Can NDVI response indicate the effective flood extent in macrophyte dominated floodplain wetlands?

Sue POWELL, Anthony Jakeman, Barry Croke

    Research output: Contribution to journalArticle

    17 Citations (Scopus)

    Abstract

    Many of Australia’s river systems support extensive floodplains and wetlands but are threatened by water resource development and water extraction. To return beneficial environmental flows to these systems a better understanding of the temporal and spatial dynamics of the flood pulse is required.Remote sensing provides a source of data to assess past flood events critical to understanding the system processes; however in expansive floodplain and wetland systems with high landscape complexity, rapid vegetation response, canopy cover and shallow water depths, conventional analysis of open water may not be possible. Using readily available time-series of Normalised Difference Vegetation Index (NDVI), a decision tree was used to identify and map the likely flood extent using the vegetation response in the Gwydir wetlands, Australia. This ‘effective inundation’ over a range of flood events can be defined by flood frequency and connectivity to provide a simple conceptual model of the floodplains and wetlands. The results show that high NDVI response occurs following flooding in the floodplain and wetlands and was significantly correlated to 40 day inflow volumes. For Landsat and MODIS derived vegetation indices, an NDVI response greater than 0.75 was significant, while NDVI greater than 0.52 was significant for AVHRR data. In the Gwydir wetlands floods of up to 50 GL have occurred in 60% of years since the completion of Copeton Dam (1977), with almost 3000 ha of effective inundation. In contrast, moderately large floods of 100–200 GL occur in 30–50% of years and result in effective inundation of over 95 000 ha. The Gwydir wetlands could be simplified to 17 discrete patches, with each patch representing a connected landscape at defined flood frequency. This conceptual model can be used to develop hydrological models over the system at scales relevant to environmental flow management.
    Original languageEnglish
    Pages (from-to)486-493
    Number of pages8
    JournalEcological Indicators
    Volume45
    DOIs
    Publication statusPublished - 2014

    Fingerprint

    macrophyte
    NDVI
    floodplains
    floodplain
    wetlands
    wetland
    flood frequency
    vegetation
    dams (hydrology)
    support systems
    vegetation index
    normalized difference vegetation index
    Wetlands
    Vegetation
    water
    open water
    moderate resolution imaging spectroradiometer
    AVHRR
    Landsat
    river system

    Cite this

    POWELL, Sue ; Jakeman, Anthony ; Croke, Barry. / Can NDVI response indicate the effective flood extent in macrophyte dominated floodplain wetlands?. In: Ecological Indicators. 2014 ; Vol. 45. pp. 486-493.
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    abstract = "Many of Australia’s river systems support extensive floodplains and wetlands but are threatened by water resource development and water extraction. To return beneficial environmental flows to these systems a better understanding of the temporal and spatial dynamics of the flood pulse is required.Remote sensing provides a source of data to assess past flood events critical to understanding the system processes; however in expansive floodplain and wetland systems with high landscape complexity, rapid vegetation response, canopy cover and shallow water depths, conventional analysis of open water may not be possible. Using readily available time-series of Normalised Difference Vegetation Index (NDVI), a decision tree was used to identify and map the likely flood extent using the vegetation response in the Gwydir wetlands, Australia. This ‘effective inundation’ over a range of flood events can be defined by flood frequency and connectivity to provide a simple conceptual model of the floodplains and wetlands. The results show that high NDVI response occurs following flooding in the floodplain and wetlands and was significantly correlated to 40 day inflow volumes. For Landsat and MODIS derived vegetation indices, an NDVI response greater than 0.75 was significant, while NDVI greater than 0.52 was significant for AVHRR data. In the Gwydir wetlands floods of up to 50 GL have occurred in 60{\%} of years since the completion of Copeton Dam (1977), with almost 3000 ha of effective inundation. In contrast, moderately large floods of 100–200 GL occur in 30–50{\%} of years and result in effective inundation of over 95 000 ha. The Gwydir wetlands could be simplified to 17 discrete patches, with each patch representing a connected landscape at defined flood frequency. This conceptual model can be used to develop hydrological models over the system at scales relevant to environmental flow management.",
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    Can NDVI response indicate the effective flood extent in macrophyte dominated floodplain wetlands? / POWELL, Sue; Jakeman, Anthony; Croke, Barry.

    In: Ecological Indicators, Vol. 45, 2014, p. 486-493.

    Research output: Contribution to journalArticle

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    AU - Jakeman, Anthony

    AU - Croke, Barry

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    AB - Many of Australia’s river systems support extensive floodplains and wetlands but are threatened by water resource development and water extraction. To return beneficial environmental flows to these systems a better understanding of the temporal and spatial dynamics of the flood pulse is required.Remote sensing provides a source of data to assess past flood events critical to understanding the system processes; however in expansive floodplain and wetland systems with high landscape complexity, rapid vegetation response, canopy cover and shallow water depths, conventional analysis of open water may not be possible. Using readily available time-series of Normalised Difference Vegetation Index (NDVI), a decision tree was used to identify and map the likely flood extent using the vegetation response in the Gwydir wetlands, Australia. This ‘effective inundation’ over a range of flood events can be defined by flood frequency and connectivity to provide a simple conceptual model of the floodplains and wetlands. The results show that high NDVI response occurs following flooding in the floodplain and wetlands and was significantly correlated to 40 day inflow volumes. For Landsat and MODIS derived vegetation indices, an NDVI response greater than 0.75 was significant, while NDVI greater than 0.52 was significant for AVHRR data. In the Gwydir wetlands floods of up to 50 GL have occurred in 60% of years since the completion of Copeton Dam (1977), with almost 3000 ha of effective inundation. In contrast, moderately large floods of 100–200 GL occur in 30–50% of years and result in effective inundation of over 95 000 ha. The Gwydir wetlands could be simplified to 17 discrete patches, with each patch representing a connected landscape at defined flood frequency. This conceptual model can be used to develop hydrological models over the system at scales relevant to environmental flow management.

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