PDF version - the USGS

Vulnerability of U.S. National Parks to Sea-Level Rise andCoastal ChangeIntroductionThe National Park Service (NPS)manages nearly 12,000 kilometers(7,500 miles) of shorelines along oceansand the Great Lakes. In 2001, the U.S.Geological Survey (USGS), in partnershipwith the NPS Geologic ResourcesDivision, began conducting hazardassessments and creating map products(fig. 1) to assist the NPS in managingvulnerable coastal resources.One of the most important andpractical issues in coastal geology isdetermining the physical response ofcoastal environments to water-levelchanges. Two trends may affect shorelinesin U.S. national parks: rising globalsea level and falling Great Lakeswater levels.Global sea level has risen about 18centimeters (7.1 inches) in the past century(Douglas, 1997). Computer modelssuggest that climate change will causean additional rise of 48 cm (18.9 in.) bythe year 2100 (Intergovernmental Panelon Climate Change, 2001), which ismore than double the rate of sea-levelrise over the past century. Thus, sealevelrise is expected to have a large,sustained impact on future coastal evolution.Potential effects include coastalerosion, saltwater intrusion into groundwateraquifers, inundation of wetlandsand estuaries, and threats to culturaland historic resources, as well as parkinfrastructure.Water levels in the Great Lakes havefluctuated over the past century by asmuch as 1.9 meters (6.2 feet). Changingclimate is predicted to cause lake levels todecline by as much as 2.4 m (7.9 ft) overthe next century (Great Lakes RegionalAssessment Group, 2000). Potentialeffects include reducing areas accessibleto cargo and recreational boats, exposingtoxic sediments, and declining productionof plankton that support fish.Variables Affecting CoastalVulnerabilityPredicting future coastal evolutionand vulnerability to change is difficultbecause many factors are involved. TheUSGS is implementing a classificationof the relative vulnerability of differentU.S. coastal environments to future sealevelrise (see Hammar-Klose and Thieler,2001) and water-level changes in theGreat Lakes. For coastal regions, thevulnerability classification is based onthe relative contributions and interactionsof six variables:1. Tidal range, which contributes toinundation hazards2. Wave height, which is linked to inundationhazards3. Coastal slope (steepness or flatness ofthe coastal region), which is linked tothe susceptibility of a coast to inundationby flooding and to the rapidityof shoreline retreat or advance4. Historic shoreline change rates, whichindicate how fast a section of shorelinehas been eroding or accreting5. Geomorphology, which indicates therelative erodibility of a section ofshoreline6. Historical rates of relative sea-levelchange, which correspond to how theglobal (eustatic) sea-level rise andlocal vertical land motion, such astectonic uplift or subsidence, haveaffected a section of shorelineThe Vulnerability IndexThe USGS rating system classifiesthe data variables according to risk. Amathematical formula allows scientiststo relate different types of data and tocalculate an index value. This approachcombines the coastal system’s susceptibilityto change with its natural abilityto adapt to changing environmental conditions,yielding a quantitative measureof the park’s vulnerability to the effectsCOASTAL VULNERABILITY INDEXCape Cod National SeashoreKilometers0 5NRisk RankingLowModerateHighVery highFigure 1. Map of the coastal vulnerability index(CVI) for Cape Cod National Seashore in Massachusettsshowing the relative vulnerability ofthe coast to changes in sea level. Areas alongthe coast are assigned a ranking from low tovery high risk, based on the analysis of physicalvariables that contribute to coastal change.of sea-level rise or changes in lakelevel. The coastal vulnerability index(CVI) value is a relative ranking of thelikelihood that physical change willoccur along the shoreline as sea level orlake level changes, and it serves as anobjective tool for scientists and parkmanagers.U.S. Department of the InteriorU.S. Geological SurveyUSGS Fact Sheet FS–095–02September 2002

Figure 2. A narrow beach and eroded dunesresult from a recent winter storm at CoastGuard Beach, Cape Cod National Seashore,Mass. Photograph courtesy of the NationalPark Service.Assessment of NationalPark System UnitsPilot assessments have been completedfor Cape Cod National Seashorein Massachusetts, Gulf Islands NationalSeashore in Mississippi and Florida,and Olympic National Park in Washington.Preliminary results from the USGSinvestigations show important differencesin and among parks in terms oftheir vulnerability to coastal changedue to future sea-level rise. For example,Cape Cod National Seashore has avariable coastal landscape consisting ofhigh glacial bluffs, beaches, sand spits,and salt-marsh wetlands. The areasmost vulnerable to sea-level rise (fig. 1)have the lowest regional coastal slopes,geomorphologic types that are susceptibleto inundation, and the highest ratesof shoreline change (fig. 2). Areasbacked by glacial bluffs, comprisingmuch of the coast, have a CVI indicatinglow risk. Conversely, Gulf IslandsNational Seashore has large areas ofvery high risk, because it is almostentirely a low-lying barrier-island systemlocated on a low regional coastalslope (fig. 3).Some park areas that are at thegreatest risk are also culturally significantor very popular. In Gulf IslandsNational Seashore, Civil War-era FortFigure 4. Kalaloch Lodge in Olympic NationalPark, Wash., is threatened by erosion. Longtermplans call for moving the lodge back fromthe cliff edge. Photograph by Erika Hammar-Klose, USGS.Massachusetts is at great risk becauseof high rates of erosion, the low-slopingcoastal plain, and the low-lying barrierisland morphology. In contrast, most ofCape Cod National Seashore’s infrastructureis located on high-elevationuplands away from the shore, and mosthigh-visitor-use areas are accessibleprimarily by foot.National Park Service staff areusing the CVI data for long-termresource management plans, park facilitiesplanning such as relocating coastalbuildings or roads, and assessing longtermthreats to cultural resources. Forexample, data from the Olympic NationalPark CVI study were used to identifyvulnerable infrastructure and implementplans to relocate the Kalaloch Lodge(fig. 4). The data are also being integratedinto the park’s general managementplan, the primary long-term planningdocument for the park. Future work forthis cooperative project between theUSGS and the NPS will map the coastalvulnerability index at additional parksthroughout the United States and U.S.territories.ReferencesDouglas, B.C., 1997, Global sea rise; Aredetermination: Surveys in Geophysics,v. 18, p. 279–292.Great Lakes Regional AssessmentGroup, 2000, Preparing for a changingclimate; The potential consequencesof climate variability andchange—Great Lakes overview(edited by P.J. Sousounis and J.M.Bisanz): Ann Arbor, MI, Universityof Michigan, 106 p.Hammar-Klose, E.S., and Thieler, E.R.,2001, Coastal vulnerability to sealevelrise: A preliminary databasefor the U.S. Atlantic, Pacific, andGulf of Mexico coasts: U.S. GeologicalSurvey Digital Data SeriesDDS–68, one CD-ROM (Availableonline athttp://pubs.usgs.gov/dds/dds68/)Intergovernmental Panel on ClimateChange, 2001, Climate change 2001;The scientific basis, contribution ofWorking Group I to the third assessmentreport of the IntergovernmentalPanel on Climate Change: Cambridge,England, Cambridge University Press,944 p. (Available online athttp://www.ipcc.ch/)For additional information, pleasecontact:E. Robert Thieler andS. Jeffress WilliamsU.S. Geological Survey384 Woods Hole RoadWoods Hole, MA 02543–1598E-mail: rthieler@usgs.govjwilliams@usgs.govTelephone: 508–548–8700Web: http://woodshole.er.usgs.gov/project-pages/nps-cvi/Rebecca BeaversNational Park ServiceNatural Resource Program CenterGeologic Resources DivisionP.O. Box 25287Denver, CO 80225–0287E-mail: Rebecca_Beavers@nps.govTelephone: 303–987–6945Figure 3. Most of the Gulf Islands National Seashore, Miss. and Fla., is composed of low-lying barrier islands. In many locations, you can seefrom the ocean to the sound, as shown above. A combination of variables makes this seashore highly vulnerable to predicted sea-level rise.Photograph by Erika Hammar-Klose, USGS.