Stability analysis and morphometric characterization of palaeo-lakes of the Benjamin Matienzo basin, Las Cuevas River, Argentina

Abstract

Natural dams are caused by the blockage of streams as a result of the sudden arrival of detritus material during a glacial surge advance or fast slope collapse threatening downstream populations. Nevertheless, origin, morphological characteristics and stability of dammed lakes are frequently ignored. Six impounded palaeo-lakes were geomorphologically studied in the Benjamin Matienzo gully (32°14′ S–70°02′ W), denominated, from north to south: Goyete, Negro, Casa de Piedra, Lagunita, Susanita and Matienzo. We determined the origin, morphometric parameters, stability index and rate of streamflow rupture for these dammed ancient lakes in order to shed light on the potential outburst flood hazard in this Andean mountain region. According to our findings, we concluded that palaeo-lakes would have had a short life as they turned out to be unstable, except for the Goyete Lake, matching with the lack of fine lacustrine sediments in all river blockages. We also estimated the maximum peak discharge of a probable outburst flow generated during a drastic collapse of these dams. Obtained values range between 22 and 151 m3/s being notably higher than the average annual streamflow of Las Cuevas River (6.6 m3/s), but similar to the instantaneous streamflow of this river (157 m3/s, 2-year recurrence time).