Effectiveness of flood management measures on peak discharges in the Rhine basin under climate change

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 (10 000 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.