Large areas of southern California have turned to ash and smoke in the blazing fires— one of the most destructive ones in the state’s history. These fires are different from wildfires, which spread across shrublands and forests and burn them down. In contrast, urban fires spread across by burning through buildings, becoming the fuel to the fires. Areas of Los Angeles caught fire and went up into smoke after many houses caught fire.
According to Ann Jeffers, a structural engineer and fire expert at the University of Michigan in Ann Arbor, the wilderness fires spread into urban areas, leading to an urban conflagration. 12,000 structures have been destroyed, and at least 24 people have been killed in the fires. The alarming rate at which urban fires are becoming common due to climate change is enormous. Scientists have just figured out how these urban fires are spreading across large areas and what could be done to prevent them.
What is causing the urban fires?
There are many causes behind urban fires, but one phenomenon that has caught the eye of many scientists is hydroclimate whiplash— a sudden switch between dry and wet conditions, a phenomenon likely to rise as the temperature of the Earth goes up. The Los Angeles area received eerily large amounts of rain in 2023 and early 2024, which supported plant growth. However, less than 1 millimeter has fallen since 1 July, and all grass and bush dried into tinder.
The other reason is directly connected to the large number of homes across the steep terrains of Los Angeles and the possible “fanning” of the fires by strong winds. These reasons increased the intensity of the wildfire. Human decisions are intervening in these meteorological factors, and more and more people are moving into the interface between wilderness and urban areas. According to scientists, fires that start in these interfaces leak and spread into purely urban areas, causing massive devastation. Examples of such fires are widespread, from Lahaina, Hawaii, to Chile’s Valparaíso. As the population density grows within these boundaries, the risk of fire spilling into urban areas will rise.
How do urban fires behave?
Urban fires spread in different ways, which researchers have just started to understand by simulating such conditions in reality and on computers.
One research frontier conducted by the Tampa, Florida-based Insurance Institute for Business & Home Safety is trying to understand how radiant heat (heat from one place to another in the form of electromagnetic waves) can spread fire from one building into a nearby building. In their experiment, the researchers are showering embers and walls of fire to understand under what conditions a building may burn. One of their first conclusions is the space between two buildings to prevent fire from spreading in a domino-style cascade.
A research team at Berkeley has chosen to use a computer simulation of urban fires. The model tests how flying embers and radiant heat energy combined to spread urban fires in California in 2017. Jeffers’ model works in a similar area, trying to figure out how embers travel in the wind and bounce off to form a pile.
How to build houses resilient to urban fires?
In a recent study of wildfires in California and Portugal, Guillermo Rein, a fire scientist at Imperial College London, and his colleagues emphasized various small measures to prevent urban fires from setting buildings and structures alight. For example, covering the vents with screens can prevent embers from causing a fire, and metal roofs can be used instead of flammable ones. The roof geometry can also be switched to prevent embers from getting trapped. In California, buildings and structures made post-2008 are primarily made of fire-resistant material, owing to statewide regulations. As per a study, these regulations have made the homes 40% more fire-resistant. However, many homes in Los Angeles predate those regulations.
A rebuilding effort is currently in place, but different scenarios can complicate the situation at hand, says Jeffers. However, on the hopeful side, multiple strategies are in place to mitigate these issues.
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