Mapping dryland salinity with hyperspectral imagery

Hyperspectral imagery is used to map the various indicators of dryland salinity at Dicks Creek, a site in the Yass River catchment of New South Wales. These indicators include salt-source debris-flow deposits, degraded soil profiles, halophytic grasses and a closely associated drainage line community of grasses and reeds. No diagnostic evaporite minerals can be recognized but the high spectral resolution of HyMap allows non-saline fallow soils, rock outcrops and saline soils to be differentiated from one another. Mineral analysis using field spectrometry and X-Ray Diffraction (XRD) techniques confirms the likely presence of an aeolian, smectite clay, component in certain horizons of the soil profile. This distinctive yellow clay allows these soils to be separately mapped with HyMap imagery. The soils within the region are considered to be combinations of the normal weathering products of the basement rocks and a salt-enhanced windblown dust that accumulated during cold and and glacial periods. The soils have subsequently been redistributed from the valley sides to the valley floors as debris-flows. Integration of hyperspectral image products with a digital terrain model allows for the recognition of a close association of saline seeps with major geological structures