Susceptibilidade às cheias na área metropolitana de Lisboa norte factores de predisposição e impa ctes das mudanças de uso do solo

Abstract

Twelve drainage basins in the Northern Lisbon Metropolitan Area (LMA) were analysed and compared because they are affected by floods that threaten life and livelihoods. The methodology was based on the calculation of quantitative indicators that reflect natural and human factors of floods (basin geometry, geological substrate, relief and drainage network in the 1st case; land use classes and land usage changes in the 2nd case). Susceptibility indexes to flooding were developed based on these indicators, using Geographical Information Systems. The results of this study led to the identification of: (i) the basins with highest susceptibility to flooding; (ii) the conditioning factors that mostly contribute to the formation of floods in each basin; (iii) the impacts of changes in land use on the concentration times and peak discharges, which increase the flood hazard; (iv) the urban growth in the flood-prone zones, which increases exposure and the flood risk in the LMA.