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Abstract. The vulnerability of flood-prone areas is determined by
the susceptibility of the exposed assets to the hazard. It is a crucial
component in risk assessment studies, both for climate change adaptation and
disaster risk reduction. In this study, we analyse patterns of vulnerability
for the residential sector in a frequently hit urban area of Milan, Italy.
The conceptual foundation for a quantitative assessment of the structural
dimensions of vulnerability is based on the modified
source–pathway–receptor–consequence model. This conceptual model is used to
improve the parameterization of the flood risk analysis, describing (i) hazard scenario definitions performed by hydraulic modelling based on past
event data (source estimation) and morphological features and land-use
evaluation (pathway estimation) and (ii) the exposure and vulnerability
assessment which consists of recognizing elements potentially at risk
(receptor estimation) and event losses (consequence estimation). We
characterized flood hazard intensity on the basis of variability in water
depth during a recent event and spatial exposure also as a function of a
building's surroundings and buildings' intrinsic characteristics as a
determinant vulnerability indicator of the elements at risk. In this sense
the use of a geographic scale sufficient to depict spatial differences in
vulnerability allowed us to identify structural vulnerability patterns to
inform depth–damage curves and calculate potential losses from mesoscale
(land-use level) to microscale (building level). Results produces accurate
estimates of the flood characteristics, with mean error in flood depth
estimation in the range 0.2–0.3 m and provide a basis to obtain
site-specific damage curves and damage mapping. Findings show that the
nature of flood pathways varies spatially, is influenced by landscape
characteristics and alters vulnerability spatial distribution and hazard
propagation. At the mesoscale, the "continuous urban fabric" Urban Atlas
2018 land-use class with the occurrence of at least 80 % of soil sealing
shows higher absolute damage values. At microscale, evidence demonstrated
that even events with moderate magnitude in terms of flood depth in a
complex urbanized area may cause more damage than one would expect.