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A Dissertation submitted to the Faculty of science, University of the Witwatersrand, Johannesburg, for the Degree of Doctor of Philosophy / The Late Proterozoic Damara Oroqen (750-450 Ma} in Namibia forms part of the Pan-African mobile belt system which dissects southern Africa. The Khomas Trough in the inland branch of the orogen comprises thick multiply deformed metagraywackes and pelites of the Kuisab Formation. (Abbreviation abstract). / Andrew Chakane 2019

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Sedimentological analyses, including detailed facies characterization and lateral profiling, demonstrate deposition in a bedload-dominated fluvial system for the quartzose sandstones of Lee Formation. Internal (architectural) elements of the sandstones consist primarily of truncated channel-fIll sequences. Individual channel elements, up to 20 meters thick, contain a complex hierarchy of bedform deposits. The principal internal component of channels were downstream-accreting (mid-channel?) macroforms; channel elements frequently contain deposits of more than one macroform. Reconstruction of the macroforms reveals accretion primarily by superposed bedforms that migrated down a low-angle front. Steeper, giant foresets, transitional along flow with the low-angle facies, indicate that the macroform episodically developed a steep slipface. Uppermost channels within the Rockcastle Member contain macroform elements with components of lateral accretion, interpreted as deposits of alternate bank-attached macroforms. Also recognized within channel-fill deposits are minor-channel, sandy-bedform, gravity-flow (attributed to bank slumping), and channel-bottom elements. The latter element is contained within a facies sequence that suggests rising- to flood- to waning-stage deposition. In general, deposition was probably during relatively high stage; little evidence of low-stage flow was recognized. Subordinate fine-grained facies are interpreted as levee and overbank deposits. Strongly unimodal paleocurrents, lack of facies that suggest low-stage reworking and paucity of lateral-accretion features indicate deposition in a single-channel, low-sinuousity, system (i.e., a low braiding index). Fluvial architecture similar to that found in the Lee Formation has been previously explained by deposition in multi-channel, braided-river systems. However, the internal architecture of sandstone members is also consistent with a single-channel origin. Individual channels were temporarily confined, during which time the passage of several macroforms aggraded the channel. Position of the channel in the alluvial plain was largely controlled by avulsion of the river from fully aggraded channel belts to other areas of the plain. Calculations reveal that avulsion of a single-channel system across a wide alluvial plain is a plausible mechanism for building the sheet-like sandstone bodies of the Lee Formation. Spatial arrangement of individual sandstone members of the Lee Formation was probably controlled by tectonic processes. Episodic thrust-loading in the orogenic belt to the east and subsequent flexure of the crust in the foreland basin caused a step-wise progression of the river system towards the west. Petrographic, sedimentologic and stratigraphic data indicate that source area and climate functioned as the primary controls on the mature composition of sandstones in the Lee Formation. Source areas were composed primarily of quartz-rich sedimentary rocks and were located chiefly to the northeast/north. A east/southeast source area supplied subordinate and low-grade metamorphic rock fragments. Intense weathering, associated with humid tropical climates, acted upon the detritus throughout the sedimentation cycle. Less important controls on composition were tectonics and transport/depositional processes that extended exposure of the sediments to the severe climatic conditions. Quartzose sandstones of the Lee Formation reflect lower rates of tectonic subsidence and greater recycling of sand-sized grains during transportation and temporary deposition on the alluvial plain, relative to lithic time equivalents to the east. / Ph. D.

The Baviaanskloof catchment is a semi-arid catchment located in the Cape Fold Mountains of South Africa. Little is known about the functioning of the complicated Baviaanskloof fluvial system and the role alluvial fans in the fluvial landscape. This thesis will contribute to field of geomorphology and, more specifically, to the field of fan morphometry by producing a standalone fan framework outlining methods to investigate the influence of external and internal control variables on alluvial fans. In this thesis, outcomes of the applied framework and case study are used to develop fan restoration guidelines for the Baviaanskloof Valley. The framework incorporates external and internal fan control variables at a valley-wide and local fan scale. External control variables include accommodation space, base-level change, and drainage basin inputs. Internal control variables include fan style, morphometry and fan channels. In order to apply the framework, fan morphometry data was required. This data was collected by creating a spatial plan of fans and basins in the valley. Outcomes of the applied framework include; an understanding of baselevel change on fans, relationships between fan basin characteristics and the fan surface and insight into fan channel processes. Results of the applied framework are investigated further using bivariate (correlation matrix) and multivariate (principle component analysis and regression analysis) analysis techniques. Significant relationships identified are: drainage basin area versus fan area, fan area and fan slope and drainage basin ruggedness and basin size. The primary outcomes of this thesis include an alluvial fan form-process framework, key considerations to be included in alluvial fan restoration projects and fan restoration guidelines. Contributions of this thesis to broader alluvial fan morphology science includes new insights into general fan literature by compiling a form-process alluvial fan classification framework to identify external and internal fan control variables and identify fan form. Additions have been made to Clarke’s (2010) evolutionary stages to describe stages 4 and 5 of fan evolution that has been adapted to describe fan evolution and differentiate between stages of mature fan evolution. This thesis has also contributed to the study of alluvial fans in South Africa, particularly in the Baviaanskloof Valley. The layout of the procedural guidelines and key considerations for an alluvial fan project provides a guide for rapid fan assessment for maximum cost and time benefits for stakeholders.

Nonpoint source pollution from cropland has been identified as the primary source of nitrogen and sediment, and a significant source of phosphorus in the Chesapeake Bay. These pollutants, whether from point or nonpoint sources, have been found to be the primary cause of declining water quality in the Bay. Numerous studies have indicated that, for many watersheds, a few critical areas are responsible for a disproportionate amount of the nutrient and sediment yield. Consequently, if pollution control activities are concentrated in these critical areas, then a far greater improvement in downstream water quality can be expected with limited funds. In this research a phosphorus transport model is incorporated into ANSWERS, a distributed parameter watershed model. The version of ANSWERS used has an extended sediment transport model which is capable of simulating the transport of individual particle classes in a sediment mixture during the overland flow process. The phosphorus model uses a nonequilibrium desorption equation to account for the desorption of phosphorus from the soil surface into surface runoff. The sediment-bound phosphorus is modeled as a function of the specific surface area of the soil and transported sediment. The equilibrium between the soluble and sediment-bound phosphorus is modeled using a Langmuir isotherm. The extended ANSWERS model was verified using water quality data collected from rainfall simulator plot studies conducted on the Prices Fork Research Farm in Blacksburg, Virginia. The plots consisted of four 5.5 m wide by 18.3 m long strips with average slopes ranging from 6.2 to 11 percent. Two of the plots were tilled conventionally, and the remaining two were no-till. Simulated rainfall at an intensity of 5 cm/h was applied to the plots and runoff samples were analysed for sediment and phosphorus. The model was then verified by comparing the simulated responce with the observed data. The results of the verification runs ranged from satisfactory to excellent. Also developed is a technique for selecting a design storm for ANSWERS. The technique creates an n-year recurrence interval storm with a duration equal to the time of concentration of the watershed. The intensity pattern is simulated on a ten-minute interval using a first-order Markov model with a lognormal distribution. Using a two-year recurrence interval design storm, the use of the model is demonstrated for evaluating the application of conservation practices to critical areas on a Virginia watershed. Application of BMP's to critical areas is shown to be substantially more cost effective in terms of pollutant reduction than nonselective placement of BMP's if cost sharing funds are involved. / M.S.

Sedimentation (erosion, transport, and deposition) is a primary and growing environmental, engineering, and agricultural issue around the world. However, collection of the data needed to develop solutions to sedimentation issues has declined by about three-fourths since 1983. Suspended-sediment surrogates have the potential to obtain sediment data using methods that are more accurate, of higher spatial and temporal resolution, and with less manually intensive, costly, and hazardous methods. The improved quality of sediment data from high-resolution surrogates may inform improved understanding and solutions to environmental, engineering, and agricultural sedimentation problems. The field experiments for this research includ physical samples of suspended sediment collected concurrently with surrogate metrics from instruments including 1.2, 1.5, and 3.0 megahertz frequency acoustic doppler current profilers, a nephelometric turbidity sensor, and a laser-diffraction particle size analyzer. This comprehensive data set was collected over five storms in 2009 and 2010 at Yellow River near Atlanta, Georgia. This research project has proposed, developed, and tested a new method for evaluation of sediment size from theoretical acoustic attenuation; evaluated and further developed recently introduced empirical methods for estimating acoustic attenuation by sediment; found and quantified data mischaracterization issues for laser-diffraction metrics; defined deterministic causes for observed hysteresis and variance in suspended sediment to surrogate relations; compared the accuracy of sediment concentration models and loads for each tested surrogate; and compared sediment surrogate technologies on the basis of reliability and operational considerations.

The Permo-Carboniferous Dwyka Group and Vryheid Formation of the Karoo. Sequence in the Highveld Coalfield are analysed to determine the depositional systems operative during sedimentation. The investigation involves the processing of "629" borehole cores and logs in an area of 860km2.[Abbreviated Abstract. Open document to view full version] / AC2017