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This paper demonstrates a framework for producing probabilistic flood risk estimates, focusing on two sections of the Rhine River. We used an ensemble of six (bias-corrected) regional climate model (RCM) future simulations to create a 3000-year time-series through resampling. This was complemented with 12 global climate model (GCM)-based future time-series, constructed by resampling observed time-series of daily precipitation and temperature and modifying these to represent future climate conditions using an advanced delta change approach. We used the resampled time-series as input in the hydrological model Hydrologiska Byrans Vattenbalansavdelning (HBV)-96 to simulate daily discharge and extreme discharge quantiles for return periods up to 3000 years. To convert extreme discharges to estimates of flood damage and risk, we coupled a simple inundation model with a damage model. We then fitted probability density functions (PDFs) for the RCM, GCM, and combined ensembles. The framework allows for the assessment of the probability distribution of flood risk under future climate scenario conditions. Because this paper represents a demonstration of a methodological framework, the absolute figures should not be used in decision making at this time.

Climate change increases flood probabilities in the Rhine river basin, which complicates long-term flood management planning. This paper explores a method to evaluate the effectiveness of flood management measures for the river Rhine assuming a relatively extreme climate change scenario for the year 2050. Considered are planned measures described in the Rhine Action Plan on Floods (APF) and several additional measures, which include the restoration of abandoned meanders, a bypass around Cologne, the implementation of additional retention polders and land-use change to forest. The method includes resampling of meteorological data and a hydrological model to simulate long discharge series (10000 years), and can be considered as a process-based approach to estimate peak discharges of low-probability flood events. It is found that upstream flooding in Germany has a profound decreasing effect on the simulated peak water levels and discharges along the main Rhine branch and downstream in the Netherlands. Currently implemented and proposed measures in the APF, as well as most additional measures, seem inadequate to cope with the increased flood probabilities that are expected in the future climate change scenario. © The Authors. Journal of Flood Risk Management © 2010 The Chartered Institution of Water and Environmental Management.