The Urban Heat Island in Louisville

The Project:

The Office of Sustainability and APCD applied for and received a $60,000 grant from the Funders’ Network for Smart Growth and Livable Communities and its partner, the Urban Sustainability Directors Network, to perform a comprehensive urban heat island study and heat mitigation plan. Two local private foundations matched this amount with a grant of $75,000. The heat management plan will identify zones in the city most suitable for implementing heat mitigation strategies such as tree planting, white and green roofs and cool paving materials that will decrease the urban heat island effect. The study also will establish the city’s urban heat baseline and will be used to inform city policy decisions and resource allocation. The study will be conducted by Dr. Stone of Georgia Institute of Technology and will be complete in Spring 2015.

Background Rationale for Project

In 2012, Dr. Brian Stone from Georgia Institute of Technology presented findings that Louisville is among the most rapidly warming cities in the country and is a significant Urban Heat Island (UHI). On July 10, 2010, more than 95 square miles in Louisville exhibited surface temperatures above 93.5 degrees Fahrenheit at 11:00am, which is prior to reaching the daily high temperature of 94 degrees Fahrenheit. In addition, more than five square miles exhibited surface temperatures in excess of 100 degrees Fahrenheit (the 99th percentile) in six hotspots, including the Ford Truck Plant, Ford Assembly Plant, Shelbyville Mall, the GE Appliance Park, the airport and a ½ square mile area of downtown. According to recent research, Louisville’s average temperature is increasing by approximately 0.5 degrees per decade and the urban heat island (UHI) effect in Louisville has increased more rapidly than any other US city since the 1960s. Excessive heat days are expected to triple over the next several decades, putting our at-risk residents – the very old, the very young, and the chronically ill – in grave danger and driving energy bills and pollution levels ever higher.

The reason behind this problem is relatively straightforward: dark, dense materials such as asphalt, concrete, brick, and metal get hot in the sun and stay hot at night. On hot, sunny summer days, roof and pavement surface temperatures can be 50–90°F hotter than the air, while shaded or moist surfaces—like those in more rural surroundings—remain close to the ambient air temperatures. Air temperatures in cities, particularly after sunset, can be as much as 22°F warmer than the air in neighboring, less developed regions. Dark asphalt and concrete absorb heat and tall buildings help trap it, and as cities expand, cooling vegetation is generally lost to buildings, roads, and parking lots.

Awareness of Louisville’s UHI problem and the primary prompt for the project at hand was Dr. Brian Stone, Associate Professor of City and Regional Planning at Georgia Tech and Director of the Institute’s Urban Climate Lab, 2012 presentation in Louisville. While in Louisville, Dr. Stone reported his preliminary findings about Louisville’s urban heat island and its potentially dire public health impacts. These findings, presented in context of a review of major US metropolitan areas, showed that Louisville is leading the nation in rapid growth of its urban heat island. The extent of Louisville’s UHI problem is a serious issue and, though we may lead the nation in UHI growth, we are committed to leading the way in mitigating the problem.

Project Goals/Purpose

Through a partnership between the Louisville Metro Government (LMG) Director of Sustainability, The Augusta Brown Holland Philanthropic Foundation, The Owsley Brown Charitable Foundation, and Brightside, a public/private partnership and 501(c)(3), we will engage Dr. Brian Stone, a distinguished researcher of the drivers of urban heat and its impact, to perform a comprehensive UHI assessment for Louisville Metro (the boundaries of the city are equal to that of Jefferson County since a merger of the city and county governments) and create an urban heat mitigation plan. As noted above, Dr. Brian Stone is particularly familiar with Louisville and has already spoken on this issue in community forums, including a presentation of preliminary research and recommendations to the Louisville Metro Tree Advisory Commission. Dr. Stone has carried out in-depth research on the UHI phenomenon, and has published papers and books on the subject, including how climate change is affecting cities at a more rapid pace than rural areas. Dr. Stone's urban climate work is supported through funding from the National Institutes of Health, the U.S. Environmental Protection Agency, and the U.S. Centers for Disease Control and Prevention, and has been featured in the last year by Louisville’s The Courier-Journal, National Public Radio, and the Washington Post.

Based on Dr. Stone’s specialized skills and national expertise, the grant application to the Local Sustainability Funders Network was written specifically to partner and contract with Dr. Stone to further refine his research in Louisville. By engaging Dr. Stone to develop the first comprehensive urban heat management plan in the country, we will be on the cutting edge of this type of analysis and able to use this valuable decision-making tool in our city planning efforts as well as in our partnership and grant project building efforts. This project will create a national model for UHI assessment that can be shared widely with other local governments.

The project will develop a comprehensive UHI assessment for Louisville Metro. The assessment data will be used to develop an urban heat mitigation plan. Included in the UHI assessment will be a surface temperature analysis at the most refined level possible (preferably at the city block level). This assessment will identify UHI “hotspots” so that resources can be strategically applied to have the most impact where relief is most needed. Preliminary analysis indicates that these areas are largely in the downtown district, and the west-to-southwest areas of the city. These are also areas that often face socio-economic challenges and, in many cases, environmental justice issues.

Additionally, the UHI assessment will include a surface materials inventory. By understanding what materials cover the land and comprise the buildings in those UHI hotspots, we will be able to identify the strategies that will have the most impact in that specific location. Further it will allow us to engage stakeholders with elements targeted specifically to those living in areas feeling the greatest urban heat impact.

Dr. Stone’s research also makes use of scenario modeling, the ability to model different strategies to analyze their likely outcomes and choose between them. For example, this assessment could reveal areas with potential for tree planting projects, one of the most effective UHI mitigation strategies. Through this project, we will also seek to build capacity for this modeling technique locally. This will include involvement and support from the Louisville Metro Air Pollution Control District and LOJIC – the Louisville/Jefferson County Information Consortium, a multi-agency effort to build and maintain a comprehensive Geographic Information System (GIS) that serves all of Louisville Metro.