Mapping green spaces’ effect on heat islands, flash flooding

Mapping green spaces’ effect on heat islands, flash flooding

A mapping tool developed by the Environmental Protection Agency is illustrating climate injustice in low-income neighborhoods.

The non-profit Trust for Public Land is using EJSCREEN, the EPA’s mapping and screening tool to identify areas affected by the “urban heat island effect,” which makes cities hotter. Pavement and man-built materials absorb and and re-radiate heat, raising local temperatures by as much as five degrees Fahrenheit during the day and 22 degrees at night, according to an EPA report.

Trees can mitigate some of the heat island effect, but the availability of tree canopies and green infrastructure that naturally reduce urban heat islands “strongly correlate” with income, meaning these types of coverage are usually found in wealthier neighborhoods, according to a blog post by Jad Daley, director of the Climate-Smart Cities Program.

To locate heat islands and areas with low green infrastructure, Daley turned to EJSCREEN, the EPA’s web-based tool that blends environmental data from the EPA and demographic data from the Census Bureau to identify those locations where insufficient tree canopies overlap with the most vulnerable populations.

Daley also looks for correlation between a high rate of flash flooding in urban areas and insufficient green space, which can lead to basement flooding.

“If we see where these problems of heat islands and water management overlap, then we can develop green infrastructure solutions like green alleys that are designed to address both issues,” Daley wrote.

The Trust for Public Land uses GIS mapping and EPA tools to graphically illustrate environmental justice issues in at-risk neighborhoods for policy makers and help them see where making the proper investments can address urban heat islands and flash flooding.

According to Daley, the Trust for Public Land’s work on climate justice issues has gotten attention from city agencies in Boston, New Orleans and Chattanooga, Tenn.  

About the Author

Amanda Ziadeh is a former reporter/producer for GCN.


  • business meeting (Monkey Business Images/

    Civic tech volunteers help states with legacy systems

    As COVID-19 exposed vulnerabilities in state and local government IT systems, the newly formed U.S. Digital Response stepped in to help. Its successes offer insight into existing barriers and the future of the civic tech movement.

  • data analytics (

    More visible data helps drive DOD decision-making

    CDOs in the Defense Department are opening up their data to take advantage of artificial intelligence and machine learning tools that help surface insights and improve decision-making.

Stay Connected