Assessment of rehabilitated surface mine lands using geospatial technology a case study: Anglogold Ashanti Iduapriem Mine, Tarkwa, W/R - Ghana

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Increased awareness of the importance of environmental sustainability has put pressure on mine reclamation projects, as stakeholders demand close monitoring and detailed reporting. Non-compliance with standard acceptable practices and regulatory requirements can result in the levying of huge fines and loss of social license and legal right to operate a mine. Existing ground-based monitoring techniques such as the Ecological Function Analysis (EFA) and Landscape Function Analysis (LFA) are time and labor intensive when utilized for monitoring vegetation change with periodic assessments. Airborne Light Detection and Ranging (LIDAR) and Landsat spaceborne remote sensing technologies offer a quick, less demanding alternative in monitoring post-mining reclamation projects. To demonstrate the utility and effectiveness of LIDAR and Landsat in reclamation monitoring, the technologies were applied in the assessment and monitoring of reclaimed disturbed mine-lands at the AngloGold Ashanti Iduapriem mine in the Tarkwa area of the Western Region of Ghana. Digital surface and elevation models were extracted from LiDAR dataset and used to estimate vegetation canopy height as well as percentage canopy cover. Derived canopy heights were validated with field measurements. Stepwise regression analysis yielded a linear model with a strong correlation of R2 = 0.913 with RMSE = 1.961. The study also utilized Landsat 4 Thematic Mapper (TM), Landsat 7 Enhanced Thematic Mapper (ETM+) and Landsat 8 Operational Land Imager (OLI) Imagery for the monitoring of land reclamation projects within the study area, using vegetation cover as proxy for ecosystem health. Spectral vegetation indices were employed to monitor temporal changes of vegetation productivity from 1991 to 2014 of the ecosystem. LiDAR analysis shows mean tree height of 11.59 meters for 10 years old reclaimed site, which compares well with 17.88 metres mean height recorded for adjacent undisturbed natural forest. A Canopy cover percentage, nearing 100% depicting a dense canopy for the reclaimed sites was also recorded. Normalized difference vegetation indices computed shows an average of 0.473 in 1991, -0.005 in 2000 and 0.681 in 2014 with a standard deviation of 0.054, 0.154 and 0.057 respectively. It is demonstrated that LIDAR and Landsat can be effective and relatively precise for monitoring and assessment of reclaimed mined out lands to help take up remedial measures required for environmental sustainability.
A thesis submitted to the Department of Geomatic Engineering Kwame Nkrumah University of Science and Technology, Kumasi, Ghana in partial fulfilment of the requirements for the degree of Master of Philosophy in Geomatic Engineering, 2016