A new tool is helping the Twin Cities metro area brace for climate change impacts

Minneapolis Powderhorn Lake in its namesake park
Minneapolis' Powderhorn Lake sits in its namesake park on the city's south side.
Minneapolis Park Board

During a heat wave July 22, 2016, the land surface temperature on the southern shore of Minneapolis' Powderhorn Lake ranged from 83.2 degrees to 88.65 degrees.

Up a grassy hillside and one block west out of lake's namesake park, it got much hotter that summer day. The corner of 34th and Elliot avenues, some two and a half blocks away, the ground temps were between 99.57 degrees and 125.21 degrees.

Temperature and rainfall are the two biggest climate change indicators in Minnesota. As the state continues getting hotter and having more heavy rain events, cities need as much detail as they can get regarding how every little piece of land will respond to extreme heat and flooding.

To give the Twin Cities metro area a start, the Metropolitan Council has released a tool it's calling the Climate Vulnerability Assessment. Essentially, it's detailed maps showing how at-risk different spots are to flooding and extreme heat.

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Studying how vulnerable cities are to climate change is a "dollars and cents issue," said Met Council senior planner Eric Wojchik. Many cities are already feeling the effects of the warmer, wetter world.

"They are seeing impacts on their assets, impacts on their infrastructure," Wojchik said. "It is becoming more and more of an issue as cities plan for their future."

Making heat islands cool

Summer heat waves are going to get more frequent in the future, and the urban heat island effect makes things worse in cities.

The Met Council notes that paved areas hold heat longer than natural surfaces, buildings block wind from cooling the hot air, and cars and other machines create heat of their own.

So, as cities explore ways to mitigate the heat island effect, they need to know where the hot spots are.

This screenshot shows the tool's detailed heat map.
This screenshot shows the Met Council tool's detailed heat map.
Screenshot via Met Council

The Met Council's heat data come from a land surface temperature snapshot taken during the July 22, 2016 heatwave.

The Met Council's thinking is once cities see where their hot spots are, they can plan out where to make changes like planting more trees for shade cover for or changing how the land is used.

Where to target flood risk

Much stormwater infrastructure in Minnesota is old and small.

"We've actually built our infrastructure for a historic climate that doesn't exist anymore," Wojchik said. "Most of our infrastructure was designed and built based off, really, precipitation measures from the 1970s."

Certain places in cities are more likely to see localized flooding, the Met Council says.

Its flooding information is based on topographical data from LiDAR, a remote sensing program. Essentially, it's showing low-lying places, Wojchik said. "Think of it as a terrain analysis."

Once cities find their most at-risk spots, they can consider adding rain gardens or making infrastructure improvements. Or, Wojchik said, a solution can be something as simple as making sure storm drains are clear in flood-prone areas.

As the climate gets wetter, flooding is happening in places where it never had before. Knowing the most flood-prone spots, the Met Council hopes, will help cities make the best prevention decisions for the future.

The Met Council tool, Wojchik said, is "sort of like having a map for where we've been but not exactly knowing where we're going.

"So the best thing you can do is really provide some measure to try to figure out how to get to our future."

This article is based on an interview from Climate Cast, the MPR News show on the latest news and research on our changing climate.