Riparian vegetation

Riparian vegetation provides the interface between the land and body of water.

For details on why Riparian zone is important refer to the WetlandInfo riparian vegetation web page.

The Queensland Government website has additional information on vegetation management including mapping, monitoring and approvals.

Why do we measure it?

Riparian vegetation is measured spatially in order to give a degree of naturalness to the estuary, which is then used in the calculation of the Biological Health Rating (BHR). This value forms a total of 15 per cent of the complete Ecosystem Health Index (EHI).

Riparian vegetation performs many functions including;

  • providing habitat for a wide range of species
  • preventing erosion of riverbanks
  • blocking nutrients and sediments from entering the water column.

Removal of riparian habitat in estuaries reduces the biodiversity and productivity of the system. As a result, it can lead to a reduction in water quality and ecosystem health.

In estuaries, mangroves are common in the riparian zone and provide crucial nursery habitats to many aquatic species including commercially important fish and prawn species. Riparian habitats in south-east Queensland estuaries are under considerable threat from modification through urbanisation and agriculture.

Methods

The Ecosystem Health Monitoring Program (EHMP) measures the extent of riparian habitat in the estuaries as the percentage of the total system that has retained unmodified riparian habitat. To do this, the department designed an assessment tool that combines a touch screen laptop, a global positioning unit and a specifically designed software tool, enabling easy recording of the observed habitat type and structure along the length of the estuary. The system has been designed to operate continuously from a vessel travelling slowly along the estuary.

The data recorded is split into two zones: the intertidal zone–the area between the high tide and low tide; and the background zone—the area from the high tide mark to 100 metres beyond.

As the intertidal zone is more easily seen from the water, more detailed observations are required including:

  • vegetation type, density and height
  • any built structures such as retaining walls, wharfs or boardwalks
  • any point features like storm water pipes, drains, jetties and boat ramps
  • the substrate type.

The background observations are less detailed and are limited to one of 12 land use types.

The software tool records the data entered through the touch screen laptop, along with a GPS co-ordinate, every two seconds. Back in the office the data is analysed to assess the extent of unmodified habitat in both the intertidal and background zones. To be classified as unmodified habitat in the intertidal zone, mangroves must be present, the substrate must be either mud, sand, natural rock or dirt with no structures, bank modifications or point features present. To be classified as unmodified habitat in the background, the land use selected must be a vegetation type.

The resulting calculation is the percentage of unmodified habitat in the intertidal and background zones on both banks. This is then averaged to one value for the estuary, which in turn is used in calculating the Biological Health Rating (BHR). This rating comprises 30 per cent of the report card grade compiled by the EHMP. The riparian assessment comprises half of the BHR.

More information

For data and reports on riparian vegetation monitoring visit our publications page.