Quantifying Flood Risk

1. Quantifying Flood Risk Environmental Risk Analysis and Management Hack A., Schitzenhofer K., Sturmlechner M., Szinetár M.

2. Content • Introduction • Definitions • Methods for quantifying flood impacts • Case studies: • Germany (Fahrenzhausen, Bavaria) • India (Mumbai, Maharashtra) • Discussion and conclusions • Summary

3. Scientific Question How to quantify the impacts of floods in an … • Economic (direct and indirect impacts) • Social (loss of life, welfare, social disruption) and • Environmental (not always negative) perspective, … when taking into account short and long term impacts.

4. Definition ofRisk … a combination of a random event (hazardous event) with a specific probability of occurrence and its negative consequences (damages) =

5. QuantificationofRisk • These negative consequencesneedstobequantifiedtoget a valuefor a certainhazardousevent. • Why do weneedtoquantifyit? • Financeandinsuranceindustry • Evaluation ofefficiencyoffloodprotectionmeasures • This canbedone in different ways...  Methodsforquantifyingfloodimpacts

6. Methodsforquantifyingfloodimpacts Stage-damagecurve

7. HAZUS-MH • Exposure of selectedarea • Level of intenzityofhazardevent > waterdepth • Potentiallosses • More than 900 stage-damage curves • Actualpotentialdamage ratio

8. Case Study: Fahrenzhausen, Bavaria, Germany • 25 km north of Munich (GER) • 4500 inhabitants • River “Amper” • MQ = 37 m3/s • HQ100 = 210 m3/s • HQ100,CC = 240 m3/s (including 15 % CC factor) • Catchment area ≈ 2300 km2

10. Potential Damage

11. Plannedmeaures

12. Potential Damage

13. Case Study: Mumbai, Maharashtra, India • 18.4 Mio inhabitants • 60% of population in informal settlements • Located on a peninsula ->Vulnerability to different types of floods • Up to 50% of annual rainfall in 2-3 events in July and August • No long term precipitation data available (longest time series: 30 years)

14. Economicimpactsoffloods in Mumbai Estimation of total losses due to various types of flood events at present and future conditions (Hallegatte et al. 2010)

15. Economicimpactsoffloods in Mumbai Change in total value-added (excluding housing sector) for a 1-in-100 years event and the 2005 flood

16. Economicimpactsoffloods in Mumbai • Noinsurancesystem -> longlastingeconomicimpacts • Impacts on marginalizedpopulationand informal businessesimportant • Reconstructioncostsforonefullydamagedhousehold • Total average: 950$ (1417$ average per capita income) • Average in slums: 108$ (193$ average per household income)

17. Socialand environmental impacts • Social • 445 fatalities • 39% ofhouseholdsofmarginalizedpopulationsufferedfromreducedfoodintake • 97 schoolbuildingscollapsed • 437 primaryhealth centresand rural hospitalsdamaged • Environmental • nodataavailable • Not ofprimaryinterestforpopulationof Mumbai andthemunicipality • Nosufficientsewersystem • Builtfor 25mm rainfall/hourandrunoffcoefficientof 0.5

18. Discussion - Economicaspects Fahrenzhausen (GER) Mumbai (IND) No calculated inundation areas Reoccurrence probabilities unknown 1 destroyed house =$ 950 (average) Houses in the slums hit hardest Big differences in incomes in different castes • Inundation areas calculated nationwide • Maps of these areas available via internet • Calculated for different reoccurrence probabilities • 1 destroyed house = € 50,000 • Cost-benefit-ratio for flood protection measures

19. Discussion - Socialaspects Fahrenzhausen (GER) Mumbai (IND) No advance warning time even though floods are quite regular (monsoon) Very poor people hit hardest in the slums Hardly any catastrophe management Need for international help Many casualties • Important structures of social life have higher factor • Flood forecast systems reduce risk of life losses • Advance warning time gives the population the time to rescue important personal values • Highly developed catastrophe management plans

20. Discussion - Environmental aspects Fahrenzhausen (GER) Mumbai (IND) Sewer system not adjusted to flood runoff Sewer overflow through the slums poses health and environmental problems E.g. tanneries in the slums are flooded as well (highly aggressive chemicals used there) • Flood protection through natural retention areas • Companies in the inundation areas using chemicals had to declare them • Protection of small creeks within the village even during flood event (do not fall dry)

21. Conclusion • Series ofdisastrousfloodeventsduringthe last years • Topic isin theforefrontofpublicconcern • Different methods for quantification of risk • Economicimpactseasiertoquantifythansocialorespecially environmental impacts • Regional Differencesbetweencountries andregions • Floodriskmanagement , Floodoccurence, Socialdifferences, Vulnerability • Estimationoftheconsequencesimportantforeffectivefloodprotectionmeasures (cost-benefit-analysis) • Further research on integratedfloodriskmanagement (-assessment) • Implementation ofalreadyexistingmeasures in a proper way in regionswithpoorlydevelopedfloodriskmanagement

22. References • Aldrete, G. S., 2007. Floods of the Tiber in Ancient Rome. Ancient Society and History. Baltimore: The Johns Hopkins University Press. • Asian Development Bank, 2013. Key Indicators for Asia and the Pacific 2013 – India. Retrieved 28.04. 2014. From http://www.adb.org/sites/default/files/ki/2013/pdf/IND.pdf.  • Germany Trade & Invest, 2013. Wirtschaftsdatenkompakt: Indien. Bonn: Germany Trade & Invest.  • Gregory, B., Baecher, Quantifying flood risk, University of Maryland, Washington DC, US (2009) • Gupta, K., 2010. CORFU –Case Study: Mumbai. Mumbai: Indian Institute of Technology.  • Hallegatte, S. et al., 2010. Flood Risks, Climate Change Impacts and Adaptation Benefits in Mumbai: An Initial Assessment of Socio-Economic Consequences of Present and Climate Change Induced Flood Risks and of PossibleAdaptation Options. OECD Environment Working Papers,No. 27. s.l.: OECD Publishing. • Jui-Lin, K., Ming-Daw, S., and Ling-Fang, C., “ Loss Functions and Framework for Regional Flood Damage Estimation in Residential Area,” Jornal of Marine Science and techonolgy, Vol. 13, No. 3,pp.193-199(2005

23. References • Munich Re, 2014: Natural catastrophes 2013. Analysis, assessments, positions. Available at:https://www.munichre.com/site/corporate/get/documents_E435413367/mr/assetpool.shared/Documents/0_Corporate%20Website/_Publications/302-08121_en.pdf [06th May 2014] • Penning-Rowsell, E.C., Chatteron, J.B., The benefits of Flood Alleviation: A Manual of Assessment Techniques, Gower, Aldershot, England (1977) • Smith, D.I., “Flood Damage Estimation- A Review of Urban Stage-Damage Curves and Loss Functions,” Water SA, Vol.20, No.3, pp.231-238(1994) • Smith, D.I., Handmer, J. W., Floos Warning in Australia:Policies, Institutions and Technologies, Center of Resource and Environmental Studies, Australia National University, Canberra • S.N.,Jonkman at al., “ An overview of quantitative risk measures for loss of life and economic damage,” Journal of Hazardous Matearials, A99, pp.1-30( 2003) • Taiwan Water Resource Agency, National Flood Insurance Program Pilot Study: A Case Studies and for Tang-Dee-Yang Area (Project Report), Taipei, Taiwan, (1994) • United Nations Office for Disaster Risk Reduction, 2007. Terminology on Disaster Risk Reduction. Available at: http://www.unisdr.org/we/inform/terminology#letter-f [06th May 2014]

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