Articles | Volume 4, issue 1
Earth Surf. Dynam., 4, 47–70, 2016
Earth Surf. Dynam., 4, 47–70, 2016

Research article 20 Jan 2016

Research article | 20 Jan 2016

Storm-triggered landslides in the Peruvian Andes and implications for topography, carbon cycles, and biodiversity

K. E. Clark1,a, A. J. West2, R. G. Hilton3, G. P. Asner4, C. A. Quesada5, M. R. Silman6, S. S. Saatchi7, W. Farfan-Rios6, R. E. Martin4, A. B. Horwath8,b, K. Halladay1, M. New1,9,10, and Y. Malhi1 K. E. Clark et al.
  • 1Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, UK
  • 2Department of Earth Sciences, University of Southern California, Los Angeles, CA, USA
  • 3Department of Geography, Durham University, Durham, UK
  • 4Department of Global Ecology, Carnegie Institution for Science, Stanford, CA, USA
  • 5Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil
  • 6Department of Biology and Center for Energy, Environment, and Sustainability, Wake Forest University, Winston-Salem, NC, USA
  • 7Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
  • 8Department of Plant Sciences, University of Cambridge, Cambridge, UK
  • 9African Climate and Development Initiative, University of Cape Town, Rondebosch, Cape Town, South Africa
  • 10School of International Development, University of East Anglia, Norwich, UK
  • anow at: Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA, USA
  • bnow at: Department of Biology, University of Stirling, Stirling, UK

Abstract. In this study, we assess the geomorphic role of a rare, large-magnitude landslide-triggering event and consider its effect on mountain forest ecosystems and the erosion of organic carbon in an Andean river catchment. Proximal triggers such as large rain storms are known to cause large numbers of landslides, but the relative effects of such low-frequency, high-magnitude events are not well known in the context of more regular, smaller events. We develop a 25-year duration, annual-resolution landslide inventory by mapping landslide occurrence in the Kosñipata Valley, Peru, from 1988 to 2012 using Landsat, QuickBird, and WorldView satellite images. Catchment-wide landslide rates were high, averaging 0.076 % yr−1 by area. As a result, landslides on average completely turn over hillslopes every  ∼  1320 years, although our data suggest that landslide occurrence varies spatially and temporally, such that turnover times are likely to be non-uniform. In total, landslides stripped 26 ± 4 tC km−2 yr−1 of organic carbon from soil (80 %) and vegetation (20 %) during the study period. A single rain storm in March 2010 accounted for 27 % of all landslide area observed during the 25-year study and accounted for 26 % of the landslide-associated organic carbon flux. An approximately linear magnitude–frequency relationship for annual landslide areas suggests that large storms contribute an equivalent landslide failure area to the sum of lower-frequency landslide events occurring over the same period. However, the spatial distribution of landslides associated with the 2010 storm is distinct. On the basis of precipitation statistics and landscape morphology, we hypothesise that focusing of storm-triggered landslide erosion at lower elevations in the Kosñipata catchment may be characteristic of longer-term patterns. These patterns may have implications for the source and composition of sediments and organic material supplied to river systems of the Amazon Basin, and, through focusing of regular ecological disturbance, for the species composition of forested ecosystems in the region.

Short summary
The key findings of this paper are that landslides in the eastern Andes of Peru in the Kosñipata Valley rapidly turn over the landscape in ~1320 years, with a rate of 0.076% yr-1. Additionally, landslides were concentrated at lower elevations, due to an intense storm in 2010 accounting for ~1/4 of the total landslide area over the 25-year remote sensing study. Valley-wide carbon stocks were determined, and we estimate that 26 tC km-2 yr-1 of soil and biomass are stripped by landslides.