EGU General Assembly 2022
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the Creative Commons Attribution 4.0 License.

A conceptual workflow for cost-benefit analysis of flood polders along the Bavarian Danube.

Amelie Hoffmann and Daniel Straub
Amelie Hoffmann and Daniel Straub
  • Technical University of Munich, Engineering Risk Analysis Group, School of Engineering and Design, Garching b. München, Germany (

As part of the Bavarian flood protection program 2020plus, a system of controlled flood polders is planned along the Danube River in order to reduce the risk associated with overload flood events and avoid catastrophic flooding. Flood polders work by reducing the maximum discharge during very large flood events, thereby relieving stress on downstream river dikes. Thus, flood polders can effectively contribute to preventing the occurrence of dike breaches.

Since flood polders are expensive to implement, their economic efficiency is investigated using cost-benefit analysis (CBA). The CBA weighs all societal costs against the monetized benefits in the form of an economic efficiency criterion. Different challenges arise in the evaluation. In particular, requirements for data availability and consistency are difficult to meet when evaluating protection measures that are located in and take effect across different agency jurisdictions. Because the CBA has to be conducted within a fixed time frame and budget, it must use models that can work with readily available data. Furthermore, the future effectiveness of flood polders is subject to considerable uncertainty, e.g., concerning return periods of flood events as well as future development of assets, population density and interest rates.

We present a conceptual workflow for CBA of the flood polder program. Its main focus lies on assessing the expected damages, as the reduction thereof is the flood polders’ primary benefit. For this purpose, we perform a comprehensive risk analysis, which involves combining different models for hazard, exposure and vulnerability. The process of hazard analysis is particularly demanding as it includes a catalogue of deterministic flood events routed in a 1D-hydraulic model in combination with a probabilistic dike breach analysis. The large number of hazard areas resulting from different breach locations and characteristics are investigated by means of GIS analysis.

In addition, we highlight the importance of performing sensitivity and uncertainty analysis as part of the evaluation process. This is crucial to address the challenges related to the inherent uncertainties in the occurrence of overload events and future developments as well as model choices, e.g., with regard to model resolution and data sources. We show that the effects of uncertainty on the economic efficiency criterion should be communicated to the decision-makers in order to facilitate robust decisions.

How to cite: Hoffmann, A. and Straub, D.: A conceptual workflow for cost-benefit analysis of flood polders along the Bavarian Danube., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9925,, 2022.