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Item Hydraulic and hydrological modelling of the Nyl River floodplain for environmental impact assessment(2006-03-13) Kleynhans, Martin ThomasThere have been various threats from upstream catchment developments to the water supply of the ecologically important Nylsvlei floodplain in South Africa. Hydrological modelling of the catchments and unsteady hydraulic modelling of the floodplain (including measured losses to evapotranspiration and infiltration) with biotic links to Oryza longistaminata revealed that existing developments within the catchments have decreased areas suitable for growth of this plant in the Nylsvley Reserve by 9% on average from 1973/74 to 2000/01 compared to the catchment in a virgin state. Construction of the proposed Olifantspruit Dam with environmental flow releases would have reduced these suitable areas by a further 9% on average. Catchment developments were found to have the greatest impact on floodplain inundation in average to dry years and would also reduce the frequency of occurrence of suitable conditions for growth of Oryza longistaminata.Item Mining landscapes of the Gauteng City-Region(Gauteng City-Region Observatory, 2018-01) Bobbins, Kerry; Trangos, GuyThe extraction of gold along the Witwatersrand mining belt has fundamentally shaped the Gauteng City-Region (GCR) over more than a century. Mining in the region occurred across a vast area. The Witwatersrand basin is made up of three sub-basins – the West’, ‘Central’ and ‘East’ Rand – and stretches across a further seven distinct gold mining areas. These goldfields attracted prospectors, industrialists and work-seekers from across South Africa and around the world. They were responsible for the formation of Johannesburg and, over time, the development of large parts of the extended metropolis around it. For many years, gold mining produced immense wealth for mining companies, banks and residents – indeed the wealth extracted fired the entire South African economy. But there have been negatives. Gold mining also spawned a war, entrenched deep social divides, instilled exploitative labour practices, and devastated the natural environment. Though the industry is now in decline, the landscapes affected by mining are still identifiable by toxic scars that traverse the city-region. This Research Report, GCRO’s seventh, considers how the legacies of mining have been imprinted on the towns and cities of the Gauteng City-Region. The report uses ‘mining landscapes’ as a conceptual device to structure an analysis of the diverse impacts of mining, and to highlight the need for a comprehensive and collaborative approach to manage its after-effects. The report makes a unique contribution to existing literature on mining and mining waste in the city-region by presenting an integrated perspective on their urban, environmental, social and economic processes, characteristics and consequences, both historical and contemporary. While accounts are often told from the viewpoint of specific disciplines (such as history, geography or sociology), the analyses presented in this report – comprising of written pieces, archival excerpts and photo essays – are unbounded by distinctive disciplinary conforms. This allows for the diversity of the landscape to be explored in new ways. The report makes a call for the GCR’s mining landscapes to be understood as a connected landscape of systems rather than a set of isolated and forgotten features of a bygone mining era. From the abandoned mine areas that scatter the surface of the GCR, to earth tremors caused by hollowed out cavities below the earth, silicosis, acid mine drainage, distressed mining towns and more recent histories of artisanal mining – the legacy of gold mining in Gauteng has a variety of expressions, all emerging from the same interconnected history. The concluding chapter looks to the future and considers the possibilities for innovative and collaborative approaches to unshackle the towns and cities of the Witwatersrand from their gold-mining inheritance. This includes the prospects for spatial transformation, repairing social divisions, cultivating natural assets, and remedying the destructive health and environmental effects of a century of mining activity.Item A statistical investigation into the properties and dynamics of biological populations experiencing environmental variability(2007-02-15T11:30:22Z) Varughese, Melvin MathewMuch research has been devoted towards the understanding of population behaviour. Such understanding has often been furthered through the development of theoretical population models. This research report explores a variety of population models and their implications. The implications of the various models are explored using both analytical results and simulations. Specific aspects of population behaviour studied include gross fluctuation characteristics and extinction probabilities for a population. This research report starts with an overview of Deterministic Models. This is followed by a study of Birth and Death Processes, Branching Processes and Models that incorporate environmental variability. Finally, we study the maximum likelihood approach to population parameter estimation. The more notable theoretical results derived include: the development of models that incorporate the population’s history; models that incorporate discontinuous environmental changes and the development of a means of parameter estimation for a Stochastic Differential Equation.Item Towards applying a green infrastructure approach in the Gauteng City-Region(Gauteng City-Region Observatory, 2019-12) Culwick, Christina; Khanyile, Samkelisiwe; Bobbins, Kerry; Dunsmore, Stuart; Fitchett, Anne; Monama, Lerato; Naidu, Raishan; Sykes, Gillian; van den Bussche, Jennifer; Vieira, MarcoThe Gauteng City-Region (GCR) regularly experiences heatwaves, raising renewed concerns over water security, as well as heavy and persistent rains, leading to severe flooding in some areas. In this context of heightened climate variability, thinking about ways to redesign our urban areas with more sustainable infrastructure solutions is becoming more and more important. Green infrastructure (GI) is emerging as an alternative approach to traditional (‘grey’) infrastructure in urban planning and development. Its emergence can be understood in terms of the growing demand for infrastructure and services, increased concerns over natural resource constraints and climate change, and the negative impacts associated with traditional approaches to designing and building cities. It has been proposed that GI can provide the same services as traditional infrastructure at a similar capital cost, while also providing a range of additional benefits. However, despite greater policy interest in green infrastructure in recent years, traditional infrastructure solutions to urban problems continue to dominate. This is partly due to the lack of a systematic evidence base to support GI implementation. There have been calls from decision-makers for more concrete examples of the benefits of successful urban GI applications, as well as for practical guidelines on their implementation. Towards applying a green infrastructure approach in the Gauteng City-Region is the GCRO’s eleventh Research Report. This report builds on the findings of two previous green infrastructure reports, as well as a CityLab process run with academics and government officials between 2014 and 2016. These outputs and the CityLab discussions highlighted as critical the need to for a deeper evidence base in building support for, and enhancing investment in, the GI approach. Unlike the earlier studies which were more theoretically grounded and policy oriented, this report comprises a number of technical investigations that more practically reflect on how a GI approach could be incorporated into urban planning in the GCR, and in other similar urban contexts.