Andersson, H.

Arns, A. 

Dangendorf, S.

Jensen, J.

Jönsson, A.

Knudsen, Per

Leijala, U.

Madsen, K. S.

Nerheim, S.

Nilsen, J. E. Ø.

Pellikka, H.

Ravndal, O.

Sande, H.

Simpson, M. J. R. 

Sørensen , P.

Sørensen, Carlo Sass

Online Research Database In Technology

                       General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.  • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal   If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.     Downloaded from orbit.dtu.dk on: Nov 09, 2017Towards a Regional Assessment of Coastal Flood Risk: A review of Methods Appliedin Norway, Sweden, Finland, Denmark, and GermanyNilsen, J. E. Ø. ; Sørensen, Carlo Sass; Dangendorf, S.; Andersson, H.; Arns, A. ; Jensen, J. ; Jönsson,A.; Knudsen, Per; Leijala, U. ; Madsen, K. S.; Nerheim, S.;  Pellikka, H.; Ravndal, O.; Sande, H.; Simpson,M. J. R. ; Sørensen , P.Publication date:2017Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Nilsen, J. E. Ø., Sørensen, C. S., Dangendorf, S., Andersson, H., Arns, A., Jensen, J., ... Sørensen , P. (2017).Towards a Regional Assessment of Coastal Flood Risk: A review of Methods Applied in Norway, Sweden,Finland, Denmark, and Germany. Poster session presented at International WCRP/IOC Conference 2017:Regional Sea Level Changes and Coastal Impacts, New York, United States.METHODOLOGICAL DIFFERENCESPHYSICAL DIFFERENCESTowards a Regional Assessment of Coastal Flood Risk A review of Methods Applied in Norway, Sweden, Finland, Denmark, and GermanyJ.E.Ø. Nilsen1, C. Sørensen2, S. Dangendorf3, H. Andersson4, A. Arns3, J. Jensen3, A. Jönsson4, P. Knudsen2, U. Leijala5, K.S. Madsen6 , S. Nerheim4, H. Pellikka5, O. Ravndal7, H. Sande7, M.J.R. Simpson8, and P. Sørensen9Jan Even Øie Nilsen, Nansen Environmental and Remote Sensing Center, even@nersc.no, +47 952 93 329  |  www.nersc.no  |  www.bjerknessenteret.no Affiliations and acknowledgements1: Nansen Environmental and Remote Sensing Center and Bjerknes Centre for Climate Research, Bergen, Norway (even@nersc.no)2: DTU Space, Kgs. Lyngby, Denmark (carlos@space.dtu.dk; pk@space.dtu.dk)3: Research Institute for Water and Environment, University of Siegen, Siegen, Germany (soenke.dangendorf@uni-siegen.de; arne.arns@uni-siegen.de; juergen.jensen@uni-siegen.de)4: Swedish Meteorological and Hydrological Institute (helen.andersson@smhi.se; anette.jonsson@smhi.se; signild.nerheim@smhi.se) 5: Finnish Meteorological Institute (ulpu.leijala@fmi.fi; havu.pellikka@fmi.fi)6: Danish Meteorological Institute (kma@dmi.dk)7: Hydrographic Service, Norwegian Mapping Authority, Stavanger, Norway (oda.ravndal@kartverket.no; hilde.sande.borck@kartverket.no)8: Geodetic Institute, Norwegian Mapping Authority, Hønefoss, Norway (matthew.simpson@kartverket.no)9: Danish Coastal Authority, Lemvig, Denmark (pso@kyst.dk)Extreme Value Analyses and return water levels usedRavndal & Sande (2016) Norway:• 23 tide gauges• 25–100 year series • Detrended• ACER-method• 20, 200, 1000 years RWL• analysis between tide gauge stations  done using local tide and nearest observed weather effectSørensen et al. (2012)Denmark:• 68 tide gauges• 15–125 year series • Detrended• POT-method (mostly)• 20, 50, 100 years RWL• Interpolation between tide gauge stationsSweden:• 23 tide gauges• 40–130 year series• Detrended• GEV-method• 100, 200 years RWL• Regional recommendations for lowest allowed building (RWL+safety)• Tides partially included in EVANerheim et al. (2013)Germany:• Different methods between states• Both 100 and 200 years RWL used as design levels• + some safety North SeaDeterministicapproach EVA Design floodArns et al. (2013)Finland:• 14 tide gauges• 84–130 year series• Detrended• Exponential distribution fitted to monthly maxima of the last 30 years• 20, 50, 100, 250,1000 years RWL• Lowest recommended building heights based on 1/250 events/year in 2100 + wave margin• Interpolation between tide gauge stationsDifferent impact potentials: urban- and geomorphology1ThyborønHamburg A ‘hallig’StavangerKabelvågMarit Hommedal/SCANPIXBryggenSkanörFärjestadenA PIC FROM FINLAND?Tidal rangesAVISO/CNESReturn Water Levels~2 m~1 m~5 m200 year return heights~3 mWahl et al. (pers. comm.)Simpson et al. (2015)~2 mProjected Sea Level ChangesRef: IPCC AR5 Chapter 13.  Data: http://icdc.zmaw.de/ar5_slr.html- 10 cm+ 80 cm+ 40 cmSea level projections used1In general no political decided number to use …Germany:• IPCC AR5 based• Coastal protection climate change surcharge depends on federal state (e.g., 50 cm in Schleswig-Holstein)Norway:• IPCC AR5 based• Land uplift based on observations• National recommendation RCP8.5 & 95% boundStavangermetersSimpson et al. (2015)Denmark:• IPCC AR5 based• Grinsted et al. (2015)HIGHERVALUESHIGHENDFOCUSPROBABILISTICMETHODGrinsted et al. (2015)ReferencesArns, A., Wahl, T., Dangendorf, S., Mudersbach, C., Jensen, J., (2013). Ermittlung regionalisierter Extremwasserstände für die Schleswig-Holsteinische Nordseeküste. Hydrologie und Wasserbewirtschaftung, HW57, 2013, H. 6.Church, J.A., et al. (2013): Sea Level Change. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I  to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.Grinsted A., S. Jevrejeva, R.E.M. Riva, D. Dahl-Jensen (2015). Sea level rise projections for northern Europe under RCP8.5. Clim. Res. 64, doi: 10.3354/cr01309.Jevrejeva, S., A. Grinsted, J.C. Moore (2014). Upper limit for sea level projections by 2100. Environ. Res. Lett. 9, doi:10.1088/1748-9326/9/10/104008.Nerheim. S., M. Asp, D. Eklund, J. Södling (2013). Pilotstudie: Metoder för att ta fram extrema havsvattenstånd med låg sannolikhet. SMHI rapp. nr. 2013-46.Ravndal, O.R., Sande B., H. (2016) Ekstremverdianalyse av vannstandsdata langs norskekysten, Internal report, NMA Hydr. Serv. rep.Simpson, M.J.R., J.E.Ø. Nilsen, O.R. Ravndal, K. Breili, H. Sande, H.P. Kierulf, H. Steffen, E. Jansen, M. Carson and O. Vestøl (2015). Sea Level Change for Norway: Past and Present Observations and Projections to 2100. Norwegian Centre for Climate Services report 1/2015, ISSN 2387-3027, Oslo, Norway. 155 pp. doi: 10.13140/RG.2.1.2224.9440.Sørensen, C., H.T. Madsen, S.B. Knudsen (2013). Højvandsstatistikker 2012. Rapport fra Kystdirektoratet.Wahl et al. (pers. comm.)Are methodological differences important? Hornbæk Havn 20127 yrs∆100-200 yrs ≈ 10 cm∆ method ≈ 10-15 cm10 cm ≈ double frequency = double likelyhood+10 cm ≈ 1 million €/km200 yrs100 yrsWith 80 cm of future sea level riseWith 30 cm of future sea level riseTV2Tides1 year200 years20 years1000 years‘Bryggen’inBergen, NorwayFrequency050100150200250 300-50-100350Projected 50 cm sea level rise by 2100 (ensemble mean)Weather effectsSea level rise giveshigher return heights andflooding more oftenMAP ZEROkartverket.no/sehavnivaFlood risk – a combination of tidal-regime, extreme values, and sea level rise20 years return height, Jan Lillebø/BT 2007Return water levels (RWL)Conclusion›Regional collaboration is needed•Share views and experiences•Learn from each other and develop relevant methods•Gain a deeper understanding of current and future physical processes governing extreme events•Discuss potential challenges in the work ahead•Foster cross-disciplinary research•Improve collaboration between science and governanceResults from (~50%) subsamples diverge severely› Study in Sweden› Demand for upper bound, for design values › Worst storm in present climate is unknown› Statistical EVA is problematic for return periods longer than twice the time series• Most countries have at best 100 or some years time series› Modelling deemed more suitable for design values• Models need to preserve energy at all frequencies• Forcing at borders needs to have realistic extremes• But hard to assess what a worst possible low pressure system isDoes an upper bound exist? 1902 Christmas storm in Lomma 206 cmWhat about the more rare extremes?Nerheim et al. (2013)Finland:• An ensemble of several recent GMSL predictions, including IPCC AR5 (details in Johansson et al. 2014)• Land uplift, uneven distribution of GMSL rise, and changes in the Baltic Sea water balance accounted for.Sweden:• IPCC AR5 based• Land uplift based on updated modelling• Recommendation RCP8.5 & 95% bound from regional authoritiesHelsinkiAn alternative method to assess rare extremes is to include evidence of historic events. See also poster 45 today by Madsen et al.

Towards a Regional Assessment of Coastal Flood Risk: A review of Methods Applied in Norway, Sweden, Finland, Denmark, and Germany

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Towards a Regional Assessment of Coastal Flood Risk: A review of Methods Applied in Norway, Sweden, Finland, Denmark, and Germany

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