This indicator measures the percentage of land covered by surfaces that do not allow water to soak into the soil and can contribute to the heat island effect. For more information, see: The California Department of Public Health’s California Building Resilience Against Climate Effects (CalBRACE) Impervious Surfaces Narrative.

Our homes, neighborhoods and workplaces should help protect us from climate-related health threats, like heat waves and flooding. Impervious surfaces are materials that do not allow water to soak into the soil. For example, buildings, pavement, and concrete are impervious surfaces. Areas covered by these surfaces can impact health by capturing heat in what is known as the “heat-island effect”, intensifying the dangers of extreme heat events. Communities of color and low-income communities tend to be disproportionately exposed to the heat-island effect. By preventing the absorption of water, impervious surfaces can make flooding events worse, transport pollutants and reduce water quality, intensify the impacts of drought by preventing groundwater sources from being refreshed, and reduce water quality and availability.^{136, 137}

Addressing the health impacts of Impervious Surfaces requires a range of measures designed to prepare communities and households for climate events such as extreme heat, flooding and storm water surges, to increase resilience.⁶⁹

Plan for Resilience

Assess Vulnerabilities

Legislation enacted in 2015 (SB 379) requires California jurisdictions to conduct vulnerability assessments and define resiliency goals, policies, and objectives in either the safety element of their General Plan, or by incorporating it in local hazard mitigation planning. Local jurisdictions can reduce the health impacts of extreme heat by using these planning processes to understand likely climate changes and impacts, assess vulnerability, and craft interventions. The State of California has developed the Adaptation Planning Guide, a step-by-step guide for local governments, and the U.S. Centers for Disease Control and Prevention’s Building Resilience Against Climate Effects (BRACE) Framework offers guidance for health agencies and others seeking to address the health effects of climate change.

Assessing vulnerability to climate impacts is a particularly important step in resilience planning. While climate change impacts all Californians, some individuals and families are more impacted, and have fewer resources to draw upon to help them adapt. The health impacts of climate change often deepen existing social inequities—magnifying or layering new risks on top of economic, social, environmental, biological, and health disparities. Using the BRACE framework, the California Department of Public Health has produced Climate Change and Health Profile Reports, summarizing health risks and vulnerability by county. They have also published Climate Change and Health Vulnerability Indicators to help local jurisdictions understand climate change and health vulnerability. The Healthy Places Index can also be used to assess underlying social vulnerabilities at the census tract level.

Maximize Health Benefits

Actions designed to improve climate resilience also provide the opportunity to maximize additional health or quality of life benefits that can be achieved in addition to increased resilience. Adaptation measures designed to address impervious surfaces create several opportunities for additional benefits. For instance, urban greening can simultaneously address storm water surges and mitigate the heat-island effect. Urban greening can also provide opportunities for active transportation, support “soft” armoring strategies for sea level rise, create spaces to grow and learn about healthy food, and provide job opportunities in communities with high rates of unemployment. Local governments should prioritize interventions that minimize risk in low-income communities or communities of color, while maximizing benefits that meet support healthier community conditions.

Ensure Participation

Resilience efforts should prioritize the participation of community members in each step of the process. This will help ensure that community standards, expectations and requirements are effectively addressed, while building buy-in and support for resilience measures, and improving community capacity to envision and address climate impacts. For more information, see: The California Department of Public Health’s Climate Action for Health, and the Urban Sustainability Directors Network’s Equitable, Community Driven Climate Preparedness Planning.

Policy Actions

In the short term, communities with a high percentage of impervious surfaces should make sure they are Getting Ready, by reviewing and improving emergency response plans and systems to warn and protect residents during extreme heat events. When heat events strike, effective and targeted Emergency Response systems should be in place. Jurisdictions can also help their residents become Heat Resilient Households through home weatherization, air conditioning, education, and other programs.

In the longer term, governments should work to decrease these impervious surfaces by creating Green Communities that provide shade, mitigate heat-island effect, and manage storm water runoff, and pursuing Smart Growth strategies to limit future impervious surfaces. Where Impervious Surfaces are combined with Extreme Heat, local governments should also work to limit heat-island effect and prepare for heat events. They can create Cool Communities by prioritizing cool infrastructure and recreation facilities. Finally, local governments should help foster Community Power and Connection which has been shown to reduce social vulnerability and lessen the health impacts of climate events.

Although climate resilience actions tend to save money in the long term, some come with a high immediate cost. Several funding sources and technical assistance programs can support local government efforts to improve resilience. For more information, see: The U.S. Climate Resilience Toolkit’s Funding Opportunities Page, and the Federal Emergency Management Agency‘s Hazard Mitigation Grant Program.