GVWSA Fire Risk Supplementary Figures

Greater Victoria Water Supply Area – Fire Risk Elements

Supplementary parameters and figures for burn probability analysis


FBP System Fuel Type map (from BC Wildfire Service provincial fuel type layer):GVWSA_FuelTypes

Human ignitions and ignition probability grid – see text for description:GVWSA_History_Human2

Lightning ignitions and ignition probability grid – see text for description:GVWSA_History_firecounts-Lx

Ignition grids were normalized prior to modelling to equalize the total probability of human and lightning ignition sources across the southern Vancouver Island region. This was done by multiplying the individual human ignition grid cells by the ratio of the sum of all lightning probabilities over the sum of all human grid probabilities:

Phf = Ph*(∑Pl/∑Ph) ,

where Phf is the final probability of a human ignition in a grid cell, Ph is the original modelled probability of human ignition in that cell, and ∑Pl and ∑Ph are the total summed probabilities of lightning and human ignition grids, respectively.

The ignition probability figures above appear to show many more high probability cells associated with human ignitions; this is simply a factor of the figures being zoomed in on the GVWSA study area. Total grid probabilities across the southern Vancouver Island modelling surface are identical.


Annual escaped fire probability distribution (actual and smoothed); smoothed values were used for modelling:

1 fire: 30 %;   2 fires: 17.5 %;   0,  3, 4, 5, 6 or 7 fires: 7.5 %

8, 9, 10, or 11 fires: 1.875 %

Total: 100 %


Frequency distribution of spread-event days (1-4 burning days per fire):

1: 55%

2: 35%

3: 8%

4: 2%


Minimum fire size: 1 ha

Supplementary Outputs:

Total Fuel Consumption grid:GVWSA_BurnProb_80k_TFCAvr

Perimeters of all fires that reached the GVWSA:GVWSA_BurnProb_80000_perims

BP Perimeters: 600-1,300 ha

BP Perimeters: 1300+ ha




Intelligence for wildfire researchers and managers

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