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Evolution of a human-induced mass movement under the influence of rainfall and soil moisture: The Porciles landslide case study (NW Spain)

Abstract:

The excavation of the trench of the future A-63 as it passed through the village of Porciles (43°24′N 06°18′W) in NW Spain, posed several stability problems from its inception. On March 6, 2016, after three extraordinarily rainy months, an instability event took place, moving more than 10,000 m3 of land downslope, completely occupying the road and interrupting traffic for 7 months. This study is focused on the role of rainfall and soil moisture as factors involved in the triggering and evolution of the instability event. The lapse of more than 4 months between the landslide occurrence and the removal of the displaced material allowed the study of the progression of the mass displacement by the analysis of (i) weekly oblique photographs taken from three fixed points; (ii) four digital terrain models: two from previous topographic data and two more obtained from later drone flights; and (iii) rainfall and soil moisture measurements, including pre-landslide data. This work highlights the relevance of human activity as a preparatory factor and the role of precipitation and soil moisture as triggering and sustaining factors which condition the mass movement process.