One challenge that governments face when deciding whether to implement a managed retreat strategy is how to develop that strategy in the context of public infrastructure assets, such as roads and bridges.See footnote 1 Rising sea levels in some areas are causing coastal roads and other public infrastructure to experience more frequent inundation during king tides or even daily high tides, more severe erosion and flooding from coastal storm events, and in some cases inundation or pooling from below that extends further inland as groundwater tables rise. These impacts create public safety hazards and prevent public infrastructure from functioning as intended, as flooded roads cause traffic delays, require detours, and in some cases, temporarily cut off sole access to communities. Roads that have been eroded, washed out, or weakened structurally (e.g., by heightened groundwater tables) can require more frequent and costly maintenance and repairs. Infrastructure agencies are increasingly confronting these challenges and can benefit from tools to help evaluate the tradeoffs of different policy, planning, design, and operational and maintenance strategies to minimize travel-related impacts from coastal hazards. This section currently focuses primarily on decisionmaking considerations for public roads in a managed retreat context, but does include several case studies and examples applicable to other types of infrastructure (e.g., drainage assets).
|Road damage from Hurricane Sandy in Delaware. Source: Delaware Department of Natural Resources and Environmental Control.
Departments of transportation (DOTs) and other authorities overseeing roads and bridges have many factors to consider in making decisions about infrastructure capital investments, maintenance, and operations. Climate change and sea-level rise increasingly pose a challenge for cost-conscious agencies that must now factor in higher upfront adaptation costs or higher maintenance costs over the lifetime of assets. An expectation that assets will be subject to more frequent and severe flooding and erosion requires infrastructure agencies to consider whether to protect or modify the designs of their assets to withstand future conditions, to realign or relocate certain assets to less vulnerable areas, or to disinvest by phasing out maintenance or abandoning assets altogether.
Further complicating matters, managed retreat strategies may require collaboration between multiple levels of government. Authority over roads and bridges may often be shared by state, county (if the state has county government structure), and municipal governments, as well as regional agencies such as metropolitan planning organizations (MPOs) for urbanized areas. For example, a particular road or bridge asset may primarily serve a specific municipality but may be under state or county jurisdiction; and multiple state agencies and local governments might oversee different types of infrastructure that all occupy the same area, such as roads, bridges, dams, and levees or dikes. In the context of managed retreat, infrastructure owners and operators will likely need to collaborate with other agencies and decisionmakers at local and state levels to ensure that the approaches to infrastructure resilience or retreat are consistent with the larger strategy.
|Utqiagvik, Alaska. Source: NOAA.
This section focuses on the policy options for state and local governments, particularly transportation agencies, to prepare public transportation infrastructure assets for coastal impacts of climate change by (1) modifying asset design or adding protective features, (2) relocating or realigning assets, or (3) disinvesting in assets in high-exposure areas. These strategies each come with important legal, fiscal, and practical considerations that must be weighed by the decisionmakers overseeing assets, such as asset use and criticality, design life and anticipated lifecycle costs, potential for legal challenges, and more. For each of the policy options, there is an overview of the option, discussion of policy tradeoffs, practice tips to aid in implementation, and case study examples on how some of these options have been implemented in practice.