Catastrophic debris flows near Machu Picchu village (Aguas Calientes), Peru

Slope movements together with intensive river erosion and the following accumulation are the leading processes in the landscape evolution in the area of Machu Picchu village (former Aguas Calientes), which is located close to the Machu Picchu Sanctuary. Debris flows affect not only the bottoms of valleys or canyons, but also debris fans at the termini of the drainage basins, which are heavily inhabited at some places. The most recent event in the Machu Picchu village occurred in April 2004, but several others were documented in a broader area in the last 50 years. The field inspections at Machu Picchu (May and September 2004; June and September 2005) together with oral testimony revealed the nature and behavior of the debris flow. Machu Picchu village can be assessed as a zone with high landslide risk in relation to its urban development. Despite that, the village recorded a rapid growth (threefold population increase) without urban control within the past two decades. Precipitation, which is the main triggering factor of the debris flows, and natural hazard management of the Machu Picchu village are discussed in this paper.     

Geomorphological research of large-scale slope instability at Machu Picchu, Peru

A multidisciplinary approach has been adopted to study the slope movements and landscape evolution at the archaeological site of Machu Picchu and its immediate surroundings. The basic event in the paleogeomorphological evolution of the area was the large-scale slope movement, which destroyed the originally higher ridge between Mt. Machupicchu and Mt. Huaynapicchu. Within remnants of that primary deformation, several younger generations of slope movements occurred. The laboratory analyses of granitoids revealed highly-strained zones on the slopes of Mt. Machupicchu, which strongly affect the largest slope deformation. The borders of the largest slope deformation are structurally predisposed by the existence of fault zones. The majority of various types of slope movements on the so-called Front Slope (E facing) and Back Slope (W facing) are influenced by the alignment between topography and joints. Along with slope movements, fluvial erosion and tectonic disturbance of the rocks have been affecting the evolution of the landscape. A monitoring network for dilatometric and extensometric measurements was used to detect the present-day activity of rock displacements within the archaeological site. In addition to standard mapping of surface hydrogeological phenomena, eleven express slug tests were conducted to verify the infiltration potential of precipitation. The results of these surveys indicate that recent large-scale slope movement as suggested by some previous studies is doubtful, and the detected movements can be explained by individual movements of rock blocks or several other mechanisms including sinking of archaeological structures, subsurface erosion and annual changes in the water content of the soils.