Evaluation of PALSAR data for wetland mapping in the Mekong River Basin and in the Murray-Darling Basin.
Anthony Milne(1) and Ian Tapley(2)
(1) University of New South Wales, Kensington, 2052 SYDNEY, Australia
(2) Horizon Geoscience Consulting Pty Ltd, 12 Viewcrest Way, 6020 Sorrento, Australia
Evaluation of PALSAR data for wetland mapping in the Mekong River
Basin and in the Murray-Darling Basin.
Tony Milne*, Ian J. Tapley**
* School of Biological, Earth and Environmental Sciences,
University of New South Wales, Sydney.
**Horizon Geoscience Consulting, Perth, Western Australia
This paper outlines the application of PALSAR data to investigations being conducted in the Mekong River Basin in South East Asia and the Murray-Darling Basin in Australia to delineate and characterise wetland environments and to map and monitor the passage of floodwaters through these environments.
Within the Lower Mekong significant changes in river flow and total discharge can expected to occur as a result of dam building in the upper reaches of the Basin. Future as well as current land use and environmental planning in the Basin are therefore intimately linked to the changing flood conditions. The Basin is itself subject to significant economic development and to the threat of serious environmental degradation.
The Murray-Darling Basin is one of Australia's largest drainage divisions and covers one-seventh of the continent or 1,061,469 square kilometres and contains the three largest rivers in Australia, the Murray River, the Darling River and the Murrumbidgee River. Despite the size of the Basin, it only receives 6% of the total continental rainfall. Despite the paucity of precipitation, over 70% Australia's irrigation areas are located within the basin. The long-term productivity and sustainability however, is under threat from the over-allocation of water resources, salinity and the impacts of climate change (Australian Government, Department of Environment, Water, Heritage and the Arts,2008) .
L-band SAR capabilities based on published studies of JERS L-band HH data show good-to-very good results for wetland delineation, inundation mapping, and discrimination between woody and non-woody vegetation. However, discrimination among wetland forest types is only fair using single PALSAR coverages. Multi-date imagery shows that forest types can be better discriminated using inundation periodicity information. Also, since the PALSAR system has the capacity to provide dual- and quad-polarization data, improved definition of wetlands can expected over that obtainable from single-polarized data.
Determining the spatial pattern of vegetation classes in freshwater wetlands and the associated sequence of floodplain draining and drying that accompanies flood events are important first steps in assessing the hydrologic, geomorphic and ecological processes operating within flooded ecosystems. It is also a necessary pre-requisite to the formulation of management plans relating to the sustainable use, conservation and rehabilitation of such environments. Both the Mekong and the Murray-Darling Basins are under threat in terms of water availability and landscape degradation resulting from overuse and land clearing.
Products to be derived from this research include maps of wetland cover and of annual changes in wetland cover, along with flood maps showing flood extent and seasonal floodwater recession patterns.