A cost sharing approach to flood risk management decision-making

The flood event of August 2005 at the river Inn and the actual hazard zone mapping indicated a need for flood protection in the Lower Inn Valley in Tyrol (Austria). To ensure an appropriate protection of settlements, industrial areas and infrastructure up to a return period of 100 years, extensive planning activities for protection and compensation measurements were initiated. In accordance with the Austrian Water Law, a so-called water association was established to bundle decision-making, planning and financing of all protection measurements. The members of the water association are the affected communities and the local operators of infrastructure.
The majority of the cost of flood protection is carried by the federal and state government in Austria. The remaining cost in the Lower Inn Valley has to be divided between the members of the water association.
In order to guarantee a reasonable and fair distribution of costs, as well as voting rights, a specific approach for cost sharing was developed. The allocation of costs and voting rights is based on the protected area and the length of the protected riverbank in the communities. The areas were categorized by actual land use and by the intensity of an expected flood event and weighted respectively in the assessment. Further, the costs for communities were reduced for contributing compensatory measures, such as flood retention space. Operators of infrastructure contribute a fixed share.
In addition to the technical aspects of flood risk management and socio-economic aspects, an essential component in the decision-making is the cost and vote distribution of the affected communities, which thus has far-reaching influence on the entire project.

In this contribution we will detail the fair and specific approach for cost and vote sharing and provide an overview over the process that led to the foundation of the water association. We will report difficulties and the consequences of the chosen approach and give an outlook on the future of the project.