Thesis (MTech (Civil Engineering))--Cape Technikon, 1992. / In the Western Cape, gully ("donga") erosion is characteristic of the Swartland area where the effects of the problem have reached spectacular dimensions. In 1942 the Social and Economic Planning Council commissioned an investigation into the distribution and prevention of gully erosion. This investigation was led by Professor W J Talbot of the University of Cape Town, with the collaboration of researchers from the University of Stellenbosch. This led to the "Swartland and Sandveld" publication in August 1945. Little progress has since been made. The gullies identified by Prof Talbot's team remain to this day. In most cases they have grown even longer and deeper. The present investigation aims to study a typical network in one catchment area and to propose measures for the reclamation or stabilization of gullies. Such measures must not only be effective but also economically justifiable. In reclaiming or stabilizing a donga, a key factor is the establishment of a foundation structure. Such a structure is essential for supporting semi-permanent structures and promoting the growth of grass and bushes. At present, however, no satisfactory methods are known for the design and construction of supporting walls In narrow, deep dongas, other than those methods that require a rock foundation. Furthermore, conventional methods would require a buttress of length 17 m for a retaining wall of height 4,4 m. The amount of concrete needed, would clearly be excessive. It is therefore one of the aims of this study to develop a retaining wall with a relatively short buttress. If finances permit, the retaining structure, will be built and the stabilization process carefully monitored for possible applications in the future.

Commercial forestry is recognized for both its economic contribution as well as its environmental impact. Of particular concern, is the soil erosion and sedimentation of watercourses associated with forestry plantations. Environmental laws regulate many of the activities of the forestry sector. It is critical that the forestry sector ensure that its operations are compliant with the legal requirements that govern its use of natural resources. In pursuing legal compliance it is necessary to ensure that erosion control strategies are developed so as to ensure the positive effects of any interventions are optimised. The identification of areas that are particularly at risk to erosion or contribute to sediment delivery is an essential component in prioritising areas for management interventions. Establishing the erosion potential for commercial forestry areas is readily accomplished through the application of existing models. Process based erosion models generally have greater data requirements than the empirically derived USLE-based models. Given the paucity of data available, the latter approach was adopted. Two methods of topographic sub-factor derivation were investigated, those associated with the RUSLE (Renard, Foster, Weesies & McCool1991) and the Unit Stream Power method presented by Moore and Burch (1986). Since no existing methods identifying delivery risk areas existed, a method was developed based on principles and factors identified in the literature. Additionally, methods for identifying topographic assets, in terms of sediment attenuation, were developed. From these models three indices were derived; sediment supply, delivery risk and sediment attenuation. Thereafter, the mean Sediment Supply Index was divided by stream length for small catchments defined within the landscape to derive an index of sediment loading to streams. This index is used to identify priorities for management intervention across the landscape. The mean slope and sediment supply is used to develop buffer width recommendations for the streams draining the catchments, using a method developed by Karssies and Prosser (2001). Using the three indices in conjunction it is possible to make on-site and off-site erosion control recommendations as well as identify and exploit any natural features that can be utilized in erosion control. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2002

Thesis (MA (History))--University of Stellenbosch, 2009. / Although the environment is of obvious and primary importance in agriculture, the historical relationship between agriculture and the environment has not been widely researched. A socio-environmental paradigm provides a useful, inter-disciplinary framework for writing history. It takes into account the fact that ‘natural disasters’ are not merely happening to farmers, governments and communities, subsequently disturbing economic growth-patterns and reverberating amongst policy-makers and politicians. The relationship is much more reciprocal. The environment is not perceived as a player that sometimes disrupts the historical narrative, forcing the plot in a certain direction before returning to the wings. It is rather percieved as an agent within agricultural history. The social-cultural as well as material relationships between people (in this case white farmers), state and the environment are explored as an ecosystem. The thesis focuses on a time period after the First World War to just after the Second World War (c.1920 – c.1950). It asks questions: whom and what has informed the ideas of the state with regards to agriculture and to what extent did it filtered through to the farming communities themselves? The motives behind these approaches are explored. The thesis will also look at how officials translated the policies, legislation and education into what was perceived as functional for the farmers and effective for the environment, tracing how it changed over time. The shifting perception of the farmers about the environment and themselves, and the role of the state played in ‘management’ of the environment are analysed, using press correspondence, marketing campaigns and popular texts. Two themes that garnered much debate in the agricultural sector at the state, farmer and environment interface, include the ‘disasters’ of soil erosion and locust plagues. On the level of ‘scientific agriculture,’ the shift from Europe as a point of reference to the United States is discussed. This is done against the backdrop of South Africa’s semi-arid landscape and how farmers came to grips with this ostensibly hostile environment in an era where mechanisation and urbanisation are thought to have radically altered the conceptualisation of the natural environment.

A history of land degradation is reconstructed in a part of the dividing ridge between the Great Fish and Keiskamma rivers, in Peddie District, former Ciskei. The study entails a comparative investigation of the progressive changes in land use, vegetation and soil erosion in three tenure units, namely: former commercial farms, traditional and betterment villages. Analysis of the sequential aerial photography of the area for 1938,1954, 1965, 1975 and 1988 is employed. This is backed by groundtruthing exercises. Data thus obtained are quantified, and linkages between degradation, anthropogenic and physical factors are derived using PC ARC/INFO GIS. Differences in land tenure systems emerge as the main controlling factor to variations in land degradation. Confinement of vegetation diminution and erosion to traditional and betterment villages is observed at all dates. Scantily vegetated surfaces and riparian vegetation removal are a characteristic feature of both areas throughout the study period. 'Betterment,' introduced in the early 1960s to curb land degradation is, instead observed to exacerbate it, particularly soil erosion. Trends in land use change are characterised by the abandonment of cultivated land, which is noted to coincide with a sharp rise in population. Erosion intensification into severe forms particularly between 1965 and 1975, coincident with a period of extreme rainfall events, emerges as the most significant degradation trend. A close spatial correlation between abandoned cultivated land and intricate gullies is identified. So is the case between grazing land and severe sheet erosion. Within the grazing lands, an examination of erosion and categories of vegetated surfaces reveals that erosion occurs predominantly on the scanty vegetation category. Such erosion-vegetation interaction largely explains the non-recovery of the scanty vegetation category, even during periods of intense rainfall. Extensive channel degradation is evident along stream courses with scanty riparian vegetation. Physical factors are noted to have a significant bearing on erosion. The high prevalence of erosion on the Ecca group of rocks confirms its erosion-prone nature. Pockets of colluvium and alluvium accumulation in the steep bottomlands are identified as the sites of the most severe gully erosion. Field surveys at some of the sites indicate that a dolerite sill through the area forms a boundary of colluvium accumulation and the upslope limit to gully incision. That these sites are recognised as formerly cultivated land, portrays the interaction between physical and anthropogenic variables with regard to inducing degradation in the area.

Due to the particular nature of accelerated soil erosion, its impact on food security is usually very intense. The impact starts first on the farmer, and then to his/ her environment. This is why soil erosion, when unchecked, is very devastating. Therefore this study was set to evaluate the perceived impact of soil erosion on food security in the Upper and Lower Areas of Didimana, Eastern Cape of South Africa, and the role farmers’ adoption behaviours play in the interaction. Three specific objectives were put forward by the study, vis-à-vis: (1) to establish farmers’ perceptions on the impact of soil erosion on food security of the study area; (2) to establish farmers’ innovation adoption behaviour with respect to soil erosion control in the study area; and (3) to establish farmers’ perceptions on the impact of extension activities with respect to soil erosion-control in the study area. The central argument of discussion is that soil erosion like every other agricultural problem, is the result of farmers’ non-adoption or inappropriate adoption of improved and recommended soil management technologies in the study area. The survey method of research was adopted for the study, where data were collected, using a well structured questionnaire, from a total of 60 farmers in the study area, through a simple random sampling process. Farmers’ perception suggested that the impact of soil erosion in their area is severe. This severity is demonstrated firstly in the form of climate change, as the time of rain in their area is gradually changing, and thus changing their time of cropping. Similarly the livelihoods of farmers are being negatively affected, as farmers’ crops, livestock, and even household feeding are being affected. More so, findings indicate that most farmers now plant fewer crops and there is an estimation of crop loss by most farmers of well between 21-60 percent of crops every year. Farmers’ perception further revealed that due to soil erosion, over 50 percent of farmers are unsustainable and a total of 71.7 percent of farmers’ population admitted that the amount of food available for their households is being severely affected. In virtually every sphere of human endeavours improved technologies have been developed to solve human problems, but the main reason problems like soil erosion is still very evident is the fact of farmers’ non-adoption or inappropriate adoption of specific recommended technologies. In the study area, the role of farmers’ adoption behaviour in the interaction of the impact of soil erosion on food security was very prominent. Findings indicate that despite the presence of certain recommended soil management technologies in the study area, majority of farmers do not use them neither extension advices. Moreover their satisfaction with those technologies was found to be low, which could be an explanation why they do not use them. For innovation to be adopted, rejected or utilized inappropriately, the effectiveness and performance of agricultural extension, as well as farmers’ perception play a great role. Thus in the study area, farmers’ perception on extension effectiveness indicates that extension hardly talk about soil erosion and its control during times of their visit. Similarly, farmers’ rating for extension services and advices was as well very low (23.4 percent). In fact, a comparison of farmers’ traditional methods of soil erosion control with extension recommendations (53.4 percent) indicated that farmers perceive their local methods of more importance than extension methods. In the same vein, majority of farmers in the area indicated that extension officers are inadequate in their jobs. Reasons offered range from issues of unreliability, lack of regular visits, communication problems, less attention for crop farming, and other reasons such as extension being unconcerned for subsistence farmers, as well as the fact that they focus more on cooperatives. In all, the findings of the descriptive statistics reveal that the impact of soil erosion on food security in the study area is very significant, and the results of the linear regression model of relationships in the study reveal that soil erosion relates positively with age of farmers, their product quality, and their sustainability. In a similar note, the innovation adoption behaviours of farmers was also found to be positively related to farm yield and food accessibility. Thus showing that innovation adoption behaviour of farmers in the interaction of soil erosion and food security in the study area is significant. Therefore, efforts should be geared toward improving factors that increases yield and accessibility of farmers to serve as boosters of farmers’ motivation towards the adoption of appropriate soil management technologies in their area.

Aggregate stability and aggregate size distribution on soil surface that is impacted by rain drops affect soil erosion yet little is known about less weathered coarse textured soils. The objectives of the current study were to determine (i) the aggregate stability and associated aggregate fraction size distribution and (ii) the impact of the initial aggregate size on the aggregate stability and the resulting sediment fraction size distribution following rain drop impact in some quartz dominated coarse textured soils in the Eastern Cape Province. Soil samples for this experiment were collected from 14 ecotopes on the surface with a natural slope between 7.5 to 11% and at the depth between 0 to 0.2 m in the Eastern Cape Province. In each ecotope, twenty-five different spots were sampled using a spade at depth 0 to 0.2 m in other to eradicate biasness and ensure homogeneity. Thereafter, the soil samples were mixed to make a composite sample. The composited soil samples were then placed in rigid containers and taken to the soil science laboratory of the University of Fort Hare, Alice Campus where analyses were carried out. The soil properties were determined by passing the < 5 mm soil sample through a 2 mm sieve. The total Na, Ca and Mg contents in the soil samples were also determined using the wet digestion with sulphuric acid method. The total Soil organic matter content (SOM) was determined by the process known as weight loss on ignition. Thereafter, the fraction size distribution and aggregate stability was done by passing < 5 mm soil samples through a 3 mm sieve. The obtained calibrated aggregates between 3 and 5 mm were oven dried at 40o C. Thereafter, five gram (5g) of oven dried calibrated aggregates was immersed in a 50 mL deionized water in a 250 mL beaker for 10 minutes. The soil material left was transferred to a 0.053 mm sieve already immersed in ethanol and moved five times in the ethanol to separate < 0.053 mm from > 0.053 mm fragments. The remaining > 0.053 mm was re-immersed in ethanol and further oven dried at 40o C for 5 minutes. Thereafter, the > 0.053 mm fraction was transferred from 0.053 mm sieve, oven dried at 40o C, dry sieved using Digital Electromagnetic Shaker on a six column of sieves: 2 mm, 1 mm, 0.5 mm, 0.25 mm, 0.106 mm, and 0.053 mm. The aggregate stability was determined using the resulting size distribution in seven classes by calculating the mean weight diameter (MWD, mm). The soils were very stable, moderately stable or unstable. The presence of smectite and cultivation as opposed to pasture lowered aggregate stability. The studied soils showed three different aggregate size distributions. Unstable soils were dominated by 0.106 – 0.25 mm aggregate size and showed a positively skewed aggregate fraction size distribution. Aggregates finer than 0.106 mm were limited because of the coarse nature of the soil texture. Moderately stable soils broke down to both micro aggregates, 0.106 – 0.25 mm and macro aggregates, 2 – 5 mm giving a bimodal distribution. The aggregate size distribution in the very stable soils was dominated by the aggregate fraction size 2 – 5 mm and a negatively skewed aggregate fraction size distribution. The smaller the initial aggregate size the higher was the aggregate stability but the reverse was true for splash erosion. It was thought that the short 5 minutes duration of the rainfall might not have been enough to cause a total breakdown of the aggregates. Alternatively, ecotopes that were dominated by primary soil minerals such as quartz showed different breakdown behaviour compared to those containing secondary minerals such as kaolinite or smectite.

Thesis (MBA)--Stellenbosch University, 2005 / ENGLISH ABSTRACT: Strong scientific evidence suggests that global warming is altering the world's climate and that this phenomenon is being accelerated as a result of human activities. Climate change is affecting weather patterns and, in addition to demonstrated sea-level rise, these in turn have and are likely to continue having significant, mostly negative, impacts - both economic and loss of life - on governments, industries and people. Ocean levels rose between 15 and 20 centimeters in the 20th century, mostly as a result of melting glaciers and thermal expansion of the oceans. The International Panel on Climate Change (IPCC, 2001a: 16) in its 2001 estimate suggests a potential rise in average sea level from nine to 88 centimeters from 1990 to 2100. Areas of risk in the City of Cape Town are residential property, infrastructure and beaches in low-lying areas. These areas are likely to be impacted as a result of increasing sea-level rise and increasing severity and frequency of storms. This study seeks to • demonstrate that sufficient evidence exists to compel decision-makers in the City of Cape Town that climate change and the impacts of sea-level rise and increasing frequency and severity of storms need to be considered in development planning; and • test cost-benefit analysis (through climate change impact analysis) as a tool for decision-makers to consider adaptation measures, using Langebaan as a case study. The research comprises a comprehensive literature study of the impacts of climate change, particularly with respect to coastal areas. A case study based on the eroding beaches at Langebaan is used to test cost-benefit analysis as a tool for decision-makers in dealing with the impacts. Despite the uncertainties associated with the impacts of climate change (time, place and extent) the issues of sea-level rise and severe storms seem to warrant further investigation, especially at a local level. This study provides local context to a global problem and makes recommendations for decision-makers in the City of Cape Town. Climate impact analysis (incorporating cost-benefit analysis) is suggested as a tool to quantify avoided damages at vulnerable coastal sites in the City of Cape Town. In conclusion, the impacts of climate change are a complex and multivariate problem. However, there are a number of identified vulnerable areas along the coastline of the City of Cape Town and using tools like climate impact analysis and cost-benefit analysis may assist in identifying, costing and managing these economic risks before the problem becomes unmanageable - a case for quantifying avoided damage. / AFRIKAANSE OPSOMMING: Sterk wetenskaplike bewyse bestaan dat globale verwarming besig is om die wêreld se klimaat te verander en hierdie verskynsel word versnel deur die mens se handelinge. Klimaatsverandering affekteer weerpatrone en bykomend tot gedemonstreerde stygende seevlakke, sal dit waarskynlik 'n langdurige en meestal negatiewe impak - beide ekonomies en lewensverlies - op regerings, industrieë en mense hê. Seevlakke het in die twintigste eeu met tussen 15 en 20 sentimeter gestyg, meestal as gevolg van smeltende ysberge en hitte uitsetting van die oseane. Die 'International Panel on Climate Change' (IPCC, 2001a: 16) het in hul skatting 'n waarskynlike seevlak styging van tussen 9 en 88 sentimeters voorspel vir die tydperk 1990 - 2100. Risikogebiede in die Stad Kaapstad is residensiële gebiede, infrastruktuur en strande in laagliggende gebiede. Hierdie gebiede sal ge-affekteer word deur stygende seevlakke en groter en meer gereelde storms. Hierdie studie poog om • te demonstreer dat voldoende bewyse bestaan om besluitnemers van die Stad Kaapstad te oortuig dat weerveranderinge en die impak van seevlakstygings en toenemende storms in aanmerking geneem moet word in ontwikkelings beplanning; en • koste-voordeel analises (deur klimaatsverandering impak analises) te beproef as 'n hulpmiddel vir besluitnemers om aanpasbare maatreëls te oorweeg, deur Langebaan as 'n voorbeeld te gebruik. Ten spyte van onsekerhede wat saamgaan met die impak van klimaatverandering (tyd, plek en omvang) regverdig die problem van stygende seevlakke en erge storms verdere ondersoek, meer spesifiek op plaaslike vlak. Hierdie studie gee plaaslike konteks aan 'n globale probleem en maak aanbevelings aan beplanners van die Stad Kaapstad. Klimaat impak analises word as hulpmiddel voorgestel om vermybare skades by kwesbare kusgebiede in die Stad Kaapstad te kwantifiseer. Ten slotte: die impak van klimaatsverandering is 'n komplekse probleem met baie fasette. Nietemin is daar verskere sensitiewe areas langs die kus van Stad Kaapstad, en klimaat impak analises en koste-voordeel analises kan help met die identifisering, kosteberekening en bestuur van hierdie ekonomiese risiko areas, voordat dit onhanteerbaar raak.

Thesis (MSc (Earth Sciences))--Stellenbosch University, 2008. / This study aims to provide a practical tool for the prediction and management of dust generated by the activities of an opencast mining operation. The study was conducted on opencast gypsum mines in the semi-arid environment of the Bushmanland, 90 km north of Loeriesfontein in the Northern Cape Province from April 2000 to October 2007. The vertical and horizontal components of wind transported sediment were sampled and a dust settling model was designed to predict the settling pattern of dust generated by opencast mining operations. The model was applied to soil samples collected from an area surrounding a mine. The influence sphere of the mining operation was predicted by the application of the model and then mapped. Once the influence sphere is mapped, the dust influence can be managed with the aid of an onsite weather station. By further applying the predictions based on climatic data, the influence sphere can be modelled. The model is not only applicable to the planning phase of an opencast mine to plan the position of dust sensitive areas like the living quarters, office buildings and workshops etc., but also to indicate the historical impact that a mining operation had once a quarry on an active mine is worked out and rehabilitated or a mine is closed. The model application can also aid with the explanation and visual or graphic representation of the predicted impact of planned mining operations on communities or neighbouring activities to them and thus avoid later penalties.

Soil erosion is a persistent problem that requires continued control efforts as agricultural land loses productivity and communities dependent on the land become increasingly vulnerable to decreased food security. The negative effects of soil erosion in Khamopele River catchment, in the Mount Fletcher southern Drakensberg region of South Africa, are manifest in extensive gullying and wetland loss. Soil erosion has resulted in siltation in a recently constructed dam and the alteration of aquatic habitats. This research was undertaken to identify the sources of eroded sediment in the small upper catchments of the Mzimvubu River catchment to inform broader catchment management strategies. The scale of erosion was quantified using field surveys of gully extent and form. Environmental magnetic tracing techniques were used to determine the sources of eroded sediment in Khamopele River and upper Tina River catchments. The radionuclide ¹³⁷Cs was used to determine soil loss over a 55 year period in Khamopele River catchment. The Landscape Connectivity framework was used to describe the sediment source, pathway and sink interactions at sample area level. Results indicated that historical and contemporary land management practices such as uncontrolled grazing, grassland burning and furrows promoted soil erosion in the catchment. Soil erosion was most pronounced in the Taung sample area where there was extensive gullying, tunnelling and subsurface erosion. Environmental magnetic tracing results indicated that there were clear differences in source areas. Despite its prevalence in the area, gully erosion was not shown to be a major source of sediment to downstream sinks. Topsoil and hillslope derived sediment were shown to be mobile in the catchment, suggesting that sheet erosion processes were dominant in the catchment. Radionuclide tracing studies showed that at least 20 cm of soil had been eroded from the Khamopele River catchment surface since 1956. This research has shown that it is possible to distinguish source areas of erosion in the catchment by matching catchment mineral magnetic signatures to those in sink areas. This means that rehabilitation projects can use resources efficiently as the areas needing the most attention can be identified.

[Portion of abstract]: Sediment dynamics are influenced by transformed landscape connectivity in catchments worldwide. The upper Thina catchment, an important high rainfall resource in the northern Eastern Cape, South Africa, is an example of where ongoing subsistence farming on communal land has led to overgrazing and trampling that has initiated large erosive features (e.g. gullies) and river incision. The formation of gullies led to increased hillslope-channel connectivity and the resultant river incision decreased the channel-valley fill connectivity. These two changes in connectivity led to increased sediment export from the catchment that has various down-stream ecological and socio-economic impacts. This study investigates how the change in hillslope-channel and channel-valley fill connectivity has altered the sediment dynamics in the Vuvu catchment, a headwater tributary of the Thina River. A combination of methods were used to assess the changes in hillslope-channel and channel-valley fill connectivity. High resolution aerial images were used to map source features, such as fields, gullies, sheet erosion, landslides, roads and livestock tracks. Topographic and geological characteristics of the source features were extracted using a Geographic Information System. Furthermore, hillslope-channel pathways, such as the natural drainage network, continuous gullies, discontinuous gullies, roads and livestock tracks were mapped and analysed in terms of topographic and geological characteristics. Historic aerial images were assessed to calculate the date the larger gullies began forming. Recent aerial photos and cross sectional surveys of the valley fill were combined to map the various sediment sinks. Particle size and organic content were analysed for flood bench cores and terrace samples. The chronology of the flood benches was determined using unsupported Pb-210 and Cs-137 dating, and determined for the terraces using Optically Stimulated Luminescence dating. Quantitative and qualitative sediment tracing approaches, using mineral magnetic properties, were used to trace the origin of suspended sediment (collected during flood events), sediment stored in the flood benches and sediment stored in the terraces. Hydrological monitoring was used to assess the potential to store sediment on flood benches along the valley fill through flood bench inundation frequency. Hydrological and hydraulic modelling extended the measured inundation frequencies to a 73 year period and other cross sections along the valley fill. Furthermore, a future scenario of an increased vegetation cover and reduced hillslope-channel connectivity was assessed in terms of channel-valley fill inundation frequency.