Modelling and optimisation of extinction actions for wildfire suppression

Figures & data

Table 1. Summary of the most typical wildfire suppression strategies (National Wildfire Coordinating Group 1996).

Strategy	Description
Control line	Either fire line (remove fuel, scrape down to soil) or wet line (increase fuel moisture content)
Burning out	Use small torches to preemptively burn forest fuel
Backburn	Burn from control line towards fire
Flanking	Spray fire sides, start from behind, overtake – small fires only
Hot spotting	Target hot spots (often aerial)
Knock down	Extinguish hot spots
Cold trailing	Prevent re-ignition once the temperature is lower than the ignition temperature
Aerial attack	Use helicopters or airplanes to drop substance (e.g., water mist)
Fireline explosives	Fell trees and break dense bush using explosives, time efficient
Mop-up	Clean up along a completed control line

Figure 1. Monte Carlo Tree Search algorithm (e.g., see Chaslot et al. 2021) adapted for wildfire suppression.

Figure 2. Terrain schematic with the three firebreak extinction actions for the model fire simulation. The $(3|8)H$ action (green) corresponds to the first stage, the $(8|7)H$ action (yellow) corresponds to the second stage, and the $(13|8)H$ action (gray) corresponds to the third stage in the underlying Monte Carlo tree (see Supplementary Material, Figure A2). The treasure is displayed in black.

Figure 3. Selected area of investigation for the real fire scenario (left) and terrain schematic with the four firebreak extinction actions obtained from MCTS (right). The $(10|8)V$ action (green) corresponds to the first stage, the $(11|5)V$ action (yellow) corresponds to the second stage, the $(10|2)V$ action (gray) corresponds to the third stage, and the $(8|2)H$ action (dark gray) corresponds to the fourth stage in the underlying Monte Carlo tree (see Figure A3 in the Supplementary Material). The red star on the left map indicates the ignition location of the fire in the real scenario (Mastorakos et al. 2023). The fire in the area of interest is modeled as a fire front approaching the domain from west to east.

Table 2. Space and time model parameters for the real fire scenario: $t_{\mathrm{e}\mathrm{n}\mathrm{d}}$ is the total simulated time, $\mathrm{\Delta }t$ is the simulation timestep, $\mathrm{\Delta }x$ and $\mathrm{\Delta }y$ indicate the grid size in the $x$ and $y$ directions, $n_x$ and $n_y$ are the number of cells in the $x$ and $y$ directions, respectively.

Time		Space
$t_{\mathrm{e}\mathrm{n}\mathrm{d}}$ (s)	$\mathrm{\Delta }t$ (s)	$\mathrm{\Delta }x$ (m)	$\mathrm{\Delta }y$ (m)	$n_x$	$n_y$
$1000$	$0.2$	$50$	$50$	21	9

Figure 4. Simulation result at different time instants for the real fire scenario. For each time, the top plot shows the advancement of the fire front (burnt area is indicated by black color); the bottom plot shows the utility map with orange color used to indicate the destroyed cells.

National Wildfire Coordinating Group. 1996. Wildland Fire Suppression Tactics Reference Guide. Boise, ID, US: National Wildfire Coordinating Group.

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