5.0 Climate Change Effects

Sidebar 5-2: Case Study on the Puget Sound Regional Council Interactive Regional Hazards Map

The Puget Sound Regional Council (PSRC) has developed an interactive hazards map to show which areas of King, Kitsap, Pierce, and Snohomish counties are vulnerable to various hazards, including many climate change effects (Figure 5‑4). This tool could be used during project screening and scoping to identify potential areas of vulnerability to climate change effects.

5.3 Tools and Methods for Project-Level Assessment of Climate Change Effects

Project-level assessment of climate change effects most often focuses on the vulnerability of the project to climate change (e.g., potential for damage or disruption due to flooding, storm surge, or extreme heat). Climate change effects also include a project’s potential impact on the human and natural environments, which may be exacerbated due to the effects of climate change on the environment.

An asset’s vulnerability to climate change effects is a function of its exposure, sensitivity, and adaptive capacity.

Different levels of assessment may be warranted based on the proposed project’s vulnerability to particular climate change effects. For some projects, such as those advanced through the environmental process under a CE, limited levels of exposure may not suggest the need for a project-level assessment.

A few states have developed guidance to support a vulnerability and resilience assessment at the project level. An example from Washington State is shown in Sidebar 5-3:

The WSDOT guidance explains how climate and extreme weather preparedness are considered in all program areas. Even in cases where a programmatic assessment has been completed, project sponsors may choose to complete a project-level assessment where the level of exposure to climate-related threats and hazards is expected to rise, or consequences of failure are particularly high. FHWA’s synthesis of recommendations and approaches in the Synthesis of Approaches for Addressing Resilience in Project Development (FHWA 2017a) highlights a challenge with using historical data to assess future impacts: namely, historical data may no longer be relied upon to accurately describe future changes over the life of the transportation asset. Figure 5‑5 shows a decision-making framework that can inform when project planners may choose to perform a project-level assessment of a proposed project. This framework was developed considering precipitation, sea level, storm surge, heat, drought, and wildfire. The synthesis addresses coastal hydraulics, riverine flooding, pavement and soils, and mechanical and electrical systems.

Appendix B provides detailed information on tools that can be used to support a project-level evaluation of climate change effects. Table 5-4 provides a summary of the types of climate change effects covered in these tools. Some of the tools offer sophisticated modeling capabilities that can simulate changing hydrologic geologic processes, such as the Precipitation Runoff Modeling System. Others provide information on state-specific impacts, such as the Cal Adapt Climate Tools. The particular tool that can support the analysis may be informed by the level of exposure or potential risk to an asset.

Increasingly, a best practice for assessing impacts is to incorporate a life-cycle approach that considers climate change effects over time and the non-linear progression of many climate change effects. Some of the tools summarized in Appendix B incorporate these changing risks, and an increasing number of state guides recommend this approach. The FHWA Highway Engineering Circular HEC-25 (FHWA 2020) indicates that life cycle cost analysis incorporating Monte Carlo-like simulations and other techniques may be necessary to simulate different cumulative damage scenarios. Such analyses can incorporate many different management decisions and can account for changing conditions over time. This approach also supports incorporating economic valuations of different alternatives. Note that this approach also supports FHWA’s Asset Management Rule, which calls for state DOTs to include lifecycle planning in their asset management planning and to incorporate climate change, resiliency, and other factors that could affect an asset’s performance over its lifetime (FHWA 2016e).

FHWA has developed transportation-specific tools relevant to transportation planners that can be used to incorporate multiple climate effects and expected impacts on certain transportation assets. These are summarized on the FHWA Climate Change Adaptation Tools website and include:

• Coupled Model Intercomparison Project (CMIP) Climate Data Processing Tool (2018) – Spreadsheet tool that processes downscaled climate projects from the World Climate Research Program into relevant statistics for transportation planners. Climate effects include temperature, precipitation, and sea level rise.
• Sensitivity Matrix (2015) – Spreadsheet tool that documents the sensitivity of roads, bridges, airports, ports, pipelines, and rail to 11 climate impacts, including temperature and extreme heat, precipitation-driven inland flooding, sea level rise/extreme high tides, storm surge, wind, drought, dust storms, wildfire, winter storms, changes in freeze-thaw, and permafrost thaw.
• Vulnerability Assessment Scoring Tool (2019) – Spreadsheet tool that supports a quantitative assessment of assets to temperature change, precipitation change, sea level rise, storm surge, and wind.

Table 5-4.  Climate Change Effects Covered in Key Resources

Unlike other topic areas, it is common for climate effects to be incorporated into many different resource topics within an environmental review document. For example, the climate effects associated with the river environment may be addressed in the hydrology section of an environmental review. Some long-established guidance documents, such as the Hydraulic Engineering Circulars, are expanding to incorporate likely climate effects (see Sidebar 5-4). While detailed hydraulic engineering is not likely to be completed at the time environmental documentation is complete, environmental documents can reference the intent to consider climate change information, such as projected precipitation and discharges consistent with one or more climate change scenarios, rather than simply relying upon historical data.

5.4 Equity Considerations

5.4.1 Transportation Climate Change Effects and Equity

Equity is considered in environmental review according to federal requirements and guidance, as outlined in Section 3.2, to identify and address the disproportionately high adverse human health and environmental effects of their programs, policies, and activities on low-income and minority populations.

Climate change effects can impact equity-focus communities directly, indirectly, and cumulatively. A local community may be directly threatened or forced to move as a result of sea level rise, or indirectly threatened as increasing summer temperatures make traditional agricultural practices impossible or extreme heat more difficult to cope with. While some effects may be broadly related to global climate change and the incremental impacts of a project indiscernible, there also may be specific localized effects that are exacerbated or mitigated by the project, such as loss of transportation accessibility due to extreme weather events or changes in local hydrology.

The impacts of climate change will not be borne equally or fairly. Recent evidence suggests that climate change will most impact equity-focus communities including people of color, low-income households, undocumented migrants, individuals with lower levels of educational attainment, renters, women, unemployed persons, single-parent households, the elderly, the young, individuals who experience housing insecurity, individuals with disabilities, rural communities, resource-based communities (including agricultural workers, fishing communities, miners, and others), and American Indian and Alaska Native Tribes (Lynn, MacKendrick, and Donoghue 2011; Cutter et al. 2009; U.S. EPA 2021a).

In some cases, it may not be possible to directly measure impacts because there may not be an appropriate data source. For example, while certain air quality changes can be generally understood to have a connection to certain health outcomes, data may not be available to quantify the link between climate change, air quality, and health outcomes for a particular community. Similarly, because it may not be possible to measure impacts on religious or traditional beliefs (Ulibarri, Perez Figueroa, and Grant 2022), it may not be possible to quantify those impacts in a NEPA analysis, although they may be addressed qualitatively.

An equity analysis in the context of climate change, which might also be considered or termed a climate justice analysis, can explore where there are communities that may be disproportionately affected by climate change effects due to factors such as income or economic stability, access to transportation services, health, age, exposure to climate hazards, and access to transportation services – particularly where transportation projects or even planning efforts are under consideration.

5.4.2 Tools and Methods for Equity Analysis Related to Climate Change Effects

Screening tools can help agencies determine where disproportionately impacted communities might exist. Appendix B identifies tools that could support agencies and equity-focus communities in evaluating the potential climate change effects related to a proposed project.

In selecting a tool, key considerations include the vintage of the data within the tool, indicators included within the tool’s data, the level of geography supported, and the objectives for the assessment. Note that none of the tools discussed below are sufficient for identifying an environmental justice population consistent with the implementing guidance for Executive Order 12898, and they must be used in conjunction with data gathered from the U.S. Census.

Each of the tools can provide insight into specific questions of climate risk, vulnerability, and resilience. The tools are strongest for their ability to identify environmental risks through project development, from initial scoping through an analysis of effects. All of the tools have contributed to the analysis and mapping of climate risks, and share many commonalities as well as unique use cases. The discussion below focuses on the tools’ usefulness for analysts conducting an assessment under NEPA.

The most commonly used tools for identifying demographic information for NEPA assessments appear to be the American Association of State Highway Transportation Officials (AASHTO) Census Transportation Planning Products (CTPP) and the Census Bureau’s On the Map tool, which summarizes the Longitudinal Employer Households Dynamics Origin-Destination Employment Statistics (LODES). While the CTPP is built on American Community Survey (ACS) data and generally includes more detailed demographic information than the LODES data, the vintage of some of the data contained in the most recent release is more than 10 years old as of January 2023 (drawing on ACS data gathered starting in 2012). The LODES data uses administrative data drawn from the State Quarterly Census of Employment and Wages (QCEW), which has the advantage of providing a more recent and complete sample (approximately 95 percent of the total United States workforce) but with less demographic detail.

For questions about community capital, environmental resilience, and institutional resilience, the Federal Emergency Management Agency (FEMA) National Risk Index can be used to identify communities most at risk from 18 natural hazards. The dataset includes metrics on expected annual losses from natural hazards, social vulnerability, and community resilience. The National Risk Index incorporates both the University of South Carolina’s Baseline Resilience Indicators for Communities (BRIC), as well as the Social Vulnerability Index for the United States (SoVI), though those datasets are only available at the county level and the data vintage should be noted. An example of the type of available output from this analysis is shown in Figure 5-6.

The Climate and Economic Justice Screening Tool (CEJST) can provide information on environmental factors, climate risk, and various community characteristics (including the built environment, economic characteristics, race/ethnicity, and transportation). This tool was developed by the CEQ in 2022 pursuant to EO 14008. The tool identifies communities that are “disadvantaged” based on more than 100 indicators, including a combination of climate and environmental indicators (e.g., expected agriculture loss rate, energy burden, traffic proximity and volume, exposure to air pollutants) and social indicators (income and access to education). The tool also provides detailed underlying data on each census tract’s score for each of those indicators. This tool was developed with wide collaboration, including nearly 3,000 public comments and active involvement from many organizations with subject matter expertise in specific topic areas. The tool also proactively treats certain variables to remove common ‘noise’ in certain indicators. For example, the presence of housing built prior to 1960 is often used as a proxy to indicate the likely presence of lead paint, but high-value housing built prior to 1960 has likely had lead-containing paint removed. The CEJST addresses much of this ‘noise’ by using calculated values; in the case of the lead paint indicator, the CEJST uses a calculated value that factors in both the percent of housing units built prior to 1960 and the median home value of owner-occupied units.

An overview of the available tools is included in Table 5-5.

Table 5-5. Equity Considerations Covered in Key Tools and Data Resources

Beyond data analysis, it is important to directly engage affected communities to understand the climate and weather effects they are experiencing and may experience in the future in ways that are meaningful to them. As Ulibarri et al. (2022) observe, “The public lacks the knowledge to translate their fears into specific quantifiable units that the agency can (or is allowed to) understand, the agency lacks the skill to facilitate a more mutually intelligible conversation, and both lack specific data (besides lived experience) that would point to the harm being present.”

Community engagement is required as part of an EIS completed under NEPA and encouraged as part of Environmental Assessment preparation. Agencies are required to provide meaningful opportunities for public participation in the NEPA process, particularly in the scoping process (when agencies decide on the range of issues to be addressed in the environmental review) and when the NEPA document is published for public review and comment (U.S. EPA undated). The Federal Interagency Working Group’s Promising Practices for EJ Methodologies in NEPA Reviews (EJIWG 2016) highlights the importance of both the method and the timing of that engagement, with the most successful engagement strategies incorporating innovative approaches to public outreach that begin from the outset of the NEPA process.

However, one of the barriers to meaningful engagement is the perception that decisions are often final by the time the NEPA process has been started. A criticism expressed by nongovernmental and community organizations contacted in the development of this guide, as well as in other recent research (Ulibarri, Perez Figueroa, and Grant 2022), is that public engagement during the NEPA process is too late to meaningfully influence the project’s outcomes.

A best practice for incorporating equity considerations into the analysis of greenhouse gas (GHG) emissions or climate change effects is to engage community members outside of the project development process, including during long-range planning and programming efforts. This may include a programmatic vulnerability assessment (see Section 5.2) or other practices consistent with a Planning and Environmental Linkages approach in which information developed in planning informs environmental review.

5.4.3 Resources for Outreach to Environmental Justice and Equity-Focus Communities

A number of resources have been published on engaging disadvantaged communities, including environmental justice populations, in transportation planning, project development, and environmental review. These resources are directly relevant to the consideration of GHG emissions and climate change effects as well. Examples include:

• FHWA (2006). How to Engage Low-Literacy and Limited-English-Proficiency Populations in Transportation Decisionmaking.
• FHWA (2015b). Public Involvement Techniques for Transportation Decision-Making.
• FHWA (2016c). Climate Change and Environmental Justice: Considerations for Transportation Decision-making.
• FHWA (2017b). Developing and Advancing Effective Public Involvement and Environmental Justice Strategies for Rural and Small Communities.
• FHWA (2022a). Virtual Public Involvement.
• FHWA (2022b). Promising Practices for Meaningful Public Involvement in Transportation Decision-Making.
• Morris and Fragala (2010). NCHRP Synthesis 407: Effective Public Involvement Using Limited Resources.
• Salerno et al. (2019). NCHRP Synthesis 538: Practices for Online Public Involvement.
• Twaddell and Zgoda (2020). TCRP Research Report 214: Equity Analysis in Regional Transportation Planning Processes.
• U.S. EPA (2013). Model Guidelines for Public Participation: An Update to the 1996 NEJAC Model Plan for Public Participation.

Appendix A contains additional descriptions of each resource.

5.5 Communicating Findings and Drawing Conclusions

Both before and after an agency has conducted an analysis of the potential effects that climate change may have on a particular project or geographic area, it is important to consider the best methods for communicating those findings to the public and to determine how the information should be used. For example, do the climate change effects amount to “significant” effects? Do they warrant mitigation measures, or are adequate resilience measures already built into the project design alternatives?

As discussed previously in this guide, meaningful community engagement is best carried out not only as part of the environmental review process but also well in advance of this process, such as during early planning phases. Transportation agencies undertaking planning efforts either at programmatic or project levels should work to engage the public, particularly communities that may be most affected by the plans or projects under consideration, to determine local needs and priorities and have two-way communication regarding the anticipated climate change effects for the region and lived experiences of community members.

Resources are available that draw on the latest social science to help agencies communicate with different audiences about climate change. One such resource specifically of use to transportation agencies is the Caltrans Climate Change Communication Guide (Caltrans 2020b). The Caltrans guide includes recommendations and best practices that transportation agencies can apply when communicating internally, with external partners, and with the public regarding information about climate change. For example, in engaging with members of the public, the Caltrans guide recommends tailoring messages to the audience with sensitivity to cultural, educational, and political backgrounds, using storytelling, focusing on local impacts, and using effective visualizations.

Many of the tools included in Appendix B can be used to support communication of a particular climate effect or be used to explain why a project area is being studied further. For example, the National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Information (NCEI) County Time Series can be used to show changes in historical temperature at a county level to explain why certain climate effects are being studied in greater detail (Figure 5‑7). Trend data may not accurately represent likely impacts in the future, but it can help to connect lived experience with changing conditions.

Programmatic evaluations of climate change effects can help agencies determine which projects or geographic areas may be most likely to experience meaningful climate change effects and warrant mitigation measures or integration of resilience in project design alternatives. Considerations that may be relevant in making these determinations include specific findings from the vulnerability assessment, such as areas where highly critical assets overlap with greater exposure to climate change effects, whether climate change is likely to affect the project’s performance over its design life; and the presence of communities that may be disproportionately affected by climate change effects or who may experience negative effects from transportation projects.

A climate change effects analysis may be included within an Indirect and Cumulative Effects Section of an environmental document or an Indirect and Cumulative Effects Report or appendix. In some cases climate change effects have also been described within the Air Quality section, report, or appendix. A sample outline for a section on climate change effects is shown in Sidebar 5-5: