Current approaches for assessing large-scale flood risks largely ignore basic interactions and feedbacks between atmosphere, catchments, river-floodplains, and socio-economic systems. As a consequence, risk analyses are uncertain and might be biased. In their opinion paper presented in WIREs Water, Vorogushyn et al. call for a fundamental redesign of the approaches used for large-scale flood risk assessment. The authors point the way to advance these approaches for prioritizing national investments in risk mitigation or for appraisal and management of insurance portfolios facing the challenge of increasing risks due to climate and global change.

The authors review basic interactions in the flood risk system and demonstrate their importance for shaping the spatial risks. For instance, raising levees in upstream reaches will potentially yield higher water flows downstream, and thus will partially also shift flood risk downstream. On the other hand, in the case of levee failures upstream, the downstream risk would decrease due to water retention in upstream floodplains.

In a further example looking at Thailand’s flood in 2011, the authors highlight the growing interdependencies of production chains in the globalized world. This example emphasises that interruption by large-scale long-lasting floods may cause tremendous secondary loss; an effect which has not been considered sufficiently in the insurance industry flood risk models.

Vorogushyn et al. call for new science to develop interaction-aware risk models and stress the need for adjustments of flood risk assessment procedures in the implementation of the European Flood Directive. Increasing pressure on policymakers, exerted through regulatory bodies and cascaded down to engineering consultancies, should target interaction-aware risk assessments. This would enable an effective enforcement of the solidarity principle anchored in the European Flood Directive, which calls for consideration of potential adverse consequences of risk management interventions for upstream and downstream countries or communities. Now is the very time to lay down the tracks in the lead-up to the next revision of hazard and risk maps and flood risk management plans due for the EU Member States in 2019 and 2021, respectively.

Kindly contributed by Vorogushyn et al.