Land capability and topographic data as a surrogate for the mapping and classification of wetlands: a case example from the Daly basin, Northern Territory, Australia.
The Daly River (catchment 53,000 km2) has the largest flow of all rivers in the Northern Territory and, due to the vast underground aquifers supplying the river, reliable flows of water and areas of high potential soils, is the centre of a region where water resource and agricultural development is being given serious consideration. As part of a larger assessment of environmental flow requirements, an inventory and risk assessment of water dependent ecosystems (wetlands) was undertaken for the Daly basin, a limestone dominated region, 19,382 km2 in size, located in the centre of the catchment. The assessment utilized geographic information system technology to collate, interrogate and analyse soil and topographic data that had been collected previously for the purpose of land capability analysis. The aggregated data were used as a surrogate for mapping the distribution of wetlands in the Daly basin. The land units mapped were composed of individual areas within which the soil, vegetation and landform exhibited a uniform pattern on aerial photographs. The wetland features mapped were classified using landform and hydroperiod as a basis and, to assist in the classification process, a ground-truthing exercise and a basin-wide low-level aerial survey were conducted.