Vulnerability to Flash Floods: A Simplified Structural Model for Masonry Buildings

Urban and land use planning is conditioned by flood risk analyses and is a great research challenge. While methods are available for quantitative hazard and risk modeling, there is still a major gap related to reliable rational approaches for vulnerability assessment. This is particularly true for assessing vulnerability of buildings to floods. This vulnerability, which is important for economic reasons as well as for the safety of individuals and communities, is usually conceptualized on an empirical basis. Such empirical approaches, however, are plagued by considerable uncertainties, mostly because the damage-causing mechanisms on the building envelope are poorly represented. In order to advance this area, this paper focuses on the structural vulnerability of traditional masonry buildings in alpine areas exposed to flash floods. A simplified physically based conceptual model which requires a limited amount of input data is proposed. The resistance of a wall impacted by a flash flood is studied in a limit analysis framework, considering different geometric ratios and building configurations. The resulting stability thresholds, expressed in dimensionless form as a function of the water depth, were positively compared with the results provided by numerical finite element models of the investigated geometries. The application of the proposed vulnerability model in risk mitigation strategies provides reliable information, suitable for a first-level risk assessment on large building stocks.