Table 1 Description of the studied variables

Topographic variables

 Slope

INFOCA

0–65

Qn

%

 Aspect

INFOCA

1–2

Ql

1 (sunshine)

2 (shade)

Meteorological variables

 Temperature

SIAR 2021

4.85–43.47

Qn

°C

 Relative humidity

SIAR 2021

6.14–85

Qn

%

 Wind speed (U)

SIAR 2021

0–32

Qn

km/h

Fuel variables

 Fine fuel moisture content (FFMC) (Rothermel 1983)

Own data

6.25–13.63

Qn

%

 Fuel model (UCO 40) (FM) (Molina and Rodríguez y Silva 2012)

Own data from INFOCA report (conversion of Rothermel classification to UCO 40)

1–12

Ql

1 (grass in semiarid conditions; P1, P2. P3, P4, P7)

2 (grass in subhumid conditions; P5, P6, P8)

3 (mixture of grass and shrubs lower than 60 cm high; PM1, PM3)

4 (mixture of grass and shrub higher than 60 cm high; PM2, PM4)

5 (shrub lower than 0.5 m high; M1, M2)

6 (shrub approximately 1 m in height; M3, M4, M6)

7 (chaparral shrub; M5, M7, M8, M9)

8 (grass, shrub, or litter lower than 30 cm in height or depth; HPM1, HPM2)

9 (grass, shrub, or litter between 30 and 90 cm in height or depth; HPM3, HPM4)

10 (grass, shrub, or litter more than 90 cm in height or depth; HPM5)

11 (slash and pine litter; HR5, HR7)

12 (slash and broadleaf litter; HR6, HR9, R1)

Fuel break design features

 Fuel break type (PIT)

INFOCA

1–3

Ql

1 (vegetation-free: firebreak)

2 (combination of vegetation-free and vegetated: firebreak with adjacent vegetation-treated area)

3 (vegetated: vegetation treated area)

 Fuel break location (LOC)

Own data

1–6

Ql

1 (steepest slope)

2 (flat)

3 (ridgeline)

4 (lower slope)

5 (mid-slope)

6 (canyon bottom)

 Fuel break width (W)

Own data

1.5–450

Qn

m

Suppression variables

 Type of suppression work executed on fuel break (SW)

INFOCA

1–5

Ql

1 (combined ground-aerial firefighting)

2 (ground firefighting)

3 (aerial firefighting)

4 (fire spread with no suppression due to technical reasons)

5 (fire spread with no suppression due to safety reasons)

 Firefighter safety

INFOCA

0–2

Ql

0 (non-safe)

1 (safe)

2 (unknown)

 Fuel break effectiveness (EFFEC) representing if the fire spread was controlled in the fuel break

Own data

0–1

Ql

0 (non-effective)

1 (effective)

 Cause of fuel break leap

INFOCA

1–4

Ql

1 (no leap)

2 (radiation-convection)

3 (spotting)

4 (radiation-convection and spotting)

Observed fire characteristics

 Wildfire type (WT)

INFOCA

1–3

Ql

1 (surface fire)

2 (passive crown fire)

3 (active crown fire)

 Burned area

INFOCA

0.02–9806

Qn

ha

 Wildfire front length (L) representing the length of the portion of fire that encountered the fuel break

INFOCA

1–8

Ql

1 (< 50 m)

2 (50–100 m)

3 (100–250 m)

4 (250–400 m)

5 (400–600 m)

6 (600–800 m)

7 (800–1000 m)

8 (> 1000 m)

 Alignment of forces (AF) (Campbell 2005) representing the arrangement of various factors that influence the behavior and spread of a wildfire (wind, slope, and preheat)

Own data

0–3

Ql

0 (0/3; out of alignment)

1 (1/3; half alignment: one factor)

2 (2/3; half alignment: two factors)

3 (3/3; full alignment: wind, slope, and preheat)

 Propagation vector

INFOCA

1–4

Ql

1 (fuel)

2 (wind)

3 (topography)

4 (convective)

 Intersection angle between fire and fuel break (encounter type) (ANG)

Own data

1–3

Ql

1 (almost parallel, flanking)

2 (lateral, flanking)

3 (perpendicular, heading)

Predicted fire behavior

 Rate of spread (ROS) (Andrews 2009)

Own data

0.1–263

Qn

m/min

 Flame length (FL) (Byram 1959)

Own data

0.1–17.15

Qn

m

 Spotting distance (Albini 1976)

Own data

0.8–288.35

Qn

m