Flood risk management for an uncertain future: economic efficiency and system robustness perspectives compared for the Meuse River (Netherlands)

Flood risk management planning involves making decisions on which measures to implement and when to do so. This is particularly difficult in view of global changes, which are inherently uncertain. Rational decision making on which comprehensive strategy to implement, or on which measures to take first, requires ex-ante assessments that question whether flood risk is effectively reduced and against which societal costs. Such decision making is usually supported by cost benefit analysis or cost effectiveness analysis. However, these metrics treat low-probability/large-consequence risk and high-probability/small-consequence risk as equal, which is often considered unsatisfactory. Robustness analysis can account for this flaw, as it gives insight into the relationship between flood magnitude and flood consequences at the scale of an entire flood risk system. A robust system can cope with a variety of extreme floods, including those that exceed the design flood. This paper aims to examine how different key decision criteria may advise diverse decisions. To this end, it examines how a variety of strategic alternatives for flood risk management along the Meuse River in the Netherlands score on two different economic criteria and how they would rank from a robustness perspective. The strategies include making room for the river, strengthening embankments and various combinations of these. The results show that the three criteria indeed lead to a different ranking of which strategy to prefer. This supports our claim that a robustness perspective may help to select a strategy that is not only economically efficient but may also be more sustainable in view of uncertainties into the future.