Federal Coordinating Lead Authors:
Jeffrey Payne, National Oceanic and Atmospheric Administration
William V. Sweet, National Oceanic and Atmospheric Administration
Chapter Lead:
Elizabeth Fleming, U.S. Army Corps of Engineers
Chapter Authors:
Michael Craghan, U.S. Environmental Protection Agency
John Haines, U.S. Geological Survey
Juliette Finzi Hart, U.S. Geological Survey
Heidi Stiller, National Oceanic and Atmospheric Administration
Ariana Sutton-Grier, National Oceanic and Atmospheric Administration
Review Editor:
Michael Kruk, ERT, Inc.
USGCRP Coordinators:
Matthew Dzaugis, Program Coordinator
Christopher W. Avery, Senior Manager
Allyza Lustig, Program Coordinator
Fredric Lipschultz, Senior Scientist and Regional Coordinator

Coastal Effects

U.S. coasts are dynamic environments and economically vibrant places to live and work. As of 2013, coastal shoreline counties were home to 133.2 million people, or 42% of the population.1 The coasts are economic engines that support jobs in defense, fishing, transportation, and tourism industries; contribute substantially to the U.S. gross domestic product (GDP; Table 8.1);1,26 and serve as hubs of commerce, with seaports connecting the country with global trade partners.2 Coasts are home to diverse ecosystems such as beaches, intertidal zones, reefs, seagrasses, salt marshes, estuaries, and deltas3,4,5 that support a range of important services including fisheries, recreation, and coastal storm protection. U.S. coasts span three oceans as well as the Gulf of Mexico, the Great Lakes, and Pacific and Caribbean islands.

Table 8.1: Economic Importance of U.S. Coastal Areas

Region Employment GDP Population % Land Area
Millions % of US Trillions % of US Millions % of US
United States 134.0 $16.7 316.5
All Coastal States 109.2 81.5% $13.9 83.7% 257.9 81.5% 57.0%
Coastal Zone Counties 56.2 42.0% $8.0 48.0% 133.2 42.1% 19.6%
Shore-Adjacent Counties 50.2 37.5% $7.2 43.2% 118.4 37.4% 18.1%
Table 8.1: The coast is a critical component of the U.S. economy. This table shows U.S. employment, GDP, population, and land area compared to coastal areas as of 2013. “Coastal zone counties” comprise shore-adjacent counties plus non-shore-adjacent counties. For more complete definitions, visit this web site. Source: Kildow et al. 2016.1

The social, economic, and environmental systems along the coasts are being affected by climate change. Threats from sea level rise (SLR) are exacerbated by dynamic processes such as high tide and storm surge flooding (Ch. 19: Southeast, KM 2),6,7,8 erosion (Ch. 26: Alaska, KM 2),9 waves and their effects,10,11,12,13 saltwater intrusion into coastal aquifers and elevated groundwater tables (Ch. 27: Hawaiʻi & Pacific Islands, KM 1; Ch. 3: Water, KM 1),14,15,16,17 local rainfall (Ch. 3: Water, KM 1),18 river runoff (Ch. 3: Water, KM 1),19,20 increasing water and surface air temperatures (Ch. 9: Oceans, KM 3),21,22 and ocean acidification (see Ch. 2: Climate, KM 3 and Ch. 9: Oceans, KM 1, 2, and 3 for more information on ocean acidification, hypoxia, and ocean warming).23,24

   

Figure 8.1: Cumulative Costs of Sea Level Rise and Storm Surge to Coastal Property

Figure 8.1: This figure shows that cumulative damages (in 2015 dollars) to coastal property across the contiguous United States would be significantly reduced if protective adaptation measures were implemented, compared to a scenario where no adaptation occurs. Without adaptation, cumulative damages under the higher scenario (RCP8.5) are estimated at $3.6 trillion through 2100 (discounted at 3%), compared to $820 billion in the scenario where cost‐effective adaptation measures are implemented. Under the lower scenario (RCP4.5), costs without adaptation are reduced by $92 billion relative to RCP8.5 and are $800 billion with adaptation. Note: The stepwise nature of the graph is due to the fact that the analysis evaluates storm surge risks every 10 years, beginning in 2005. Source: adapted from EPA 2017.35

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Collectively, these threats present significant direct costs related to infrastructure.27,28 The more than 60,000 miles of U.S. roads and bridges in coastal floodplains are already demonstrably vulnerable to extreme storms and hurricanes that cost billions in repairs.29 The national average increase in the Special Flood Hazard Area by the year 2100 may approach 40% for riverine and coastal areas if shoreline recession is assumed, and 45% for riverine and coastal areas if fixed coastlines are assumed.30 Additionally, indirect economic costs (such as lost business) and adverse sociopsychological impacts have the potential to negatively affect citizens and their communities.31,32,33 People exposed to weather- or climate-related disasters have been shown to experience mental health impacts including depression, post-traumatic stress disorder, and anxiety, all of which often occur simultaneously; furthermore, among those most likely to suffer these impacts are some of society’s most vulnerable populations, including children, the elderly, those with preexisting mental illness, the economically disadvantaged, and the homeless (Ch. 14: Human Health, KM 1 and 2).34

Although storms, floods, and erosion have always been hazards, in combination with rising sea levels they now threaten approximately $1 trillion in national wealth held in coastal real estate (Figure 8.1)25 and the continued viability of coastal communities that depend on coastal water, land, and other resources for economic health and cultural integrity (Ch. 15: Tribes, KM 1 and 2). The effects of the coastal risks posed by a changing climate already are and will continue to be experienced in both intersecting and distinct ways, and coastal areas are already beginning to take actions to address and ameliorate these risks (Figure 8.2).

   

Figure 8.2: Regional Coastal Impacts and Adaptation Efforts

Alaska Northern Great Plains Region Northwest Midwest Northeast Southwest Southern Great Plains Southeast Hawaii and U.S.-Affiliated Pacific Islands U.S. Caribbean

Click on a region to see examples of coastal impacts and adaptation efforts

Northwest
Impacts
  • Increasing water temperatures
  • Saltwater intrusion
  • Ocean acidification
  • Marine species vulnerabilities
  • Storm surge
  • Sea level rise
  • Recurrent coastal flooding
  • Coastal erosion
  • Changing precipitation patterns
  • Critical infrastructure damage
  • Decreased water quality/availability
Adaptation Efforts
  • In the Yakima Basin, irrigators, conservation groups, and state and federal agencies worked together to replenish diminished tributary flows to save the salmon runs and riparian habitat during the drought.
Midwest
Impacts
  • Increasing water temperatures
  • Decreasing ice cover
  • Marine species vulnerabilities
Adaptation Efforts
  • The Great Lakes Climate Action Network (GLCAN) is a regional, member-driven peer network of local government staff who work together to identify and act on the unique climate adaptation challenges of the Great Lakes region. GLCAN is working with the Huron River Watershed Council and five Great Lakes cities (Ann Arbor, Dearborn, Bloomington, Indianapolis, and Cleveland) to develop a universal vulnerability assessment template that mainstreams the adaptation planning process and results in the integration of climate-smart and equity-focused information into all types of city planning. The template will be publicly available; its purpose is to reduce municipal workloads and save limited resources by mainstreaming existing, disparate planning domains (e.g., natural hazards, infrastructure, climate action), regardless of city size or location.
Northeast
Impacts
  • Increasing water temperatures
  • Ocean acidification
  • Marine species vulnerabilities
  • Storm surge
  • Sea level rise
  • Recurrent coastal flooding
  • Coastal erosion
  • Critical infrastructure damage
  • Recurrent coastal flooding
Adaptation Efforts
  • The Port Authority of New York and New Jersey provided guidelines for engineers when designing infrastructure assets to account for projected changes in temperature, precipitation, and sea level rise.
  • The cities of Binghamton, New York, and Boston, Massachusetts, promote the use of green infrastructure to build resilience, particularly in response to flooding risk.
  • In Jamaica Bay, New York, post–Superstorm Sandy efforts have fostered a set of local, regional, state, and federal actions that link resilience efforts to current climate risk, along with the potential for accelerated sea level rise and its implications for increased flood frequency.
Southwest
Impacts
  • Increasing water temperatures
  • Ocean acidification
  • Marine species vulnerabilities
  • Storm surge
  • Sea level rise
  • Recurrent coastal flooding
  • Coastal erosion
  • Critical infrastructure damage
  • Decreased water quality/availability
Adaptation Efforts
  • The City of San Francisco is implementing a plan that includes protection of San Francisco International Airport with berms and seawalls along the 8-mile (13 km) shoreline, terraced wetlands at India Basin to facilitate upland migration of marsh habitat, and avoidance of building in low-lying areas.
  • Golden Gate National Recreation Area has produced a detailed spatial analysis of the vulnerability of fields, paths, and buildings to different sea level rise scenarios and has developed adaptation options, including moving some key resources and establishing protective wetlands on inundated land.
  • In 2016, residents of the nine counties of the San Francisco Bay voted in favor of Measure AA, which provides funding for wetlands restoration to naturally reduce risks of flooding and inundation due to sea level rise and storm surge.
Southern Great Plains
Impacts
  • Increasing water temperatures
  • Marine species vulnerabilities
  • Storm surge
  • Sea level rise
  • Extreme events
  • Recurrent coastal flooding
  • Coastal erosion
  • Critical infrastructure damage
  • Decreased water quality/availability
  • Increasing air temperatures
Adaptation Efforts
  • The Texas Coastal Resiliency Master Plan promotes coastal resilience, defined as the ability of coastal resources and coastal infrastructure to withstand natural or human-induced disturbances and quickly rebound from coastal hazards. This definition encompasses the two dimensions of resilience: 1) taking actions to eliminate or reduce significant adverse impacts from natural and human-induced disturbances, and 2) responding effectively in instances when such adverse impacts cannot be avoided. To keep pace with the dynamic Texas coastline, the plan will be updated regularly to allow the state to continually assess changing coastal conditions and needs and to determine the most suitable way to implement the appropriate coastal protection solutions.
Southeast
Impacts
  • Saltwater intrusion
  • Storm surge
  • Sea level rise
  • Changing precipitation patterns
  • Recurrent coastal flooding
  • Critical infrastructure damage
  • Decreased water quality/availability
  • Increasing air temperatures
Adaptation Efforts
  • Charleston, South Carolina, has developed a Sea Level Rise Strategy that plans for 50 years out, based on moderate sea level rise scenarios, and reinvests in infrastructure, develops a response plan, and increases readiness. As of 2016, the City of Charleston has spent or set aside $235 million to complete ongoing drainage improvement projects to prevent current and future flooding.
  • Miami Beach, Florida, is in the process of investing $500 million into raising public roads and seawalls and improving storm water systems.
  • Biloxi, Mississippi, has put in place several adaptation strategies to lessen future climate change impacts, including enacting a new building code that requires a 1-foot freeboard to increase the elevation of structures above the base flood elevation.
  • Tampa Bay Water, the largest wholesale water utility in the Southeast, is coordinating with groups including the Florida Water and Climate Alliance to study the impact of climate change on its ability to provide clean water in the future.
  • Spartanburg Water, in South Carolina, is reinforcing the ability of the utility to “cope with, and recover from disruption, trends and variability in order to maintain services.”
  • The Seminole Tribe of Florida, which provides drinking and wastewater services, assessed flooding and sea level rise threats to their water infrastructure and developed potential adaptation measures.
Alaska
Impacts
  • Increasing water temperatures
  • Ocean acidification
  • Decreasing ice cover
  • Permafrost thaw
  • Marine species vulnerabilities
  • Storm surge
  • Sea level rise
  • Recurrent coastal flooding
  • Coastal erosion
  • Critical infrastructure damage
  • Increasing air temperatures
Adaptation Efforts
  • The City of Shaktoolik built a community driven, mile-long and 7-foot high berm made out of driftwood and gravel to protect itself from flooding and erosion during storm episodes.
  • Adaptations to decreased water availability include the use of rainwater catchment or other untreated water sources, reuse of water used to wash clothes or for hand hygiene, and rationing of water to prioritize drinking and cooking. The State of Alaska is funding the development and testing of decentralized water and sanitation systems that enable in-home treatment, water reuse, and other efficiencies that may be an alternative in homes without existing services or if centralized systems fail.
Hawaii and U.S.-Affiliated Pacific Islands
Impacts
  • Increasing water temperatures
  • Saltwater intrusion
  • Ocean acidification
  • Coral reef bleaching
  • Marine species vulnerabilities
  • Storm surge
  • Sea level rise
  • Recurrent coastal flooding
  • Coastal erosion
  • Changing precipitation patterns
  • Critical infrastructure damage
  • Decreased water quality/availability
Adaptation Efforts
  • Adaptation options in Hawaiʻi and the U.S.-Affiliated Pacific Islands are unique to their island context and more limited than in continental settings. While uncertainty exists about future climate projections and impacts, there have already been significant accomplishments through policy initiatives and adaptation programs, such as the accreditation of the Secretariat of the Pacific Regional Environment Programme to the Green Climate Fund; the passage of the Hawaiʻi Climate Adaptation Initiative Act; and the creation of separate climate change commissions for the City and County of Honolulu.
U.S. Caribbean
Impacts
  • Increasing water temperatures
  • Ocean acidification
  • Saltwater intrusion
  • Marine species vulnerabilities
  • Extreme events
  • Storm surge
  • Sea level rise
  • Recurrent coastal flooding
  • Coastal erosion
  • Decreased water quality/availability
Adaptation Efforts
  • The U.S. Fish and Wildlife Service and the Puerto Rico Department of Natural and Environmental Resources have funded wetlands and dune restoration projects at various sites along the coast of Puerto Rico as nonstructural solutions to coastal flooding and beach erosion.
  • Planners in low-lying cities are incorporating adaptable spaces that can accommodate occasional flood waters while providing services as parks or urban open space.
  • The Puerto Rico Technical Scientific Drought Committee has recommended harvesting rainwater, through the use of cisterns and other structural measures, for use in residential areas and encouraging the creation of existing residential projects and making rainwater harvesting mandatory for new projects.
  • In agriculture, the boom in electronic and worldwide communications is bringing old and new adaptation practices to a new generation of practitioners as they deal with age-old problems of water management and heat stress in crops and livestock.
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Figure 8.2: The figure shows selected coastal effects of climate change in several coastal regions of the United States. Source: NCA4 Regional Chapters.

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