Managed Retreat Toolkit
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.
Infrastructure agencies can protect or modify the design of assets like roads and bridges as a way to ensure that assets will function as intended throughout their design life, considering future sea-level rise and other changing coastal hazards. Strategies might include elevating assets, modifying materials or structural design, or adding hard or nature-based protective features. These strategies might be implemented on a case-by-case basis or provided for by state or local law, transportation planning processes, permitting decisionmaking, or design criteria and guidelines. Design modifications and asset protection may be implemented, for example, as a near-term strategy to maintain the functioning of critical assets and routes while longer-term retreat strategies are being pursued.
Beyond protecting or redesigning assets where they are, agencies can consider relocating (or “realigning”) as another alternative to formal disinvestment. Relocating or realigning roads, or high-risk segments of roads, to less vulnerable locations may offer a longer-term solution than design modifications or protective measures. This approach has been utilized in some coastal states to ensure longer-term safety of roads threatened by erosion, frequent inundation, or washout from storms, and to reduce future maintenance needs of roads.
Disinvestment, in general, refers to a process of consciously allowing an infrastructure asset to “fall below previously accepted standards of condition or performance,” and in this context, is used more specifically to refer to strategies that either phase out maintenance of roads or affirmatively abandon or discontinue roads where coastal conditions make upkeep challenging or prohibitive. Disinvestment strategies might include official abandonment, discontinuance, or closure proceedings as authorized by state law; downgrading of roads to reduce the level of service and maintenance requirements; or phasing out maintenance as environmental conditions degrade to certain threshold levels, as laid out and provided for, e.g., in plan, statute, or ordinance.