Cost-benefit analysis for flood polders at the Danube river

Floods are considered to be one of the most hazardous natural phenomena, which calls for thorough and comprehensive flood risk mitigation strategies to prevent, protect and prepare areas prone to flooding. The “Bavarian Waterbody Program of Action 2030” aims amongst others at reducing the flood risk for people and assets through integrated flood risk management including numerous diverse measures.  As part of the action program, flood detention basins (so called flood polders) are planned along the Bavarian Danube at different locations to reduce the risk of failure of existing or planned protection structures along the Danube in case of extreme flood events. Cost-benefit analyses are useful to evaluate these strategies, decide between different alternatives and comprehensively inform decision makers. Therefore, the presented TUM project funded by the LfU was initiated with the aim of setting up a model that can be used to conduct a holistic cost-benefit analysis.

In order to assess the expected benefit resulting from a flood polder, the estimation of the expected reduction of the flood damage due to the flood polder is required. Since the understanding of dike breaches is still limited and historical events rare, the failure of dikes are modelled in a dynamic probabilistic model quasi-randomly. With the help of this Monte Carlo model, the benefit-cost ratio of single flood polders as well as combinations of different polder locations can be used to help improving risk management.