Natural hazards in the Cordillera Blanca of Peru during the time of global climate change

Abstract

The Cordillera Blanca (Ancash region, Peru) is the most heavily glacierized tropical range in the world. Due to the global climate change, the retreat and thinning of most of the glaciers has recently increased. Rapid geomorphic changes, especially direct and indirect slope movements, are closely connected with the changing environment. Glacier retreat also leads to the formation and development of all types of potentially hazardous glacial lakes. A sudden water release from a glacial lake irrespective of its cause is called a glacial lake outburst flood (GLOF). The hazard of GLOF is strongly connected with dynamic slope movements (ice- and rock-falls; landslides of steep moraine slopes). About 80 % of the GLOFs in the Cordillera Blanca since the end of the Little Ice Age were caused by dynamic slope movements into the lake. The released water has a high erosion and sediment transport potential and can easily transform into various types of flow movements (e.g. debris or mud flows). These are highly hazardous and significant landscaping processes, by which the high mountainous environment evolves. Using the DesInventar database for the period from 1971 to 2009, debris flows (locally known as aluvión) have been evaluated as the most frequent type of natural hazard in the Ancash region. Several valleys in the Cordillera Blanca are currently being studied, using flood modelling, geomorphological mapping and calculation of slope stability in moraines. Conditions leading to slope movements on moraines include not only moraine properties, such as grain size and sediment structure, but also water infiltration from adjacent slopes.