Editorial on Special Issue on Wildland–Urban Interface (WUI) Fires

Abstract

Particularly sought after were studies that aim to bridge the gap between current building codes, standards, and regulations, and the latest scientific advancements in wildland fire and WUI fire research. In addition to posting on the website, the help of experts in this topical area was enlisted to help spread the word via social media channels.

In total, 25 papers were accepted as part of this special issue. Contributed papers came from all across the globe and included Algeria, Australia, Brazil, China, France, Germany, Japan, Poland, Norway, New Zealand, Spain, Sweden, and the United States of America. The global coverage of contributed papers demonstrated the growing nature of the WUI fire problem.

The first paper in the special issue discusses the efforts in ISO TC 92 Fire Safety to standardize a global approach to large outdoor fires, including WUI fires [1]. The paper highlights that although ISO TC92 has been around for several decades, there has only recently been a shift from fires that occur inside buildings to large outdoor fires.

In recent times, several devastating WUI fires have been initiated by powerline issues. Babrauskas presents a discussion on powerline clearance regulations and the relation to WUI fires in the United States of America [2]. In the paper, it is argued to improve powerline regulations in the future to help lessen the initial ignition risk from this type of infrastructure. Xu and co-workers also discuss complications with powerlines in WUI fires [3].

WUI fire damage assessments were reported from 2016 to 2023 in Norway by Mikalsen et al. [4]. It was found that the spring season and direct flame contact are the primary contributors to vegetation fires that damage buildings in Norway.

WUI fires have a significant impact on the ecosystem. In the paper by Liu and Zhou [5], a discussion is presented on the impact of local water ecosystems due to an increasing WUI fire threat in China. The results of their investigation suggest the need to improve understanding of the impacts of wildland fires on water and soil resources in China in the aftermath of these fires.

Elevated temperatures in the soil and radiant heat flux from WUI fires can be a threat to infrastructure. Wang and Zhou [6] provide a modeling discussion on radiant heat flux that a simulated wildland fire front would expose fuel tanks located in a WUI community. In many countries, propane gas tanks are stored above ground and there have been cases where WUI fire exposure has resulted in ruptures and secondary fires from these tanks. The work of Janssen [7] presented a simplified model to understand potential damage from water pipes located underground during WUI fire exposures.

Smoke and particulates emitted during WUI fire disasters are an important research topic because the pollutants may vary depending on the type of fuel, and these can also enter homes and are often responsible for severe health issues. In work from Martinent et al. [8], different local shrub species were combusted to provide information on the emissions of pollutants that homeowners would experience in WUI areas in France. It was reported that the type of shrub species has quite different combustion characteristics, and this influences the measured emissions. Another study by Piechnik et al. [9], smaller-sized vegetative samples from tree species and ground cover samples being combusted in a tube furnace. Results indicate that significantly higher concentrations of CO can be expected in the case of a coniferous forest fire compared with a fire in a deciduous forest in Germany.

As the vegetation is the fuel in wildland fires, its characterization and assessment of burning behavior provided insight in the development of and growth of wildland fires. Guillaume et al. [10] investigated the ignition and propagation of live vegetation to build a semi-empirical model. Cobian et al. [11] reported insights from bench scale experiments on effects of fuel structure and species on ignition. Similar insights are provided given by Krim et al. [12], Dias et al. [13], and Heydick et al. [14] into vegetation in Algeria, Brazil and Germany, respectively.

A method to rank flammability of ornamental vegetation is provided by Muñoz et al. [15]. The capability of ignition of vegetation by hot particles is investigated by Wang et al. [16]. Such studies are also related to the arcing of powerlines discussed above.

In WUI fires, once a wildland fire reaches a community, it is well known that structure to structure fire spread processes become important. Following many previous studies on this topic, Gorham et al. [17] investigated the response to a thermal exposure generated by a compartment fire with a single opening oriented towards the target. In the work of Tihay-Felicelli et al. [18], the combustion of ornamental vegetation also provides exposure to influence structure ignition in WUI fires, that various hedge types were studied. Finally, it is also important to quantify structures that have been damaged during WUI fire disasters, and the work of Kang et al. [19] discussed a method using deep learning methods using imagery obtained from aerial measurements.

Mitigating the ignition risks in WUI fires are of course very important. In this special issue, three studies considered these aspects. For homeowners to consider various mitigation strategies, Barrett and Quarles [20] discuss the costs of such measures. You et al. [21] investigated the use of inorganic solidified foam for forest fires. Dossi et al. [22] considered the use of sand protection measures to try to guard against firebrand accumulation processes in WUI fires.

There is no globally accepted definition as to what specifically constitutes the WUI, in terms of structure density. In the work of Elio Medina et al. [23], it is argued that an approach to define the term WUI in Northern Europe is required.

It is also important to compare and understand current WUI fire standards and codes. Hirschler [24] provided insights into a comparison between the WUI codes and standard from the International Code Council and the State of California. To also better assist future standards and codes, in a brief literature review by Penney et al. [25], it was argued that WUI fires require more engineered based approaches.

The authors declare no conflicts of interest.