Comparing structural & non-structural measures

Transcription

1 Comparing structural & non-structural measures Kees Bons Flood Risk Management and Urban Resilience Workshop II 12 februari 2010 May 28-29, 2013 Venue COEX, Seoul, Republic of Korea

2 Urban Flooding Issues o o o o o o Unplanned Urban expansion and growth into river valleys and coastal areas Water supply, Drainage, Waste water and Flood protection did not develop as fast as the growing needs Subsidence (due to overexploitation of GW) Ineffective Operation and Maintenance of flood defences, pumping stations and drains. Loss of natural defences (for example, mangroves) Climate Change? (more extremes, sea level change)

3 No solutions, just responses Structural adaptation measures (SAMs): Constructed permanent facilities to reduce the damage risk Non-structural adaptation measures (NSAMs): Responses to urban water problems that may not involve fixed or permanent facilities. Their positive contribution to risk reduction is most likely through a process of influencing behavior, usually through building capacity in all stakeholders through active learning and appropriate and effective engagement between stakeholders (Taylor and Wong, 2002).

4 12 guiding policy principles 1. Every flood risk scenario is different: there is no flood management blueprint. 2. Designs for flood management must be able to cope with a changing and uncertain future. 3. Rapid urbanization requires the integration of flood risk management into regular urban planning and governance. 4. An integrated strategy requires the use of both structural and non-structural measures and good metrics for getting the balance right. 5. Heavily engineered structural measures can transfer risk upstream and downstream. 6. It is impossible to entirely eliminate the risk from flooding. 7. Many flood management measures have multiple co-benefits over and above their flood management role. 8. It is important to consider the wider social and ecological consequences of flood management spending. 9. Clarity of responsibility for constructing and running flood risk programs is critical. 10.Implementing flood risk management measures requires multi-stakeholder cooperation. 11.Continuous communication to raise awareness and reinforce preparedness is necessary. 12.Plan to recover quickly after flooding and use the recovery to build capacity.

5 (changing) threshold strength Flood protection measures: Result of extensive vulnerability analysis (changes in) pressures probability of failure damage sensitivity o hazard map risk risk adaptability vulnerability protection strategy map protection hot spot map measures o sometimes called vulnerability or susceptibility

6 Measures we could take to reduce flood risk > 200 adaptation measures identified.. SAMs: Structural (hard) measures (# >100) Collective: e.g. dikes, drainage systems Individual: e.g. wet or dry proofing NSAMs: Non-structural (soft) measures (# > 100) Collective: e.g. contingency plans, legislation Individual: e.g. risk consciousness, insurance and counting

7 Adaptation measures Objective: Reduce vulnerability of urban areas by avoiding damage damage reduction creating redundancy and adaptability for long term, unexpected change But what is their effect and effectivity? (e.g. retention pond) In everyday situation Under design conditions (T = years) Under very extreme conditions (T = 500 >1000 years)

8 What if we rely only on structural measures - When they fail they often fail dramatically (a chain is as strong as its weakest link) - Structural measures cannot evolve with development - Structural measures generally require high investments - Structural measures often have major side-effects

9 Strategy to reduce/manage vulnerability Strengthen four capacities* to reduce vulnerability Coping capacity Adaptive capacity Threshold capacity Recovery capacity recurrence time * Graaf, R. de, N. van de Giesen and F. van de Ven, 2007, Alternative water management options to reduce vulnerability for climate change in the Netherlands, Natural Hazards nov.

10 Traditional Vulnerability reduction approach First priority: SAMs to strengthen threshold capacity for fluvial and coastal flooding e.g. World Bank (2010) Climate risk and Adaptation in Asian Coastal Megacities Consequences: Other capacities and NSAMs get neglected Increased vulnerability for other risks e.g. pluvial flooding, drought, land subsidence, heat Lock-in Effectivity in very extreme conditions (T>100 yr) is poor Adaptability is limited

11 Vulnerability reduction approach Conclusion: Strengthen all four capacities SAMs show limited adaptability Most SAMs strengthen threshold & coping capacity SAMs require high federal or regional investments NSAMs require less, local or individual investments NSAMs require study (learning) and regular training SAMs can t do without NSAMs

12 SAMs can t do without NSAMs What would have happened in Holland without effective flood early warning system in Indonesia with an effective tsunami warning system in New Orleans without an effective evacuation plan in Brisbane if their zoning plan had been water resilient SAMS are only effective if people are aware, prepared, trained and space use and construction are regulated (and preparedness, rules and regulations are maintained) Considering all the uncertainties the buzz word now is: ADAPTIVE Management NSAMS prove to be much more adaptive than SAMS Watervraag beleidsopties Waterbeschikbaarheid beleidsopties Raise level +1.1 m in spring Adapt regional water system infrastructure. Raise dikes. More water to Ijssel in spring Decrease level and adapt infrastructure (-0.8?) Lower navigation sluices. Increasing pumping capacity. Strenthen dikes. Lower inlet structures. Raise level +0.6 m Raise dikes. More water to Ijssel. Adapt regional watersystem infrastructure Decrease level within current infra (-0.6?) Accept navigation abstruction during extreme drougths Raise IJsselLake level within current infra +0.1 More water through IJssel in summer. Afh. NWW Optimising current policy Flexible water levels Current policy m NAP More efficient water use e.g. increase regional storage, flushing optimalisation, flex level control. After 2050 pumping capacity needs to be increased. Change to drougth/salt tolerant crops After 2050 pumping capacity needs to be increased Change land use Scenario s Steam

13 How to select an appropriate set of AMs? Three-step approach 1: Complete vulnerability-analysis 2: Select a strategy to reduce vulnerability 3: Select appropriate set of measures many stakeholders / many stakes many SAMs and NSAMs design and negotiation approach

14 probability (1/year) Every situation is unique and dynamic Type of flood (fluvial, pluvial, coastal, ground water) Development and (spatial) planning stage Economic and social values Culture and government style Individual vs Community Environment 0,0012 0,0010 0,0008 0,0006 0,0004 0,0002 0, year

15 Resulting portfolio of AMs Measures to strengthen 1. Threshold capacity Waterrobust infrastructure Enlarged seasonal storage High floor level vs street level Floating housing 4. Adaptive capacity Temporary houses & buildings Adaptive management Water-based spatial planning Updates water & space policies 2. Coping capacity Major drainage system; adapted street profile Wet proofing vulnerable buildings Warm grass instead cold grasses 3. Recovery capacity Redundant pumping capacity Cleaning & drying capacity Water supply capacity in extremely dry periods With the varying time and adaptation horizons

16 Resulting design New Orleans Dutch Dialogues III, April 2010,

17 Closing Thank you for your attention!