Evaluación de susceptibilidad a la generación de flujo de detritos, ladera oriental entre las localidades Chanchoquín y La Arena, valle del Tránsito, región de Atacama
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2021
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es
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Universidad Andrés Bello
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Resumen
Tras los eventos de precipitaciones ocurridos en las zonas cordilleranas de la Región de Atacama, durante el 26 al 28 de enero de 2020, tuvieron como consecuencia importantes procesos de remoción en masa de tipo flujos, afectando principalmente a la localidad de El Tránsito, Comuna de Alto del Carmen. El 27 de enero, dichos procesos se concentraron en la ladera oriental del valle, específicamente por reactivación de las quebradas La Plaza y quebradas menores ubicadas entre Chanchoquín y La Arena.
Las consecuencias durante el evento meteorológicos, según reporte del Ministerio de Desarrollo Social y Familia corresponden a daños en 133 hogares, plantaciones, corte de vías de acceso y el fallecimiento de una persona. Si bien, los movimientos en masa son eventos del natural funcionamiento de los procesos exógenos que moldean la superficie, se tornan un problema cuando se ven afectadas la vida de los seres humanos y el desarrollo de sus actividades, pudiendo considerarse como zonas de catástrofes.
En el presente trabajo se analizan los factores que inciden en estos procesos de flujos de detritos y/o barro, en base a metodología y clasificaciones previas, adaptadas a las características de la zona y la información disponible durante el desarrollo de la investigación, la cual permite determinar las zonas de mayor susceptibilidad de ocurrencia de remociones de tipo flujo. Se definen los principales factores condicionantes implicados en estos procesos, siendo los de mayor relevancia la geología, geomorfología y características geotécnicas de la zona. Los resultados obtenidos, permiten diferenciar zonas de baja, media y alta susceptibilidad, identificando las zonas de alteración hidrotermal asociadas a Intrusivos Hipabisales Andesíticos de edad Eoceno y pendientes mayores a 25°, las áreas de mayor susceptibilidad. Las zonas de media-alta susceptibilidad corresponden a depósitos coluviales finos areno-arcillosos, ubicados en zonas bajas de laderas de alta pendiente, con origen en afloramientos pertenecientes a Formación Algarrobal (Jurásico Superior).
Si bien el factor desencadenante de los flujos en la zona corresponde a eventos de precipitaciones intensas, no es posible determinar un umbral crítico general, ya que, se debe tener claridad de la distribución de precipitaciones y saturación previa existente.
After the rainfall events that occurred in the cordilleran areas of the Atacama Region, during January 26 to 28, 2020, they had as a consequence important processes of mass removal of the flow type, mainly affecting the town of El Tránsito, Commune of Alto del Carmen. On January 27, these processes were concentrated on the eastern hillside of the valley, specifically due to the reactivation of the La Plaza streams and smaller streams located between Chanchoquín and La Arena. The consequences during the meteorological event, according to a report from the Ministry of Social Development and Family correspond to damage to 133 homes, plantations, cut off access roads and the death of one person. Although, mass movements are events of the natural functioning of the exogenous processes that shape the surface, they become a problem when the lives of human beings and the development of their activities are affected, and can be considered as disaster areas. In the present work, the factors that influence these processes of debris and / or mud flows are analyzed, based on previous methodology and classifications, adapted to the characteristics of the area and the information available during the development of the investigation, which It allows determining the areas of greatest susceptibility to the occurrence of flow-type removals. The main conditioning factors involved in these processes are defined, the geology, geomorphology and geotechnical characteristics of the area being the most relevant. The results obtained allow differentiating areas of low, medium and high susceptibility, identifying the areas of hydrothermal alteration associated with Intrusive Andesite Hypabyssal of Eocene age and slopes greater than 25 °, the areas of greatest susceptibility. The areas of medium-high susceptibility correspond to fine sandy-clayey colluvial deposits, located in low areas of steep slopes, originating in outcrops belonging to the Algarrobal Formation (Upper Jurassic). Although the triggering factor of the flows in the area corresponds to events of intense rainfall, it is not possible to determine a general critical threshold, since it must be clear about the distribution of rainfall and previous existing saturation.
After the rainfall events that occurred in the cordilleran areas of the Atacama Region, during January 26 to 28, 2020, they had as a consequence important processes of mass removal of the flow type, mainly affecting the town of El Tránsito, Commune of Alto del Carmen. On January 27, these processes were concentrated on the eastern hillside of the valley, specifically due to the reactivation of the La Plaza streams and smaller streams located between Chanchoquín and La Arena. The consequences during the meteorological event, according to a report from the Ministry of Social Development and Family correspond to damage to 133 homes, plantations, cut off access roads and the death of one person. Although, mass movements are events of the natural functioning of the exogenous processes that shape the surface, they become a problem when the lives of human beings and the development of their activities are affected, and can be considered as disaster areas. In the present work, the factors that influence these processes of debris and / or mud flows are analyzed, based on previous methodology and classifications, adapted to the characteristics of the area and the information available during the development of the investigation, which It allows determining the areas of greatest susceptibility to the occurrence of flow-type removals. The main conditioning factors involved in these processes are defined, the geology, geomorphology and geotechnical characteristics of the area being the most relevant. The results obtained allow differentiating areas of low, medium and high susceptibility, identifying the areas of hydrothermal alteration associated with Intrusive Andesite Hypabyssal of Eocene age and slopes greater than 25 °, the areas of greatest susceptibility. The areas of medium-high susceptibility correspond to fine sandy-clayey colluvial deposits, located in low areas of steep slopes, originating in outcrops belonging to the Algarrobal Formation (Upper Jurassic). Although the triggering factor of the flows in the area corresponds to events of intense rainfall, it is not possible to determine a general critical threshold, since it must be clear about the distribution of rainfall and previous existing saturation.
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Tesis (Geólogo)
Palabras clave
Remociones en Masa, Variación en suelos y clima, Evaluación climática, Atacama - Chile