MENVSC (Geography) / Department of Geography and Geo-Information Sciences / Environmental degradation is a quite familiar factor of the mining industry that has been associated with South African mining industry from the beginning. The decommissioning of abandoned mines before the environment legislation, The National Environmental Management Act 107 of 1998 and the Minerals and Petroleum Resources Development Act 23 of 2002, was introduced is of great concern as the abandonment of mines without appropriate remediation and pollution monitoring was the result. Soil erosion has been recognised as an environmental hazard that emanates from abandoned mines. This study seeks to assess the soil erosion hazard around Nyala abandoned mine. The modified method of Soil Loss Estimation Model for Southern Africa (SLEMSA), for assessing soil erosion hazard, was used to estimate the spatial variation of erosion to achieve the goal of the study. Parameters that were considered for the model include relief (Slope steepness, S & slope length, L), soil erodibility (Fb), vegetation cover (C) and rainfall erosivity (E). Soil samples were collected from the field and; sieve and hydrometer analysis was conducted to determine the erodibility factor value of the study area. The model was run in a GIS environment (ArcGIS) and the parameters were multiplied to generate a soil erosion hazard map for the abandoned Nyala mine area. Results from the study indicated that 74.3 % of the watershed experiences low to moderate erosion hazard, with an estimated annual soil loss of 2.76 tons/ha/yr. The low rates of soil erosion in most parts of the watershed are associated with the low topographic ratio and low rainfall erosivity. The research demonstrated that the modified SLEMSA model used within GIS is a very useful tool as it enhances the capacity to assess and model the spatial variation of soil erosion hazard in a timeously and affordable manner. / NRF

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Coastal erosion is a worldwide hazard of which the consequences can only be mitigated via thorough and efficient monitoring of erosion and vulnerability to erosion. This study aimed to establish the accuracy, efficacy and efficiency of various remote sensing techniques for the detection and monitoring of coastal erosion and vulnerability occurring in False Bay, South Africa. There is a need to monitor the erosion in this area as well as to determine the most effective techniques for monitoring the erosion in False Bay and other similar environments in the future. This study provides an assessment of the usefulness of different data sources and techniques for change detection in the coastal environment. The data sources used were Landsat TM/ETM+ imagery and aerial photographs. Image differencing, tasselled cap transformations, vegetation index differencing, Boolean change detection, and post-classification change detection were all performed on the Landsat imagery. The aerial photographs were assessed using the Digital Shoreline Analysis System (DSAS) add-on for ArcGIS which determines statistical differences in the shoreline position as digitised in vector format. The results showed that while the resolution of the Landsat imagery was not sufficient to analyse erosion along the beach itself, the larger area covered by the satellite images enabled vulnerability indicators to be seen. Notably, the post-classification change detection indicated consistent increases in built-up areas, while sand dune, beach, and sand (not beach) all decreased. NDVI differencing showed consistent decreases in NDVI indicating decreasing plant health and density. The results of image differencing with both band 4 and the brightness band led to conclusions that vegetation health was decreasing while reflective surfaces such as bare sand and roads were increasing. All of these indicate an increased vulnerability to coastal erosion. The Boolean change detection method was found not to be useful in this case. Aerial photographs were studied on four focus areas: Bayview Heights, Macassar Beach, Strand, and Pringle Bay. The results showed erosion at all four areas, with Strand experiencing only erosion (no accretion) at an average of 53 cm erosion per year. Erosion at Macassar Beach and Pringle Bay was also severe, with Bayview Heights being the least severe and showing a combination of erosion and accretion. The higher resolution available on the aerial photographs was vital to view changes on the beach itself. In future studies requiring assessment of changes in the position or condition of the beach itself, aerial photographs or high resolution satellite data should be used. Studies of vulnerability extending over the entire coastal zone may make use of Landsat TM images. Post-classification change detection provides powerful change direction information and can indicate the percentage of area change from one class to another. However, image differencing and vegetation index differencing are much faster to perform and can provide information about general trends in the changes occurring. Therefore post-classification change detection might be used in areas of high and rapid change while image differencing and vegetation index differencing can be useful to cover vast areas where little change is expected. / AFRIKAANSE OPSOMMING: Kus-erosie is ‘n wêreldwye gevaar waarvan die gevolge slegs deur deeglike en doeltreffende monitering van erosie en kwesbaarheid vir erosie verminder kan word. Hierdie studie poog om die akkuraatheid, doeltreffendheid en effektiwiteit van verskillende afstandswaarneming tegnieke vas te stel vir die opsporing en monitering van kus-erosie en kwesbaarheid in Valsbaai, Suid Afrika. Daar is ‘n behoefte aan die monitering van erosie in hierdie area, sowel as om die mees doeltreffende tegnieke van die monitering hiervan in Valsbaai en ander soortgelyke omgewings in die toekoms te bepaal. Hierdie studie bied ‘n evaluering van die nut van verskillende data-bronne en tegnieke vir die opsporing van verandering in ‘n kusomgewing. Die data-bronne wat gebruik is, is Landsat TM/ETM+ beelde asook lugfoto’s. Beeld differensievorming, “tasselled cap” transformasies, plantegroei indeks differensievorming, Boolse verandering en post-klassifikasie verandering is toegepas op die Landsat beelde. Die lugfotos is ge-evalueer deur die Digitale Kuslyn Analise Stelsel (Digital Shoreline Analysis System – DSAS). DSAS is ‘n bykomstige sagteware vir ArcGIS wat statistiese verskille in gedigitaliseerde kuslyn posisie bepaal. Die resultate toon dat terwyl die resolusie van die Landsat beelde nie voldoende was om strand-erosie self te analiseer, die groter area wat deur die satellietbeelde gedek word toegelaat het om kwesbaarheid aanwysers te ontleed. Spesifiek die post-klassifikasie verandering het aangedui dat konsekwente toenames in beboude areas voorkom, terwyl afnames in sandduine, strand en sand-areas voorgekom het. NDVI differensievorming het konsekwente afnames in NDVI getoon, wat dui op afnames in die gesondheid en digtheid van plantegroei. Die resultate van die beeld differensievorming met beide Landsat Band 4 en die helderheid-band het gelei tot die gevolgtrekking dat die gesondheid van plantegroei afgeneem het, terwyl reflektiewe oppervlaktes soos oop sand en paaie aan die toeneem is. Al hierdie resultate dui op die verhoogde kwesbaarheid vir kus erosie. Die Boolse verandering metode is bevind om nie van nut te wees in hierdie geval nie. Lugfoto’s van vier fokus-areas is bestudeer: Bayview Heights, Macassar Strand, Strand en Pringlebaai. Resultate van die DSAS analise het gevind dat oorwegend erosie by al vier areas plaasvind, met Strand die enigste area wat slegs erosie (geen aanwas) ervaar teen ‘n gemiddelde koers van 0.53 m per jaar. Erosie by Macassar Strand en Pringlebaai was ook ernstig, terwyl Bayview Heights die minste erosie ervaar het, met ‘n kombinasie van erosie en aanwas. Die hoër resolusie beskikbaar deur die lugfoto’s was noodsaaklik om veranderinge in strand areas waar te neem. In toekomstige studies wat die assessering van verandering in die posisie of toestand van strande noodsaak behoort lugfotos of hoë-resolusie satellietbeeld data gebruik te word. Studies oor die kwesbaarheid van ‘n hele kusstreek kan wel gebruik maak van Landsat data. Post-klassifikasie verandering bied kragtige informasie oor die rigting van verandering en kan die persentasie van verandering van een klas na ‘n ander aandui. Beeld en NDVI differensievorming is egter veel vinniger om uit te voer en kan informasie rakende die algemene tendense in verandering lewer. Post-klassifikasie verandering kan dus gebruik word in gebiede van vinnige en beduidende verandering plaasvind, terwyl beeld en NDVI differensievorming nuttig kan wees om groot areas te dek waar min verandering verwag word.

The invasion of Acacia mearnsii in the Kouga catchment, Eastern Cape, South Africa, has various negative impacts on the ecosystem. These impacts include: reduced species richness, increased water use, increased nutrients and increased N cycling rates. The native shrubby fynbos vegetation has adapted to the acidic nutrient poor soils and Mediterranean climate of the Kouga Mountains. Fynbos, however, is currently being out competed by the much taller Acacia mearnsii trees, due to their competitive nature and ability to fix nitrogen, thereby enriching the soil. The invaded sections of the valley bottoms and lower hill slopes are characterised by an almost complete monoculture of Acacia mearnsii, with very few fynbos species still present. The Department of Water and Environmental Affairs sponsored Working for Water programme started clearing Acacia mearnsii in 1996 in the Kouga Mountains. Cleared sites have remained bare for long periods, indicating that soil properties are not favourable for indigenous propagule re-establishment. The aim of this research was to assess how A. mearnsii invasion and clearing affect fynbos recovery through its impact on soils. This was done by characterising vegetation and soil properties on fynbos, infested and cleared slopes. Vegetation cover for various growth forms was determined and a species list was compiled for each plot. The slope angle, surface hardness, litter cover, bare ground cover and soil depth were measured in the field, whereas water repellency, particle size and the chemical composition were measured in the laboratory. Furthermore, the plant establishment capacity of soils from fynbos, infested and cleared slopes was calculated. This was done by germinating fynbos seeds and growing fynbos plants in soils from the various slopes. The effect that invasion and clearing has on soil erosion was quantified using erosion plots on fynbos, infested and cleared slopes. The invasion and clearing of Acacia mearnsii led to an increase in soil nutrients, especially nitrogen, phosphorus, potassium, carbon and manganese. Furthermore, soils became more acidic, with increased water repellency and reduced surface hardness. The vegetation changed to a tree-dominated structure, replacing the native species. Native plant germination was relatively unaffected by invasion and clearing, with an increase in germination just after clearing. Plant growth of a native grass, Themeda triandra, and herb, Helichrysum umbraculigerum, has increased on soils from cleared slopes. This study showed that soil movement increased on slopes which are invaded and cleared of Acacia mearnsii, with erosion rates doubling on invaded slopes

Studies of the dunefield systems crossing the Cape St. Francis headland in the Eastern Cape have focused on the role that wind plays in sediment transfer in coastal dunefield systems, with limited consideration of the role of water. The aim of this study was to improve understanding of the morphology, processes and patterns within the Oyster Bay HBD system, focussing particularly on surface water and groundwater interactions and the role of surface water in sediment transfer across the dunefield system. An extensive field survey was conducted, to collect related data, complimented by spatial and temporal analysis of the study area using GIS. The key findings from this research were the apparent differences between the western and eastern regions of the dunefield with regard to specific drivers and the respective processes and responses. Wind is the major driver of change up to and across the crest of the dunefield. In the eastern region water (ground water, surface water and the Sand River System) is the primary agent of sediment flux through processes of aggregation and slumping as well as episodic events including debris flows. This study has highlighted a need for further quantitative studies that investigate the movement of sediment through dunefield systems such as this (where water is at or near the land surface). The paradigm that sediment flux is entirely due to wind is almost certainly simplistic, and deeper understanding of these systems is needed / Maiden name: Elkington, Lauren