Flood risk assessment in an urban area: Vila Nova de Gaia

Abstract

This paper proposes a methodology for flood risk assessment in a non fluvial urban flood. Two hazard classifications were considered; one with water depth and flow velocity classes and other with the product of water depth and flow velocity. The vulnerability assessment resulted in five classes obtained by cluster and principal components analysis. Flood risk maps were achieved by hazard and vulnerability classes’ crossover. The methodology is applied to a case study in the city of Vila Nova de Gaia. DTM with one meter resolution; HEC-HMS and HEC-RAS was applied to an urban catch- ment with one hour temporal scale; the 2001 statistical census tracts provide the demographic and social information. This methodology can be considered a straightforward and successful way to assess flood risk maps. However, the differences attained by the two hazard methods point out the need of further developments in the assessment of flood risk in stepped urban areas.