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Researchers Map Portland's Hottest, Most Polluted Places

Cassandra Profita

When it's hot outside, city neighborhoods with lots of pavement get hotter and more polluted than the ones with more greenery. It's called the urban heat island effect. And as the summers in the Northwest get hotter with climate change, these hot spots pose a growing risk to human health.In Portland, researchers are mapping the city's hottest, dirtiest places, and looking for ways to cool them down.

(Sound of driving with turning signal)

Shandas: "Take this one? Right?"
Voekel: "Ah, that should take us to the airport right?"

It’s the middle of a heat wave, and Portland State University researchers Vivek Shandas and Jackson Voekel are driving across the city of Portland with a thermometer sticking out the window. It's connected to a GPS unit inside the car. Together, they're logging the temperature and location every second as the car moves through city streets. As they drive by the airport, Shandas notes lots of asphalt and a near total lack of trees.

Shandas: "This is one of the hottest places in the city."

These traverses are telling researchers something the Weather Channel can't. They're tracking the temperature differences from one block to the next at the street level where people actually feel the heat. In a heat wave, he says, he's found a 15-degree difference between places like the airport and a forested park.

Shandas: "And that can be the difference between a person's well-being in one part of the city and really quite fatal in other parts of the city depending on where you are."

Shandas uses this temperature data to map out which neighborhoods are hotter than others. Then looks at the amount of pavement, buildings and trees on the surrounding landscape to explain why.

Tim Lynch is a policy analyst for Multnomah County. He says the geography of heat waves will become more important to life in Northwest cities as climate change drives up summer temperatures.

Lynch: "So, the whole city, the whole county, the whole region will experience greater than average heat, but these areas that have urban heat island effect will experience even hotter temperatures than the rest of the city."

Credit Portland State University
A map of Portland's urban heat islands, the parts of the city that see hotter temperatures in heat waves.

The heat itself poses health risks for people in these areas, he says. But it also generates more air pollution – a double whammy for human health.

Lynch: "Climate change and the urban heat island effect are really going to compound a lot of the issues we face already."

Kari Lyons Eubanks with the Multnomah County Health Department is developing strategies to help sick and elderly people to stay cool and healthy during extreme heat events. She says the early heat waves this summer have put the county's climate change planning to the test.

Lyons Eubanks: "Here we are. We are in the changes. But I think the hotter, drier summers have come more consistently and have come quicker than maybe we had originally thought. We really are in the phase of what does it mean to adapt to this?"

Back at his office at Portland State University, Shandas shows me the result of his traverses across the city. It's a map of all the data he's collected about neighborhood temperatures. The hotter areas with lots of pavement like the airport are blazing red while the tree-lined parks are colored a cool blue.

Shandas: "So what we're looking at is basically a county-level map of the urban heat islands in the city of Portland."

But he didn't stop there. On top of that map, he's added census data about who lives where. This, he hopes, will help cities adapt to hotter summers. He clicks several boxes to find out which of the hottest neighborhoods have a large population of older adults with poor health conditions and no air conditioning.

Shandas: "We can identify specific areas that might be most vulnerable to these heat waves."

This information could be very useful to city planners, according to Michelle Kunec-North. She works with the Portland's Bureau of Planning and Sustainability. She says this new mapping program could eventually help the city redesign the hotter neighborhoods so they stay cooler during summer heat waves.

Kunich North: "Thinking about where can we invest in bioswales or tree planting and preservation, looking at de-paving or reducing impervious surfaces like asphalt that can absorb and radiate heat."

When it's hot, many city-dwellers will go to a more natural place with trees and water to cool off, she says. Not everyone has that opportunity. But by removing pavement and adding shade and greenery, it might be possible to make the city a more natural place.

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