Robust river systems: on assessing the sensitivity of embanked rivers to discharge uncertainties, exemplified for the Netherlands' main rivers

Abstract

There is increasing attention for the robustness of systems, in view of more frequent and more extreme weather events. Calls to increase a system's robustness are usually motivated by the resulting reduced sensitivity to extreme events and uncertainties about their probability of occurrence. The concept has been elaborated for flood risk systems, but recently questions have arisen about whether subsystems, such as flood defences or rivers, should and could also be assessed on their robustness. Against the background of a recent debate in the Netherlands about whether to raise the embankments again or to make more room for the rivers in anticipation of increasing extreme river discharges into the future, we propose to define the robustness of embanked alluvial rivers by their sensitivity to uncertainties in flood discharge, expressed by the relationship between discharge and flood water level. We assess the Rhine River branches and Meuse River in the Netherlands and show how their planform, as defined by the location of the embankments and the presence of obstacles in the floodplains, causes remarkable differences in robustness per river and per river stretch. We finally discuss what this might entail for policy planning.