Geomorphic habitat mapping

The geomorphic habitats of 158 near-pristine estuaries were mapped in the Comparative Geomorphology of Estuaries Project by methods outlined in the Chapter 2. The maps comprise industry-standard ArcGIS files consisting of a base map of the estuary boundary, and vector layers showing the extent of subaerial, tidal and sub-tidal habitats. The maps are available for download in the OzEstuaries database ( where they exist alongside the maps of near-pristine and modified estuaries generated during the NLWRA (2002).

The near-pristine estuaries that were mapped in this project were chosen to reflect, as far as possible, the full range of geomorphic variability in Australia: A statistically significant number of the different types of estuaries (between 16 and 26) were chosen, and these were spread as far as practicable around the Australian coastline. These estuaries are located in all the coastal geomorphic regions of Australia (Harris et al. 2002). Within this context, state government preferences and the availability of suitable images and photographs were also taken into account. By ‘estuary types’, we refer to the major kinds of coastal waterways (i.e. wave- and tide-dominated estuaries and deltas, tidal creeks, strandplains and embayments) which experience differing amounts of wave, tide and river energy (Heap et al. 2001). By ‘coastal geomorphic regions’ (Harris et al. 2002) we refer to the North-west Coast, Gulf of Carpentaria, North-east Coast, South-east Coast and South-west Coast.

Near-pristine estuaries from Queensland and the Northern Territory comprised by far the largest proportion of the estuaries mapped during the project, accounting for 46% and 30% respectively. Significantly fewer estuaries were mapped in Western Australia (11%), Tasmania (9%), New South Wales (2%) and Victoria (<1%) style="font-weight: bold;">Remote sensing techniques and applications to near-pristine estuaries

As mentioned previously, near-pristine estuaries tend to be located along the most remote and inaccessible parts of the coastline, making them difficult to study. This is why remote sensing techniques (satellite-based or airborne sensors) and related applications (eCognitionTM) were scoped for their potential use in monitoring and gathering further information on the habitats and water quality of near-pristine estuaries. Remote sensing involves the collection of information about the earth’s surface, using sensors mounted on satellites or aeroplanes. The result of remote sensing is an image from which the spatial distribution of different landscape characteristics (e.g. mangrove forests and seagrass beds) can be mapped.

Remote sensing has been used for many years to map the coastal zone both for research and for management purposes. One relevant example was the use of aerial photography to map Australia’s coastal geomorphic habitats during the NLWRA. However, it is underscored in the remote sensing methods and applications portions of this report that more advanced satellite and /or airborne remote sensing instruments are now available, and these can be even more costeffective and objective than aerial photo interpretation. This is because the imagery can be collected at larger spatial scales (regional) and because computer software is now available that can help automate the process by which maps are made from the images. For example, the eCognitionTM software package is designed to produce maps from remote sensing images by grouping similar adjacent features (e.g. water body or forest patches) in the landscape. We present a case study from the near-pristine Wildman River in the Northern Territory (see Chapter 4) in which we demonstrate that maps made from remotely sensed images using eCognitionTM are comparable to or better than maps made using manual digitising.

The level of detail and number of physical properties that can be mapped using remote sensing imagery depend largely on the characteristics and availability ofthe remote sensing instruments. In a second case study on near-pristine estuaries in tropical northern Queensland (see Chapter 3), different types of imagery were investigated for their ability to differentiate between the dominant vegetation types in an estuarine environment. An automated mapping routine was then developed and applied to widely available satellite data (Landsat ETM) to produce maps of the Daintree River, Cooper Creek and Noah Creek. These maps were then compared to aerial photo interpretations. Although slightly different land-cover types were used, the results were comparable for the common vegetation classes. The advantage in using Landsat ETM (Enhanced Thematic Mapper) data in an automatic mapping routine over manual interpretation of aerial photographs is that it is fast and can cover large regions. The disadvantage is that user knowledge and experience cannot be applied at the same level of detail.

It can be summarised that remote sensing used in combination with eCognitionTM (or like-programs) can reduce the time and effort required for routine monitoring and mapping of Australia’s near-pristine estuaries, and allow environmental managers and researchers to regularly update habitat maps to monitor changes through time.

Language/Country:
English

Institution:
Cooperative Research Centre for Coastal Zone, Estuary and Waterway Management

Type :
PDF

Field :
GIS and Remote Sensing, Ecology

Years :
2006

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