Planning for Infrastructure Resilience

The impacts of climate change are no longer a distant threat. They are here. As the unprecedented becomes the precedent, communities will see more frequent and intense flooding — and their infrastructure facilities and systems, often expected to last for decades or more, will be at higher risk.

The coastal highway and bridge connecting a town to its hospital will be threatened by record high tides. The stormwater network on a county's drawing board will be inundated by record rainfall events — year after year. The wastewater treatment plant being completed next month will endure successive years of storm surge in a city historically unaccustomed to hurricanes.

To ensure that today's infrastructure will stand the test of time, communities must plan for infrastructure that is resilient to the flooding of tomorrow. PAS Report 596, Planning for Infrastructure Resilience, defines the threat posed by more frequent and severe flooding to public infrastructure and outlines the role of planners and plans in ensuring that infrastructure is prepared for an unpredictable future.

While infrastructure is not immune to other climate- exacerbated hazards such as drought or wildfire, this PAS Report focuses primarily on how climate change will intensify flood risks from hazards such as sea level rise, coastal storms, and extreme precipitation. It provides guidance to help planners and their communities consider future flood impacts to public municipal infrastructure: the infrastructure financed, constructed, and maintained by local governments and special districts. The information provided in this report is intended for planners across the United States, regardless of their proximity to the coasts; rivers, streams, lakes, and urban stormwater systems will all be affected by future changes.

CHANGES ARE COMING

While the need to ensure infrastructure is resilient to future climate conditions is increasingly accepted across many overlapping areas of practice, active measures to realize this on the ground are comparatively rare. Cities across the United States are taking major steps toward considering and integrating climate change and its impacts into infrastructure planning processes, but these efforts often rely upon strong political will, dedicated streams of funding, and staff capacity. Mainstreaming the use of climate information, data, and tools into planning, capital improvement processes, and infrastructure standards and guidelines is not yet common practice. Yet mainstreaming is precisely what is necessary to ensure that future climate conditions are major elements of the local community and infrastructure planning process.

Infrastructure is expensive, and it is often intended to last for a long time. Current practice for considering flood hazards in infrastructure planning and decision making is often limited to static snapshots based on historical precedent. The regulatory datasets used to establish floods of record are all based on historical models, which assume a future that is much like the present.

Climate change, however, introduces substantial uncertainties into broadly accepted and widely used but historically based flood, precipitation, natural hazard, meteorological, and climatological data. Use of historical models, while far better than not considering flood hazards at all, discounts the significant negative impacts of future changes in climate — especially the severity and frequency of flooding — on local infrastructure.

To ensure that capital investments in infrastructure expected to last decades are not at risk, local practitioners — including planners, floodplain managers, public works and engineering staff, and others — must be prepared to factor these anticipated future changes into the many processes that touch upon the planning, siting, design, and finance of these facilities and systems.

FUTURE FLOODING AND INFRASTRUCTURE IMPACTS

In the context of climate change, a series of interrelated flood hazards stand out. They are sea level rise, coastal storms and storm surge, tidal flooding and inundation, and extreme precipitation. It is critical that planners understand what these hazards entail and the potential impacts they may have on their communities. These hazards are explored in depth in Chapter 1 of the report.

Sea level rise is a gradual long-term threat to coastal communities as well as a key factor in intensifying acute coastal storm impacts through more destructive storm surge events. The current likeliest projections for 2100 point to a range of one to four feet of sea level rise on average across the globe. While this may not sound especially impactful, four additional feet of water will pose a serious existential threat to coastal communities across the United States. And not only might certain geographical contexts create local sea level rise that far exceeds these global averages, but more extreme average sea level rise scenarios of up to eight feet are entirely possible in the event of both unchecked greenhouse gas emissions and further destabilization of the Antarctic ice sheet.

While current climate models do not anticipate significant changes in the overall number of named coastal storms, these models do predict an increase in the severity of these events. Fostered by warmer oceans, severe coastal storms are likely to bring more destructive impacts not only to communities already grappling with recurrent coastal flooding, but also to communities historically unaccustomed to tropical storms and hurricanes. Flooding in the form of extreme and unprecedented rainfall (most recently exhibited by Hurricane Harvey) and highly destructive storm surge are a major consequence of coastal storms. Compounded further by rising sea levels, flooding during coastal storm events is expected to worsen considerably over the coming decades.

Heavy precipitation is a significant consequence of climate change that will impact communities across the United States, regardless of location. Some regions will see increases in average annual precipitation, while others will see less rain on average, but more heavier rainfall events. Extreme precipitation events are likely to increase in frequency, leading to severe riverine and inland flooding as well as recurring nuisance flooding.

Local public infrastructure assets and systems will bear the brunt of these coming changes. Increasingly severe and frequent rainfall may exceed the capacity of existing stormwater systems. Coastal and riverine flooding may overtop bridges, roads, and public transit infrastructure. Fire and police stations, schools, and public parks and recreational facilities in areas vulnerable to sea level rise, coastal storm surge, and tidal flooding may face interrupted operations and the possible need for relocation.

Direct flood impacts to local infrastructure will in turn cause a variety of unpredictable secondary impacts to people and the built and natural environments. Impacts as diverse as flooded roads or damaged ports could have significant negative affects on local economies. Disrupted transportation networks may impede the mobility of emergency services. Recurrent flooding of schools or public parks may seriously impact educational outcomes and quality of life. Combined sewer overflow events may precipitate public health crises.

Communities rely on infrastructure in myriad ways. When that infrastructure is damaged, impaired, or in dire need of replacement due to recurrent flooding, the potential impacts to the community can be vast and unpredictable.
The age of infrastructure and the costs of its replacement are already significant issues across the United States, independent of increasingly severe flood events. Sea walls, levies, natural infrastructure, stormwater and wastewater networks, and deteriorating drinking water facilities will require hundreds of billions of dollars in replacement, adaptation, and maintenance costs to ensure continuity of operations and resilience in the face of climate change.

Planners stand at the intersection of long-term climate resilience and infrastructure implementation. They can ensure that the plans and policies that inform public investments as directed by capital improvement planning and budgeting processes take climate risks into consideration. From finding and using data and tools, to assessing vulnerability, to linking comprehensive planning with on-the-ground actions, planners should play a critical role in advancing infrastructure resilience.

GATHERING DATA, ASSESSING VULNERABILITY, AND PLANNING FOR THE FUTURE

Chapters 2 and 3 of this report discuss two of the most critical challenges in ensuring infrastructure is resilient to future flooding: (1) understanding data and decision support tools, and (2) applying them to assessing the vulnerability of infrastructure to climate change. Only with this foundation in place can planners then begin the work of integrating long- term infrastructure goals, objectives, and actions into capital improvements planning.

Understanding the available data, information, and decision-support tools for future flooding is crucial to ensuring that local infrastructure can withstand climate change. Climate models, while always evolving, largely agree on the bigpicture impacts of climate change as they relate to flooding. It is vital for planners to understand the basics of climate science to make informed decisions on the use of data, tools, and resources as they work to plan for resilient infrastructure.

There are many interactive decision-support tools and resources available that can greatly benefit the work of planners, as discussed in Chapter 2 of this report. Resilience clearinghouses such as the National Oceanic and Atmospheric Agency's (NOAA) Climate Resilience Toolkit, and specific geospatial and visualization tools such as NOAA's Sea Level Rise Viewer or Great Lakes Lake Level Viewer, should form the foundation for planners seeking to apply climate data to infrastructure planning. These and other tools allow users to directly download geospatial data for use in GIS software, which can be critical to establishing the vulnerability of communities and infrastructure assets.

Once a community has gathered its data, the process of determining the vulnerability of infrastructure systems and assets is the next essential step to effectively plan for the future. A bridge or power station expected to function to the end of the century but designed based on flood or storm surge risk from the year 2000 will not be ready for coming impacts requiring costly maintenance or early replacement. Planners must evaluate the vulnerability of existing assets and assess future threats to upcoming projects to maximize community resilience.

The vulnerability assessment process requires assessing a planned or existing project or asset's exposure, sensitivity to flooding, and the degree to which it can accommodate more severe flood impacts. Spatial analysis combined with an understanding of asset lifespan and condition forms an effective base upon which infrastructure planning can be built. When combined with a thorough analysis of social vulnerability to more frequent and severe flooding events, the picture becomes complete and planners can take the first steps to more effective planning for an uncertain future. Chapter 3 of this report walks planners through the steps of conducting these analyses.

THE ROLE OF PLANS AND PLANNERS IN INFRASTRUCTURE RESILIENCE

Developing and overseeing the implementation of plans is the backbone of a planner's work. All too often, however, plans and infrastructure implementation processes operate independently at the local level. The prospect of more severe and frequent flooding is an opportunity to integrate and align these functions to ensure that the infrastructure planned and built today is equipped for future social and environmental conditions.

Planning for flood resilient infrastructure will require communities to use of all of their planning tools. Comprehensive planning should be at the core for local action on infrastructure resilience. As the most complete picture of where a community is today and where it wants to be at some point in the future, local comprehensive planning must play a major role in infrastructure planning processes. And to maximize future resilience outcomes, the full array of local plans and planning functions — including community visioning and public outreach, hazard mitigation planning, climate adaptation planning, open space planning, and many others — must be aligned, with goals and objectives clearly linked to actions and outcomes. Detailed guidance on the role of planners in advancing infrastructure resilience through plans can be found in Chapter 4.

As the primary link between long-term planning and the implementation of infrastructure, the capital improvements planning (CIP) process stands out as playing a key role in community resilience. CIPs document the process of providing and maintaining the infrastructure to support a community's quality of life. They assess infrastructure needs within a jurisdiction over a defined time frame, weigh these needs against overall goals and objectives, and then evaluate and prioritize specific infrastructure projects for future funding. Given the role of the CIP in determining near- and long-term infrastructure needs, resilience to future flooding must be deeply embedded within this process. Chapter 5 of this report describes the importance of planners' involvement. Practical consideration for infrastructure resilience should center on the long-term value of investments. If the community has identified certain areas as especially susceptible to sea level rise or recurrent flooding within 25 years, does new stormwater infrastructure in those areas have long-term value? These are the types of questions that must be answered in the CIP process. Planners should play a major role in facilitating these conversations and ensuring that investment outcomes link strongly with established community goals.

IMPLEMENTING RESILIENT INFRASTRUCTURE

Currently, no formal nationwide standards for resilient infrastructure have been widely accepted by engineering and public works professionals. While there has been some recent movement toward formalizing standards, and several larger cities have begun establishing basic guidelines to increase the resilience of infrastructure assets to future flood impacts, communities are still largely on their own when seeking to integrate flood resilience into the siting, design, and construction of infrastructure. By drawing from established vulnerability assessments, community-wide goals and objectives, and the resilience considerations integrated into the CIP, planners can help to oversee local processes for the development of local standards, regulations, and guidelines. Generally, local guidelines should be based on selecting flood scenarios within the defined lifespan of a project, constructing to the most probable scenario, and building redundancies into a project to allow for further adaptation based on observed impacts and changes. In practice, this can be challenging and heavily constrained by funding availability. Planners, while not driving the adoption of technical engineering standards, can help inform their development and ensure strong links to vulnerability assessments and long-term plans. More on this topic can be found in Chapter 6.

Finding the money necessary to finance expensive infrastructure projects has always been a challenge. The prospect of higher costs given the impacts of more frequent and severe flooding complicate this picture even further. While providing services and maintaining existing infrastructure are likely to be high priorities for many municipalities, longer-term adaptation of already expensive infrastructure, especially given the uncertainty of the scale of flood impacts, may not be a prime driver for local decision making. For these reasons, planners should have a clear understanding of local finance and the avenues that exist for financing resilient infrastructure.

Beyond the established mechanisms for financing local infrastructure, planners can bring to their communities awareness of emerging financial tools such as catastrophe bonds, environmental impact bonds, and resilience bonds that are specially tailored for flood hazard and climate resilience. Further, planners can leverage their knowledge of federal programs to identify funding opportunities through the Federal Emergency Management Agency's various pre- and post-disaster mitigation grant programs, post-disaster appropriations through the Community Development Block Grant program, and grant opportunities from federal agencies such as NOAA and the U.S. Environmental Protection Agency. Along with summarizing local government funding sources, Chapter 7 outlines these emerging opportunities and identifies how planners can responsibly advise financial decision making to advance infrastructure resilience.

CONCLUSION

There is no simple resolution to the difficult problem of ensuring that the infrastructure of today can meet the flooding challenges of tomorrow. It requires strong commitment to developing plans that consider future climate conditions, local willingness to actively use these plans as roadmaps for the future, and acceptance of the need to iterate, revise, and continue to improve the processes through which local infrastructure plans become on-the-ground realities.

Planners, capable of balancing the needs of today with the aspirations and challenges of the future, are uniquely suited to harnessing the many local planning tools necessary to advance resilience in the face of future flood conditions. PAS Report 596 is an affirmation of the planner's critical role in this process and a call to confront and overcome the complex challenges that more frequent and severe flooding pose to infrastructure and the long-term health and vitality of communities across the United States.