Urban Sprawl is Making Extreme Weather Events even more Extreme (Credit: Science Daily)

Credit: The Pink Armadillo

​It is likely 2018 will go down as a year of many weather extremes. These weather extremes came in a variety of forms, from life-threatening wildfires to powerful hurricanes. Hurricane Michael, a Category 4 storm at its peak, unleashed several billion dollar’s worth of damage on the Florida Panhandle and southwest Georgia. Wildfires in the West have wiped entire towns off the map. While it is easy to blame the likelihood and magnitude of these events on the changing climate, it is also important to note how humans, via urbanization, have made these events and ones like them even more extreme.

The notion of urban sprawl affecting climate change was highlighted most recently in a study published in the journal Nature. The study, coined “Urbanization exacerbated the rainfall and flooding caused by Hurricane Harvey in Houston”, used models to recreate Houston without urbanization, and compared pre-urbanized Houston’s rainfall with modern-day Houston’s rainfall. According to the study, the flood risk in Houston was made 21 times more extreme by urbanization.

The researchers who conducted the study found that Houston’s newfound urban sprawl led to more sidewalks, paved roads, and developments, all of which limited the amount of floodwater that was absorbed into the ground. This issue is not unique to Houston, and is likely affecting other flood-prone cities along the Gulf Coast and the Eastern Seaboard. Increased flooding is induced by increased rainfall, which was found in the study to be exacerbated by Houston’s skyscrapers. Gabriele Villarini, a University of Iowa researcher who led the study, told ScienceDaily that friction was created by high winds “buffeting” tall buildings, which led to a “drag effect” that was key for carrying heat higher into the atmosphere. This further amplified rainfall, indicating a correlation between Houston’s urban landscape and the magnitude of hurricane rainfall. Since the study looked solely at Harvey’s effect on Houston, it is important not to attribute every city’s extreme rainfall to the aforementioned causes. Every extreme weather event, and every city, is different. However, this study provided thought-provoking insight into how human development is affecting climate change, and the adaptation and mitigation that needs to take place in the wake of events like Harvey.

The notions of mitigation and adaptation are extremely relevant now, especially as wildfires wreak havoc in California. The Camp Fire in Butte County, California was roughly 55% contained as of the morning of November 17th. According to Cal Fire, the fire has burned nearly 150,000 acres, just 150 miles northeast of the Bay Area. Cities like San Francisco and Oakland recently reported some of the worst air quality in the world, with Oakland, a city of over 400,000 residents, having an Air Quality Index (AQI) of 225 micrograms of particular matter (PM) on November 17th, which is considered “Very Unhealthy” by the EPA’s standards. Under this classification, the most sensitive groups of people (the elderly, the physically ill, and young children) should remain indoors and most others should avoid any physical outdoor activity.

In the case of California, pollution was already an issue. According to the American Lung Association, 7 of the country’s 10 most polluted cities in terms of particulate pollution are in California. The wildfires may just have made it worse, with much of the particles consisting of not just carbon molecules from trees but likely from other vegetation and the burning of infrastructure as well. Researchers at the University of California, Berkeley, say that AQI’s of between 200 and 470, which is what has been reported recently in the Bay area, are the equivalent of smoking 10 cigarettes a day.
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The extreme weather that Houston and Oakland have experienced could be attributed to climate change. Continuous development of urban areas will only compound the issues. It is important to find a solution to these issues, and as quickly as possible. Some research points to the important role that trees play in regulating the environment, and how urban trees may be able to mitigate disaster. A mature tree can absorb upwards of 150kg of Carbon Dioxide per year. The proper placement of trees around buildings (land management) can also lead to more efficient energy usage by reducing the need for air conditioning and heat. While baby steps, if all cities can adopt at least some measures like these, climate-change related issues will be less amplified within cities in the decades to come. 

For more on the effects of climate change, click here!

©2018 Weather Forecaster Jacob Dolinger