Need for a paradigm shift Transition towards resilient approaches

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Insight into costs/benefits of flood proofing
buildings in the Netherlands
Berry Gersonius UNESCO-IHE
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Content
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• Need for a paradigm shift
• Resilient approaches
• Strategies to cope with uncertainty
• Investigated flood mitigation strategies

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Need for a paradigm shiftTowards resilient
approaches
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• Triggers
• Urbanisation breaking the spiral
• Climate change and extremes
• Opportunities for innovations (re)development
  projects

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Urbanisation Breaking the spiralSocial feedback
(after Geldof)
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Unsafe
Society
water system
Technique
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Urbanisation Breaking the spiralSocial feedback
(after Geldof)
?
safe
Society
water system
Techniek
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Urbanisation Breaking the spiralSocial feedback
(after Geldof)
?
unsafe
Society
water- systeem
Techniek
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Climate changeIncrease in probability of extreme
precipitation
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• Source Palmer and Räisänen (2002)

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Climate changeIncreased uncertainty
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• CC is trend breaker future climate cannot be
  predicted on the basis of past events

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Climate change alone not sufficient
incentiveLook for synergy Maasbommel
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• Tipping point is near to adjust current flood
  management policies on local scale in hot spot
  areas

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Paradigm shiftKey components of way forward
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• Demonstration and experimentation
• Take a long-term perspective
• More holistic approach weakest link
• Plan for failure
• Stakeholder involvement
• Clear definition of responsibilities
• Climate change adaptability

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Plan for extreme events (e.g. failure of
defences)New Orleans (ASCE, 2007)
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• No breaching Breaching

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Stakeholder involvementPreparedness and active
role in decision making
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Clear definition of responsibilitiesWho pays
when? (Kron, 2007)
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Climate change adaptability(after Defra, 2006a)
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Multiple interventions
Acceptable risk level
Big infrastructure investment
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Attainable through adopting a resilient approach
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• Address all floods, not just one
• Impact driven
• Extreme events (e.g. failure of defences) as
  design variable
• Counteract uncertainty by providing system
  resilience

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Design principles of resilient systems(Pelling
et al, 2005)
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• Some degree of excess capacity
• Redundancy / overlapping functions
• Information
• Adaptability / reponsive decision making
• Diversity
• Autonomy (in life support systems)
• Redistribute costs (insurance)
• Learning from past / experimentation / innovation

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Strategies for urban areas
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• Designing multi-use spaces
• Creating flood resistant cells and back-up
  systems
• compartmentalizion
• controlled inundation
• Integration of design with evacuation
• Early warning systems and response plans
• Tools to assess effectiveness of strategies

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Strategies for urban areasUFM project
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Main dyke
Second defence line
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Strategies for urban areasUFM project
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Vertical evacuation
Dry proofing, wet proofing
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HafencityLarge scale application
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HafencityVertical evacuation
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Strategies and their performanceEffectiveness
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Resistance strategy
Loss
Resilience strategy
Recurrence time
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0.3 m3/m2
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0.3 m3/m2
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0.3 m3/m2
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0.3 m3/m2
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Estimating lossesPenning-Rowsell
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Assemble all available data that links flood
damage to key determinants for different types of
property
Yes
Is any flood damage data available?
Assemble data for a synthetic flood damage
database
No
28
Estimating lossesPenning-Rowsell
?
Assemble all available data that links flood
damage to key determinants for different types of
property
Yes
Is any flood damage data available?
In the Netherlands only on meso scale
Assemble data for a synthetic flood damage
database
No
29
Components of synthetic approachesPenning-Rowsell

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• Asset values at risk (buildings and contents)
• Asset susceptibility (the percentage loss)
• Key determinants of flood damage (depth,
  duration, warning, velocity)
• Level of aggregation (individual buildings)

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House typesUFM Dordrecht
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• Detached single-family dwelling of 60 m2
• Semi-detached single-family dwelling of 53 m2
• Terraced house of 48 m2
• Terraced house of 40 m2
• Ground floor flat of 80 m2

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Flood Damage Duration lt 6h
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Flood DamageDuration gt 72h
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Flood DamageDuration lt 6h
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• Depth lt 0.2m

• Depth lt 1.0m

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Flood DamageDuration gt 72h
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• Depth lt 0.2m

• Depth lt 1.0m

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Investigated flood mitigation strategies
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Investigated flood mitigation strategiesExtra
cost
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Potential reduction in flood damage Duration lt 6h
?
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Potential reduction in flood damage Duration gt
72h
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Components of synthetic approachesPenning-Rowsell

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• Asset values at risk (buildings and contents)
• Asset susceptibility (the percentage loss)
• Key determinants of flood damage (depth,
  duration, warning, velocity)
• Level of aggregation (individual buildings)
• Flood probability data
• In order to convert event damages into annual
  average damages

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Potential reduction in annual flood damageCity
of Dordrecht
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• 3000 homes not protected by primairy defence
• Major redevelopments planned outside primairy
  defence

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Potential reduction in annual flood
damageProbability data and elevation
?
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Potential reduction in annual flood damageWater
level-frequency relationship
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Potential reduction in annual flood
damageComponents
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• Elevation
• Water level-frequency relationship

• Annual damage

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Potential reduction in annual flood
damageBenefits reduction of annual flood damage
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Loss
Normal building
Recurrence time
With flood mitigation
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Cost benefit ratios as a function of land
elevation Duration lt 6h
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1/10 1/200 1/4000 1/10000
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Cost benefit ratios as a function of land
elevation Duration gt 72h
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1/10 1/200 1/4000 1/10000
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Feasibility of flood mitigation strategiesCity
of Dordrecht
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