Mapping Social-Ecological Vulnerability to Flooding

Abstract

In the last decades river flooding has produced immense economical and ecological damages in Germany. Therefore, disaster management aims at detecting vulnerabilities and capacities in order to reduce flood disaster risk. This study contributes to the mapping of social-ecological vulnerability at sub-national scale through the development of appropriate tools and methods. Vulnerability is assessed for the two sectors forest and agriculture in this research.<br /> A modified version of the Turner vulnerability model was selected as conceptual framework for the vulnerability assessment. The model depicts processes and characteristics of social-ecological systems and defines vulnerability as composed of exposure, susceptibility and capacities. Although some analytical limitations could be detected in the framework, such as the missing definition of risk or the strong interrelations between the components susceptibility and capacities, the model acted as valuable framework and was also successfully operationalized. <br /> Indicators were used as tools for assessing vulnerability at regional level. Indicators simplify complex issues and thus make the notion and concept of vulnerability understandable and accessible also for practitioners. The development of indicators was effected through a number of consecutive work steps including impact analysis, the building of vulnerability categories, the identification of indicators, and the collection of data for mapping vulnerability. Expert interviews and literature review were carried out to gather all necessary information. 15 indicators were finally selected to assess vulnerability of the agricultural sector, and 14 to represent forest sector vulnerability. <br /> Mapping vulnerability of the two sectors agriculture and forest across districts required the development of a composite indicator for each sector. Therefore, single indicators were normalized, weighted and aggregated. After a careful evaluation of distinct methods the ‘weighted sums’ technique was applied to build the composite indicators. A Geographical Information System (GIS) facilitated the calculation and mapping of the components exposure, susceptibility and capacities as well as the vulnerability composite indicator. Thus, vulnerable hot-spots can be easily detected and visualized. The produced maps reveal that most hot-spots are located in the ‘new federal states’. This is not completely unexpected since East Germany has not yet fully recovered in terms of socio-economic standards since the reunification in 1990. <br /> By combining the hazard characteristic ‘inundation extent’ with vulnerability in districts along the rivers Elbe and Rhine it could be shown that in the case of data availability risk maps can easily be produced in a GIS. <br /> Some analytical shortcomings and technical inaccuracies could not be avoided during the vulnerability assessment. For that reason the approach was thoroughly evaluated to verify the assessment and quantify uncertainties. The approach was tested for its feasibility, conceptual underpinning, data basis and its methodological robustness. Furthermore, sensitivity and uncertainty analyses were conducted. Methods and techniques turned out to be sufficiently robust. In future, however, a clear analytical distinction should be made between the two components susceptibility and capacities to avoid coupling effects.