Articles | Volume 18, issue 5
Research article
15 May 2018
Research article |  | 15 May 2018

Risk-based flood protection planning under climate change and modeling uncertainty: a pre-alpine case study

Beatrice Dittes, Maria Kaiser, Olga Špačková, Wolfgang Rieger, Markus Disse, and Daniel Straub

Abstract. Planning authorities are faced with a range of questions when planning flood protection measures: is the existing protection adequate for current and future demands or should it be extended? How will flood patterns change in the future? How should the uncertainty pertaining to this influence the planning decision, e.g., for delaying planning or including a safety margin? Is it sufficient to follow a protection criterion (e.g., to protect from the 100-year flood) or should the planning be conducted in a risk-based way? How important is it for flood protection planning to accurately estimate flood frequency (changes), costs and damage? These are questions that we address for a medium-sized pre-alpine catchment in southern Germany, using a sequential Bayesian decision making framework that quantitatively addresses the full spectrum of uncertainty. We evaluate different flood protection systems considered by local agencies in a test study catchment. Despite large uncertainties in damage, cost and climate, the recommendation is robust for the most conservative approach. This demonstrates the feasibility of making robust decisions under large uncertainty. Furthermore, by comparison to a previous study, it highlights the benefits of risk-based planning over the planning of flood protection to a prescribed return period.

Short summary
We study flood protection options in a pre-alpine catchment in southern Germany. Protection systems are evaluated probabilistically, taking into account climatic and other uncertainties as well as the possibility of future adjustments. Despite large uncertainty in damage, cost, and climate, we arrive at a rough recommendation. Hence, one can make good decisions under large uncertainty. The results also show it is preferable to plan risk-based rather than protecting from a specific design flood.
Final-revised paper