Movimentos de vertente no norte de Portugal: importância do comportamento hidrológico das formações superficiais = Slope Movements in Northern Portugal: Importance of Surficial Formations Hydrological Behavior

Abstract

The occurrence of landslides in northern Portugal has motivated the development of several case studies, rehearsing different methodologies that seek to defi ne and characterize the conditioning factors with the greatest infl uence over the geomorphologic instability processes. This paper presents the results obtained for Frades (Arcos de Valdevez) debris fl ow, discussing the importance of morphostructural context, surfi cial formations and their hydrological behavior, analyzed by in situ and laboratory tests, namely, grain size, mineralogy, hydraulic conductivity, penetration resistance and seismic refraction. The developed study shows the existence of preferential paths of internal water circulation, in combination with constraints linked to the characteristics of the surficial formations, revealing also that the subsurface drainage network has an obvious link with the fl ow that takes place at the surface, although it may present changes motivated by underlying structures.