Ecohydrological controls on soil erosion and landscape evolution

G Hancock, Kenneth Evans, J McDonnell, L Hopp

    Research output: Contribution to journalArticleResearchpeer-review

    Abstract

    The ecohydrological controls on soil erosion and landscape evolution are difficult to quantify and poorly understood. In many parts of the world, cyclone-induced tree throw is a major source of disturbance. Tree throw may increase sediment transport by exposing a mound of fresh soil as well as providing a pit which may act as a knickpoint triggering gully erosion. Alternatively, while tree throw provides characteristic pit–mound topography, the amount of soil disturbed or exposed in a mound is relatively small on the hillslope and catchment scale and the effects may be minimal. The April 2006 tropical cyclone Monica that impacted the coast of northern Australia with winds' speeds > 100 m s−1 uprooted approximately 50% of the trees in the study catchment. We use a landscape evolution model with repeated occurrence of the cyclone over a 1000-year simulated period to quantify the effect of pit–mound topography distributions on both sediment transport and landscape evolution by including the fallen trees into the digital elevation model both as a pit–mound and also as a pit–mound and tree trunk. The results show that the inclusion of pit–mound topography substantially reduced erosion for the first 10–15 years of its introduction and adding pit–mound–trunk topography reduced erosion rates even further. The pit–mound and pit–mound–trunk acted as sediment traps, capturing sediment from upslope and storing it in debris dams reducing hillslope connectivity. Model simulations predict average denudation rates for the catchment approximating field measured data. These findings suggest that any tree throw is unlikely to result in landscape instability.
    Original languageEnglish
    Pages (from-to)478-490
    Number of pages13
    JournalEcohydrology
    Volume5
    Issue number4
    DOIs
    Publication statusPublished - 2012

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    landscape evolution
    soil erosion
    topography
    sediment transport
    catchment
    hillslope
    cyclone
    gully erosion
    disturbed soils
    dams (hydrology)
    digital elevation models
    hurricanes
    wind speed
    sediment trap
    tree trunk
    denudation
    erosion rate
    tropical cyclone
    simulation models
    digital elevation model

    Cite this

    Hancock, G., Evans, K., McDonnell, J., & Hopp, L. (2012). Ecohydrological controls on soil erosion and landscape evolution. Ecohydrology, 5(4), 478-490. https://doi.org/10.1002/eco.241
    Hancock, G ; Evans, Kenneth ; McDonnell, J ; Hopp, L. / Ecohydrological controls on soil erosion and landscape evolution. In: Ecohydrology. 2012 ; Vol. 5, No. 4. pp. 478-490.
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    abstract = "The ecohydrological controls on soil erosion and landscape evolution are difficult to quantify and poorly understood. In many parts of the world, cyclone-induced tree throw is a major source of disturbance. Tree throw may increase sediment transport by exposing a mound of fresh soil as well as providing a pit which may act as a knickpoint triggering gully erosion. Alternatively, while tree throw provides characteristic pit–mound topography, the amount of soil disturbed or exposed in a mound is relatively small on the hillslope and catchment scale and the effects may be minimal. The April 2006 tropical cyclone Monica that impacted the coast of northern Australia with winds' speeds > 100 m s−1 uprooted approximately 50{\%} of the trees in the study catchment. We use a landscape evolution model with repeated occurrence of the cyclone over a 1000-year simulated period to quantify the effect of pit–mound topography distributions on both sediment transport and landscape evolution by including the fallen trees into the digital elevation model both as a pit–mound and also as a pit–mound and tree trunk. The results show that the inclusion of pit–mound topography substantially reduced erosion for the first 10–15 years of its introduction and adding pit–mound–trunk topography reduced erosion rates even further. The pit–mound and pit–mound–trunk acted as sediment traps, capturing sediment from upslope and storing it in debris dams reducing hillslope connectivity. Model simulations predict average denudation rates for the catchment approximating field measured data. These findings suggest that any tree throw is unlikely to result in landscape instability.",
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    Hancock, G, Evans, K, McDonnell, J & Hopp, L 2012, 'Ecohydrological controls on soil erosion and landscape evolution', Ecohydrology, vol. 5, no. 4, pp. 478-490. https://doi.org/10.1002/eco.241

    Ecohydrological controls on soil erosion and landscape evolution. / Hancock, G; Evans, Kenneth; McDonnell, J; Hopp, L.

    In: Ecohydrology, Vol. 5, No. 4, 2012, p. 478-490.

    Research output: Contribution to journalArticleResearchpeer-review

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    AB - The ecohydrological controls on soil erosion and landscape evolution are difficult to quantify and poorly understood. In many parts of the world, cyclone-induced tree throw is a major source of disturbance. Tree throw may increase sediment transport by exposing a mound of fresh soil as well as providing a pit which may act as a knickpoint triggering gully erosion. Alternatively, while tree throw provides characteristic pit–mound topography, the amount of soil disturbed or exposed in a mound is relatively small on the hillslope and catchment scale and the effects may be minimal. The April 2006 tropical cyclone Monica that impacted the coast of northern Australia with winds' speeds > 100 m s−1 uprooted approximately 50% of the trees in the study catchment. We use a landscape evolution model with repeated occurrence of the cyclone over a 1000-year simulated period to quantify the effect of pit–mound topography distributions on both sediment transport and landscape evolution by including the fallen trees into the digital elevation model both as a pit–mound and also as a pit–mound and tree trunk. The results show that the inclusion of pit–mound topography substantially reduced erosion for the first 10–15 years of its introduction and adding pit–mound–trunk topography reduced erosion rates even further. The pit–mound and pit–mound–trunk acted as sediment traps, capturing sediment from upslope and storing it in debris dams reducing hillslope connectivity. Model simulations predict average denudation rates for the catchment approximating field measured data. These findings suggest that any tree throw is unlikely to result in landscape instability.

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