Quantifying vulnerability to flooding induced by climate change: The case of Verdal, Norway

Abstract

Lujala, P., Lein, H. & Rosvoldaune, R. 2014. Quantifying vulnerability to flooding induced by climate change: The case of Verdal, Norway. Norsk Geografisk Tidsskrift–Norwegian Journal of Geography Vol. 68, 34–49. ISSN 0029-1951.

The article presents a methodology for the measurement of exposure and social vulnerability to hazards at local level. Using the small town of Verdal in central Norway as a case study, the authors examine its vulnerability to flooding induced by climate change both at present and its potential vulnerability in the future. Data on river and surge flooding and sea level rise scenarios, which are overlapped spatially with present-day maps for land use, transport networks, and buildings, are used to assess exposure to flooding. In addition, the authors assess the study area's level of social vulnerability. The two measures are then combined to assess the integrated vulnerability for Verdal. The results of the analysis show that there are considerable differences across the study area regarding which statistical units (subdivisions of the municipality) will experience the largest increases in vulnerability. The methodology used in the study is transferrable to other towns and municipalities, as well as to other types of hazards, both natural and man-made.

Keywords:

• climate change
• exposure
• flooding
• hazard of place
• sea level rise
• vulnerability

Acknowledgements

This research was supported by a grant from the Research Council of Norway (Project No. 196346/S30). The authors are grateful to Ivar Berthling, Ivar Holand, Wenche Larsen, Jan Ketil Rød, Catriona Turrner, and two anonymous reviewers for help, suggestions, and valuable comments on earlier versions of the article.

Notes

1. The actual weighting for Eq. 2–4 is discussed in the section headed ‘Quantification of Vulnerability Indices for Verdal’.

2. For a more detailed account of factor analysis see, for example, Goldberg & Velicer (2006).

3. Further information on the existing flood-zone data for Verdal can be obtained from the Norwegian Water Resources and Energy Directorate (Norwegian Water Resources and Energy Directorate 2009; Norges vassdrags- og energidirektorat 2009).

4. We use the shortened form ‘basic unit’ for basic statistical units in this article.

5. The Tables in this article include all necessary raw data for calculations of EI and SoVI. This enables other researchers to try other weighting schemes, to see how they affect results.

6. Natural Breaks is a data classification method that optimizes the partition of the data based on natural groups in the data distribution. The method determines class breaks so that the variance within classes is minimized and the variance between classes is maximized.

7. An alternative would be to weight the individual variables included in the index instead of conducting factor analysis. The weights could be based on, for example, expert evaluations or surveys, but this type of subjective weighting is currently undertheorized and not fully developed. Factor analysis is considered an empirically objective method for such weight selection (Jones & Andrey 2007).

8. Information on historical development in Verdal was obtained from Rudolf Holmvik, former chief officer in Verdal Municipality, 19 October 2010.