The threatening reactivation of the Sebrango landslide of June 2013 (Cantabria, Spain).
Creators: name: González-Díez, Alberto
name: Bruschi, Viola María
name: Sánchez Espeso, Javier Maria
name: Zarroca, Mario
name: Linares, Rogelio
name: Díaz de Terán, José Ramón
name: BONACHEA, JAIME
name: Martínez Cedrún, Patricio
name: Fernandez Maroto, Gema
name: Rodríguez, Verónica
name: Hoyos, Sonia
name: San Millán, Eliecer
name: Remondo, Juan
name: Cendrero, Antonio
Publisher: name: Zenodo
Year: 2013

description: This work presents an analysis of the activities carried out during the last paroxysmal phase of the Sebrango Landslide. This is an important landslide, not only because of the volume of material involved, which was over two million cubic meters; but also because of the extensive media coverage, since this dangerous reactivation threatened the village of Sebrango and the town of Los Llanos (Cantabria, Spain), two localities placed in the heart of the Picos de Europa, in the area with the highest summits of the Cantabrian Range. Thanks to the data obtained in this paroxysmal phase, early mitigation measures could be taken, such as evacuation of people and their personal properties, construction of alternative routes for evacuation, protection of buildings, etc. The landslide began its most energetic activity in mid-June 2013, after a spring in which intense and continuous precipitations were registered in the area. Following the declaration of emergency zone, the authorities constituted a wide research team to carry out the analysis of the reactivation and the emergency. Different tools, such as typical geological and geomorphological measurements, Electrical Resistivity Tomography, (ERT), Global Positioning Systems (GPS), remote sensing (RS), Geographic Information Systems (GIS), etc. were used in this work, in order to obtain data on the paroxysmal peak. These tools have provided general information about: the landslide geometry, the landslide activity, its temporal occurrence, the geo-mechanical characterization of the materials involved, the geological structure of the landslide area and finally the role played by the main triggering factors. The research team had only a short time to gather the data, since this had to be done during the emergency phase, as this information would then form the basis on which subsequent decisions would be taken by the decision-makers. Using these techniques, a detailed description of the spatial and temporal occurrence of the different internal units that compound this reactivation is presented. The main conclusion of this work is that the main triggering factor of the landslide reactivation seems to be the accumulation of material in the header, due to the fall of a wedge of a large volume of rocks, whereas the water inside the system may have acted only as an important conditioning factor. From a methodological point of view, the tools used for this study have proved useful for the analysis of landslides in the paroxysmal stage, especially either the positioning tools used for mapping the landslide features and limits, or the ERT geophysical techniques for defining the prism of material involved, but certainly the most versatile tool employed has been the geomorphological techniques.