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The National Academies

NCHRP 23-33 [Anticipated]

Guidance in Planning for Managed Retreat as an Extreme Weather and Climate Adaptation Strategy

  Project Data
Source: AASHTO Committee on Transportation System Security and Resilience
Funds: $500,000
Staff Responsibility: Camille Crichton-Sumners
Fiscal Year: 2023

This project has been tentatively selected and a project statement (request for proposals) is expected to be available on this website. The problem statement below will be the starting point for a panel of experts to develop the project statement.

Climate change impacts increasingly affect transportation systems in the United States. Transportation agencies across the country already face substantial impacts from extreme weather and other climate events, with future projections suggesting this trend will continue and possibly increase. Impacts to transportation infrastructure from such events can cause immediate or longer-term changes in the way people use local infrastructure and where they choose to permanently locate or relocate. State and local governments often allow development in known high-risk areas, requiring ongoing investment from transportation agencies to repeatedly repair or maintain such assets. Such development can also exacerbate risks in neighboring areas if they displace natural protections such as wetlands or greenspace. State departments of transportation (DOTs) will ultimately have significant financial and operational responsibility with respect to these assets as their exposures increase. Abandoning infrastructure assets may be as challenging and expensive as migrating the transportation infrastructure itself.

Managed retreat—movement of assets and people away from risks—needs to be a strategy available to transportation planners. It includes evaluation of alternative routes, structures, contexts, and other considerations to more efficiently use transportation funding while preserving critical access to people, freight, and emergency services. It also requires a complex understanding of place attachment, the community in which the transportation system exists, the interconnectedness of the infrastructure at issue with other systems and people, and whether laws and regulations authorize a state DOT to make managed retreat decisions. There is a need for research that develops information about managed retreat strategies in a way that supports state DOT transportation systems decision-making. A successful managed retreat plan can decrease risk to the entire system, save valuable resources that may be better allocated elsewhere, and protect lives and livelihoods. Moreover, embedded in these decisions are social justice issues to consider and state DOTs often do not have the experience and tools needed to approach these issues.

The research will develop a practice-ready managed retreat framework and guidance targeted to state DOTs, enabling an informed approach to discuss and to facilitate decision-making. It will provide guidance for how to determine and measure transportation performance thresholds and which retreat strategies should be implemented. The final product will draw from experiences and outcomes across the United States and abroad, written from the perspective of managed retreat as a viable resilience strategy that can have positive, long-term benefits.

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