Fourth National Climate Assessment, Vol II — Impacts, Risks,

Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States Chapter 8 Coastal Effects Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States nca2018.globalchange.gov 1

Ch. 8 Coastal Effects 8 Key Message #1 Coastal Economies and Property Are Already at Risk America’s trillion-dollar coastal property market and public infrastructure are threatened by the ongoing increase in the frequency, depth, and extent of tidal flooding due to sea level rise, with cascading impacts to the larger economy. Higher storm surges due to sea level rise and the increased probability of heavy precipitation events exacerbate the risk. Under a higher scenario (RCP8.5), many coastal communities will be transformed by the latter part of this century, and even under lower scenarios (RCP4.5 or RCP2.6), many individuals and communities will suffer financial impacts as chronic high tide flooding leads to higher costs and lower property values. Actions to plan for and adapt to more frequent, widespread, and severe coastal flooding would decrease direct losses and cascading economic impacts. Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States nca2018.globalchange.gov 2

Ch. 8 Coastal Effects 8 Key Message #2 Coastal Environments Are Already at Risk Fisheries, tourism, human health, and public safety depend on healthy coastal ecosystems that are being transformed, degraded, or lost due in part to climate change impacts, particularly sea level rise and higher numbers of extreme weather events. Restoring and conserving coastal ecosystems and adopting natural and nature-based infrastructure solutions can enhance community and ecosystem resilience to climate change, help to ensure their health and vitality, and decrease both direct and indirect impacts of climate change. Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States nca2018.globalchange.gov 3

Ch. 8 Coastal Effects 8 Key Message #3 Social Challenges Intensified As the pace and extent of coastal flooding and erosion accelerate, climate change impacts along our coasts are exacerbating preexisting social inequities, as communities face difficult questions about determining who will pay for current impacts and future adaptation and mitigation strategies and if, how, or when to relocate. In response to actual or projected climate change losses and damages, coastal communities will be among the first in the Nation to test existing climate-relevant legal frameworks and policies against these impacts and, thus, will establish precedents that will affect both coastal and non-coastal regions. Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States nca2018.globalchange.gov 4

Ch. 8 Coastal Effects Employment GDP Population Region % Land Area Millions % of US Trillions % of US 16.7 Millions % of US United States 134.0 316.5 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: Economic Importance of U.S. Coastal Areas 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, see: http://www.oceaneconomics.org/Market/coastal/coastal geographies.aspx. Source: Kildow et al.1 Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States nca2018.globalchange.gov 5

Ch. 8 Coastal Effects Fig. 8.1: Cumulative Costs of Sea Level Rise and Storm Surge to Coastal Property 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 Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States nca2018.globalchange.gov 6

Ch. 8 Coastal Effects Fig. 8.2: Regional Coastal Impacts and Adaptation Efforts The figure shows selected coastal effects of climate change in several coastal regions of the United States. See the online version of this figure at http://nca2018.globalchange.gov /chapter/8#fig-8-2 for additional examples. Source: NCA4 Regional Chapters. Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States nca2018.globalchange.gov 7

Ch. 8 Coastal Effects Fig. 8.3: Flooding Impacts in Miami Beach Tidewater is pumped back into a canal near the Venetian Causeway entrance from Purdy Avenue, where the seawall is also being raised, during a seasonal king tide in Miami Beach, Florida, in 2016. Source: Max Reed/The New York Times/Redux Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States nca2018.globalchange.gov 8

Ch. 8 Coastal Effects Fig. 8.4: Natural and Nature-Based Infrastructure Habitats Natural and nature-based infrastructure habitats include seagrass meadows (not shown), (a) coastal wetlands, (b) barrier islands, (c) beaches, (d) corals, (e) oyster reefs, and (f) dunes. Each of these habitats provides storm and erosion risk reduction by causing waves to break or slow as they roll over the ecosystem. Waves slow down, for example, as they flow across the rough surfaces and crests of reef ecosystems; likewise, water decelerates as it pushes through the vegetation of wetland ecosystems. This slowing decreases wave height and energy as the wave proceeds through or across each ecosystem, reducing the amount of erosion that the wave would otherwise cause. Photo credits: (a) Gretchen L. Grammer, NOAA National Ocean Service; (b) Erik Zobrist, NOAA Restoration Center; (c) NOAA; (d) LCDR Eric Johnson, NOAA Corps.; (e) Jonathan Wilker, Purdue University; (f) Ann Tihansky, USGS. Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States nca2018.globalchange.gov 9

Ch. 8 Coastal Effects Fig. 8.5: Societal Options for Resource Allocation in a Changing Climate Society has limited resources to help individuals and communities adapt to climate change. Panel (a) illustrates that there are finite resources available and that individuals and communities are starting from different levels of readiness to adapt. Panel (b) illustrates the option for society to choose an equal allocation of resources where everyone gets the same amount of help, or as illustrated in Panel (c), society can choose to distribute resources equitably to give people what they need to reach the same level of adaptation. Source: adapted with permission from Craig Froehle. Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States nca2018.globalchange.gov 10

Ch. 8 Coastal Effects Fig. 8.6: Impacts of the 2017 Hurricane Season Quintana Perez dumps water from a cooler into floodwaters in the aftermath of Hurricane Irma in Immokalee, Florida. Photo credit: AP Photo/Gerald Herbert. Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States nca2018.globalchange.gov 11

Ch. 8 Coastal Effects Fig. 8.7: Vision 2100: Designing the Coastal Community of the Future The City of Norfolk is building a longterm strategy to address the flooding challenges due to sea level rise. Green areas are at low risk of coastal flooding and have great potential for high-density, mixed-use, and mixedincome development. Red areas are home to key economic assets that are essential to the city’s future. Brown areas are established neighborhoods that experience more frequent flooding. Purple areas are established neighborhoods at less risk of coastal flooding. (Descriptions in the legend are from the original City of Norfolk publication.) Source: City of Norfolk 2016.120 Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States nca2018.globalchange.gov 12

Ch. 8 Coastal Effects 8 Chapter Author Team F eder a lCoor d inatin gLead Aut ho r s J effery Payne,Nati onalOc eanica ndAtm osphe ricAd minist ration WiliamV. Swee t,Nati onalOc eanica ndAtm osphe ricAd minist ration C hapt e r Lead E lizabet hFlem ing,U.S . Arm yCo rpsofE nginee rs C hapt e r Aut h or s M ichae lCragh an,U.S . Env ironm entalP rotec tionAg ency J ohnHa ines,U.S. Geo logica lSurv ey J ulietteF inziHar t,U.S . Geo logicalS urvey HeidiStile r,Nati onalOceanic andAt mosph ericAd minist ratio n ArianaS utton- Grier ,Natio nalOce anicand Atmo sphe ricAd ministr ation R eviewE dit or M ichae lKruk, ERT ,Inc. Click to edit text Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States nca2018.globalchange.gov 13

Ch. 8 Coastal Effects 8 Acknowledgments Click USGCRP to edit Coordinators text Matthew Dzaugis, Program Coordinator Christopher W. Avery, Senior Manager Allyza Lustig, Program Coordinator Fredric Lipschultz, Senior Scientist and Regional Coordinator Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States nca2018.globalchange.gov 14

Recommended chapter citation Fleming, E., J. Payne, W. Sweet, M. Craghan, J. Haines, J.F. Hart, H. Stiller, and A. Sutton-Grier, 2018: Coastal Effects. In Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change Research Program, Washington, DC, USA. doi: 10.7930/NCA4.2018.CH8 Read the full chapter https://nca2018.globalchange.gov/chapter/coastal nca2018.globalchange.gov Fourth National Climate Assessment, Vol II — Impacts, Risks, and Adaptation in the United States nca2018.globalchange.gov 15