This dissertation focuses on both a hydrodynamic and geomorphological study of the Mgeni Estuary. Within the hydrodynamic study, the channel discharge, suspended sediment fluxes and estuary bed sediment characteristics and dynamics were established. Within the geomorphological study, cross-shore topographical surveying of the lower estuary region, measurement of slope angles and surface sediment characteristics were established. The results of this study illustrate strong seasonal variability. Maximum channel discharges, suspended sediment concentrations and fluxes occur during the summer months, as a result of large amounts of rainfall. Furthermore, maximum suspended sediment concentrations and fluxes occur during spring tides, as a result of a greater tidal range, which enhances bed sediment re-suspension via concomitant increased turbulence. Generally, maximum fluxes occur along the flood tide and ebb tide, during spring tides and neap tides, respectively, which suggest that the estuary is a sink for marine sediment during spring tides and an exporter of sediment during neap tides. The estuary bed sediments are very well sorted and predominantly classified as near-symmetrical, as a result of strong tidal currents that constantly transport and re-work the sediments. On average, the bed sediments are medium sand and in all probability are largely derived from the marine environment. Estuary bed sediments contain negligible mud and organic contents, which as research suggests, is common in such highenergy estuary mouths. Apart from the seasonal variability, the survey profiles and surface sediments illustrate alongshore and cross-shore variations. The profiles become flatter and finer from the Beachwood Mangroves section of the barrier towards the estuary mouth in the south, as a result of sheltering due to the engineered groyne, conforming to Bascom (1959) and Komar’s (1998) sheltered and exposed coasts concept. The survey profiles conform to the summer and winter profiles put forward by Dardis and Grindley (1988). The winter profiles consist of higher, distinct berms and berm crests, as well as vertical erosional faces, whilst the summer profiles are lower, flatter, and consist of unclear berms and berm crests. Sediments are coarsest along the lagoonward slope and finest within the estuary. A strong, positive correlation was generated between slope angle and mean grain size. Despite the low organic contents, the estuary sediments consist of the highest values of organic matter, with the beach and barrier sediments displaying negligible amounts. Thus, the Mgeni can be classified as a very dynamic and active zone. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2009.

South African estuaries have high biodiversity value and provide many benefits to society, including food, real estate, a place for recreation and economic enterprise. However, they are facing growing human pressures such as urban encroachment, development in river catchments and interference in hydrological cycles. This dissertation provides an exploratory study of the environmental history of the Mgeni River Estuary, KwaZulu-Natal in an attempt to improve the understanding of the forces that drive environmental change. Through the application of the techniques and methodologies of environmental history, it explores the dynamics, characteristics and impacts of human interaction with the Mgeni River Estuary over time. It focuses on the emergence of a capitalist! industrial society in the twentieth century as this period has been characterised by the most significant environmental alteration and degradation. With the aid of the techniques and methodologies employed, the study highlights a complexity of natural and human events that have altered the estuary over time. Comparative analysis of aerial photographs between 1937 and 1996 reveals that physical changes to the estuary were linked to prevalent social and economic activities. The study describes cultural beliefs, modes of resource use and the political economy as significant and interwoven factors that facilitate environmentally intrusive activities. The study has provided insights into the complexity of factors that influence the rate and extent of change of an estuarine system. It concludes that to improve the understanding of the causes of environmental change, it is necessary to look further than the physical impacts on the environment to the attitudes and beliefs that underlie them. While the solutions to the problems facing the Mgeni River Estuary are not easily at hand, such analysis should assist policy makers and managers in finding a way to initiate more sustainable estuarine development in the future. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

Natural vegetation has been converted to land uses, such as agriculture, commercial forestry and urban use, to meet increasing human demands for food, fuel and shelter. These land use changes modify the surface conditions of an area, resulting in changes in hydrological responses. Urban land use, in particular, has a significant impact on catchment hydrology as a result of the increased impervious areas such as concrete, tar and roofs. To assess the future hydrological impacts of urban land use, the scale and location of future urban areas must be considered. The objective of this study was to assess the hydrological responses to future urban growth in the Mgeni catchment, South Africa. An urban growth model was used to generate scenarios of plausible future urban growth and these scenarios were modelled using a hydrological model to determine the hydrological responses to urban growth. The plausible future urban growth in the Mgeni catchment was modelled using the SLEUTH Urban Growth model (SLEUTH). The SLEUTH acronym stands for the input layers required for the model viz. Slope, Land use, Excluded areas, Urban Extent, Transport routes and Hillshade. SLEUTH is able to provide the scale and location of future urban growth required to assess the hydrological impacts of future urban growth. The data requirements and modelling procedure for SLEUTH is relatively simply and therefore it is well suited to a South African context. SLEUTH was calibrated and applied to the Mgeni catchment to project future urban land use. When assessing the 95-100% probability class, the results revealed that the Henley, Pietermaritzburg and Durban areas would experience the highest urban growth in the Mgeni catchment by the year 2050. The outputs of the SLEUTH Model for the Mgeni catchment showed a number of similarities to another application of SLEUTH in Cape Town. These similarities indicate the SLEUTH performs in a similar way for the two South African cities. Therefore, it was concluded that the SLEUTH Model is suitable to account for urban growth in the Mgeni catchment, as required for use in hydrological impact studies. The hydrological responses to urban growth in the Mgeni catchment were assessed using the ACRU model. The scenarios of plausible future urban growth generated by SLEUTH were overlaid with current land cover layers to generate maps of plausible future urban land use. The results showed extensive urban growth of >95% probability occurring in the Midmar, Albert Falls, Henley, Pietermaritzburg, Table Mountain, Inanda and Durban Water Management Areas (WMAs) by 2050. Increases in mean annual streamflows were observed in many of these areas; however the Henley, Pietermaritzburg and Table Mountain WMAs were shown to have greater increases in mean annual streamflow than the other areas that showed similar increases in urban growth, thus indicating that these WMAs could be particularly responsive to urban growth in the future. Furthermore, the results showed that the type of urban land use is important in determining the hydrological responses of urban land use, as the imperviousness differs between the different urban land uses. Streamflow responses were shown to be influenced by the scale and location of urban growth in the Mgeni catchment and specific areas, such as the WMAs along the Msunduzi River, were identified as potentially responsive to urban growth. Summer streamflows were indicated as being more responsive to urban land use changes than winter streamflows and increases in streamflows due to urban growth start to over-ride the impacts of other land uses which have substantial impacts on hydrological responses such as commercial forestry, and commercial sugarcane by 2050, whereas in other areas increases were mitigated by the presence of major dams. Lastly, it was shown that the type of urban land use, such as built up urban areas when compared to informal urban areas for example, have a significant impact on streamflow responses. These results are useful as they can be used to inform both water resources planning as well as urban planning to ensure that South Africa’s valuable water resources are protected. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.