Assessing the success of asbestos mine rehabilitation using high resolution satellite images: the case study of asbestos mines in Whitebank, Northern Cape Province
Date
2018
Authors
Tengela, Singalone Wongama
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Abstract
In 2012, Mintek was contracted to undertake the rehabilitation of the asbestos mines in the Whitebank area in Kuruman, Northern Cape Province. This was achieved by revegetating the abandoned asbestos mining sites. The aim of this study was to investigate whether remote sensing data and vegetation cover can be effectively used to assess the success of asbestos mine rehabilitation. The spatio-temporal changes of vegetation cover on and around the rehabilitated mine sites were identified and analysed using object-based classification. SPOT-5 and -6 images were used to map rehabilitated areas and to track vegetation cover change, at two-year intervals, between 2008 and 2016. NDVIs were computed from SPOT data to detect the vegetation recovery and density in the rehabilitated mine sites. RapidEye image data was also used to classify the flora in the study area using the Random Forest (RF) classifier to understand the species composition on the rehabilitated sites and surrounding areas. Between 2008 and 2010, the land surrounding the mine was left degraded and without any vegetation. The area experienced slow vegetation growth in 2012 (6 months after rehabilitation), but between 2014 and 2016, there was an increase in vegetation cover. Of the plant species identified, Grewia flava was the dominant species with a total of 390.0416 hectares classified. Four other predominant species were identified: Tarchonanthus camphoratus (637.945 hectares), Eragrostis lehmanniana (458.0825 hectares), Acacia mellifera (12.1075 hectares) and Themeda triandra (558.0875 hectares). Regarding the mean decrease in the Gini index, the most predominant band was the Near Infrared (Band 5), which was located around 760-880 nm. The Blue (Band 1: 440-510 nm) and the Green bands (Band 2: 520-590 nm) also significantly contributed to the classification of these species. The Red band (Band 3: 630-685 nm) did not play a major role in the species separability. The study showed the potential of remote sensing technology as a plausible tool for assessing mine site rehabilitation progress using high-resolution satellite imagery.
Description
A research report submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the Degree of Master of Science (Geographical Information Systems and Remote Sensing), School of Geography, Archaeology and Environmental Studies
Johannesburg, 2018