School of Civil & Environmental Engineering (ETDs)

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Subject: search.filters.subject.SDG-11: Sustainable cities and communities

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    Determining the parameters for the sizing of sediment traps in the city of Johannesburg
    (University of the Witwatersrand, Johannesburg, 2024) Raliengoane, Mankoe Francis; Fitchett, Anne
    Urban land practices usually involve soil compaction and vegetation removal as cities expand and grow. This has led to increased flood peak flows and high stormwater runoff volumes associated with sediments, nutrients and other pollutants that load downstream water resources. To address these issues, there has been a growth of practices involving Sustainable Drainage Systems (SuDS) for managing stormwater runoff quantity and quality from urban areas. For example, this involves the application of attenuation ponds, and wetlands which temporarily store urban stormwater runoff, thereby reducing the sediment loads, pollutants, and release of peak flows to the downstream water resources at flow rates that mimic the pre-development flow patterns. This practice is gaining momentum in South African urban areas, which are supported by the policies and legislation set up by local authorities to address stormwater management. However, these stormwater application practices often do not perform according to their design capacities because they get filled with sediments and their effectiveness in attenuating peak flows is reduced. Therefore, it is important to reduce sediments coming into these structures by applying sediment traps and basins located at the head of such structures. The sediment trap’s main function is to slow down the stormwater runoff and help in the reduction of sediments before stormwater runoff is discharged out of the construction site and other disturbed areas. The City of Johannesburg Stormwater Management By-laws and Stormwater Design Manual have limited information for the management of sediment using sediment traps and basins and which parameters need to be considered when sizing sediment traps. Therefore, the main aim of the current research was to determine the parameters that should be considered when sizing sediment traps specifically for the city of Johannesburg. The following parameters: design rainfall, daily rainfall, catchment area, evaporation, land cover and land use, percentage of permeable and impermeable areas, topographical data, peak flow, runoff volume, catchment topography, soil types and infiltration characteristics, sediment particle size distribution, sediment settling velocity, sediment loading rate/yield were modelled through Personal Computer Stormwater Management Model (PCSWMM), ArcSWAT ArcGIS, and Excel Spreadsheet Models. Further, the sensitivity analysis was undertaken using different values of imperviousness and infiltration rates while observing peak flow and runoff volume changes in PCSWMM outputs. Modelling in PCSWMM showed that peak flows and runoff volumes increased due to an increase in the values of the imperviousness used. However, the range of infiltration rates for the soils in both sub- catchments S22 and S23 did not change the peak flows and runoff volumes. Though it was not the scope of the current study, it was observed that higher infiltration rates than the ones that were determined from the sub-catchments S22 and S23 indeed reduced peak flows and runoff volumes. On the other hand, particle settling velocity showed that gravel particles took a short time to settle and required a smaller sediment trap iii storage capacity. In comparison, silt particles took longer to settle and required a larger sediment trap storage capacity. Lastly, sediment yield from both sub-catchments S22 and S23 showed that sediment yield is driven by rainfall, whereby months with high rainfall had higher sediment yield than the months with low rainfall. It is therefore, concluded that the following parameters: design rainfall, daily rainfall, evaporation, land cover and land use, percentage of permeable and impermeable areas, topographical data, contributing catchment area, peak flow, runoff volume, catchment topography, soil types and infiltration characteristics, sediment particle size distribution, sediment settling velocity, sediment loading yield should be considered by the engineers, designers and planners when sizing sediment traps in the City of Johannesburg and possibly in other places as well.
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    The Impact of South Africa’s Response to Informal Settlements and Affordable Housing Development when compared to the responses adopted in Brazil and India
    (University of the Witwatersrand, Johannesburg, 2024) Mlotsa, Cebile; Biyela, Precious
    In South Africa, informal settlements are prevalent in all the major urban centers, including some long-established informal settlements, such as ones within Alexandria township in the City of Johannesburg, Nyanga in the City of Cape Town and Kennedy Road in the City of eThekwini. New informal settlements are continuing to develop across South Africa’s urban centers. Various policies and interventions have been implemented to address this phenomena. This study aimed to investigate the impact and effectiveness of South Africa’s policies and interventions on informal settlements and compared them to policies and interventions of India Brazil. The study begins with a literature review of the policies and strategies of the three countries alongside best practices recommended by international organizations such as UN-Habitat and the World Bank. The effectiveness of the policies was assessed, and the general issues that affect informal settlements globally were identified. Research questions were formulated based on the literature review to gain further insights into South Africa's response strategies. Semi-structured Interviews were conducted with three professionals working in organizations addressing informal settlements across different provinces, focusing on current strategies, their impact and effectiveness, and potential improvements. A field visit to Mahlakong informal settlement in Limpopo was also carried out which included interviews with two residents to understand challenges and interventions underway to address them. The study found some progressive policies and strategies underway in South Africa, such as the strong emphasis on participation and approval by residents of informal settlements when interventions are carried out, and incremental construction of infrastructure in informal settlements. The study also identified areas that if addressed can improve South Africa’s response to informal settlements, such as recognizing multi-storey inner city buildings as informal settlements, encouraging private developers to invest in affordable housing development, and diversifying tenure legalization option.
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    Emerging Contractor Development through the Provision of Low-cost Housing in the Eastern Cape
    (University of the Witwatersrand, Johannesburg, 2024) Joseph, Shati; Fitchett, Anne
    The construction industry is an economic stimulant and enabler of growth particularly in developing nations such as South Africa. The industry’s low entry barriers and the nature of work being labour-intensive attract emerging contractors. These contractors create jobs, upskill the community and transfer wealth to the previously marginalised. However, studies have shown that despite these several benefits, emerging contractors are prone to fail. Therefore, this research investigated the challenges facing emerging contractors and in addition, examined the low-cost housing programme. The positivism paradigm was adopted because of the nature of the research questions, its efficiency in the collection of voluminous data, and its perceived credibility by the policymakers. The collated data from 66 out of 173 contractors on the Eastern Cape Department of Human Settlements database were statistically analysed. The findings showed that most of emerging contractors are typically owned by a black male with a tertiary education, employ less than 20 employees, are capable of work worth less than R20 million and do not have a background in construction. The findings presented that the government was the primary employer of emerging contractors while some rely on subcontracting. Several contractors reported that they spent between 30 to 60 per cent of the contract value on materials. The start-up funds for emerging contractors are largely from family’s savings due to limited access to low- interest loans. During operation, the contractors heavily depend on monthly payment certificates to meet their expenses hence the importance of promptly settling these certificates. Emerging contractors receive training, it is largely from unaccredited mentors, which limits the upskilling of these contractors and leads to poor performance. The study then proposed possible initiatives that can employed for a progressive developmental programme based on the findings.
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    The Informal Waste Sector in the City of Ekurhuleni
    (University of the Witwatersrand, Johannesburg, 2024) Nyirenda, Irene N. Inan; Fitchett, Anne
    In South Africa, landfilling has traditionally been the primary method for dealing with general municipal solid waste. However, in recent years, there has been a shift in focus towards promoting a circular economy, which has brought about a change in waste management practices. The focus is now on minimising waste generation and reducing the waste stream rather than simply disposing of it. This approach aligns with South African National Waste Management Strategy 2020, which encourages such practices. The study focused on City of Ekurhuleni and the opportunities that exist in the formalisation of the informal waste sector with particular focus on landfill waste pickers and by analysing the amount of waste disposed of at the landfill site over a six (6) year period and comparing it to the percentage of materials that informal waste pickers recovered and reclaimed, the study provided valuable insights. This study utilised a mixed-method design that involved collecting and analysing both quantitative and qualitative data through desktop surveys, face- to-face interviews, and questionnaires. The practice of informal recycling at landfill sites encounters numerous environmental and health hazards for those who reclaim materials, because the waste is not sorted before disposal. The municipality lacks adequate resources for waste reduction initiatives, regulatory framework and capacity, educational campaigns, and enforcements, unlike those carried out by private companies or organisations. The study highlighted that some of the key inconsistencies in the interpretation of informal sector activities and their integration thereof in the context of the municipal regulatory framework are vague and unsupported.