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Item A maintenance control system for rural roads.(1983) Curtayne, Peter C.; Knight, Kenneth.; Fleming, C. J.No abstract available.Item Recycling of bituminous pavement materials.(1984) Servas, Vladis P.; Knight, Kenneth.; Everitt, Philip Robert.No abstract available.Item Item Development of sounding equipment for the assessment of the time- settlement characteristics of recent alluvial deposits when subjected to embankment loads.(1992) Jones, Geraint Alan.; Knight, Kenneth.The whole of this thesis is my work unless specifically indicated to the contrary in the text, and has not been submitted in part or in whole to any other University. Some thirty years ago the author operated a deep sounding machine, one of the first in the country, on a misty lake in Ireland and marvelled at the way subsoil information could be garnered. The magic of the moment never entirely passed and when the opportunity arose to use the technique in Natal the die was cast. The development of the national road system surged in the early 1970's and since many of these roads on the Natal coastal routes crossed extensive recent alluvial deposits, the geotechnical problems of instability and settlement became major factors in the road design. Traditional methods of investigation consisted of boreholes with sampling and laboratory testing. Whilst these were satisfactory, provided they were of adequate quality, they were relatively expensive if sufficiently detailed models of the subsoil were to be obtained for design purposes. Cone penetration testing provided a potential a solution and this led to research work conducted over a period of twenty five years which continues today. The initial development of ideas for improvements to the mechanical equipment took place whilst the author was carrying out preliminary investigations for freeway routes over the coastal alluvial deposits. This was followed by a period devoted largely to cone penetration testing research and deVelopment and to embankment design methods at the National Institute for Transport and Road Research, and to the initial registration for a Master's degree under the supervision of Professor K Knight in 1975. This research programme was completed as originally envisaged, but not submitted because during its course the author conceived the idea of the piezometer cone. This proved to be such an exciting prospect that the research and development continued for a number of years until piezometer cone testing has now become almost routine for geotechnical investigations on alluvial deposits. In 1983, due to Professor Knight's retirement from the University, Mr Phillip Everitt was appointed as the supervisor. At that stage piezometer testing was becoming accepted internationally and new aspects and information frequently appeared. It was apparent, however, that the essential proof of the system for the prediction of embankment performance was to use it at embankments where the performance had been monitored. Eventually grants were provided by the Department of Transport for this, which enabled two research projects to be conducted during 1989 - 1990 and 1991 - 1992. After completion of the first of these a presentation of the author's work on cone penetration testing since the mid 1960's was made to the Faculty of Engineering at the University of Natal. The Executive Committee of the University Senate subsequently approved, in August 1991, that the registration be upgraded to doctoral status. Mr Everitt's encouragement during this extended period has been a vital factor in ensuring an outcome for this task and the author wishes to express his gratitude for this.Item Development of sounding equipment for the assessment of the time- settlement characteristics of recent alluvial deposits when subjected to embankment loads.(1992) Jones, Geraint Alan.; Knight, Kenneth.Many embankments on the soft, highly variable, recent alluvial deposits along the South African coast have suffered large settlements necessitating ongoing costly repairs. Due to the soft variable soils, borehole sampling is difficult and laboratory testing requires to be extensive for adequate subsoil modelling; cone penetration testing was considered to be a potential means to overcome these problems. Twenty five years ago in South Africa, as elsewhere, cone penetration testing equipment was relatively crude and the methods of interpretation were simplistic. The application of cone penetration testing to recent alluvial deposits therefore required improvements to both the equipment and the derivation of soil parameters. The equipment was upgraded by introducing strain gauge load cells capable of measuring cone pressures in soft clays with adequate accuracy. Hence, correlations of cone pressures with compressibility and shear strength became possible. Predictions of settlement times and magnitudes are of equal importance and a consolidometer-cone system was developed to assess both of these. A piezometer was incorporated into a cone to ascertain whether the settlements were due to consolidation. The piezometer cone performed so well that it superseded the consolidometer-cone and by 1977 a field piezometer cone was in regular use. Developments in piezocone interpretation have taken place concurrently with those in equipment; coefficients of consolidation are evaluated from pore pressure dissipations, and soils identified from the ratio of pore and cone pressures. These developments have been validated in two recent research projects, by comparing measured and predicted settlements at eleven embankments monitored for up to fifteen years. The data shows that for embankments on the recent alluvial deposits the constrained modulus coefficient, am is : am = 2,6 ± 0,6 The data also shows that coefficients of consolidation from piezometer cone dissipation tests are correlated with those from laboratory tests and back analysed embankment performance as follows : Embankment c = 3 CPTU c = 6 Lab cv It is concluded that piezometer cone penetration testing is particularly suitable for the geotechnical investigation and the subsequent design of embankments on recent alluvial deposits and should be considered as complementary to boreholes with sampling and laboratory testing. The existing database of embankment performance should be expanded with particular emphasis on long term measurements and on thorough initial determination of basic soil parametersItem Traffic circles in South Africa : traffic performance and driver behaviour.(1997) Krogscheepers, Johann Christoff.; Roebuck, Christopher S.This thesis presents the results of an investigation into traffic operations and driver behaviour at traffic circles under South African conditions. The scarcity of local traffic circles necessitated the development of a simulation program (TRACSIM) to assist in the research process. This microscopic program for single lane circles is based on event updates and was calibrated and validated based on local data. Because the acceptance of gaps is such a vital part of the operation of a traffic circle, it was examined in detail. Specific attention was given to the possible use of a gap acceptance model based on variables other than time. Since the gap acceptance process also depends on the gap distribution in the circulating stream, the effect of the origin-destination pattern was also investigated. Two existing analysis techniques are evaluated and verified for local conditions, improving them where possible. Generally these techniques under-estimate traffic delay at local circles. Observations indicate a difference between the acceptance of gaps/lags in the entering and circulating stream of conflicting traffic as well as a difference between critical gaps and critical lags. The mean observed critical gaps/lags are larger than in other countries, which indicates that delays at local circles will be greater. Gap/lag acceptance based on critical distances rather than critical times was applied successfully in the simulation program TRACSIM. A method is proposed to estimate critical distances from the geometric layout of the circle. Critical gaps are not fixed, but should vary with at least the conflicting flows. The investigation of the effect of unbalanced flows on delay, showed that the variability in drivers' critical gaps is more a function of delay than of conflicting flow. Entry delays increase because of an increase in conflicting flows or because of an unfavourable imbalance of conflicting flows. In both instances the drivers' critical gaps will decrease. A variable critical gap model only based on conflicting flows will show no change in the drivers' critical gaps if the conflicting volumes remain constant, even though the actual average delay might increase because of an unfavourable imbalance in conflicting flows.Item The impact of the affirmative procurement policy on affirmable business enterprises in the South African construction industry.(2000) Gounden, Sivandran Munsami.; Schreiner, Hilson Deneys.; Taylor, Robert Gordon.The construction industry in South Africa is envisaged to play a pivotal role in the reconstruction of the South African economy, via the delivery of economic and social infrastructure. The skewed ownership I patterns prevalent in the construction sector, resulted in the South African government utilising public sector procurement as a mechanism to address these imbalances, and to promote wider participation I in public sector construction opportunities. This dissertation analyses the role of the construction industry in South Africa, and explores the rationale behind utilising public sector procurement as a mechanism to promote wider participation in the construction industry in South Africa. The research then focuses on the application of the Affirmative Procurement Policy (APP) on construction projects procured by the National Department of Public Works, in order to evaluate the impact which this policy has had on the growth and development of Affirmable Business Enterprises (ABEs). The research evaluates the primary policy outcomes, via the development of appropriate indices and a diagnostic quadrant comparator, and concludes that the application of the APP has had a positive impact on ABE participation, with levels of participation varying across construction sub sectors and categories. It was also found that financial premiums, borne by the State in adopting this policy, were nominal when compared with the initial projected outcomes and the overall benefits. The overall performance of ABEs, measured against that of non-ABEs, was then tested to ascertain whether the adoption of the APP was a necessary and sufficient condition for ABE enablement and empowerment. The research concludes that there is a difference in overall performance between J ABEs and non-ABEs, and that supply side interventions and capacitation programmes are required to mitigate the increased risk exposure by the State, when engaging ABEs on construction projects. The : research also analyses the variation in the levels of participation of ABEs, in the different construction sub sectors and concludes that the manner in which ABEs are structured and their internal business processes tend to establish operational limitations, which influence their scope of activitiies to a larger extent than the existence of eternal sub sector thresholds. Similar characteristics were,observed in non-ABEs of a similar size, inferring that the problems encountered relate to business development and growth of small and medium enterprises, in general. The research also. analyses the impact that the APP has had on subcontracting relationships and the promotion of structured joint ventures. It concludes that whilst the requirements of the APP has seen the development of formalised subcontracting relationships, the form of subcontracts that are currently utilised do not comply with the requirements outlined in the APP, which are aimed at eradicating unfair subcontracting conditions. The adoption of the APP has seen an increase in structured joint ventures between ABEs and larger established contractors. The analysis of these joint ventures concludes that they provide an effective means of transferring expertise, provided that they are structured appropriately. The dissertation concludes with recommendations on APP policy refinements, mechanisms to enhance compliance and opportunities for international application. The recent enactment of the Preferential Procurement Policy Act (Act 5 of 20(0) in South Africa indicates that several elements of the APP are likely to be prescribed as mandatory requirements for public sector procurement by different government institutions and across the different industrial sectors. It is therefore important that the areas identified for further research be pursued, to ensure optimal policy outcomes across a range of industrial sectors.Item A numerical study of bacteria transport through porous media using the green element method.(2000) Ramsuroop, Suresh.; Onyejekwe, Okey Oseloka.The continued widespread contamination of the subsurface environment by microbial pathogens and chemical wastes has resulted in an increased interest in the factors that influence microbial transport through porous media. In this work a numerical study is undertaken to determine the influence of various processes that contribute to microbial transport in porous media. The evaluations were conducted by the simulation of a typical macroscopic transport model, using a novel numerical technique referred to as the Green Element Method (GEM). This computational method applies the singular boundary integral theory of the Boundary Element Method (BEM) to a discretised domain in a typical Finite Element Method (FEM) procedure. Three models are presented to evaluate the effects of the various parameters and factors: a constant porosity model was formulated to verify the GEM formulation against an analytical solution, a variable porosity linear model was developed and used for the simulation of the transport process involving first order type clogging, and a variable porosity nonlinear model used to evaluate effects of nonlinear type clogging. All three models were validated by simulations in specific applications in which analytical or deduced solutions were available. The parameters and factors evaluated included the effects of substrate concentrations, decay rates, source concentrations (boundary conditions), flow velocity, clogging rates, dispersivity, point and distributed sources, and nonlinear clogging. The results show that the trends predicted were consistent with the trends expected from theory. The conditions that enhanced bacteria transport included high velocities, low decay rate constants, high substrate concentrations, and low clogging rates. The range of dispersivities investigated showed little variation in the bacteria concentration in the longitudinal direction. Reduction in porosity resulted in retardation of the migrating plume. Conditions that led to significant loss in porosity are high bacteria loadings and high growth rates. The GEM formulation showed no restrictions or limitations in solving transient linear and transient nonlinear applications. In the nonlinear application, the Newton Raphson algorithm was successfully used for the iterative solution procedures. In addition, the GEM formulation easily facilitated the application of distributed and point sources in the problem domain.Item Gaseous and particulate emissions.(2000) Beebal, Nisha.; Lutchmiah, Johnny Soobramoney.The need to limit sulphur dioxide, nitrous oxides and particulate matter emissions from fossil fuel combustion processes is now a major factor in the design, construction and operation of plants. Over the past 5 to 10 years, most developed countries have introduced legislations to control these. emissions. This report was done to investigate emissions of sulphur dioxide (S02), nitrogen oxides (NOx) and particulate matter from coal fired power plants. S02 emissions contribute to an air pollution load that has been found to be linked to respiratory and heart problems. It increases the formation of acid precipitation, called acid rain. NOx oxides to nitrogen dioxide (N02). N02 acts as an irritant to the respiratory tract, alveoli of the lungs and causes chest pains. Toxic elements concentrate on fine particulate matter because of their high surface-area to volume ratio. These particles penetrate and settle onto the lung wall, leading to respiratory disorders and lung diseases. Due to the strict legislative requirements, flue gas detoxification processes were investigated. They include: • Wet scrubbing • Spray dry scrubbing • Dual-alkali • Well man-Lord • Activated carbon • Magnesium oxides • Selective catalytic recovery • Circulating fluidised bed combustion • Electromembrane desulphurisation A study was done to show the possible cost implications associated with the wet scrubbing, spray dry scrubbing, selective catalytic recovery, circulating fluidised bed and electromembrane desulphurisation process. A variety of methods were used to calculate cost, due to costs being difficult to obtain. Most of the information was based on European, Asian and American installations. The objective of this economic analysis was to compare the different technologies. Because of the assumptions used, costs were always "order of magnitude" estimates. Capital and operating costs were calculated for these technologies, but they can only be used as an indication of costs and to allow for comparisons between the technologies. The costs were converted using the January 2000 exchange rates. Due to this, costs may be more inflated than what would normally be expected due to equipment being purchased earlier than January 2000. Of the processes investigated, the circulating fluidised bed process was found to be the most economical. There is no inexpensive route for the removal of sulphur dioxide, nitrous oxides and particulate matter. The most suitable detoxification process will depend on the legislative requirements per country. South Africa is a signatory of the Montreal Protocol and the Framework for Climatic Change. Legislations for gaseous emissions were not considered a priority. Currently, Eskom's drive is to electrify townships rather than spend money on detoxification processes. However, future legislations may require more stringent control measures.Item Rural road maintenance through labour-based lengthmen system in Zambia.(2000) Mwango, Abraham.; Little, Robert.Rural road maintenance has received little or no attention in Zambia for a long time, resulting in an adverse impact on the economy. Meanwhile Road Authorities have continued to use traditional capital-intensive periodic and routine maintenance at the expense of scarce foreign exchange. The system has not performed well, hence the current state of roads. Labour-based methods for routine maintenance under the Lengthmen System used in Kenya, Lesotho and other developing countries in the Sub-Saharan Africa have proved to be technically and economically viable. In this report the author examines the desirability of using the Labour-Based Lengthmen System as an alternative to the existing capital -intensive methods in Zambia. This is done through rev iewing rural road maintenance in Zambia and then carrying out a comparative analysis of the same bctween Zambia, Kenya and Lesotho The comparative analysis shows that Zambia is not performing well when compared to Kenya and Lesotho. Meanwhile, the Lengthmen System is more desirable compared to other methods under the current economic conditions. Recommendations, based on the comparative analysis, have been given to improve rural road maintenance in Zambia.Item A linear catchment model for real time flood forecasting.(2001) Sinclair, D. S.; Pegram, Geoffrey Guy Sinclair.A linear reservoir cell model is presented which is proposed as a good candidate for real time flood forecasting applications. The model is designed to be computationally efficient since it should be able to run on a P.C and must operate online in real time. The model parameters and forecasts can be easily updated in order to allow for a more accurate forecast based on real time observations of streamflow and rainfall. The final model, once calibrated, should be able to operate effectively without requiring highly skilled and knowledgeable operators. Thus it is hoped to provide a tool which can be incorporated into an early warning system for mitigation of flood damage, giving water resources managers the extra lead-time to implement any contingency plans which may be neccssary to ensure the safety of people and prevent damage to property. The use of linear models for describing hydrological systems is not new, however the model presented in this thesis departs from previous implementations. A particular departure is the novel method used in the conversion of observed to effective rainlfall. The physical processes that result in the rainfall to runoff conversion are non-linear in nature. Most of the significant non-linearity results from rainfall losses, which occur largely due to evaporation and human extraction. The remaining rainfall is converted to runoff. These losses are particularly significant in the South African climate and in some regions may be as much as 70-90 % of the total observed rainfall. Loss parameters are an integral part of the model formulation and allow for losses to be dealt with directly. Thus, input to the model is observed rainfall and not the "effective" rainfall normally associated with conceptual catchment models. The model is formulated in Finite Difference form similar to an Auto Regressive Moving Average (ARMA) model; it is this formulation which provides the required computational efficiency. The ARMA equation is a discretely coincident form of the State-Space equations that govern the response of an arrangement of linear reservoirs. This results in a functional relationship between the reservoir response constants and the ARMA coefficients, which guarantees stationarity of the ARMA model.Item Numerical and experimental study of transient heat transfer through concrete.(2001) Mabuya, Thabo Gordon.; Onyejekwe, Okey Oseloka.The increase in temperature of developing concrete as a result of heat liberated by cementing reactions is the primary cause for thermally induced cracks in large concrete elements. It is very essential, in engineering to predict the temperature rises in order to be able to minimise the potential of crack formation. This thesis covers the experimental determination of the heat of hydration curve using the adiabatic calorimeter and experimental determination of transient heat transfer obtained from measurement of temperature variations in concrete at its early ages of hydration. The measured temperature profiles from a one-dimensional heat transfer scenario are then compared with the predicted temperature profiles. The adiabatic hydration curve of a concrete beam sample is used as input into a numerical technique known as the Green Element Method for the calculation of temperature profiles. Time-based boundary conditions are imposed on the equation governing the model and will be solved using the Green Element Method coded in Fortran Power Station 4.0.Item Costing calculation of operation and maintenance in community water supplies.(2001) Mwangi, Patrick Nduati.; Otieno, Fredrick Alfred Ochieng.; Ndiritu, John Gatherv.Studies of community water have been on the increase since the International Drinking Water Supply and Sanitation Decade, 1981 - 1990. However there is some key areas of community water supply that still require research as the literature survey in this thesis illustrates. The Operation and Maintenance of community water supplies has been identified to be as important in sustainability of the services as the institutional factors. Due to the increased number of failure of the community water supplies to continue operation after short periods of time compared to urban water supplies, effort is required to identify the least amount of in puts to ensure continued operation. Through literature survey and field collection of data on management of existing projects a model was developed in order to calculate the minimum amount of funds required for the operation and maintenance. The research showed that the current monthly charges by water committees were sufficient to operate and maintain the systems. The initial calculations using the model also revealed that the current charges would not be sufficient to pay replacement costs. The presence of subsidisation through materials and labour by the central government requires planners to study each project thoroughly before the determination of monthly costs. The conclusion was that further research and data collection was required for the determination of the replacement cost. The model was found to be capable of assisting planners, managers and engineers in the calculation of the cost of operation and maintenance of community water supplies.Item Ultimate load and deflection behaviour of cellular beams.(2001) Warren, Juliet.; Dougherty, B.Cellular beams were developed in 1987 and are an adaptation of castellated beams having many of the same advantages and disadvantages. There are no published results of tests on cellular beams and there is only one recognised method of analysis and design. Full scale destructive tests were carried out for this investigation on eight cellular beams. Beams loaded at midspan and at the third points were tested. Failure load, failure mode and deflections were obtained for each beam. The existing analysis method as well as three new methods for both ultimate load behaviour and deflections were checked against the experimental results. The existing method of analysis was found to be over-conservative in predicting failure loads and inaccurate in predicting deflections. The analysis method which best predicted the failure loads and modes was the design chart which was developed for this investigation. The theoretical method which best predicted the deflection was the Vierendeel method which was also developed for this investigation.Item An assessment of water services in a peri-urban area of Umtata.(2001) Ntuli, MzwaBantu.; Otieno, Fredrick Alfred Ochieng.No abstract available.Item Environmental study of the rehabilitation of the Monze-Zimba Road in Zambia.(2001) Samu, Silupumbwe Justine.; Joslin, Paul.It is very unfortunate that despite laws that require adequate incorporation and integration of environmental concerns at all phases of the economic developmental projects in Zambia, the research findings of this dissertation show that they are not applied well. The dissertation consists of six chapters. The Introduction (Chapter One) gives a general overview of Zambia, its geographical position in relation to other African countries, its macro and micro economic policies and its economic needs for a sound transport infrastructure. It also gives a rationale for the Monze-Zimba road rehabilitation project. Chapter Two reviews and states existing policies, legal, strategies and the institutional framework for environmental management and protection in Zambia. It also states and identifies key institutions involved in administering the various environmental laws/regulations and briefly refers to applicable International Conventions. Chapter Three gives a descriptive overview of baseline information - particularly within the catchment area of the road - regarding the biophysical, socioeconomic and cultural environments. The baseline studies provide insights into the normal background environmental variability such that appropriate monitoring programmes can be designed. It is now abundantly and evidently clear that the despoiling of the environment has negative repercussions on the health and wellbeing, culture and economic opportunities of humans. Chapter Four, therefore, provides in-depth discussions of each of the major impacts identified, their nature and scale and appropriate practical measures for their mitigation. The measures are incorporated into an Environmental Management Plan. Chapter Five addresses the environmental monitoring of the impacts resulting from the activities of the road. The Conclusion (Chapter Six) gives substantiated opinions on the overall findings of the research. Recommendations are given to the government of Zambia and all stakeholders on the best ways that environmental issues should be handled at all levels of society.Item Urban poverty reduction through municipal solid waste management (MSWM) : a case study of Maseru and Maputsoe in Lesotho.(2002) Mvuma, Godfrey Ganizani Kwantha.; Otieno, Fredrick Alfred Ochieng.The study was designed to generate data and information necessary for designing an appropriate sustainable solid waste management system, and examining the socio-economic benefits of urban municipal so lid waste management through job creation opportunities (albeit mainly informal) in Lesotho. The review of literature on the integrated solid waste management systems at international, regional and local levels in relation to job creation was carried out with a view to establish the necessity of carrying out this research. In addition, specific solid waste management experiences and practices in other countries have been cited. In Lesotho, investors and donors have, for long expressed the need for formulation of solid waste management policy and guidelines formulated in the country in order to create an enabling environment for investment. However, the process of preparing policy and guidelines requires substantial data and information. This study supplemented this effort by gathering data and information. The data and information gathered were on the existing policies and regulatory framework concerning waste management; waste generation rates, types and quantity from domestic, industrial and commercial establishments; recycling activities; and the waste harvesting (scavenging) activities. The study was undertaken in Maseru and Maputsoe, being the hub of commercial and industrial activities in the country. The data and information may also be useful to other SADC countries From the results of the study, it has been concluded that in Lesotho, paper was the most commonly generated waste in all the categories: domestic, industrial and commercial establishments. Plastic was the second category of the most commonly generated waste, which was followed by organic waste, and then, beverage cans. The study established that the weighted average household generation rate for the surveyed areas was: 0.13 Kg per capita day-I. In the same findings, it occurred that overall, households contribution to waste generation in the surveyed areas ranked second to commercial establishments despite their low per capita, in comparison with industrial establishments. The study has further concluded that out of an estimated total quantity of 157552 tonnes per annum of waste generated in Maseru, commercial establishments contributed 82%, while households contribute 15% and industrial establishments 3%. Households generated more waste than industries because they were in large numbers and hence contributed more than fewer industries. It has also been established that the household waste generation is dependent on incomes ofthese households, but had poor relationship with regard to the number of persons per household. To this effect, it was seen that high-income households generated more waste than low-income. The study further showed that where the municipal council offered waste collection service, not all recipients paid for this service. However, there was a general willingness- to- pay for the waste collection service by all sectors, on condition that there was an improvement in the offering of this service; and if made available where currently not offered. Furthermore, there was a general indication of affordability for these services up to a certain amount (albeit minimal) per different sectors. On the other hand, the information collected strongly indicated the need to invest more in solid waste management if this would be a means of employment creation and improvement of the environment. On the overall, the study revealed that there was a low level of awareness on waste related policy and regulatory instruments, and fragmented legal framework on waste management in Lesotho. The study also established that currently, solid waste as an informal sector generated an estimated profit of MO.7rnillion per annum from waste recycling related activities and that this informal sector generated about 282 jobs. In addition to these benefits, the question of solid waste as a source of biomass energy was another beneficial route in Lesotho. It has been established that the combustible organic waste was highly sought after as a source of energy for cooking and heating. However, besides the benefits, these activities also gave rise to some adverse impacts. The waste harvesters expressed that their health had been negatively impacted upon by the waste scavenging activities. Needless to suggest that there would be a need by the government to intervene in this problem by formalising these waste harvesting activities. It is hoped that this study would serve as a reservoiur for the source of data and information and for Lesotho and that other countries in the SADC Region shall fmd this document a useful tool.Item Monitoring the health of the rivers of the Durban Metropolitan Area using fresh water invertebrates. A pilot study.(2002) Nunkumar, Shamilla.; Dickens, Christopher William Spencer.; Olorunsogo, F.This document is aimed at all parties involved with conservation, planning and management of rivers within the Greater Durban Metropolitan Area, South Africa. The intentions of this study were to provide information on the health of the rivers using freshwater invertebrates and to identify areas where investigative efforts should be focused. In doing so, this document incorporates two data processing methods or techniques used in biomonitoring, the South African Scoring System (SASS) Rapid Bioassessment Technique (RBA) version 4 and the Integrated Habitat Assessment System (IHAS version 2c). The history, current status and future prospects and potential benefits of biological indicators both globally and in South Africa are reviewed and discussed. The RBA (SASS4) involved the standardised collection of samples using the "kick and sweep" technique from defined habitat types at representative sites on river stretches using a standardised net following defined methods. The total score per site is calculated for each family represented in the sample, which is then summed to give the SASS4 score. Lower scores are given to families with a high level of tolerance for polluted waters. The Average Score Per Taxon (ASPT) computation is obtained by dividing the SASS4 total by the number of taxa (families) in the sample. Both scores were considered when determining water quality impairment. The number and abundance of the different taxa and the number of biotopes present were considered as other measures of the river condition. The presence of numerous families of highly tolerant organisms (sludge worms and leeches) usually indicated poor water quality as represented in the Umlaas River, iSiphingo River, Tongati River, and the Ohlanga River. Several different types (or taxa) of stoneflies, mayflies and caddisflies (higher biodiversity) indicated a healthy site for example the iLovu River. Moderate river sites were characterized by declination in invertebrate diversity. Invertebrate diversity declines as the degradation of water quality increases. The manner in which SASS4 scores varied with "degree of anthropogenic impact" showed that the assessment does yield results, which follow water quality changes, provided that when SASS4 scores are less than 50, little attention is given to ASPT. At intermediate and high impacted sites ASPT did not follow habitat quality. However at low impacted water quality sites both SASS and ASPT tended to be greatest where habitat quality was the best. This study has identified that water quality "appears" to have a greater effect on macro invertebrate communities than the physical habitat and SASS distinguished sites with differing levels of water quality. This method was not designed to enable the exact nature of the disturbance to be determined, and it was intended that once an impairment of water quality had been established, it would be further assessed via intensive chemical and other studies. The use of more ecological indicators for example the inclusion of IHAS (version 2c) allowed a more comprehensive assessment of river health and more confidence could be linked to the outcome.Item Application of digital imaging in measuring cross track drift of vessels entering a port.(2002) Patel, Sahil Ramesh.; Stretch, Derek Dewey.Durban is the busiest container port in Africa and there are plans for significant expansion during the next few years. This expansion includes the widening of the port entrance channel to accommodate larger "post-panamax" vessels. Complex crosscurrents near the port entrance, coupled with severe wind and wave conditions, may lead to the intermittent closure of the port which in turn could lead to significant economic implications. Information on the nature of the crosscurrents and how they affect the ships could assist harbour pilots in developing their skills and reduce the risks associated with steering ships into the port. The research involved a case study to develop an innovative new method for directly measuring the effect of wind, waves and crosscurrents on ships entering the port. The technology is based on the application of digital image processing to track the position of ships as they manoeuvre in the port approach channel. The key innovation of this research is the extraction of the heading direction of the ship from the image data. The angle between this heading direction and the true velocity vector (the "crab angle") is then a direct measure of the cross-track drift velocity (CTDV) due to the combined effects of wind, waves and currents. The crosscurrents are usually the main contributing factor to the cross-track drift. The aim of this research was to develop a fully automated image processing system for real-time ship monitoring, and to determine cross-track drift within a wide range of weather conditions and ship parameters. The methodology presented in this research allows the spatial structure of the CTDV along the harbour approach channel to be studied. The relationship of the CTDV to local surface winds was analysed. For deep draught vessels, measured CTDVs were found to be poorly correlated to surface winds. The spatial structure of the measured CTDVs shows distinct regions along the approach channel where vessels experience significantly larger drift velocities. In summary, with the software tools developed by this research, digital images can be captured automatically and analysed to produce ship tracks and crab angles. From this information an extensive database for ship manoeuvring in the approach channel can be developed and the safety and efficiency of port operations improved.Item Prediction, management and control of odour from landfill sites.(2002) Laister, Guy.; Stretch, Derek Dewey.Due to the spread of urbanisation and increased environmental awareness, odour has become a major problem in communities surrounding landfills. The aim of this research was to investigate odour emissions from landfills and develop a management tool that operators could use to assist in minimising the impacts of odour. The management tool would be in the form of real-time predictions of odour concentrations in the vicinity of a source. The Bisasar Road landfill in Springfield, Durban was a case study site for the research. The methodologies used in this project can be divided into three broad categories. Firstly, flow visualisation experiments were conducted on the case study site to investigate the effects of complex terrain and the results compared to predictions from a dispersion model. Secondly, source characterisation was done on-site. Sources of odour were identified using a portable odour monitor (Electronic nose). Sources of odour were then sampled using sorbent tubes and analysis done using Gas Chromatography - Mass Spectrometry. Thirdly, numerical dispersion modelling was done. Five available dispersion models were assessed and compared against one another in order to select the most suitable model for this application. A software management tool or 'Odour Management System' (OMS), was designed and implemented on a computer at the Bisasar Road landfill. Qualitative results of the flow visualisation experiments show that terrain does have an effect on a dispersing plume path for short-range predictions. Comparisons between the flow experiments and model predictions are qualitatively consistent. Quantitative results were not obtained for the emission flow rate and emission concentration of landfill gas. The chemical composition of the fresh waste gas was determined. ADMSTM(Advanced Dispersion Modelling System) was found to be the most suitable dispersion model for this application. The OMS has been installed on-site to produce odour concentration graphics every ten minutes. A fence line odour control misting system has been installed along approximately 600 metres of the landfill border based on work done as part of this project. Weather conditions and information provided by the OMS, assist in running the odour control system economically.