Evaluación integral de la cuenca del río Mariño (Abancay, Apurímac) para la prevención de desastres de origen geológico y geo-hidrológico - [Boletín C 71]

Abstract

[ENG] In the last times, the city of Abancay (located in Apurímac, a region of southern Peru) has suffered a very fast population growth which has led to doing an improper land use by the occupation of unstable areas without considering the geographic, geodynamic and climatic characteristics of the area. The constant rains, extreme in some cases, trigger various geo-hydrological phenomena that affect the city and generate important personal and economic losses in the city and its surrounding villages. Regarding this situation, the Geological, Mining and Metallurgical Institute of Peru (INGEMMET), in collaboration with the University of Geneva (Switzerland), within the framework of the “National Program of Geological Risks”, chose the micro-basin of the Mariño River in Abancay to develop geological, hydrogeological, geophysical and dendrochronological detailed studies in order to assess future potential of geo-hydrological events in the area. The results of the study show that a large part of the Mariño River basin is highly prone to the occurrence of geo-hydrological events (such as landslides and avalanches). This susceptibility is mainly related with three factors i) the steep topography, ii) the presence of ancient mass movements often reactivated during the rainy season due to the water infiltration and subsurface flow and the strong weathering suffer by the bedrock which facilitates the tendency to fracture and cavities formation. Furthermore, from the simulation of the debris flow event occurred in Chuyllurpata mountain in 1951, it can be observed that Tamburco and Abancay districts are especially sensitive to the debris flow occurrence. Also, that the current structural measures carried out by the local authorities in the Sahuanay stream wouldn’t be enough to control a new event similar or superior to the 1951 event. On the other hand, results from the dendrochronological survey show that P. Glomeratus tress is useful in order to complete the lack of climatic data in the Abancay area (and of central Peru). Likewise, the eucalyptus trees located along the Sahuanay stream are useful as indicators of the 2012 debris flow event magnitude and to help the calibration of the numerical models of this event and other possible scenarios. He final objective of this study is to share the results with the local authorities and residents of the city of Abancay, which will allow greater technical arguments, when it is decided to take decisions that generate improvements to the current risk management plans.