WPI Experts Weigh in on Tragic Wildfires

Albert Simeoni  Michael Ahern Mimi Sheller James Urban  

Why do wildfires destroy some structures, while some things remain standing? 

Simeoni: Communities include very different types of potential fuel for a wildfire. For example, in residential neighborhoods you'll find cars, houses, fences, sheds, and mulch, along with vegetation, which can be either natural and likely dry, or landscaped and regularly watered and thus moist. When a wildfire reaches the first houses, it can ignite them and from this point, it is a very different kind of fire spread. The fire will spread through communities and the first houses burning release a lot of embers, called firebrands, which fly forward with the wind and land on the roofs of other houses, fences, and mulch, and they spread the fire in a discontinuous way. When firebrands land on dry vegetation (pine needle beds on the ground), they can ignite it but when they land on green foliage, it doesn’t happen. Green ornamental vegetation is usually cleaned and has grass below it, instead of more fuel for the flames. Most trees burn because there are flames below them, which dry and heat up their foliage. 

How can electrical wires and infrastructure spark wildfires? 

Urban: Powerlines and related infrastructure can spark wildfires in several ways. Research of past fires has shown that powerline-involved wildfires occur more frequently during dry weather and high winds. Wildfires can be ignited when dry vegetation contacts live wires. Also, high temperatures can cause the powerlines to sag, and high winds can cause them to “slap,” a scenario in which uninsulated lines come into contact with each other, causing a rapid discharge of electricity. This discharge causes rapid localized heating, which can melt the conductors and even locally vaporize, ejecting hot metal particles or globules of molten metal onto the ground or flammable materials below. 

How do investigators try to determine the point of origin and cause of a wildfire? 

Urban: Post-fire investigations can be complicated, because there is always the risk that the fire has damaged or destroyed evidence. However, when a fire is first ignited, it is not initially at the same intensity and scale: in some powerline-involved fires, for example, a fire might start off very small before quickly growing. As a result, near the origin, fire damage might be different compared to other areas impacted when the fire is much larger. If conductors are suspected, investigators will likely inspect nearby utility equipment for evidence of tree or vegetation interactions, line slapping, or other damage. Parts of this infrastructure will likely survive the fire. Surveillance video footage, along with data from the power company, may also be used.

Why are unmanaged grasslands so susceptible to fire and fire spread?

Urban: Fine fuels—small twigs, leaves, needles, grasses, and other small-diameter material—ignite very easily and quickly compared to larger fuels. If the grass isn’t managed, it may grow long, and a significant portion may be dead and will dry out in a drought, leading to a high fuel load. The higher fuel loading of fine fuel typically causes longer flame lengths, which can support faster fire spread. Grass that is mowed is typically greener, wetter, and closer to the ground, which makes it harder to ignite. 

Simeoni: A lot of grass in Maui is old cane sugar fields with non-native grass. In the summer it gets cured and very dry. So, basically, you had all the conditions—the fuel, the heat, the wind and the ignition sources—to create a catastrophe.

Sheller: Any island that has been exploited for plantation agriculture has been transformed in ways that leave it more vulnerable to climate-related disasters today—through the clearing of forests, eradication of native species, introduction of invasive species, and other changes to the land that lead to desiccation (such as damming streams). It has been known since the 18th century that small islands that had tree cover removed had less cloud formation and therefore less rainfall. Colonialism also created unequal economic conditions between native Hawaiians and wealthy visitors and buyers that concentrated the service-sector labor force in “affordable” areas that are often the most vulnerable to disasters.

What can communities do to better protect buildings against wildfire risk? 

Urban: There are a variety of newer construction methods and materials that have become commercially available that can help. However, one of the most achievable ways to fire-proof buildings is to reduce the fuel loading near the building exterior (ornamental vegetation, sheds, outdoor furniture, etc.).

What critical infrastructure improvements need to be examined in Maui and other susceptible areas? 

Ahern: The wildfires in California and Maui have underscored the need to enhance the resilience of power systems. Additional vegetation management around power infrastructure, faster protection system trip settings, greater use of (partially insulated) tree wire, and aerial cables would all reduce the risk of sparking wildfires. These infrastructure investments would also boost reliability.  

In the near term, public safety emergency response protocols could mitigate the risk of such incidents but at a cost to reliability. This approach would mean that utilities would de-energize the power system in dry, windy areas that are susceptible to wildfires. This has already been implemented in parts of California.

Lahaina’s economy has been ravaged. Does this increase the likelihood of a mass migration? 

Sheller: People without livelihoods will likely be displaced to anywhere they can find places to live and work. It is crucial to protect against this by creating opportunities in Maui. Sustainable tourism could be one way to help in this effort. There should be programs to rebuild locally owned businesses that operate sustainably, local farming, and construction of affordable housing.

How should tourism be considered in the disaster recovery? 

Sheller:  The disaster recovery raises important issues around the tension between tourism and other local economic activity: the high costs of housing and land developed for tourism and second-home owners, concentration of water rights in private developments that serve tourist resorts and golf courses and prevent local farming, and, more generally, the over-dependence of the economy on tourism.  The question is how to re-build sustainable tourism rather than extractive tourism.