Apr 16, 2024 - Climate

How Raleigh is working to reduce urban heat islands

heat islands in Raleigh

A graphic rendering of downtown Raleigh's heat islands. Photo: Courtesy of ESRI

Raleigh is using digital maps to guide city efforts of remediating its heat islands — many of them in the city's lowest-income neighborhoods.

Why it matters: Heat islands — wherein heat is trapped by heat-absorbing surfaces and structures — can make cities less livable and increase the risk of heat-related health complications, Axios' Alex Fitzpatrick previously reported.

  • In Raleigh, nearly a quarter of residents live in neighborhoods where summer temperatures climb much higher than the city's average due to the urban heat island effect, Axios reported last year.

Between the lines: Low-income neighborhoods tend to be more vulnerable to heat islands — especially as cities locally have a history of planting more shade-giving trees in richer neighborhoods.

Driving the news: Raleigh is using software from a firm called Esri to map and pinpoint which parts of the city are experiencing the hottest heat island effects, down to the street block level, James Alberque, Raleigh's GIS and emerging technology manager, told Axios.

  • Raleigh uses federal grants from the National Oceanic and Atmospheric Administration and Inflation Reduction Act to fund the city's digital mapping and heat remediation efforts. At the same time, it is studying which neighborhoods have a large amount of impervious surfaces, making stormwater runoff worse.
  • Durham, likewise, received a grant from NOAA to map its heat islands.

Zoom in: Using data from its mapping of the city, Raleigh has launched several pilots to address heat islands in areas like Southeast Raleigh, Alberque said.

One is called the Street Tree Equity Project, which used the Esri mapping tools to determine where street tree distribution was most unequal.

  • It found that neighborhoods in Southeast Raleigh had one street tree every 1,000 feet, while newer parts of the city had them every 4o feet.
  • The pilot began planting street trees in this area last year, with 350 trees planted in January of 2023, and 350 planted this past January. Next January, 350 more are planned.

The city is also piloting using more reflective road paint, made of titanium dioxide, in areas with heat islands.

  • The city is currently studying how effective the paint is, Alberque said, but previous studies have shown it can cool summertime road temperatures by 5 to 20 degrees Fahrenheit.
  • The streets where asphalt rejuvenation has been paired with titanium dioxide application include Noble Creek Lane, Benton Ridge Drive and Paschall Court, per Alberque.

What they're saying: "Heat affects people in the city differently based on where they are, their experiences and their access to resources," Alberque said.

  • "We are trying to address this through both a physical infrastructure perspective, but also a general socio-economic equity perspective," he added.
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