>Magister Scientiae - MSc / Gully erosion and headcut migration has been at the crux of wetland degradation in South Africa. The resulting erosion and draining effect has seen more than 50% of wetlands in the country degraded. This study investigated the degradation of indigenous Palmiet, peat forming, wetlands through headcut erosion. This was done by exploring the relationship between headcut migration rate and morphodynamic characteristics through the use of multiple regression analysis. Wetlands investigated in this study occurred in the Kromme River catchment and Nuwejaars River catchment, in the Eastern Cape and Western Cape respectively. Morphodynamic characteristics assessed include headcut dimensions, gully characteristics, soil characteristics and drainage basin characteristics. These parameters were determined either through infield assessment, image analysis or laboratory analysis. Three headcut migration rate types were calculated through a combination of infield measurements and image analysis techniques executed within ArcGIS. These migration rate types include apex advancement (m/a), gully expansion (m2/a) and volume erosion (m3/a). Statistical analysis revealed significant relationships between morphodynamic characteristics and both volume erosion and gully expansion. Morphodynamic characteristics such as drop height, apex width, gully width, drainage rate and sand content were found to have a direct relationship with migration rates, whereas characteristics such as average drainage basin slope, clay content, silt content, SOM content and soil saturation were found to have an indirect relationship with headcut migration rates. Results provide insight into the headcut migration process, its influencing factors and the potential for headcut migration rate prediction. An evaluation of these results using WET-Health found that the wetland management tool captures wetland geomorphic controls to an accuracy of 68% and 70%. Furthermore, the influence of morphodynamic characteristics on migration rates contributes to the wetland rehabilitation process as it allows for the identification of headcut sites most susceptible to erosion. This will then allow for timely wetland rehabilitation, decreasing the rate of net wetland degradation and improving the management and efficiency of wetland restoration.

Doctor Educationis / Recent research has highlighted the importance of cut-and-fill cycles in valley-bottom wetlands. This study considers the impact of longitudinal and lateral sediment connectivity on the natural recovery potential of valley-bottom wetlands. Pietersielieskloof is a Prionium serratum (commonly known as palmiet) dominated discontinuous valley-bottom wetland. P. serratum is considered to be a peat-forming ecosystem engineer that enhances sediment infill in valleybottom wetlands. Due to its ecological importance and potential as a carbon store, this wetland has been earmarked for rehabilitation by Working for Wetlands. The study ascertains the importance of including sedimentological and geomorphological input in wetland rehabilitation and management strategies. A study of wetland geomorphology was conducted to develop an understanding of the natural dynamic of cut-and-fill processes as context for recent erosion and deposition events. Sediment samples from gully walls and cores were collected for organic content and particle size analysis and five sediment samples predating the current phase of erosion were radiocarbon dated. The valley form was surveyed using cross-sections and long profiles, and historical change was digitised using 30 m – 5 to 30 mm resolution aerial imagery from 1938-2016 in ArcMap.

Water, a fundamental and irreplaceable resource, is an all-pervasive issue that underpins the social fabric of every society. Rapid population growth and expansion of human activities increases the amount of waste and pollution generated and many local authorities are encountering serious water pollution problems, often concentrated in the lower reaches of catchments and adjacent coastal areas. This problem is predominantly acute in urbanized catchment areas, where waste is concentrated into localized areas, and the authorities are constantly under pressure to provide adequate management and mitigation measures. The Palmiet River system, located in the northern fringe of the city of Durban and draining the highly industrialized Pinetown region in KwaZulu-Natal, South Africa, illustrates a system that has been altered due to human impacts, particularly in its headwaters where the industrial sites are located and, in the lower catchment where a densely populated informal settlement occurs. A range of chemical and biotic indicators were monitored seasonally and these confirm the influence of the aforementioned human impacts on the quality of the Palmiet River system. Results from the present study were compared with studies conducted over a period of two decades and clearly demonstrate a pattern of increasing pollution loads for the upper and lower parts of the catchment. This study confirms that the Palmiet River is severely degraded in its lower reaches whilst the middle reaches of the catchment where a nature reserve is located is still in a fairly pristine condition. Additionally, the Palmiet River issues discussed in this thesis have direct impacts on the estuarine and adjacent marine ecosystems. / Thesis (M.A.)-University of KwaZulu-Natal, Durban,2005.