Current landslide-dammed lakes in the Central Andes of Argentina (31º - 36º S)

Abstract

In mountain regions around the world, natural dammed lakes formed by landslides are a common geomorphological feature. Assessing the stability of these lakes is crucial when communities and infrastructures are exposed to the hazard related to the potential collapse of these dams, a phenomenon known as Landslide Lake Outburst Floods (LLOF). In this paper, we study current landslide-dammed lakes in the Central Andes of Argentina to characterize the lakes, the natural dams, and the outburst flood record. Moreover, we analyze dam stability through classical geomorphic indexes (Blockage Index or the Dimensionless Blockage Index) and by a qualitative assessment of the apparent stability of the dams. We identified a total of 19 landslides currently damming lakes that correspond to historical dams as well as palaeo-dams. We observed that current lakes might be long-lasting and considered stable by the classical indexes and nevertheless constitute sources of potential LLOFs. In the study area, lake destabilizing factors could be related to extreme climatic conditions or to seismicity, yet the classical stability indexes do not consider these factors. Consequently, the qualitative approach used is a simple method to identify lakes that need periodic revision. The historical occurrence of LLOFs, as well as paleo-LLOFs, suggests that this type of dangerous flooding is a common phenomenon in the study area, indicating the need for continuous monitoring since the apparent stability of the dams might be disturbed by external factors.