The use of airborne geophysics, digital elevation data and high resolution digital camera imagery for assessing the impact of historical uranium mine sites in the Upper South Alligator River Valley, Northern Territory, Australia

This paper describes the use of remotely sensed data for the assessment of the state of historical mine sites in the upper South Alligator River Valley, Kakadu National Park in Northern Territory, Australia. A number of small uranium mines and prospects operated from 1956 to 1964 in the upper South Alligator River Valley. By 1964 the sites were abandoned, at a time when contemporary environmental mine site rehabilitation legislation did not exist. In order to gain a synoptic view of the state of abandoned uranium mine sites, and in particular any radiological pollution risk within the valley, a number of remotely sensed data sets were acquired. The primary data set was a high resolution 50 m-line spaced airborne geophysics survey, which resulted in the collection of airborne radiometric data (eU, eTh, K and total count rates), magnetic intensity, and digital elevation data. A digital airborne camera was also flown over the valley, with approximately 600 scenes recorded in colour-infrared, at 50 cm resolution. This paper illustrates the results of using the airborne radiometric eU channel, combined with digital elevation data and high resolution colour-infrared imagery. The eU channel demonstrated that the survey area is naturally highly mineralised. The highest counts were overlayed on the mosaic of high resolution ADAR imagery to gain insight into landscape components at the mine sites. Draping the ADAR imagery with the highest eU count rates over the digital elevation data provided a three dimensional topographical aspect The results showed that the highest eU count rates all correspond to known mining related locations, that the signal was contained within these sites, and that no significant erosion of radioactive materials was detected within the mine sites. The use of airborne gamma data, combined with high resolution ADAR imagery and digital elevation data resulted in synoptic coverage of radiological issues at the abandoned mine sites in the South Alligator Valley, and provided information to land managers for assessing the need for future rehabilitation measures