Coastal flood defence in a changing climate: the Schleswig-Holstein approach

Transcription

1 Coastal flood defence in a changing climate: the Schleswig-Holstein approach Jacobus Hofstede Dr. Jacobus Hofstede MELUR SH 1

2 World map of natural hazards (Munich Re ) Dr. Jacobus Hofstede MELUR SH 2

3 The German situation Federally organised in 16 States (not comparable to DK regions) Five coastal states (16 million inhabitants); coastal lowlands (2.5 million) Five coastal States are responsible for coastal risk management State Acts define CRM responsibilities (state, municipalities, boards) State coastal risk management strategies are described in master plans State schemes all apply uniform safety standards => no risk considerations Dr. Jacobus Hofstede MELUR SH 3

4 The Schleswig-Holstein case What is coastal flood-prone? - Area: 3,900 km 2 - Inhabitants: 354,000 - Capital assets: 48 billion How do we protect? - State dikes: 433 km - Regional dikes: 92 km - Second dike line: 550 km - Sluices, barrages: Revetments: 187 ha - Sand suppletion: 1 Mio. m 3 /a State budget: 68 million /a Employees: ca. 650 Dr. Jacobus Hofstede MELUR SH 4

5 Schleswig-Holstein State Water Act Coastal risk management is in the responsibility of the persons who profit, unless.. Building and maintenance of dikes and dams that are in public interest, is a public obligation (coastal flood defence). The responsibility falls to: - the State for State dikes and regional dikes on islands - Water Boards or Municipalities for other regional dikes, secondary dikes and dams Safeguarding the islands from coastal retreat is a State responsibility, as far as it is in public interest (coastal protection) Safeguarding the Wadden Sea from erosion is a State responsibility, as far as it is in the public interest (energy dissipation zone) Salt marsh management is a State responsibility, as far as necessary to maintain its functionality to protect State dikes (energy dissipation zone) Dr. Jacobus Hofstede MELUR SH 5

6 Financing schemes in CRM State budget (ca. 68 Mio. /a) originates from: State Government: 50% Federal Government: 35% EU-funds: 15% Co-funding of third parties (water boards and municipalities) Mostly upon application (criteria dependent, no guarantee) Up to 90% of total costs CRM in municipality of Scharbeutz Dr. Jacobus Hofstede MELUR SH 6

7 Master plan coastal risk management Contents: 1. Introduction 2. Strategic objectives 3. Overview 4. Framework (Climate Change) 5. Balance since Coastal flood defense 7. Coastal protection 8. Coastal risk management 9. Summary and outlook Dr. Jacobus Hofstede MELUR SH 7

8 Master plan novelties One safety standard for all State dikes (storm water level probability 0.5%/a) Introduction of the concept building reserve Implementation of the EU-Floods-Directive (risk areas and maps) Safety considerations for the second dike-line Establishment of a Common Strategy Wadden Sea 2100 for nature conservation and coastal risk management Introduction of the Coastal Risk Management Cycle Dr. Jacobus Hofstede MELUR SH 8

9 Climate Change Frenzel 2008 Dr. Jacobus Hofstede MELUR SH 9

10 Sea level (cm; varying base levels) Mean sea level change since Travemünde Delfzijl Mean Cuxhaven Den Helder 6th order polynomal Since 1885: MSL-rise of 0.17 cm/y = 20.4 cm (R 2 = 0,82) Years Dr. Jacobus Hofstede MELUR SH 10

11 Storm surge development Travemünde (Baltic Sea) Husum (North Sea) Dr. Jacobus Hofstede MELUR SH 11

12 Sea level (cm) Global mean SLR-projections Unknown factors: result SLR Greenland and West Antarctic ice caps CO 2 sinks (ocean, tropical forests) NO emissions (ocean floor, permafrost) What happens after 2100? Snow precipitation on Antarctica? Blockung of Gulf Stream?? 25 0 Sea level scenarios ( ): IPCC (2007): m Horton et al. (2008): m Delta Commission (2008): m Grinsted (2009): m Vermeer/Rahmstorf (2009) m m! IPCC Years Dr. Jacobus Hofstede MELUR SH 12

13 Storm surge projections (2100) Institut für Ostseeforschung Warnemünde (2011) Helmholz-Zentrum-Geesthacht (2006) Dr. Jacobus Hofstede MELUR SH 13

14 The challenge of climate change Mean sea level rise: 0,5 1.0 m until 2100 Storm wind setup: few decimeters until 2100 Storm surge water levels: 0,5 1.5 m until 2100 conclusions: Coastal risk management has to adapt in the mid to long term to strongly increasing hydrographic forcing and stresses (hazards of coastal flooding and coastal erosion)! The uncertainties about the exact magnitude are large (and even increasing) Key messages for adaptation: Flexibility => no-regret measures Sustainability => integrated and holistic approaches (CRM-cycle) Dr. Jacobus Hofstede MELUR SH 14

15 No-regret adaptation 1: safety margin Safety margin: 0.5 m Storm wave run up Storm water level Mean tidal high water Mean sea level Dr. Jacobus Hofstede MELUR SH 15

16 No-regret adaptation 2: building reserve Ca. 1.5 m Building reserve in case of stronger sea-level rise (> 0.5 m) Dike profile considering the option of a building reserve traditional dike strengthening considering a safety margin for sea-level rise of 0.5 m Underdimensioned dike Dr. Jacobus Hofstede MELUR SH 16

17 Integrated and holistic approach: CRM-cycle A natural hazard (e.g., coastal flooding, coastal retreat) is an event in the physical environment that is perceived by mankind as a threat to life and property Risk is a combination of the probability of that hazard with its harmfulness (damage expectations) Coastal risk management involves all (structural and non-structural) measures to avoid and reduce vulnerabilities against coastal hazards Technical flood defence and protection aims at reducing the probability Regional and town planning as well as disaster management aim at reducing the damage expectations Dr. Jacobus Hofstede MELUR SH 17

18 Reduce damage expectations Regional (development) planning: Building ban in areas up to 50 m behind shorelines, cliffs and sea walls Building codes in coastal lowlands not protected by state sea walls: Residential buildings: > NHN +3.5 m Other buildings: > NHN +3.0 m Infrastructure: > NHN +3.0 m Storage of hazardous substances: > NHN +3.5 m Areas of preference and of reservation for CRM Town (building) planning: flood-proof housing Dr. Jacobus Hofstede MLUR SH 18

19 Preparedness (risk communication) Brochure to all households Flood warning Dr. Jacobus Hofstede MELUR SH 19

20 TAK FOR OPMÆRKSOMHEDEN! Dr. Jacobus Hofstede MELUR SH 20