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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

The rating of sluicing flumes in combination with sharp-crested and crump weirs under modular and non-modular flow conditions

Bruce, H. G. S. 12 1900 (has links)
Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: As part of a previous WRC project, three types of sluicing flumes were developed for use in compound weirs in combination with sharp-crested and crump weirs, (Rossouw et al., 1998). These sluicing flumes have several advantages which make them ideal structures for flow measurement in South African rivers. These are a high modular limit, stable modular flow characteristics, an ability to measure a wide range of flows accurately, as well as good sediment handling characteristics. These three flumes have been calibrated under modular or free flow conditions in combination with sharpcrested and crump weirs. There is a high degree of variability of flow in South African rivers. Flood discharges are part of this variability, and can form an important part of the mean annual runoff. Measuring weirs cannot always be built so that they do not become submerged during floods, but it is nevertheless important that flood discharges be recorded. It is therefore important that these compound weirs be calibrated for flow measurement under non-modular or submerged conditions. The purpose of the research undertaken for this WRC project is to find a method to calculate the non-modular discharge over compound weirs consisting of sluicing flumes in combination with sharp-crested and crump weirs. By analysis of existing data from the previous WRC project, as well as data from laboratory tests undertaken as part of this project, the submergence effect of sluicing flumes has been quantified. A range of configurations of sharp-crested weirs as well as crump weirs in combination with the sluicing flume have been tested. A new method has been developed to calculate the submerged discharge over these compound weirs. This method is suitably accurate, and can be recommended to the DWAF for use. The calculation procedure that must be followed in order to calculate the submerged discharge over these compound weirs becomes rather complicated due to the iterations that must be carried out. In order to clarify these procedures, flow charts are provided which set out the steps that must be followed. Calibration curves for all the combinations of compound weirs analysed in this report are also provided. These can be used to obtain estimates of the discharge in the field, and can also be used as a check on any calculations carried out. The principal goal of this project, namely that of finding a suitably accurate method to calculate the non-modular discharge over these compound weirs has therefore been achieved. / AFRIKAANSE OPSOMMING: As deel van 'n vorige Water Navorsings Kommisie (WNK) projek, is drie spoelgeute ontwikkel vir gebruik in saamgestelde meetwalle in kombinasie met skerp-kruin en Crump oorlope, (Rossouwet al., 1998). Die spoelgeute het eienskappe wat hulle gunstig maak vir vloeimeting in Suid Afrikaanse riviere. Vanhierdie eienskappe is 'n hoë modulêre limiet, stabiele modulêre vloei eienskappe, goeie sediment hanterings eienskappe en 'n vermoë om oor 'n wye bereik vloeie akkuraat te kan meet. Hierdie drie geute is in kombinasie met skerpkruin en Crump oorlope gekalibreer onder vryvloei toestande. Vloeie varieër baie in Suid Afrikaanse riviere. Vloede is deel van hierdie variasies en maak 'n belangrike deel uit van die gemiddelde jaarlikse afloop. Meetwalle kan nie altyd gebou word sodat hulle nie versuip tydens vloede nie, maar dit is nogtans belangrik dat hierdie vloeie gemeet word. Daarom is dit belangrik dat saamgestelde meetwalle gekalibreer is vir vloeimeting onder versuipte of nie-modulêre toestande. Die doel van die navorsing wat gedoen is vir hierde WNK projek was om 'n geskikte metode te ontwikkel om die nie-modulêre vloeie oor saamgestelde meetwalle, wat bestaan uit spoelgeute in kombinasie met skerpkruin en Crump oorlope, te kan bereken. Met die analise van bestaande data van die vorige WNK projek, asook data van labratoriumtoetse wat gedoen is as deel van hierdie projek, is die versuiping van spoelgeute beskryf. 'n Hele reeks skerpkruin asook crump oorlope is getoets in kombinasie met die spoelgeute. 'n Nuwe metode is ontwikkel om die nie-modulêre vloei oor hierdie saamgestelde meetstrukture te kan bereken. Hierdie metode IS akkuraat genoeg om aan die Departement van Waterwese te kan aanbeveel. Die berekingsproses wat gevolg moet word om die versuipte vloei oor die saamgestelde meetstrukture te bereken, raak ingewikkeld as gevolg van die iterasies wat uitgevoer moet word. Vloeidiagramme is opgestel wat hierdie prosedures duidelik uiteensit. Kalibrasie kurwes is ook ontwikkel vir al die kombinasies van saamgestelde meetwalle wat geanaliseer is in hierdie verslag. Hierdie kurwes kan gebruik word om skattings te maak van vloeie in die veld, maar ook om enige berekings wat gedoen is te kontroleer. Die hoofdoel van hierdie projek, naamlik om 'n geskikte metode te ontwikkel wat die nie-modulêre vloeie oor saamgestelde meetwalle akuraat kan bereken, is bereik.
32

Reliability assessment of a prestressed concrete member

Brand, W. W. (Willem Wouter) 12 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: First-order second-moment structural reliability methods are used to assess the reliability of a prestressed concrete beam. This beam was designed for imposed office floor loads and partitions following the limit states design method as provided for by the applicable South African structural codes, viz SABS 0100-1:1992 and SABS 0160:1989. The reliability is examined at two limit states. At the ultimate limit state of flexure the ultimate moment of resistance must exceed the applied external moment at the critical section, while at the serviceability limit state of deflection the deflection must satisfy the codespecified deflection criteria. Realistic theoretical models are selected to express the flexural strength and deflection of the prestressed concrete member, while appropriate probabilistic models are gathered from the literature for loading, resistance and modelling uncertainties. The calculated reliability index at the ultimate limit state of flexure (3.10) is lower than expected in view of the fact that this represents a non-critical limit state in the case of a Class 2 prestressed concrete member. This condition can be explained with reference to the relatively high uncertainty associated with the modelling error for flexural strength. The calculated reliability index at the serviceability limit state of deflection (l.67) compares well with acceptable practice. The study further focuses on the sensitivity of the reliability at the two limit states of interest to uncertainty in the various design parameters. The ultimate limit state of flexure is dominated by the uncertainty associated with the modelling error for flexural strength, while the contribution to the overall uncertainty of the ultimate strength and area of the prestressing steel and the effective depth is less significant. In comparison the reliability at the serviceability limit state of deflection is not dominated by the uncertainty associated with a single basic variable. Instead, the uncertainty associated with the modelling error, creep factor and prestress loss factor are all significant. It was also demonstrated that the variability in beam stiffness is not a major source of uncertainty in the case of a Class 2 prestressed concrete member. It is recommended that the present code provisions for ultimate strength and deflection should be reviewed to formulate theoretical models with reduced systematic and random errors. The effect of the uncertainty associated with the creep and prestressed loss factors should also be adressed by adjustment of the partial material factor for concrete at the serviceability limit state of deflection. Furthermore, research must be directed towards formulating an objective failure criterion for deflection. The uncertainty in the deflection limit must therefore be quantified with a probability distribution. / AFRIKAANSE OPSOMMING: Eerste-orde tweede-moment struktuur betroubaarheid metodes word ingespan om die betroubaarheid van 'n voorspanbeton balk te bereken. Hierdie balk is ontwerp vir opgelegte kantoor vloerbelasting en partisies volgens die grenstoestand ontwerp metode soos beskryf in die toepaslike Suid-Afrikaanse boukodes, naamlik SABS 0100-1: 1992 en SABS 0160: 1989. Die betroubaarheid word ondersoek by twee grenstoestande. By die swiglimiet van buiging moet die weerstandsmoment die eksterne aangewende moment oorskrei by die kritieke balksnit, terwyl die defleksie die kriteria soos voorgeskryf deur die kode moet bevredig by die dienslimiet van defleksie. Realistiese teoretiese modelle word gebruik om die buigsterkte en defleksie van die voorspanbeton balk te bereken. Verder is geskikte waarskynlikheid modelle uit die literatuur versamelom die belasting, weerstand en modelonsekerhede te karakteriseer. Die betroubaarheid indeks soos bereken vir die swiglimiet van buiging (3.10) is laer as wat verwag sou word in die lig van die feit dat hierdie nie 'n kritieke grenstoestand verteenwoordig in die geval van 'n Klas 2 voorspan element nie. Dit kan verklaar word met verwysing na die relatiewe groot onsekerheid wat geassosieer word met die modellering fout vir buigsterkte. Die berekende betroubaarheid indeks vir die dienslimiet van defleksie (1.67) vergelyk goed met aanvaarde praktyk. Die studie fokus verder op die sensitiwiteit van die betroubaarheid by die twee grenstoestande onder beskouing ten opsigte van die onsekerheid in die verskillende ontwerp parameters. By die swiglimiet van buiging word die onsekerheid oorheers deur die bydrae van die modelering fout vir buigsterkte. Die bydraes tot die totale onsekerheid deur die swigsterkte en area van die voorspanstaal sowel as die effektiewe diepte is minder belangrik. By die dienslimiet van defleksie word die betroubaarheid nie oorheers deur die onsekerheid van 'n enkele basiese veranderlike nie. In stede hiervan is die onsekerheid van die modellerings fout, kruipfaktor en voorspan verliesfaktor almal noemenswaardig. Daar word verder aangetoon dat die veranderlikheid in balkstyfheid nie 'n belangrike bron van onsekerheid in die geval van 'n Klas 2 voorspan element is nie. Daar word aanbeveel dat die bestaande voorskrifte in die kode vir buigsterkte en defleksie aangespreek moet word deur teoretiese modelle met klein modelonsekerhede te formuleer. Die uitwerking van die onsekerheid van die kruip- en voorspan verliesfaktore kan aangespreek word deur 'n aanpassing te maak in die parsiële materiaalfaktor vir beton in die geval van die dienslimiet van defleksie. Navorsing moet verder daarop gemik wees om 'n objektiewe falingskriterium vir defleksie te formuleer. Die onsekerheid van die toelaatbare defleksie moet dus gekwatifiseer word deur 'n waarskynlikheidsverdeling.
33

Discharge measurement at natural controls in Western Cape rivers

Barnard, M. M January 2003 (has links)
Thesis (MEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: This study sets out to explore the possibilities and accuracy of flow measurement at natural controls, focussing specifically on Western Cape cobble-bed rivers. These rivers are regarded as being difficult in terms of flow measurement, mostly due to their large scale roughness and very turbulent and uneven flows. The aim is to determine a system through which various types of natural controls can be calibrated, by establishing a relationship between the discharge coefficient and the physical characteristics of each control type. This was achieved by conducting an extensive field investigation, focussing on the identification and gauging of both critical and uniform natural controls. Two types of critical controls were identified and investigated, namely step-pool controls and horizontal constriction controls as well as one type of uniform flow control, namely the plane bed control. Step-pool controls were found to be very robust controls which provided efficient critical controls for a wide range of flows. Horizontal constriction controls proved to be reasonably accurate measurement sites and, because of their physical characteristics, they are able to measure the full range of flows from low to flood flows. Uniform controls are widely used for flow measurements on deep rivers, but such measurements become highly unreliable when flow depths are small and bed roughness high as is the case with cobble-bed rivers. Under conditions of high roughness, generally speaking critical controls can be calibrated more accurately than uniform controls and are therefore to be preferred. The field study was followed by a series of laboratory tests, focussing on horizontal constriction controls. Calibration equations were derived by which the discharge coefficient value can be determined for a given constriction ratio and upstream energy head. Results from both the fieldwork and laboratory work were analysed and integrated to determine a calibration system applicable to natural controls in Western Cape cobbleand boulder-bed rivers. Reasonably accurate values of the discharge coefficients for different types of natural controls were established, which should be widely applicable. Additionally, guidelines were drawn up for the measurement of flow at natural controls, to be used by both engineers and non-engineers. Discharge measurement at natural controls in the Western Cape was found to be a viable and reasonably accurate way of determining river discharge. It proves to be an environmentally acceptable way of measurement, using the natural river characteristics rather than seriously interfering with them or damaging them. These advantages make discharge measurement at natural controls a promising means of determining river discharge in the future. / AFRIKAANSE OPSOMMING: Die beste posisie vir vloeirneting in riviere is waar die topografie van die rivier 'n unieke verhouding tussen die deurstroming en die water diepte bewerkstellig. Hierdie studie ondersoek die uitvoerbaarheid en akkuraatheid van vloeirneting by natuurlike kontroles met die fokus op Wes-Kaapse spoelklip riviere. Vloeirneting in spoelklip riviere word as baie ingewikkeld beskou weens die grootte van die bedpartikels relatieftot die vloeidiepte en gevolglike onewe, turbulente vloeie. Die doel van die studie was om 'n stelsel te ontwikkel waardeur verskillende tipes natuurlike kontroles gekalibreer kan word deur verwantskappe te bepaal tussen die deurstromings koëffisiënt en die stroom-op energie hoogte. Bogenoemde is bepaal met behulp van 'n uitgebreide veldstudie waarin die hoof tipes natuurlike kontroles, nl. die kritiese vloei kontrole en die uniforme vloei kontrole, geidentifiseer en gekalibreer is. Twee tipes kritiese vloei kontroles is ondersoek, naamlik die trap-poel ("step-pool") kontrole en die horisontale vernouing kontrole. Daar is bevind dat beide die trap-poel kontrole en die horisontale vernouing baie effektiewe kritiese kontroles is, waarmee 'n wye reeks van vloeie gemeet kan word. Uniforme vloei kontroles word algemeen vir vloeimeting in diep vloeiende riviere gebruik, maar sulke metings word hoogs onbetroubaar wanner die vloeidiepte klein is relatief tot die partikel grootte van die rivierbed, soos in die geval van spoelklip riviere. Onder hierdie omstandighede kan kritiese kontroles in die algemeen meer akkuraat gekalibreer word en word hul gevolglik bo uniforme vloei kontroles verkies. Die veldstudie is gevolg deur 'n reeks laboratorium toetse, wat fokus op die horisontale vernouing kontrole. Kalibrasie vergelykings is afgelei waarmee die deurstromings koëffisient vir 'n gegewe stroom-op energiehoogte en vernouings-verhouding bereken kan word. Resultate van beide die veldstudie en die laboratorium toetse is geanaliseer en geïntegreer om 'n kalibrasie stelsel te bepaal wat van toepassing is op natuurlike kontroles in Wes-Kaapse spoelklip riviere. Aanvaarbare waardes vir die deurstromings koëffisiente vir verskeie tipes natuurlike kontroles is bepaal, wat algemeen toepasbaar behoort te wees. Riglyne vir die meting van riviervloei by natuurlike kontroles is opgestel vir die gebruik deur beide ingenieurs en nie-ingenieurs. Vloeimeting deur middel van natuurlike kontroles is 'n lewensvatbare metingsmetode waarmee riviervloei redelik akkuraat bepaal kan word. Dit is 'n omgewingsaanvaarbare metings metode wat die natuurlike karakter van die rivier gebruik, eerder as om ernstig daarmee in te meng of dit te beskadig. Hierde positiewe eienskappe maak vloeimeting deur middel van natuurlike kontroles 'n belowende metingsmetode vir die toekoms.
34

Verification of the inlet capacities of modified stormwater kerb inlets and the development of new design curves

Grobler, Pieter 03 1900 (has links)
Thesis (MEng)--Stellenbosch University, 1994. / ENGLISH ABSTRACT: Various aspects affecting the inlet capacities of modified stormwater kerb inlets were investigated. Investigations centred on the influence of effective inlet length, ratios of upstream transition section length to inlet section length and road crossfall. The suitability of existing design curves for use in the design of modified kerb inlets was verified and new more "user-friendly" design curves were developed. Attempts were made to develop a sound theoretical model to predict inlet capacities for stormwater kerb inlets as the lack of such a model had previously been identified as a major shortcoming in the design of stormwater kerb inlets. A detailed study of relevant literature and of various full scale model test results confirmed the fact that the effective inlet length is the most important variable affecting the inlet capacity at stormwater kerb inlets. Model studies on various combinations of transition section lengths and inlet section lengths have indicated that in the case of supercritical flow the inlet capacity of stormwater kerb inlets is not sensitive to changes in the ratio between the inlet section length and the upstream transition section length. Furthermore no marked effect on the inlet capacity of a modified stormwater kerb inlet was detected when the road crossfall was increased from 2% to 3%. The inlet capacities predicted by the existing design curves were found to be consistent, although on the conservative side, when compared to the inlet capacities obtained from the full scale model tests. New design curves derived from the existing design curves were developed to provide a less cumbersome procedure in the design of stormwater kerb inlets. The development of an improved comprehensive theoretical model based on pure hydraulic principles was not possible due to the extremely complex nature of flow conditions at stormwater kerb inlets. The most important findings emanating from this research project are: - The confirmation of the "effective inlet length” concept, whereby a part of the expensive inlet section is replaced by an equivalent length of inexpensive transition section upstream of the kerb inlet. which does not affect the inlet capacity of the kerb inlet negatively and thereby results in a substantial saving in the cost of stormwater kerb inlets. - Model tests revealed that for supercritical flows the upstream transition section can be made up to 6 times longer than the inlet section with a maximum length of 6m. without any negative effect on the inlet capacity of the kerb inlet. Similarly an analysis of previous research results has indicated that even in cases of subcritical flow the upstream transition section can be made twice the length of the inlet section. - The full scale model tests also indicated that an upward adjustment of 30% in the inlet capacities as predicted by the existing design curves was justified. The modified design curves proved to be suitable for the design of conventional stormwater kerb inlets as well as for modified stormwater kerb inlets where part of the inlet section is replaced by a transition section. A new set of "easy to use" design curves was developed specifically for urban applications. - Guidelines for determining upstream transition section lengths were drawn up for use in conjunction with the existing and new design curves for the design of stormwater kerb inlets. / AFRIKAANSE OPSOMMING: Verskeie aspekte wat die inlaatkapasiteit van verbeterde randsteeninlate belnvloed is ondersook. Die belangrikste aspekte wat ondersoek is, was die invlood van effektiewe inlaatlengte en die moontlike verhouding van die stroomop oorgangslengte tot die werklike inlaatlengte sowel as dwarshelling. Die ontwerpgrafieke wat tans gebruik word om randsteeninlaatlengtes te bepaal is ook ondersoek aan die hand van modeltoetse op volskaalse modelle om die grafieke se akkuraatheid te toots. Meer gebruikersvriendelike ontwerpgrafieke is ook ontwikkel. 'n Belangrike tekortkoming tot op datum, naamlik 'n geskikte teoretiese model om die inlaatkapasiteit van randsteeninlate te beskryf, is aangespreek. 'n Voorvereiste vir so 'n model was dat die model gebaseer moes word op suiwer hidrouliese beginsels. Die bestudering van vorige navorsing asook die uitvoering van verskeie modelstudies op volskaalse randsteeninlate het die effektiewe inlaatlengte as die belangrikste veranderlike wat die inlaatkapasiteit van randsteeninlate bepaal geYdentifiseer. Tydens tootse uitgevoer op volskaalse modelle onder superkritiese vlooitoostande met verskillende kombinasies van oorgangslengtes en inlaatlengtes, vir die dieselfde totale lengte het dit geblyk dat die inlaatkapasiteit grootliks onatbanklik is van die verhouding van die oorgangslengte tot die inlaatlengte. Vit die modeltootse het dit oak geblyk dat paddwarsval 'n baie beperkte invlood op die inlaatkapasiteit van ransteeninlate gehad het toe die paddwarsval verander is van 2%na 3%. Die resultate wat verkry is uit die modeltoetse het ook aangetoon dat die bestaande ontwerpgrafieke konserwatief is in hul voorspelling van inlaatkapasieit van randsteeninlate. Die bestaande ontwerpgrafieke is voorts gebruik om nuwe meer gebruikersvriendelike ontwerpgrafieke te ontwikkel. Die ontwikkeling van 'n teoretiese model am inlaatkapasiteite volledig te voorspel was egter nie moontlik nie vanwee die uiters komplekse aard van die vloei by randsteeninlate. Die belangrikste bevindinge van hierdie studie kan soos volg opgesom word: - Afdoende bewyse is gevind dat die "effektiewe inlaatlengte" konsep, waarvolgens 'n gedeelte van die duur inlaatgedeelte met 'n goedkoper oorgangsstuk van dieselfde Iengte vervang kan word sonder om inlaatkapasiteit in te boet, weI suksesvol aangewend kan word om kostes in die ontwerp van stOlIDwater randsteeninlate te bespaar. - Afdoende bewyse is gevind dat die "effektiewe inlaatlengte" konsep, waarvolgens 'n gedeelte van die duur inlaatgedeelte met 'n goedkoper oorgangsstuk van dieselfde Iengte vervang kan word sonder om inlaatkapasiteit in te boet, weI suksesvol aangewend kan word om kostes in die ontwerp van stOlIDwater randsteeninlate te bespaar. - Afdoende bewyse is gevind dat die "effektiewe inlaatlengte" konsep, waarvolgens 'n gedeelte van die duur inlaatgedeelte met 'n goedkoper oorgangsstuk van dieselfde Iengte vervang kan word sonder om inlaatkapasiteit in te boet, weI suksesvol aangewend kan word om kostes in die ontwerp van stOlIDwater randsteeninlate te bespaar. - Riglyne is ook ontwikkel vir die bepaling van stroomop oorgangslengtes. Die riglyne kan saam met die bestaande en die nuwe ontwerpgrafieke gebruik word by die ontwerp van stormwater nmdsteeninlate.
35

Investigation of turbidity and chlorine disinfection in South African waters.

19 October 2010 (has links)
All natural waters containing particulate matter, such as clay, silt, colloidal particles, plankton / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007
36

Long term emission from pre treated waste : column studies.

20 October 2010 (has links)
Emissions resulting from waste degradation processes have a high polluting potential / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2006.
37

Stabilisation of waste in shallow test cells : focus on biogas.

Chetty, Nevendra Krishniah. January 2006 (has links)
Present day society generates large volumes of waste that present an environmental hazard when disposed of in landfills. As our population grows, so does the volume of waste generated and hence the threat to our environment. One method of reducing harmful emissions in landfills is the mechanical-biological pretreatment of waste prior to landfilling. The purpose of this dissertation is to investigate the degree of stabilization of waste in shallow landfills (simulated by test cells) with particular focus on biogas production and quality. Municipal waste was composted in aerobic, open windrows for periods of eight and sixteen weeks. Five test cells, designed and operated according to the PAF model (Pretreatment, Aeration and Flushing) were constructed at the Bisasar Road landfill site. These cells were used to simulate large scale municipal landfill sites. They were filled with fresh and pretreated waste and were used to monitor the dynamics of prolonged aeration and degradation of waste over a period of six months. The cells were monitored on a weekly basis while being aerated. Two flushing events were conducted at the beginning of the passive aeration. Gas emissions were also monitored by recording the methane, carbon dioxide and oxygen volumes per volume of air in probes strategically placed in each cell. These results were then analysed to assess the effect of mechanical-biological pretreatment of municipal solid waste on the emission quality of sanitary landfills and the appropriateness of prolonging the aeration in shallow landfills, as often used in sub-tropical countries. It was found that the design of the test cells was appropriate for the landfilling and stabilization of waste that was aerobically treated. After six months in the test cells, analysis of the waste from each cell showed that the waste was completely degraded. The PAF model, when applied to shallow landfills, is very effective in stabilising waste and would be appropriate for a sub-tropical climate. Waste that is pretreated, placed in shallow landfills, initially flushed and then aerated over a six month period was fully stabilized. The requirement for such treatment would be relatively small amounts of waste, a wet climate and the availability of open space for shallow landfills. This method, therefore, would be very appropriate in a South African context. The major problem with this method may be the generation of large quantities of leachate which will have to be treated and disposed of in an environmentally safe manner. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2006.
38

The study of the kinetics of degradation of mechanical-biological pretreated waste using test cells.

02 November 2010 (has links)
This research was carried out at the Bisasar Road Landfill site, Durban, South Africa, / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007.
39

Environmental impacts of the construction phase of an intensive development project on a coastal forest wetland : case study : Seaward Estates, Ballito.

14 January 2011 (has links)
Storm water runoff is a leading cause of degradation in the water quality of receiving water bodies. Although legislation requires that Environmental Impact Assessments (EIA) are performed and Environmental Management Plans (EMP) put in place for the construction of high density housing developments, there is generally very little evidence that real measures are developed to monitor and actually assess the extent of the impact that construction activities have on the environment during the physical construction stage. The water quality of stormwater runoff from a mixed use catchment including construction sites in Seaward Estates, Ballito, KwaZulu-Natal that enters a coastal forest wetland system was characterised by monitoring programmes established at three study areas. The effect thereof on the quality of the wetland water and sediments was further monitored at five points along the drainage line of the system. The investigation focussed on obtaining representative stormwater samples in order to quantitatively identify pollutant constituents transported within stormwater runoff from construction sites during rainfall events. Storm water runoff event mean concentration (EMC), atmospheric deposition and wetland water and sediment samples were collected over an eight month period. The characterisation of stormwater runoff for this investigation included heavy metals, oxygen demanding substances, sediments and physico-chemical analysis for pH, conductivity and ammonia and nitrates. The majority of contaminant EMC exceeded the South African wastewater discharge general and special limits. The findings from this investigation will provide planners and decision-makers with a greater understanding of the pollution dynamics of construction sites aiding in improved best management practice decisions with regard to minimizing impacts on coastal forest wetlands and water resources. This will lead to improved EMP and stormwater management plans (SWMP) incorporating stormwater pollution prevention plans (SWPPP) for construction sites. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007.
40

Spatio-temporal rainfall estimation and nowcasting for flash flood forecasting.

Sinclair, Scott January 2007 (has links)
Floods cannot be prevented, but their devastating effects can be minimized if advance warning of the event is available. The South African Disaster Management Act (Act 57 of 2002) advocates a paradigm shift from the current "bucket and blanket brigade" response-based mind set to one where disaster prevention or mitigation are the preferred options. It is in the context of mitigating the effects of floods that the development and implementation of a reli able flood forecasting system has major significance. In the case of flash floods, a few hours lead time can afford disaster managers the opportunity to take steps which may significantly reduce loss of life and damage to property. The engineering challenges in developing and implementing such a system are numerous. In this thesis, the design and implement at ion of a flash flood forecasting system in South Africa is critically examined. The technical aspect s relating to spatio-temporal rainfall estimation and now casting are a key area in which new contributions are made. In particular, field and optical flow advection algorithms are adapted and refined to help pred ict future path s of storms; fast and pragmatic algorithms for combining rain gauge and remote sensing (rada r and satellite) estimates are re fi ned and validated; a two-dimensional adaptation of Empirical Mode Decomposition is devised to extract the temporally persistent structure embedded in rainfall fields. A second area of significant contribution relates to real-time fore cast updates, made in response to the most recent observed information. A number of techniques embedded in the rich Kalm an and adaptive filtering literature are adopted for this purpose. The work captures the current "state of play" in the South African context and hopes to provide a blueprint for future development of an essential tool for disaster management. There are a number of natural spin-offs from this work for related field s in water resources management. / Thesis (Ph.D.Eng.)-University of KwaZulu-Natal, Durban, 2007.

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