Climate change increases the frequency and intensity of weather extremes throughout the United States, such as heat waves and heavy rainfall
In late September of this year, New York City experienced flash flooding that inundated neighbourhood streets and subway stairways. This event resulted in cancelled flights, closed roads, and city officials advising residents to stay home or seek shelter. Some areas of the city received up to 2.58 inches of rain in a single day, nearly 50% beyond the capacity of the city’s sewer system, causing wastewater issues for numerous low-lying homes and businesses.
Urban design features
Common intuition suggests that in the face of an extreme weather event, a city with a larger population will have more affected individuals. 83% of the U.S. population lives in urban areas, which is expected to rise in the coming decades, emphasising the crucial importance of urban climate resilience.
It’s important to note that cities are products of human design and construction. Therefore, while certain approaches to land development may heighten population vulnerability to extreme weather, others might mitigate or even reduce these vulnerabilities as the climate evolves in the decades ahead.
Urban growth
Looking into this concept, Jing Gao, a researcher at the University of Delaware and assistant professor in the College of Earth, Ocean, and Environment, along with her colleague Melissa Bukovsky, an associate professor in the Haub School of Environment and Natural Resources at the University of Wyoming, examined the impact of future changes in urban land and population on exposures to weather extremes under the end of the 21st-century climate conditions.
The study encompassed urban areas throughout the United States, looking at cities of various sizes, development densities, and climate regions. Utilising a data-driven model developed by Gao, the researchers projected the growth of urban areas across the country by 2100 based on observed development patterns over the past four decades.
The research team assessed how these anticipated changes in urban land might influence weather extremes such as heat waves, cold waves, heavy rainfall, and severe thunderstorms. They examined the potential population exposures to these extremes under different climate and urban development scenarios envisioned for the close of the century.
Insights for a changing climate
The simulations conducted by the research team indicated that by the close of the 21st century, a city’s spatial arrangement or urban land pattern could diminish population vulnerabilities to forthcoming weather extremes, including heatwaves, even in scenarios of extensive urban expansion. The design of the urban landscape, encompassing factors like the clustering or dispersion of buildings and their integration with the surrounding environment, is more influential than the size of a city. This holds even as climate change contributes to heightened population exposures.
These findings apply to all cities, from large metropolitan areas like New York City to smaller towns in more rural contexts, such as Newark, Delaware.
“Regardless of the size of a city, well-planned urban land patterns can reduce population exposures to weather extremes,” Gao said.
“In other words, cities large and small can reduce their risks caused by weather extremes by better arranging their land developments.”
From research to action
The researchers are working to pinpoint specific features in a city that can enhance or diminish its resilience to future weather extremes. Identifying these patterns can guide more sustainable development in the face of increasing extreme weather events.
The goal is to offer practical recommendations for designing urban areas that reduce residents’ exposure to weather extremes in the long term.
The researchers note that these characteristics will likely vary between regions, currently and as the climate changes. What’s effective in arid Phoenix, Arizona, may differ from strategies suitable for humid New Orleans, Louisiana. Additionally, what works for a city today may need adjustments in the future as climate conditions evolve.
