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Effect of ENSO events on sediment production in a large coastal basin in northern Peru

Authors

  • Carolien Tote,

    Corresponding author
    1. Flemish Institute for Technological Research, Centre for Remote Sensing and Earth Observation Processes, Mol, Belgium
    • Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Heverlee, Belgium
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    • Current Address: Flemish Institute for Technology Research Centre for Remote Sensing and Earth Observation, Boeretang 200,2400 Mol, Belguim
  • Gerard Govers,

    1. Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Heverlee, Belgium
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  • Stijn Van Kerckhoven,

    1. Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Heverlee, Belgium
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  • Isabel Filiberto,

    1. Unidad de Gestión de Proyecto Binacional Catamayo-Chira, Piura, Peru
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    • Current Address: Av. Marginal s/n Pemba, Mozambique
  • Gert Verstraeten,

    1. Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Heverlee, Belgium
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  • Herman Eerens

    1. Flemish Institute for Technological Research, Centre for Remote Sensing and Earth Observation Processes, Mol, Belgium
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C. Tote, Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Celestijnenlaan 200E, 3001 Heverlee, Belgium. E-mail: carolien.tote@vito.be

ABSTRACT

Although the importance of ENSO on hydrological anomalies has been recognized, variations in sediment fluxes caused by these extreme events are poorly documented. The effect of ENSO is not limited to changes in sediment mobilization. Since ENSO events can affect terrestrial ecosystems, they may have important effects on sediment production and transport in river basins over time spans that are longer than the duration of the event itself. The Catamayo-Chira basin is an interesting casestudy for investigating these geomorphic implications. The objectives were: (i) to study the effect of ENSO on stream flow and sediment yields in the basin, (ii) to investigate if ENSO events affect sediment yields in the post-ENSO period and (iii) to understand which factors control the ENSO and post-ENSO basin response. During strong negative ENSO periods, mean annual stream flow discharge at the inlet of the Poechos reservoir in the lower basin was 5.4 times higher than normal annual discharges, while average sediment fluxes exceeded those of normal years by a factor of about 11. In two heavily affected periods, 45.9% of the total sediment yield in the 29 years observation period was generated. Sediment fluxes in the post-ENSO period are lower than expected, which proves post-ENSO event dynamics are significantly different from pre-event dynamics. Our analysis indicates the increase of vegetation growth in the lower basin is not the main reason explaining considerable sediment flux decrease in post-ENSO periods. During strong ENSO events, sediment in alluvial stores in the lower part of the basin is removed due to enlarging and deepening of channels. In post-ENSO periods, normal discharges and persisting sediment supplies from the middle/upper basin lead to river aggradation and storage of large amounts of sediment in alluvial plains. The decrease in sediment export will last for several years until the equilibrium is re-established. Copyright © 2011 John Wiley & Sons, Ltd.

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