How ornamental vegetation burns: from particle flammability to vertical flame propagation
Comment la végétation ornementale brûle : de l'inflammabilité des particules à la propagation verticale des flammes
Ganteaume, A. ; Bertin, A. ; Audouard, M. ; Guerra, F. ; Lopez, J.M. ; Morge, D. ; Travaglini, C. ; Jappiot, M.
Type de document
Communication scientifique avec actes
Affiliation de l'auteur
IRSTEA AIX EN PROVENCE UR RECOVER FRA ; IRSTEA AIX EN PROVENCE UR RECOVER FRA ; IRSTEA AIX EN PROVENCE UR RECOVER FRA ; IRSTEA AIX EN PROVENCE UR RECOVER FRA ; IRSTEA AIX EN PROVENCE UR RECOVER FRA ; IRSTEA AIX EN PROVENCE UR RECOVER FRA ; IRSTEA AIX EN PROVENCE UR RECOVER FRA ; IRSTEA AIX EN PROVENCE UR RECOVER FRA
Résumé / Abstract
In WUI, the ornamental vegetation can be an efficient vector of fire propagation towards the housing. Assessing this vegetation flammability and ranking ornamental species accordingly can be a way to assess the fire risk in these areas. As both live and dead surface fuels are targeted in fire propagation (due to spot fire or radiant heat), the flammability of both types of fuel was assessed for each species, as well as, at larger scale, the fire propagation from the litter to the first branch. The objectives of this work were to show if the ranking of species varied from one type of fuel to the other, but also according to the fuel scale, from the finest (particle=live leaf) to intermediate (litter samples), and to larger scale (fire propagation from litter to branch). The flammability of the 15 main ornamental species used in WUI of SE France was assessed for these different fuel scales using a fire bench to burn the litter samples and to assess the fire propagation from litter to branch (tested on 4 species) while live leaves were burned on an epiradiator. In each case, the different species were ranked from the least flammable to the most flammable according to the flammability variables recorded during the burning experiments. Then, the different rankings were compared with one another. The comparison of rankings of species for live leaf and litter showed that the ranking did not vary for only two species (regardless of fuel type, Pittosporum tobira: least flammable species and Cotoneaster franchetti: most flammable species). However, for most species, the ranking varied; some species having litters more flammable than live leaves and some presented the opposite pattern. The fire propagation from the litter to the branch significantly varied according to species (Elaeagnus being the most flammable species and Pyracantha the least flammable species), even if, on the whole, fire propagated very well vertically and horizontally, consuming the branch almost completely. In this case, the ranking of species was the same as that of live leaves for Prunus (intermediate flammability), as that of litters for Pyracantha (low flammability) and Elaeagnus (high flammability) but was in between these rankings for Ligustrum (intermediate flammability). Ranking the ornamental species according to their flammability was not that simple especially because some species did not present the same flammability at different fuel scales. For each species, the flammability assessment should take into account the most severe ranking, along with the combustibility of the whole plant, in order to avoid an underestimation of fire risk.
ForestFire 2016: International conference on forest fires and WUI fires, 25/05/2016 - 27/05/2016, Aix-en-Provence, FRA