New Publication | Natural Hazards and Earth System Sciences
Which buildings face the greatest risk when the next cloudburst hits?
As climate change drives more frequent and intense heavy rainfall, pluvial (rainwater) flooding is an increasing hazard for densely built, heavily sealed cities. A new study by Anastasia Vogelbacher (TUHH, GHI), Malte von Szombathely, Marc Lennartz, Benjamin Poschlod (TUHH, IGWS), and Jana Sillmann — a collaboration between TUHH and Universität Hamburg, carried out within the Cluster of Excellence CLICCS — presents a high-resolution framework for assessing pluvial flood risk at the scale of individual buildings. Crucially, the framework goes beyond the flood map itself: following the IPCC risk concept, it defines risk as the combination of hazard, exposure, and vulnerability, and asks not only where water accumulates but also who is affected and how well they can cope.
The framework brings three layers together. The hazard layer is a metre-resolution hydrodynamic simulation of a 100-year cloudburst (36 mm of rain in one hour) that accounts for topography, land use, infiltration, and the capacity of the sewer network. The exposure layer is differentiated by the kind of impact: ground-floor residents are most exposed in terms of well-being, while buildings next to flooded streets are most exposed in terms of mobility and access. The vulnerability layer captures social factors such as age, income, and education that shape how severely people are affected and how readily they recover. Demonstrated with data from Hamburg, the approach pinpoints risk hotspots where high social vulnerability coincides with high flood exposure — places that a flood map alone would miss. To make the method usable in practice, the team developed and released a Python-based ArcGIS toolbox that generates building-level risk maps automatically. Co-designed with Hamburg's city adaptation offices through a series of stakeholder workshops, the transparent and flexible design makes the framework transferable to other cities, supporting climate adaptation planning and risk-informed decision-making.
Read the full open-access article: Vogelbacher, A., von Szombathely, M., Lennartz, M., Poschlod, B., and Sillmann, J. (2026): A High-Resolution Framework for Urban Pluvial Flood Risk Mapping. Natural Hazards and Earth System Sciences 26, 2765–2783. https://doi.org/10.5194/nhess-26-2765-2026
