Scenario Methodology

The port cities study determines the number of people that would be exposed to extreme water levels assuming no coastal flood protection measures, which can then be related to the economic assets that would be exposed within the city. Exposure therefore refers to the population and assets that are threatened, taking no account of any defences or other adaptation.

Existing modelling approaches used to estimate flood protection often assume economically optimum standards of protection, and where we do have data, these methods tend to overestimate protection standards in comparison to reality, especially in many poorer countries. The focus of this analysis is exposure rather than ‘residual risk’ (which includes defences and other adaptation). Flood protection is not included explicitly as it is difficult to ascertain accurate and comprehensive data on flood protection in many, if not most, of the cities under study.

A range of climate and other change factors are considered, outlined in the below table. Six main scenarios were investigated to understand changes in exposure given a 100 year return period extreme water level event. Future exposure is evaluated for the 2070s (the decade 2070-2080). The scenarios are outlined in Table 1.

Please click here to download the complete dataset including all 6 scenarios.

• (i) Current city (C): (situation in 2005);
• (ii) Future city, No environmental Change (FNC): (current environmental situation with the 2070’s economy and population. scenario);
• (iii) Current city, Climate Change (CCC) (Current socio-economic situation with the 2070’s climate change and natural subsidence/uplift);
• (iv) Current city, All Changes (CAC) (Current socio-economic situation with the 2070’s climate change, natural subsidence/uplift and human-induced subsidence);
• (v) Future city, Climate Change (FCC) (Future socio-economic situation with  2070’s climate change and natural subsidence/uplift);
• (vi) Future city, All Changes (FAC): (Future socio-economic situation with the 2070’s climate change, natural subsidence/uplift and human-induced subsidence).

A description of the data and methodologies used is included in the Methodology section of the report with a full description found in Appendix 1.

Table 1. Summary of the scenarios used to analyse the 100 year flood event (see Appendix 1 for calculation methods)

The citation for these data is:       
OECD Database (2008): Global Port Cities Today and in the Future - Exposure to Climate Extremes Supplementary Data.
OECD: Paris. www.oecd.org/env/workingpapers

       
For more information, original source information and a first analyses of these data, please see:       
RANKING PORT CITIES WITH HIGH EXPOSURE AND VULNERABILITIY TO CLIMATE EXTREMES: EXPOSURE ESTIMATES      
By      
R.J. Nicholls (1), S. Hanson (1), C. Herweijer (2), N. Patmore (2), S. Hallegatte (3), J. Corfee-Morlot (4), J. Château (4), R. Muir-Wood (2)      
1) University of Southhampton, School of Civil Engineering and the Environment, and Tyndall Centre for Climate Change Research, Southampton, UK      
2) Risk Managment Solutions Limited, London, UK      
3) Centre International de Recherche sur l'Environnement et Développement et École Nationale de la Météorologie, Météo-France, Paris, France      
4) Organisation for Economic Co-operation and Development, Paris, France      
All OECD Environment Directorate Working Papers are available through OECD's Internet Website at www.oecd.org/env/workingpapers      
See also other OECD work on climate change and cities at: www.oecd.org/env/cc       
Please cite as:       
Nicholls, R. J. et al. (2008) "Ranking Port Cities with High Exposure and Vulnerability to Climate Extremes: Exposure Estimates", OECD Environment Working Papers, No. 1, OECD: Paris.  doi: 10.1787/011766488208