Suitability of NDVI AVHRR data for wetland detection. A case study: Kakadu National Park, Australia
Internal Report 396
Supervising Scientist Division
About the report
A wetland inventory is a means of providing managers and decision-makers with base information for wetland conservation tasks (Dugan 1990, Finlayson 1996). A number of compilations on wetland occurrence in Australia have been made (eg Paijmans et al 1985, McComb and Lake 1988, ANCA 1996, Environment Australia 2001). While these provide a broad level of understanding of Australia’s wetlands, the specific features of individual wetlands – such as their spatial extent – are still incomplete, and a comprehensive inventory has not been undertaken as yet. Such inventory could be very useful to assess the state of Australia’s wetlands, or to establish priorities for wetland management (Spiers and Finlayson 1999, Watkins 1999, Russell French 2001).
The remoteness, inaccessibility and extent of many wetlands in Northern Australia make remote sensing an invaluable tool for inventorying wetlands, and the only feasible way to gather synoptic data on a regular basis in this region (Devonport and Bull 1999). Data from the AVHRR sensor are extensively used for land cover monitoring because of their broad spatial extent, temporal frequency, accessibility, and extensive archives (Benson and McKenzie 1995, Gervin et al 1985). All of these qualities are very desirable for wetland monitoring, and an optimal way to use AVHRR capabilities for that purpose should be found. In addition, the limited funding available for most wetland inventory work makes the low acquisition costs of AVHRR data very attractive.
Various global, continental and regional land cover data sets have been produced using, primarily, NDVI data obtained from the AVHRR sensor, applying diverse classification approaches (eg Tucker et al 1985, 1991, Malingreau 1986, Malingreau et al 1989, Loveland et al 1991, Loveland and Belward 1997, Townshend et al 1991, Townshend 1994, DeFries et al 1995, Cihlar et al 1996, Nemani and Running 1997, Gopal et al 1999). Most of these land cover data sets focus on types of terrestrial vegetation cover. Specific land cover classes, such as wetlands, receive little attention and their extent is usually largely underestimated.