Managed Retreat Toolkit

Design Modifications and Asset Protection

Introduction to Design Modifications and Asset Protection

Governments and infrastructure agencies are increasingly turning attention to the need to ensure that public infrastructure is planned and designed to withstand future climate conditions and extreme events. As the availability and quality of climate data and projections improve, this is slowly becoming a less daunting task. In coastal areas, design and protective modifications include measures such as elevating roads and bridges, protecting assets with hard structures or nature-based features,See footnote 1  and modifying pavement materials or structural design to be more resistant to effects from inundation or to minimize environmental impacts if flooded or washed out (e.g., “sacrificial” roads).

Corpus Christi is exploring nature-based solutions to protect a vulnerable section of Laguna Shores Road. Source: Corpus Christi MPO.Corpus Christi is exploring nature-based solutions to protect a vulnerable section of Laguna Shores Road. Source: Corpus Christi MPO.

Transportation agencies can utilize resources such as the Federal Highway Administration’s engineering circular, Highways in the Coastal Environment: Assessing Extreme Events, to help with evaluating exposure and vulnerability of coastal highways to sea-level rise and extreme events, and identifying appropriate adaptation approaches.See footnote 2 

Adaptive design approaches are being implemented on a project-by-project basis in some states and cities. However, states and local governments, and to some extent, regional transportation planning agencies, can also institutionalize climate change-informed design through the following approaches:

  • State or local law: Some states and local governments have developed legislative directives requiring agencies to consider future impacts from climate change and sea-level rise in planning or decisionmaking related to public investments. For example, New York’s Community Risk and Resiliency Act requires the state to adopt sea-level rise projections by regulation and state agencies to consider sea-level rise and storm surge risk in certain permitting, funding, and other decisions.See footnote 3  California’s A.B. 2800 (2016) required state agencies to consider “current and future impacts of climate change when planning, designing, building, operating, maintaining and investing in state infrastructure” and called for the creation of a Climate-Safe Infrastructure Working Group to examine methods for integrating climate change projections into infrastructure engineering.See footnote 4 
  • Planning processes: State DOTs can integrate managed retreat considerations and phased adaptation approaches in planning efforts, such as statewide adaptation planning,See footnote 5 long-range transportation planning (and subsequent development of Statewide Transportation Improvement Programs), and asset management planning. Already, under current federal regulations, state departments of transportation must develop risk-based asset management plans that incorporate consideration of how climate change and extreme weather events will affect lifecycle costs.See footnote 6 State DOTs and metropolitan planning organizations (MPOs) are required to consider resilience needs in long-range transportation planning processes,See footnote 7 and some are also beginning to integrate resilience into performance measures and targets that inform transportation investment decisions.See footnote 8 Some state departments of transportation have developed guidance documents to assist their departments, regional agencies, or local governments with integrating climate change and resilience considerations into transportation planning.See footnote 9 At the local level, infrastructure-related adaptation needs and phased retreat considerations might be integrated into comprehensive planning and capital improvement planning.See footnote 10  
  • Permitting and environmental review processes: Coastal vulnerability considerations can also be included as a required component of permitting or environmental review processes to ensure that for new assets or redesign, potential vulnerabilities are identified and evaluated and that the project identifies risk-reduction measures.See footnote 11  
  • Design standards or design guides: Another tool that infrastructure agencies have utilized is climate-informed design standards and guidelines. These approaches typically provide appropriate climate change and sea-level rise projections to consider, and minimum design modifications for certain infrastructure categories (e.g., critical vs. non-critical; within or outside floodplains; etc.).See footnote 12 


Design Modifications and Asset Protection in a Managed Retreat Context  

In the context of a comprehensive managed retreat strategy, asset design and protective features will likely primarily be used as an intermediate strategy to bridge the gap to more permanent solutions like disinvestment. Depending on the function or use of the asset and the timeframe for comprehensive retreat from coastal areas, a disinvestment strategy for public infrastructure may not be initially feasible. In these instances, infrastructure managers may want to consider design-related adaptation strategies to ensure the adequate functioning of assets, especially those deemed critical. Design modifications can provide an effective intermediate-term strategy for ensuring public safety and infrastructure resilience to coastal hazards while broader long-term retreat strategies and tools are being planned and considered. 


Policy Tradeoffs of Design Modifications and Asset Protection


  • Climate-informed design requires agencies to have access to localized climate change data and projections and knowledge on how to apply this information in engineering and design. Some states and local jurisdictions have developed their own projections for agencies to use; in other cases, infrastructure agencies can look to existing tools, such as those provided by the Federal Highway Administration, including the CMIP Climate Data Processing Tool and Vulnerability Assessment Scoring Tool.See footnote 13 
  • Infrastructure agencies should assess whether any climate-informed decisionmaking requirements exist and when they apply (e.g., planning, environmental review, in the context of capital investments vs. repairs and maintenance, etc.). For example, depending on the agency or level of government, different federal planning requirements that relate to resilience and risk management might apply, including in state and regional long-range planning and state asset management planning. However, states may have implemented additional requirements through legislation or other processes that may affect state agencies or local governments.
  • In some contexts, design modifications may involve additional administrative complications, such as land acquisition (e.g., with roadway elevation projects, which require widening of the roadbedSee footnote 14 ) and environmental permitting processes.


  • Design modification and asset protection can be expensive, but reduced maintenance costs, avoided travel delays, and other benefits over the lifetime of the asset may make up for these upfront costs.
  • A robust cost-benefit analysis can help agencies evaluate potential adaptation options and prioritize investments. New resources have been developed to assist transportation agencies in this process, such as the National Academies’ Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change Guidebook.See footnote 15  


  • Design modifications and asset protective features should be informed by current and future environmental conditions.
  • Environmental impacts of these strategies depend on the context and strategy adopted. Design modifications in some instances may result in a net environmental benefit (e.g., when using more environmentally sensitive materials, or elevating a road to facilitate natural processes); hard protective features will often be a detriment to the environment, while nature-based protection can provide a net benefit.


  • Some roads and bridges may be considered “critical” and therefore important to protect and preserve functioning despite high exposure to coastal flooding. This may be the case, for example, for roads and bridges serving as evacuation routes or providing sole access to hospitals or other critical services.
  • Roads that provide sole access to communities or are otherwise heavily used and serve important functions in the larger transportation network may be prioritized for adaptive design or protective features.  


Practice Tips

When considering the need for design modifications or protective features for public infrastructure, as compared to alternative strategies (relocation/realignment, disinvestment), decisionmakers may wish to consider the following practice tips to balance policy tradeoffs:

  • Build considerations of asset criticality and use into policy, planning, and programmatic approaches: Considerations of asset criticality and use can help identify investments in adaptation and infrastructure protection to prioritize. With limited budgets, agencies will need methods and tools to evaluate alternative approaches and prioritize the most critical routes for ensuring safe travel in vulnerable coastal areas. This requires an understanding of how roads are used, the communities they serve, and their roles within the transportation network. 
  • Plan ahead to phase infrastructure design solutions with appropriate lifecycle stages and in the context of longer-term retreat strategies: Policymakers and infrastructure agencies can plan and prepare proactively to integrate design changes and adaptation solutions within normal asset management and investment cycles. This might include, for example, evaluating changes in paving needs as part of maintenance and repairs or identifying timeframes for assets approaching the end of their design life to determine whether redesigning with adaptive features may be appropriate. Estimating asset lifecycle costs ahead of time, including changing maintenance and operational costs, will help infrastructure agencies balance potential adaptation investments. As noted above, risk-based asset management planning is required for state DOTs. Local governments and infrastructure agencies can develop similar approaches to ensure that decisionmaking is informed by an assessment of how future coastal conditions will affect the performance of assets.
  • Adopt an adaptive management approach: Policymakers can adopt approaches that “[track] hazards, impacts, costs, and effectiveness of adaptations and post-disaster response”See footnote 16 to inform future adaptation, realignment, or disinvestment policies and approaches. An adaptive management approach in a retreat context should consider the environmental thresholds at which design and protective features, combined with maintenance and repair, may no longer be sufficient for providing safe travel and keeping a state of good repair and may require a transition to a realignment or disinvestment strategy. Proactive monitoring can help agencies identify when these threshold or trigger conditions are approaching and adjust operational, design, or other management strategies as appropriate. For example, the California Coastal Commission, in responding to a Coastal Development Permit (CDP) application from Caltrans to improve a six-mile section of Highway 101 along Humboldt Bay in Northern California, recommended that Caltrans be required to submit a CDP amendment and Phased Adaptation Plan within one year of the first time the corridor floods at least four times during a twelve-month period (the threshold condition).See footnote 17 This phased approach with a triggering condition is intended to ensure that there is time to develop adaptation alternatives for long-term viability (e.g., design modifications, relocation, removal) before sea-level rise conditions begin to challenge travel on a monthly or daily basis.
  • Understand legal interpretations of the duty to maintain/repair and implications for coastal assets requiring more frequent maintenance: As discussed in the Crosscutting Legal Considerations>Negligence section, infrastructure owners and operators have a duty to maintain and repair the public infrastructure they oversee, and the specific responsibilities to meet the requirements of that duty varies according to state statutory and case law. Infrastructure agencies should be aware of any legal interpretations affecting their jurisdiction that might expand this duty to encompass an affirmative duty to upgrade or improve in the context of environmental conditions like sea-level rise and nuisance flooding that increasingly and more rapidly deteriorate coastal roads. Expanded duties could have implications for agency maintenance and capital budgets, and may affect considerations about when to formally disinvest as opposed to protecting or redesigning assets.


















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