Urban Heat in Roanoke, Virginia
Understanding the legacy of urban planning policies
Is it getting hotter out here?
Actually, yes.
Urban Heat Islands
Urban areas are often significantly warmer than surrounding rural areas. Cities replace natural land cover with buildings, pavement, and other surfaces that absorb and retain heat. This effect increases energy costs (for air conditioning), air pollution levels, and heat-related illness and mortality.
The Fourth National Climate Assessment identified extreme heat among the most serious threats to human health in urban areas across the United States.
A recent review of the human health impacts of heat concluded that “given projected changes in population, urbanization, and demography, heat will continue to be a substantial public health issue in the decades to come in both the developed and developing worlds.”
Health Effects and Risk Factors
Exposure to extreme heat is dangerous and can even be deadly. Rising temperatures can overwhelm the body’s capacity to cool itself, leading to heat exhaustion, cramping, fainting, and if left untreated, heat stroke.
Individuals with pre-existing conditions like heart disease and asthma are more at risk for heat-related illness. Additionally, babies and young people, seniors, and people who work or exercise outdoors are at higher risk.
A 2020 study showed increased frequency of emergency room visits during heat waves in Roanoke.
- Explore the Virginia Department of Health’s Heat-Related Illness (HRI) Dashboard to learn more about HRI in Virginia.
Social Vulnerability
Low-income and marginalized groups with lower capacity to prepare for and cope with extreme weather and climate-related events are the most affected by extreme heat. Factors like income, education, access to health care and housing can affect people’s ability to cope with climate hazards. These groups may be at more risk because:
They live in locations prone to extreme heat or that have aging infrastructure.
They have greater rates of existing medical conditions which can be worsened by heat.
They may have limited financial resources, or other cultural, language, or citizenship barriers.
Learn more about social vulnerability to climate change.
Because of these factors, adaptation actions for the most vulnerable populations should be prioritized.
The CDC/ATSDR Social
Vulnerability Index indicates the relative vulnerability of each
U.S. Census tract based on 2020 Census data. Social Vulnerability Index
(SVI) is based on 16 social factors, including unemployment, racial and
ethnic minority status, and disability, and further groups them into
four relative themes:
Socioeconomic status,
Household characteristics,
Racial & ethnic minority status, and
Housing type & transportation.
Each tract receives a ranking for each theme as well as an overall ranking. The vulnerability index is rated from zero to one, one being the most vulnerable.
Click on areas of the map to explore vulnerability status for each neighborhood.
As you can see, the neighborhoods that are the least relatively vulnerable are Downtown, South Roanoke, Greater Deyerle, and Grandin Court. Other neighborhoods are more at risk including Gainsboro/Washington Park and Mountain View/Hurt Park/West End.
History of Redlining in Roanoke, VA
Past disinvestment and discrimination shaped the modern urban landscape and created disparities in health outcomes.
Like many cities, Roanoke, Virginia bears the legacy of inequitable land use regulation including the practice of redlining in the 1930s.
Redlining refers to the federal government’s practice of rating neighborhoods to help mortgage lenders determine which areas of a city were considered risky for investment.
The federal Home Owners’ Loan Corporation (HOLC) made maps that rated neighborhoods. “Hazardous” classifications were given to low-income neighborhoods disproportionately occupied by Black families. These practices limited Black families to a small area of the city and constrained their ability to build wealth through home equity.
In 1949, The Federal Housing Act, disguised as a way to help low-income communities, paved the way for the removal of low-income minority communities.
Urban Renewal projects in Roanoke cleared “Blighted” areas in the northeast and northwest to make way for Interstate 581, the Civic Center, Post Office, and Coca-Cola plant, and other commercial and industrial uses.
(Source: Martha Park)
The government paid residents an average of $3,000 for their homes and promised that better homes would replace the ones that were cleared.
That promise was broken.
The insidious results of these policies linger today, including gaps in wealth and educational attainment, income, and health outcomes. What’s more, previously redlined areas are more likely to be hotter than their wealthier neighbors. Those poorer areas are disproportionately communities of color. Read more about redlining in Roanoke.
The map below shows the grades that the Home Owners’ Loan Corporation (HOLC) gave each area of the city. Neighborhoods were classified into four categories. “A” and “B” areas were the most attractive neighborhoods for refinancing, while “C” areas were deemed “transition zones” in decline and “D” areas in “full decline”. Race was the predominant factor in determining a neighborhood’s grade. White neighborhoods were nearly always classified A or B, while Black neighborhoods were classified D. Click on areas of the map to explore.
Looking at Urban Heat in Roanoke
In August 2020, Roanoke was one of 13 cities in a national study of the urban heat island effect. Citizen scientists collected temperature and humidity data across the city to assess where urban heat has the largest effect.
- Learn about Roanoke’s Heat Island Mapping here.
However, this data was collected shortly after a rainstorm occurred, so the data doesn’t look quite how we would expect…
Notice how areas close to the center of the city are cooler while areas to the south including Mill Mountain Park are much hotter. We would expect the opposite.
We can use land surface temperature data to get a picture of what’s really going on.
Many parts of Roanoke have excessive impervious surface that traps
and reflects heat and causes stormwater pollution and flooding in
addition to increased temperatures. These impacts will increase as
temperatures rise and weather patterns change. Understanding the
prevalence of the urban heat island effect at a more granular scale can
help to prioritize mitigation efforts within the city.
This map shows that areas surrounding Downtown are hotter than neighborhoods further outside of the urban ring. Parks and other areas of greenspace can cool an area down. Places like Mill Mountain Park are cooler than areas like Downtown that have more impervious surface.
The map below shows average temperature in each neighborhood and the overall social vulnerability index score (indicated by the blue dots). Click on the map to explore each area.
When we analyze social vulnerability and urban heat, we can see that the social vulnerability indicator for housing type and transportation (SVI Theme 4) is most closely correlated with mean temperature.
