are been used
through out the world.
DAMAGE AND DANGERS ASSOSIATED WITH FIRE DANGER INDEX
Finiza Bongani, NMMU, George Campus, Private Bag X6531, George, 6530; Email: s210095784@live.nmmu.ac.za
CONCLUSION: Understanding the FDI will help in knowing the prediction of fire occurrence, spread and behaviour. The
public should be educated in matters pertaining to the FDI determination and be assisted in understanding the FDI. The
development of a proposed methodology is recommended for the delivery of an agreed set of descriptions of each of the
different fire danger rating categories.
RED DAY
Extreme
ORANGE DAY
High
GREEN DAY
Low
YELLOW DAY
Moderate
BLUE DAY
Insignificance
Anemometer
Thermometer
189.8 Kpm
ABSTRACT: Fire danger rating systems are
designed for determining fire danger level and
indicate possible fire behaviour in a particular
area. There are a number of parties who are
responsible for calculating the fire danger index
and issue out warnings to the public of the
expected fire occurrence and damage which can
be suffered. The parties involved include the
Department of Agriculture, Fisheries and
Forestry (DAFF), South African Weather Bureau
(SAWB) they have the sole responsibility not the
other parties. The South African veld and forest
fire Act (101 of 1998) stipulates that the minister
communicates the FDR to the Fire Protection
Associations (FPAs).
FIRE PARAMETERS: The colour codes
which are used also portray the
expected fire parameters on the
particular readings of the FDI.
Red: flame heights are above 2.4
meters, development of whirl-fires,
increase in wind speed, lots of
spotting fires and all fire teams must
be on full standby.
Orange: flame heights are 1.8-2.4m,
no open fires are allowed of any
nature, maximum strike on fire.
Yellow: 1.2-1.8m of flame height,
control burn can be undertaken with
extreme caution and constantly check
weather and abort when is changing.
Green: 1.0-1.2m in flame height and
there is little threat of running fires.
Blue: 0.0-1.0m in flame height, there
is barely a threat of extreme
conditions and running fires.
FIRE DANGER RATING SYSTEMS: The FDRS which is used in South Africa
has been categorised into five fire colour codes which represent the fire
behaviour, dangers, severe damage associated with each colour code. The
easy way of building an understanding of FDR I through portray of colours.
The FDI is rated between 0 (zero) and 100 (hundred). The closer the rating
to zero, the safer the conditions are and the closer they get to 100, the
dangerous the conditions become. The colour codes are interpreted as
follows:
Blue (insignificance) 0 - 20, Green (low) 21 – 45, Yellow (moderate) 46 – 60,
Orange (high) 61 - 75, and Red (extremely high) 76 - 100.
NATIONAL FDI: In South Africa is
hard to predict the FDI at a national
due to different climate conditions
within. South African climate
categories include: South-western
Cape and adjacent interior,
Southern Cape coast, South-eastern
and eastern coast and adjacent
interior, North-eastern escarpment,
Eastern interior, Central interior and
Western interior. The FDI at a local
level can also differ due to the effect
of micro-climate, terrain,
topography and local winds. Fire
behaviour can also differ within the
local level.
LOCAL CONDITIONS: South Africa is a country of vast diverse vegetation cover, and
this must be taken into consideration when calculating the FDI. The natural vegetation
is broadly classified into seven biomes, namely: Forest; Thicket; Savannah; Grassland;
Nama Karoo; Succulent Karoo and; Fynbos. The biomes are derived from the life form
dominance and climatic characterization of natural ecosystems. Therefor when
calculating the FDI, the following must be taken into account: fuel type, wind speed
and direction, temperature, relative humidity (RH), fuel composition and moisture
content, and topography. The mentioned factors and biomes may influence and/or
respond differently to fire and thus the fire behaviour, intensity, spreading rate (with
wind), burn duration and burning pattern cannot be expected to be the same or
similar.
FOCUS: The determining of the
FDI is currently focuses in the
whole Country. The SAWB is
conveying general FDI to public
after every news bulletin. The
public does not really
understand the meaning of
colour codes which are used to
represent FDI. More focus
should be taken to the public in
trying to offer workshops during
fire awareness.
LOWVELD BURNING INDEX: It is the
most commonly used system in South
Africa to determine the FDI of the day. In
order to be able to determine FDI, firstly
burning index (BI) will be determined.
The formula for this type of FDRS and a
calculation example is as following:
FDI = (BI+WF) x RCF
FDI = (40+15) x 0.9
FDI = 49.5
Burning Index (BI), Wind Factor (WF), Rainfall
Correct Factor (RCF)
The FDI is calculated by determining the
BI in the FDI Alignment Chart, using dry-
bulb (temperature) and relative
humidity (purple arrow). Add up the BI
with WF and then multiple with the RCF
if possible. The final readings align with
the colour code will give the FDI of the
day.
The presence of wind and wind speed
will increase the FDI, though the recent
rainfall may have an impact in reducing
the FDI. The red arrow shows wind
effect and the green arrow shows the
influence of rainfall on FDI.
Anemometer
28.3Kpm
71°F = 22°C
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