Rainfall-related debris flows in Carhuacocha Valley, Cordillera Huayhuash, Peru |
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| Authors: | Zbyn??k Engel Julius ?es??k Vanessa Rios Escobar |
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| Institution: | (1) Department of Physical Geography and Geoecology, Faculty of Science, Charles University in Prague, Albertov 6, 128 43 Prague 2, Czech Republic |
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| Abstract: | Continuous heavy rainfall hit northern Peru in the second half of the 2008/2009 summer season. From the end of January to the beginning of March, the Cordillera Huayhuash experienced abnormally high precipitations that exceeded 270?mm. The antecedent rainfall, aggravated with a severe rainstorm of 20?mm on March 7 triggered a large debris flow in the upper Carhuacocha Valley early in the morning on March 8. The debris flow interrupted drainage from the upper part of the valley damming a lake in the narrow depression between the trough slope and the lateral moraine. As a result of the drainage interruption, water percolated through the moraine dam of Cangrajanca Lake where a secondary mass movement occurred in its inner slope. In September 2009, we mapped the debris flow and related landforms and estimated the total area and volume of both mass movements using geodetic measurements. About 104,000?m3 of sediments was moved from the trough slope towards the moraine from which 534,000?m3 flowed to Cangrajanca Lake subsequently. We analysed the rainfall conditions that triggered the debris flow using rainfall data from the nearby stations. We also compared the precipitation preceding the event with the rainfall thresholds for debris flow initiation. |
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