finding 12.2 : key-message-12-2

Extreme events that increasingly impact the transportation network are inducing societal and economic consequences, some of which disproportionately affect vulnerable populations (high confidence). In the absence of intervention, future changes in climate will lead to increasing transportation challenges, particularly because of system complexity, aging infrastructure, and dependency across sectors (high confidence).



This finding is from chapter 12 of Impacts, Risks, and Adaptation in the United States: The Fourth National Climate Assessment, Volume II.

Process for developing key messages:

We sought an author team that could bring diverse experiences and perspectives to the chapter, including some who have participated in prior national-level assessments within the sector. All are experts in the field of climate adaptation and transportation infrastructure. The team represents geographic expertise in the Northeast, Mid-Atlantic, South, Central, and Western regions, including urban and rural as well as coastal and inland perspectives. Team members come from the public (federal and city government and academia) and private sectors (consulting and engineering), with practitioner and research backgrounds.

The chapter was developed through technical discussions of relevant evidence and expert deliberation by the report authors at several workshops and teleconferences and via email exchanges. The authors considered inputs and comments submitted by the public, the National Academies of Sciences, Engineering, and Medicine, and federal agencies. For additional information on the overall report process, see Appendix 1: Process. The author team also engaged in targeted consultations with transportation experts during multiple listening sessions.

Because the impacts of climate change on transportation assets for the United States and globally have been widely examined elsewhere, including in the Third National Climate Assessment (NCA3),dd5b893d-4462-4bb3-9205-67b532919566 this chapter addresses previously identified climate change impacts on transportation assets that persist nationally, with a focus on recent literature that describes newly identified impacts and advances in understanding. Asset vulnerability and impacts are of national importance because there are societal and economic consequences that transcend regional or subregional boundaries when a transportation network fails to perform as designed; a chapter focus is the emerging understanding of those impacts. Further, place-based, societally relevant understanding of transportation system resilience has been strongly informed by numerous recent local and state assessments that capture regionally relevant climate impacts on transportation and collectively inform national level risks and resilience. The chapter synthesizes the transportation communities’ national awareness of and readiness for climate threats that are most relevant in the United States.


Description of evidence base:

The Key Message is largely supported by observation and empirical evidence that is well documented in the gray (non-peer-reviewed) literature and recent government reports. Because this is an important emerging area of research, the peer-reviewed scientific literature is sparse. Hence, much of the supporting materials for this Key Message are descriptions of impacts of recent events provided by news organizations and government summaries.

Many urban locations have experienced disruptive extreme events that have impacted the transportation network and led to societal and economic consequences. Louisiana experienced historic floods in 2016 that disrupted all modes of transportation and caused adverse impacts on major industries and businesses due to the halt of freight movement and employees’ inability to get to work.772e841e-180a-47f8-a799-500647586c00 The 2016 floods that affected Texas from March to June resulted in major business disruption due to the loss of a major transportation corridor.741b9a22-f7c4-42b7-ad5c-405165add8b5 In 2017, Hurricane Harvey affected population and freight mobility in Houston, Texas, when 23 ports were closed and over 700 roads were deemed impassable.f40f0b46-1b69-49d1-915e-d191f590c87f Consequences of extreme events can be magnified when events are cumulative. The 2017 hurricanes impacting the southern Atlantic and Gulf Coasts and Puerto Rico created rising freight costs because freight carriers had to deal with poor traveling conditions, an unreliable fuel stock, and limited exports for the return trip.63f91a03-3377-4198-b856-0e35d0673a35,0fabd67b-3873-4caa-98df-9a27dffba25e Low-income populations have been linked to differences in perceived risks associated with an extreme event, in how they respond, and in their ability to evacuate or relocate.f1e633d5-070a-4a7d-935b-a2281a0c9cb6 Delays in evacuations can potentially lead to significant transportation delays, affecting the timeliness of first responders and evacuations. National- and local-level decision-makers are considering strategies during storm recovery and its aftermath to identify and support vulnerable populations to ensure transportation and access to schools, work, and community services (for example, the 2016 Baton Rouge flood event).

Similar to the urban and suburban scenarios, rural areas across the country have also experienced disruptions and impacts from climate events. Hurricane Irene resulted in the damage or destruction of roads throughout New England, resulting in small towns being isolated throughout the region.e6a71298-6e58-4b80-b3e9-750385b9cc4d Similarly, Hurricane Katrina devastated rural community infrastructure across the Gulf Coast, which resulted in extended periods of isolation and population movement.6e1d67c5-05d5-4094-a5e6-1a854e3a47cf Lesser-known events are also causing regular impacts to rural communities, such as flood events in 2014 in Minnesota and in 2017 throughout the Midwest, which impacted towns for months due to damaged road infrastructure.a6f2252d-d6b9-407d-9757-f8ce76fe282e,a72fd4b2-2efd-4424-b461-d855357e7e89

Although flooding events and hurricanes receive significant attention, other weather-based events cause equal or greater impacts to rural areas. Landslide events have isolated rural communities by reducing them to single-road access.83683960-a588-4670-ad1a-819ae28689ee,d802e9b9-b00b-42e6-bb03-330b21637e6c Extreme heat events combined with drought have resulted in increases in wildfire activity that have impacted rural areas in several regions. The impacts of these wildfire events include damage to infrastructure both within rural communities and to access points to the communities.843bf8c9-7c94-4fa6-b485-f256e9adab2b

As documented, rural communities incur impacts from climate events that are similar to those experienced in urban and suburban communities. However, rural and isolated areas experience the additional concerns of recovering from extreme events with fewer resources and less capacity.52ba053e-57fc-4767-8273-c605b19a0c2c This difference often results in rural communities facing extended periods of time with limited access for commercial and residential traffic.

New information and remaining uncertainties:

Realized societal and economic impacts from transportation disruptions vary by extreme event, depending on the intensity and duration of the storm; pre-storm conditions, including cumulative events; planning mechanisms (such as zoning practices); and so on. In addition, a combination of weather stressors, such as heavy precipitation with notable storm surge, can amplify effects on different assets, compounding the societal and economic consequences. These amplifications are poorly understood but directly affect transportation users. Interdependencies among transportation and other lifeline sectors can also have significant impacts on the degree of consequences experienced. These impacts are also poorly understood.

Assessment of confidence based on evidence:

There is medium to high confidence that the urban setting can amplify heat.1b0ce605-0f6c-4e1f-8fea-71e87cb4304f There is also medium to high confidence that transportation networks are impacted by inland and coastal flooding.a29b612b-8c28-4c93-9c18-19314babce89 There is medium confidence that socioeconomic conditions are strongly related to a population’s resilience to extreme events.f1e633d5-070a-4a7d-935b-a2281a0c9cb6

There is high confidence that impacts to the transportation network from extreme events are inducing societal and economic consequences, some of which disproportionately affect vulnerable populations (medium confidence). In the absence of intervention, projected changes in climate will likely lead to increasing transportation challenges as a result of system complexity, aging infrastructure with hundreds of billions of dollars in rehabilitation backlogs,9115ee8c-84a2-43a3-96dc-09b6fcacc03f and dependency across sectors. 

References :

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