A spatial assessment of riparian vegetation density and implications for streambank erosion in relation to land tenure in the Mgwalana Catchment, Eastern Cape Province, South Africa

Riparian vegetation provides an array of various ecosystem functions and has significantly shaped the conditions of catchments. It has strong controls on fluvial geomorphology and erosion processes. The Mgwalana catchment has been intensively studied over the years and the current environmental condition of the study has been linked to land use history. The catchment has been subjected to land use/cover changes (LUCC) over the years. However, spatial variations in riparian vegetation, their implications for stream bank stability and the contribution of land tenure systems to stream channel degradation are poorly understood. The study sought to assess the implications of the spatial variations in riparian vegetation density for stream bank erosion in relation to land tenure on a catchment scale. Land tenure units comprising the catchment of study are traditional and betterment villages (communal lands), and former white commercial farms. A three-pronged approach using GIS and remote sensing, field investigations and laboratory procedures for soil analysis was employed in this study. Variations of riparian vegetation density in the catchment were mapped using ArcGIS for the two land tenure units to assess the spatial variations of riparian density along stream reaches and to determine the spatial relationship between land tenure units and riparian vegetation diminution. Other mapped shape files include sediment accumulation zones to analyse the spatial relationship between riparian vegetation density and sediment sinks. LUCC classification and analysis of the Normalized Difference Vegetation Index (NDVI) were carried out in IDRISI Selva, using Landsat 8 TM imagery of 2018 to represent the current spatial riparian vegetation variations in the catchment. Field investigations were conducted to determine the coupling among hillslope gully erosion, riparian vegetation density and sink areas; and to assess physical characteristics of soil. This would permit an assessment of the implications of riparian vegetation for stream bank erosion and sediment accumulation within the tenure units. Soil samples were taken from scantily and densely vegetated stream reaches, as well as measurements of channel widths and depths. Analyses of soil physical properties viz; grain size distribution, bulk density, soil texture and aggregate stability were done. Results demonstrated that a sparse riparian vegetation distribution was consistent with the communal villages, confined to the upper catchment area. Dense riparian vegetation distribution was consistent with former commercial farms in the lower catchment area.Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 202

OSTBC MIMO Transceiver System For Radio Signal Propagation Challenges Over Irregular Terrain In The Northern Cape, South Africa

DissertationThe Northern Cape Province in South Africa, along the Orange River valley, has radio signal reception challenges due to high mountain ranges. The South African Electricity Authority- Eskom has High Voltage assets to monitor in this region. However, due to radio signal reception challenges, it is impossible to monitor their assets via the Supervisory Control and Data Acquisition (SCADA) system. This research aims at developing a Very-High Frequency Orthogonal Space – Time Block Code Multiple-In Multiple-Out (VHF OSTBC MIMO) transceiver simulation model over a Rayleigh fading channel to address the radio communication challenges along the Orange River. The transceiver simulation model will resemble the harsh multipath environment presented by the mountainous terrain in the Northern Cape Province. In environments with irregular terrain such as hills and mountains, the radio signal comes across phenomena such as reflection, refraction, diffraction and scattering. Therefore, the transmitted radio signal undergoes heavy fading and inter-symbol interference (ISI), thus negatively impacting radio link performance. However, the Multiple-input- multiple-output (MIMO) system, which uses multiple antennas both at the transmitter and receiver, takes advantage of this drawback and makes use of the high levels of multi-paths to operate at an optimum. MIMO creates spatial diversity which accounts for better radio link performance, it also yields increased capacity and improves Signal-to-Noise Ratio (SNR) while reducing bit errors. Therefore, MIMO is one of the systems of interest considered best to exploit in this research. Space- time coding (STC) has also been considered because of its ability to increase the reliability of the channel and for its signal decoding simplicity at the receiver. A suitable lower frequency band to use for this research was also investigated. The most attractive characteristic of the low frequency (LF) band that was sought after was its ability to easily diffract over large obstacles than higher frequencies. The Very High Frequency (VHF) band at 70 MHz was found to meet the requirements for the model used. Therefore, this dissertation presents the simulation results of a VHF OSTBC MIMO transceiver model over a Rayleigh fading channel that is typical of the mountainous regions of the Northern Cape Province in South Africa, to help overcome radio signal reception challenges. The following are the different component blocks that made up the model: Random Binary Generator (RBG), Quadrature Phase Shift Key (QPSK) Modulator, Orthogonal Space-Time Block Code (OSTBC) Encoder, Multiple-In Multiple-Out (MIMO) Rayleigh Fading Channel, Added White Gaussian Noise (AWGN), Orthogonal Space-Time Block Code (OSTBC) Decoder and a Quadrature Phase Shift Key (QPSK) Demodulator. The simulation results in this research were generated using the following software packages namely: Matlab/Simulink, Atoll Wireless Network and Pathloss 4 Network. The Matlab/Simulink software was used to determine the bit-error-rate (BER) performance of four different OSTBC MIMO systems, each using different antenna arrays. TheMatlab RF Propagation Tool-SiteViewer was used to generate coverage predictions and receive signal strength (RSS) levels of three VHF OSTBC MIMO systems operating at three different low VHF frequency bands. The Atoll Wireless Network software was used to generate coverage plot predictions. The Pathloss 4 software was used to generate Line of Sight (LoS) predictions. The results have shown that employing the low band VHF OSTBC MIMO transceiver system in irregular terrain environments can greatly improve radio signal reception, data speeds, bandwidth efficiency and link reliability

A spatial assessment of riparian vegetation density and implications for streambank erosion in relation to land tenure in the Mgwalana Catchment, Eastern Cape Province, South Africa

Riparian vegetation provides an array of various ecosystem functions and has significantly shaped the conditions of catchments. It has strong controls on fluvial geomorphology and erosion processes. The Mgwalana catchment has been intensively studied over the years and the current environmental condition of the study has been linked to land use history. The catchment has been subjected to land use/cover changes (LUCC) over the years. However, spatial variations in riparian vegetation, their implications for stream bank stability and the contribution of land tenure systems to stream channel degradation are poorly understood. The study sought to assess the implications of the spatial variations in riparian vegetation density for stream bank erosion in relation to land tenure on a catchment scale. Land tenure units comprising the catchment of study are traditional and betterment villages (communal lands), and former white commercial farms. A three-pronged approach using GIS and remote sensing, field investigations and laboratory procedures for soil analysis was employed in this study. Variations of riparian vegetation density in the catchment were mapped using ArcGIS for the two land tenure units to assess the spatial variations of riparian density along stream reaches and to determine the spatial relationship between land tenure units and riparian vegetation diminution. Other mapped shape files include sediment accumulation zones to analyse the spatial relationship between riparian vegetation density and sediment sinks. LUCC classification and analysis of the Normalized Difference Vegetation Index (NDVI) were carried out in IDRISI Selva, using Landsat 8 TM imagery of 2018 to represent the current spatial riparian vegetation variations in the catchment. Field investigations were conducted to determine the coupling among hillslope gully erosion, riparian vegetation density and sink areas; and to assess physical characteristics of soil. This would permit an assessment of the implications of riparian vegetation for stream bank erosion and sediment accumulation within the tenure units. Soil samples were taken from scantily and densely vegetated stream reaches, as well as measurements of channel widths and depths. Analyses of soil physical properties viz; grain size distribution, bulk density, soil texture and aggregate stability were done. Results demonstrated that a sparse riparian vegetation distribution was consistent with the communal villages, confined to the upper catchment area. Dense riparian vegetation distribution was consistent with former commercial farms in the lower catchment area.Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 202