Evaluation of flood risk management in the Dutch Delta

Transcription

1 1 2 Traditional risk assessment and safety standards for the prevention of flooding in the Netherlands. Evaluation of flood risk management on national, regional and local level. Changing risk assessment (all hazard approach) and policy development (multi layer safety concept). Presentation by Niels Robbemont, policy advisor Waterboard Hollandse Delta Talinn Estonia, September 9, Provincial government National government Water in built areas High levels of ground water Flooding of sewers Flooding of canals Failure of regional flood defense structures Failure of primary flood defense structures Flooding of unprotected areas at sea or at rivers Local government European Union (2) Safety regions waterboard Hollandse Delta in the Dutch Delta 5 6 Impact of Flooding in terms of casualties, economic and ecological damage ; 1995 Failure of a primary flood defense structures: flooding from the sea, a lake or river, maximum depth 7 meters and casualties arle likely when not evacuated in time Failure of regional flood defense structures: failure of a dyke or a quay of a regional water system, maximum depth a few decimeters, casualties are less probable when not evacuated in time Extreme rainfall in urban, industrial and agricultural areas : maximum depth a few centimeters or decimeters, casualities are not likely. Probality of Flooding in terms of years 1

2 hectares evacuees casualties fl. 1,5 billion damage Flood Disaster North Sea Coast 1953 Flood map Delta Law (1958) : closure of sea inlets between the Westerschelde and Rotterdam Waterway, improvement of primary flood defense structures to protect the land against flooding (including the definition of safety standards for primary flood defense structures) evacuees fl. 50 million damage Storm Surge Barrier (Maeslantkering) in the Rotterdam Waterway (1997) River floods in evacuees River floods in 1995 Overall objective of the Law on Flood Defense Structures (1996): maintaining the safety that has been reached by implementing the Delta Works and the improvement of river dykes Delta Law on rivers (1995) special arrangement for the fast improvement of flood defense structures along the rivers Rhine and Meuse. Law on Flood Defense Structures (1996): general rules to insure the protection against flooding by maintaining flood defense structures. 2

3 13 14 Technical Advice committee on Water management (TAW) 2000 Safety standard for primary flood defense structures (dike sections) : average exceedance probability per year of the highest water level for which the primary flood defense structure is designed, given the factors that determine its strength (heigt, stability, erosion resistance) from average exceeding probability of dike sections (primary flood defense structures) Safety standard for dike rings : average probability per year that flooding can occur by failure of a primary flood defense structure (dike section). to assessment of the flood risk of a dike ring area. Safety standars for primary flood defense structures Acceptance? Risk analysis Calculation of the economical optimum of the protection against flooding Alternatives Once in years Policy Technical, social and economical development Costs in million Total costs Investments Flood risk Conditions Dikes Maintenance and improvement Design and review rules Once in 5 years Safety check (review) and reporting Height of dikes in meters RIVM raport Dutch dikes and risk hikes (2004) RIVM report Dutch dikes and risk hikes (2004) Evaluation of Dutch Safety Policy against Flooding (2004) The individual risk of mortality, is decreased since the Flood Disaster of The economical risk is increased. The growth of population has lead to an increase of the probability of high numbers of casualties, the group risk of flooding is bigger than alle other external safety risks combined. The present spatial planning of the financial and economical value of the dike ring areas is not consistent with the spatial distribution of safety standards of the Law on primary flood defense structures (1996). An increase of the flood risk in the Netherlands is expected, due to climate change, sea level rise, soil fall, and further social and economical development. Water administrators and emergency response officials do not know eachother well and do not exercise together: the preparation of Flooding emergency management must improve! Survey Water safety 21 st century ( ) Ministry of Transport and Public Works and Water management Nine million inhabitants of the Netherlands are living and working in low areas that can flood from the North sea or from the rivers. 65 % of the national income is earned in this area. Sea level rise, heavy rainfall and increasing melting water from the Alps are causing higher water levels at the coast and in the rivers, and an increasing probability of floodings in the Netherlands. The consequences of floodings are also becoming more severe, because the population that lives behind the dikes and dunes is increasing and the economical value of the areas protected by dikes and dunes is increasing. Is the present Dutch prevention policy against flooding and the Law on primary flood defense structures (1996) still adequate, sufficient? * How can we assure that the Netherlands in future has an acceptable level of Water safety? * Must attention be directed more to the limitation of the consequences in stead of the prevention of flooding? * How can civilians, private companies and public administrations be made more aware of Water safety and what can they do themselves? 3

4 19 20 Primary flood defense structures (2006): comply with the safety standard no judgement, more research is needed 1. National Safety review on primary flood defense structures do not comply with the safety standard, improvement is necessary Flood Protection Program Hollandse Delta waterboard Improvement of primary flood defense structures at Dordrecht scenarios, strategies & capability planning National Taskforce on Flood Emergency Management (2007) and National Exercise Water Proof (2008) Floods Pandemic flu Terrorism /extremism Heat / drought Presentation Regional Flood management Plan (2009) National Risk assesment (2008) 4

5 25 26 Waarschijnlijkheid Zeer onwaarschijnlijk Mogelijk Onwaarschijnlijk Zeer waarschijnlijk Waarschijnlijk 1,0000 Catastrofaal Floods Dijkring 17 Dijkring 16 Pandemic flu Dijkring 22 Ernstige grieppandemie Milde grieppandemie Zeer ernstig Impact Dijkring 21 0,1000 Nucleair Ongeval Nuclear incident Ernstig Fires Buisleiding aardgas Brand instorting Ongeval wegtunnel Sneeuw/ijzel Ogs spoorzone Stroomuitval Extreme hitte Uitval ICT/Telecom Brand gebouw niet zelfredzame Ogs weg Onrust probleemwijk personen Onrust jaarwisseling H1N1 Epidemie Brand winkelcentrum Ongeval beroepsvaart Soc. psych. impact Buisleiding toxisch Ongeval weg Ogs bedrijven Ogs spoor Ogs water Power failure Verstoring drinkwater Aanzienlijk Regional Risk assement (2010) National Flood risk map 27 Provincial Flood risk map (2008) Uitval GMC Traffic accidents Heavy rainfall 28 Advice of 2nd Delta Committee on Climate change (2008) 29 Open and Closed Rotterdam Dordrecht Area Paniek in menigte Legionella Extreme neerslag Beperkt 0,0100 Brand binnenstad 30 Overflow areas Volkerak-Zoommeer Grevelingen 5

6 31 32 National Waterplan (2009) Objectives of the Dutch Law on Water (2009) : 1. to prevent and where necessary limit floods, effects of heavy rainfall and shortage of water, in relation with: 2. protection and improvement of the chemical and ecological quality of water systems, and; 3. realisation of functions for society of water systems such as water for fire extinguishing, drinking water, industrial water, recreation, transport, ecological purposes. Multi-layer safety as central approach Flood safety policy is aimed at flood risk management, the most important task being to deal witch uncertainties sensibly. The Cabinet uses a risk assessment to select a sustainable approach aimed at multi-layer safety. Policy is directed towards protection against water and limiting social disruption in the event of a disaster. Multi-layer safety consists of three layers: 1. Prevention as the policy cornerstone; 2. Sustainable spatial planning; 3. Systematising and sustaining disaster mitigation Evaluatie van overstromingsrisico s in de Hollandse Delta European 1. Dealing with flood risks caused by sea level rising and higher river levels: City in Water. 2. Dealing with flood risks caused by extreme rainfall: Water in the City. Flood Directive 2007/60/EC 6

7 37 38 Flood risk assessment in river bassins leads to Regional Flood hazard map Flood risk management plans in Questions for discussion * Can the concept of multy-layer safety also be applied in other European towns and regions, where are already best practices? Regional Flood risk map * Which policy choices have to be made? - to limit the possibility of floods (prevention) - to limit the effects of floods (spatial planning) - to accept floods (prepare for flood emergency management) * How are policy choices reached? - ongoing debate between politics, policy, science, public opinion - prioritizing in relation to available funding and finances - sectoral or integrated cost benefit analysis 7