Flood risk assessment of the European road network

This study presents a high-resolution object-based continental-scale assessment of direct flood risk of the European road network for the present climate, using high-resolution exposure data from OpenStreetMap. River floods pose a significant threat to road transport infrastructure in Europe. A new set of road-specific damage functions is developed. The expected annual direct damage from large river floods to road infrastructure in Europe is EUR 230 million per year. Compared to grid-based approaches, the object-based approach is more precise and provides more action perspective for road owners because it calculates damage directly for individual road segments while accounting for segment-specific attributes. This enables the identification of European hotspots, such as roads in the Alps and along the Sava River.

The study enabled a comparison with the commonly used grid-based approaches, which clearly have difficulties to accurately estimate damage to line infrastructure: road infrastructure may either be overlooked or overestimated by attributing infras- tructural damage to the wrong land use types. Also, the study introduced a new set of damage curves which puts the frequently used Huizinga curves into perspective. The expected annual damage from river floods to the road network is EUR 230 million per year, which is well below the grid-based estimates with CORINE (EUR 536 million per year) and LUISA (EUR301 million per year). Additionally, we showcased how the object-based approach can be used to identify flood hotspots in the European road network, for which the grid-based approach was unsuitable. This general- ized approach can potentially be used for other hazards such as coastal and pluvial floods. The paper especially recommends the investigation of the damage caused by flash floods and associated landslides in hilly terrain because the flow velocities and resulting damages seem to exceed what was observed for large-scale river flooding.