Bibliography: pages 122-129. / Soil erosion is regarded as a serious problem throughout the world. Erosion is caused by both water and wind. Although the two usually occur together, wind erosion has received little attention with the exception of the problems associated with croplands. Wind erosion can, however, also be a serious problem in natural grazing lands. In this research project an attempt is made to determine the areas of potential wind erosion in the Cape Province through the use of two different models. The models used were developed and applied in semi-arid areas and thus were considered to be applicable in South Africa. The models used are: The Wind Erosion Equation developed by Chepil, Woodruff and Siddoway in the United States; and Lynch and Edward's Model for the Analysis of Limited Climatic Data, developed in Australia. There are two aspects to soil erosion by wind - the erodibility of the soil as determined by moisture, grains size, aggregates, plant cover and surface topography; and soil erosivity as determined by wind strength and duration. Methods to control wind erosion are based on decreasing erosivity through the establishment of shelterbelts and by decreasing erodibility through improving plant cover, aggregate stability and moisture retention properties. Efforts at wind erosion measurement are generally ineffective. A number of models have been developed to overcome these difficulties and to allow for prediction of soil loss. Two of these models are applied to conditions in the Cape Province. This area covers a wind range of climatic, soil and agricultural conditions and as such provides an appropriate area for their application. It is, however, concluded that neither of these models can be directly applied to conditions in the Cape Province. The seasonal rainfall distribution and the uneven distribution of the data points contribute to the ineffectiveness of the models. The greatest problem, however, is the importance of management in determining whether or not wind erosion occurs. As a result, although the models illustrate the general climatic trends affecting the susceptibility of an area to wind erosion, the lack of a management factor accounts for the lack of detail.

The study examines the relationship between the spatial variation in soil erosion and various natural and anthropogenic attributes of the region between the coastal plateau and the Winterberg escarpment of Ciskei. A raster-based geographical information system is derived for four separate study catchments and data on soil erosion and various soil erosion hazard indices are read into a computerised data matrix. The independent variables (soil erosion hazard indices) used in the study are selected on the basis of a review of the literature and on the availability of data in the Ciskei region. Multivariate analyses of the relationship between soil erosion and the various independent variables reveals that the primary variables affecting the spatial variation in soil erosion are land use, dominant soil type, geology, veld type and mean annual precipitation. All of these variables are readily quantifiable at the regional scale for large areas of Ciskei. An erosion hazard assessment model for use in central Ciskei is developed based on the results of the statistical analyses. The model is tested in separate study areas and is shown to provide an efficient method of identifying areas of differing susceptibility to soil erosion. The derived model is simple to operate and has input requirements which are easily met. It can be applied without the aid of computers, or where large areas are to be mapped it is well suited to computerisation

This study originated from an evaluation of the performance of a commercially available high concentration point focus concentrator PV system. The effect of module design flaws was studied by using current-voltage (I-V) curves obtained from each module in the array. The position of reverse bias steps revealed the severity of mismatch in a string of series-connected cells. By understanding the effects of the various types of mismatch, power losses and damage to the solar cells resulting from hot spot formation can be minimized and several recommendations for improving the basic performance of similar systems were made. Concern over the extent and type of defect failure of the concentrator photovoltaic (CPV) cells prompted an investigation into the use of a light beam induced current (LBIC) technique to investigate the spatial distribution of defects. An overview of current and developing LBIC techniques revealed that the original standard LBIC techniques have found widespread application, and that far-reaching and important developments of the technique have taken place over the years. These developments are driven by natural progression as well as the availability of newly developed advanced measurement equipment. Several techniques such as Lock-in Thermography and the use of infrared cameras have developed as complementary techniques to advanced LBIC techniques. As an accurate contactless evaluation tool that is able to image spatially distributed defects in cell material, the basis of this method seemed promising for the evaluation of concentrator cells.

MSCAGR (Soil Science) / Department of Soil Science / Accelerated soil erosion is a serious agricultural problem in South Africa limiting soil productivity and little it’s known about its effect on soil quality. This study aimed to provide a less laborious, less time consuming and inexpensive protocol of estimating the effects of accelerated erosion on the soil quality. An assessment was undertaken in sites showing threat of accelerated erosion using various direct physical soil quality indicators. Four sites with different soil types were identified at initial survey. In each of the sites, two areas were selected. These areas were then classified as Not Visibly Eroded (NVE) and Visibly Eroded (VE). Each measurement in all site was done in those area classified respectively. The most stable structure and consistency were observed in NVE areas. Medium and large stones were observed in VE areas in all soil types studied. The VE soils were lighter in colour compared to soil colour in NVE. Aggregate stability and moisture content were significantly higher for the NVE and VE areas. Difference in values of water stable aggregates between NVE and VE was clear which showed that stability of aggregates is important in determining soil susceptible to erosion. Bulk density values were slightly different for the two areas. However, there was no significant difference between the bulk density of NVE and VE. Differences between soil texture for NVE and VE areas are only apparent for the sand, clay and silt particles with no changes in textural class. For all soil types investigated, silt was vulnerable to accelerated erosion with respect to soil texture. The research has provided baseline protocol for using physical soil quality indicators to find out effects of accelerated erosion. Soil functionality is critical in the restoration process of soil quality, and the methods used here could be effectively applied in a broad range assessment of erosion impact. / NRF

M.Ing. (Civil Engineering) / The purpose of this study was to determine the effectiveness of a sisal fibre natural geotextile in controlling the rate and extent of soil erosion. The effectiveness of this locally produced material was compared to other natural fibre geotextiles and other methods commonly used for the control of soil erosion. The different materials and methods were tested under the same conditions to compare the relative effectiveness of these products. The various erosion control products were subjected to laboratory tests. A rainfall simulator and an adjustable slope simulator were used to simulate the process of soil erosion. During these tests the effectiveness of the different products in controlling soil erosion was measured and conclusions were made about the effectiveness of the products. Mechanical sieve analysis tests were used to determine the erodibility of the different soil particles. Field trials that made use of the sisal fibre geotextile are also discussed.

M.Sc. (Geography) / This study concentrates. not only on the physical and chemical factors influencing erosion levels in the Pilanesberg area, but also on the impact of anthropogenic factors such as artificial drainage and other cultural irregularities that have modified the local catchment in the Pilanesberg area. For this reason, a comparative study of soil erosion has been made across the perimeter of the Pilanesberg Nature Reserve. The study'aimed to analyze the impact of climatic factors, chemical and physical properties of the soils on the local erosion system. Possible triggering mechanisms of the erosion have been discussed and conservation concerns in the Pilanesberg area have been raised. Of major importance in this study has been the'estimation of soil loss rates across the perimeter of the PNR.. This was premised on the 'rationale that population pressure has an impact on the local erosion system, Through the' analysis of sediment trapped at the monitoring sites it has been possible to indicate the tremendous impact of population pressure on the slopes of the Pilanesberg hills, just outside of the PNR. The rate at which soil is lost on the surrounding rural landscape in the Pilanesberg area has been found to be on average. nearly four times higher than inside of the PNR.

The study examines the effect of ridged pineapple cultivation on factors influencing the soil erodibility of Glenrosa and Oakleaf soil forms in the Bathurst district of South Africa. A number of physical and chemical variables influencing soil erodibility are investigated, namely soil moisture, bulk density, porosity, infiltration rate, aggregate stability, shear strength, soil texture, soil structure, penetrability, organic carbon, pH and cation exchange capacity. These soil characteristics are examined in undisturbed soils under natural vegetation and compared to those on adjacent traffic areas, pineapple ridges and pineapple furrows. The results of the analyses between the four sample sites indicate that ridged cultivation of pineapples has a negative effect on factors influencing soil erodibility on the areas studied. The results of the analysis within each of the sample sites do not illustrate any clear relationships and thus depict the complexity and multiplicity of the soil erodibility phenomenon. A further study, augmenting the soil erodibility data with actual soil loss data, is recommended

he estimation of post-emplacement kimberlite erosion in South Africa through the study of upper-crustal xenoliths is relatively unexplored; however the presence of these xenoliths has been recognized for well over 100 years. Post-emplacement erosion levels of a small number of South African kimberlite pipes have been inferred through the study of the degree of country-rock diagenesis, the depth of sill formation, the depth of the initiation of the diatreme and fission track studies. Through these studies, several estimates were proposed for the Group I Kimberley kimberlites. Although the 1400 m estimate of erosion remains widely accepted today, this estimate relies on the presence of Karoo-like basalt xenoliths in the Group I Kimberley kimberlites, as their presence proves that basalt existed in the Kimberley area when the kimberlites were emplaced. Basaltic xenoliths were described during the early stages of mining in Kimberley, though only one of these descriptions suggests that the ‘basaltic’ boulders correlate with the Karoo basalts. Because of the discrepancy between these early documentations of upper-crustal xenoliths and because the occurrence of Karoo-like basalt xenoliths in the Group I Kimberley kimberlites is under question, a re-investigation of the erosion levels and the upper crustal xenolith suites in South African, Cretaceous-aged kimberlites, including Melton Wold, Voorspoed, Roberts Victor, West End, Record Stone Quarry, Finsch, Markt, Frank Smith, Pampoenpoort, Uintjiesberg, Koffiefontein / Ebenheuyser, Monastery, Kimberley (Big Hole), Kamfersdam , Jagersfontein, Kaal Vallei, De Beers, Bultfontein, Lushof, Britstown Cluster, Hebron and Lovedale, was conducted. This study presents the analytical results for upper-crustal sandstone and basalt xenoliths collected from dumps, excavation pits and borehole core at the above-mentioned kimberlites, and demonstrates that they correlate with stratigraphic units of the Karoo Supergroup on the basis of mineral and geochemical compositions. These upper-crustal xenoliths are incorporated into kimberlites and down-rafted to levels below their stratigraphic position during kimberlite emplacement, consequently recording the broad stratigraphy into which each kimberlite is emplaced. Therefore, the Cretaceous lateral extent of the Karoo Supergroup is inferred and post-emplacement erosion estimated by reconstructing the stratigraphy based on upper-crustal xenolith suites for each kimberlite and calculating the total thickness of the now-eroded units. The distribution of sandstone xenoliths indicates that during the Cretaceous the lateral extent of the Dwyka, Ecca and Beaufort Groups encompassed all of the examined kimberlites, while the ‘Stormberg’ Group was constrained to an area outlined by the Voorspoed and Monastery kimberlites. Similarly, basalt xenoliths occur in all of the Group II and transitional (143 – 100 Ma) kimberlites but only in the Group I (90 – 74 Ma) kimberlites that lie within close proximity to the western outcrop margin of the outcrop area of the Drakensberg Group basalts (Lesotho Remnant), namely Monastery, Jagersfontein and Kaal Vallei. This trend implies an eastward-retreat of the inland erosion front of the Karoo basalts between 140 and 90 Ma and subsequent erosion of the underlying sedimentary units. It also suggests that a thicker succession of Karoo strata was present at the time of Group II and transitional kimberlite emplacement and that there has been more post-emplacement erosion in these kimberlites than the younger Group I kimberlites, except for Monastery, Jagersfontein and Kaal Vallei. Estimates are unique to each kimberlite as they are dependent on both stratigraphic location, elevation and present country rock, and range from approximately 1000 – 2500 m for the older kimberlites and less than 700 m to 1400 m for the younger kimberlites. Furthermore, the upper-crustal xenoliths found at the Group I Kimberley kimberlites and the coinciding trend of basalt erosion demonstrate that Karoo basalts were eroded from the Kimberley area by the time the Group I Kimberley kimberlites erupted (~85 Ma). Therefore, basalts are omitted from the Group I Kimberley kimberlites post-emplacement erosion estimate, and the upper Beaufort Group is considered the upper limit of the stratigraphy that was present at the time of the eruption of the Group I Kimberley pipes. Therefore, the erosion estimates decrease from a previous estimate of 1400 m down to 400 to 1100 m, where 850 m is considered a dependable intermediate estimate.

The St Francis Bay beach has experienced chronic erosion over the past three decades. This erosion can largely be attributed to the stabilisation of a large coastal dunefield which contributed +/- 80 percent of the sand supply to St Francis Bay. Stabilisation began in 1975 initially using plant cuttings and followed by the development of the Santareme holiday suburb resulting in complete stabilisation by 1985. Effects were felt from the late 1970‟s and since then the beach has retreated at between 0.5 - 3 m.yr-1. Erosion has encroached on beachfront properties since the early 1990‟s, leading to the placement of 3-4 m high unsightly rock revetments along much of the beach. Where properly maintained these structures have proved successful in protecting the properties behind, however exacerbated erosion of areas in front and adjacent to these structures is evident. Currently no dry beach is present at high tide for most of the year, leading to a significant reduction in beach amenity value. Several technical studies to investigate remediation of this beach erosion problem have been conducted since the early 1990‟s. This study includes investigations into the processes and dynamics of the existing environment and evaluation of the effectiveness and impacts of several elements of a hybrid approach to coastal protection and amenity enhancement for St Francis Bay beach. This proposal incorporated: Multi-Purpose Reefs (MPR‟s) offshore, for coastal protection and amenity enhancement in terms of surfing; beach nourishment with sand from the Kromme Estuary and dune rehabilitation with appropriate native sand binding species. Extensive fieldwork and data collection were conducted, this included: a series of bathymetric surveys; diving surveys and a helicopter flight; sediment sampling; beach profiling and deployment of a wave/current meter. Analysis of these data provided a greater understanding of the existing environment and dynamics of St Francis Bay and provided reliable inputs for numerical modelling. Numerical and physical modelling was conducted to assess the existing processes and conduct MPR design testing. In addition calibrated hydrodynamic modelling of the Kromme Estuary was conducted in order to assess the impacts of sand extraction from the large sand banks within the mouth of the Kromme Estuary for use as beach nourishment. Comparison of bathymetric survey data collected by the author in 2005/06 with survey data collected by the South African Navy Hydrographic Office (SANHO) in 1952 suggest a major loss of sand from the bay, with a volume difference of some 8.8 X 106 m3 calculated. Greater losses were measured between 10-15 m water depths, with shallow areas of +/- 5 m water depth, remaining more stable. This can be attributed to the presence of shallow reef and rocky substrate through much of the bay at this depth range. Monthly RTK GPS survey data from September 2006 to September 2007 indicates a total loss of 40 000 m3 over this period with the greatest losses measured along the northern part of the beach. The greatest losses were measured after large long period waves from a southerly to south-easterly direction occurred in conjunction with equinox tides in mid March 2007. Sediment sampling at over 100 locations within the bay indicated a high percentage of reef (26 percent) and fairly consistent grain size in the fine to medium size class throughout much of the beach, bay and large sand bank within the estuary. While the majority of the South African Coast is exposed to the predominant south westerly winds and waves, St Francis Bay‟s orientation means that waves from a south easterly to easterly direction dominate. The results of the detailed numerical modelling of the hydrodynamics agree with previous calculations and modelling results which concluded that strong unidirectional longshore currents occur along the headland due to the oblique angle of wave incidence and the close to parallel angle of wave incidence along the beach leads to weak longshore currents of variable direction. Erosion along St Francis Bay beach is a result of cross-shore erosion due to large waves from a southerly to easterly direction. Detached breakwaters are the most effective form of coastal protection in these environments and MPR‟s offer additional benefits over traditional breakwater structures. Results of empirical calculations and numerical modelling indicate that the MPR‟s will provide effective coastal protection through the processes of wave dissipation, wave rotation, salient formation and alteration of nearshore circulation. Physical modelling results allowed the MPR design to be assessed and refined in terms of surfing amenity enhancement and construction constraints. In addition numerical modelling results indicate that impacts due to the extraction of up to 600 000 m3 of sand from the lower Kromme Estuary result in highly localised velocity reduction, mainly limited to the extraction areas. The calculated rate of sediment influx into the lower Kromme Estuary indicates that limited extraction, in the order of 20 000 – 40 000 m3 per year, should be sustainable in the long term. Sedimentation of the lower estuary over recent years has had negative recreational and ecological impacts, through reduced navigability and water exchange respectively. Therefore both the estuary and beach systems prove to benefit from this approach. Although not investigated in detail as part of this study, evidence from numerous projects worldwide indicates that foredunes help to trap wind-blown sand on the beach and form a buffer to storm erosion, therefore dune rehabilitation with native sand-binding plant species was recommended as the third element of the proposed remediation of St Francis Bay beach.

Submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg as a requirement for the Degree of Master of Science. Johannesburg, 1992. / The effect of sodium on clays dominates the formation and ecology of granitic eatenas in the Eastern Transvaal Lowveld. This study reviews the process involved and explains the soil, vegetation and erosion patterns in this landscape. Weathering parent rock gives rise to sodium in sufficient amounts to promote clay dispersion. Dispersed, mobile, clays respond to seasonal pulses of laterally moving soil water resulting in alternating zones of clay illuviation and clay deposition down hillslopes [Abbreviated Abstract. Open document to view full version] / AC2017