Characterisation of Hedge Burning in the Context of Wildland Urban Interface (WUI) Fire Prevention

Abstract

With global warming, the wildfire season tends to get longer, causing fatalities and devastating damage to human property. Although many countries have implemented fire risk prevention measures, particularly in Wildland Urban Interfaces (WUI), this finding shows that there are weaknesses in the prevention measures. This is mainly due to a lack of knowledge about WUI fire exposure conditions. This paper presents field-scale experiments to characterise the burning of rockrose-reconstructed hedges (6 × 1 × 1 m) close to a building in order to provide experimental data on heat release rate (HRR), flame front geometry, and heat fluxes to the building. The mean horizontal flame extent was 4.4 (±0.7) m with values up to 5.5 m. These values are generally higher than the minimum distance to be maintained between vegetation and buildings in most countries. The fire intensity ranged from 283 to 3479 kW/m, resulting in maximum values at 3 m from the hedge of up to 45.4 kW/m² for the total heat flux and 38.1 kW/m² for the radiant heat flux. However, the flame duration is short, averaging 112.8 (±27.1) s. This type of exposure is far from those used to test the fire resistance worldwide. Therefore, the data obtained in this study are crucial for improving fire risk prevention methods worldwide, whether for fuel management in defensible zones or for testing building materials to make buildings more resistant to wildfires.