Assessing compound pluvial-fluvial flooding: Research status and ways forward

Compound weather and climate events have obtained increasing attention in recent years in the context of anthropogenic climate change. Compound pluvial-fluvial flooding (CPFF), usually referring to the superposition of heavy local rainfall in urban areas and riverbank overflow, is however rarely investigated. We perform a systematic literature review on this emerging topic and identify knowledge gaps. Major knowledge gaps concern the dependence between pluvial and fluvial flooding, and thus the co-occurrence probability, and its past and (possible) future changes. Although it is expected that CPFF increases in a warming world, we could not identify a single attempt to understand temporal changes. More systematic and comprehensive data collection and process documentation, particularly for pluvial and flash floods, are required to better understand and assess CPFF. Another major gap is the limitation of CPFF studies to hazard assessments. Implementing damage models would allow, with modest effort, to transfer hazard statements into risk statements. This would allow, in turn, to understand the scale of the problem in terms of societal relevance.