Braided channels arise due to high sediment availability in conjunction with regular competent flows and readily erodible banks. Together, these boundary conditions lead to the deposition and reworking of a network of transient bars that characterize the braided planform. However, quantifying the geomorphic response of braided systems to alterations in these boundary conditions is not straightforward, as channels adjust over a wide range of timescales, rendering traditional field-based observation intractable. As such, the development of simple yet robust relationships between channel morphology and sediment transport has the potential to allow predictions of channel response to altered hydrologic or sediment regimes. In this research, I first use laboratory flume experiments to relate particle travel distance during floods (termed particle path length) and the spacing of channel bars in braided rivers (Chapter 2), finding that deposition sites for sediment in transport can be readily predicted by the characteristic confluence-diffluence spacing in a reach. I then use the relationship between path length and channel morphology to build a simple, open-source morphodynamic model for braided rivers that computes sediment transport using path-length distributions derived from bar spacing (Chapter 3). I explore the validity of this model, specifically noting that its modular framework allows exploration of process representations in morphodynamic modeling in ways existing models do not. Finally, I employ the model to determine the role of sediment supply in braided channel bar morphodynamics (Chapter 4). Specifically, I address the relative roles of sediment sourced from upstream versus sediment sourced from within a braided reach in terms of channel morphodynamics at decadal timescales. This research demonstrates that simple scaling relationships, while necessarily imperfect, nevertheless provide insight into morphodynamic processes in braided rivers, while also allowing predictions of channel response to sediment or hydrologic forcing at the timescales of channel adjustment.

No description available.

The Koongarra uranium deposit is hosted by quartz-chlorite schists. A conceptual model for the hydrogeology of the deposit is proposed on the basis of lithologic criteria and limited hydraulic testing. Water-level and aquifer-test data are presented that indicate the deposit lies within a partially confined, heterogeneous, anisotropic fractured-rock aquifer. The aquifer is dynamic with annual, diurnal, and semidiurnal water-level fluctuations. The results of aquifer tests indicate a high degree of connectivity in the aquifer. Fracture-dominated flow is observed in some tests, but the overall aquifer response appears to be that of an equivalent porous medium. A homogeneous, anisotropic model is used to estimate the transmissivity tensor for subregions of the aquifer. Anisotropy is well-developed with north- to east-northeast-oriented principal transmissivities. Northeast directions represent large-scale drawdown patterns and are subparallel to bedrock structure and the Koongarra fault. Northerly directions are localized and may reflect a less extensive fracture fabric or a flexure in the bedrock foliation.

No description available.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

No description available.

This document is aimed at all parties involved with conservation, planning and management of rivers within the Greater Durban Metropolitan Area, South Africa. The intentions of this study were to provide information on the health of the rivers using freshwater invertebrates and to identify areas where investigative efforts should be focused. In doing so, this document incorporates two data processing methods or techniques used in biomonitoring, the South African Scoring System (SASS) Rapid Bioassessment Technique (RBA) version 4 and the Integrated Habitat Assessment System (IHAS version 2c). The history, current status and future prospects and potential benefits of biological indicators both globally and in South Africa are reviewed and discussed. The RBA (SASS4) involved the standardised collection of samples using the "kick and sweep" technique from defined habitat types at representative sites on river stretches using a standardised net following defined methods. The total score per site is calculated for each family represented in the sample, which is then summed to give the SASS4 score. Lower scores are given to families with a high level of tolerance for polluted waters. The Average Score Per Taxon (ASPT) computation is obtained by dividing the SASS4 total by the number of taxa (families) in the sample. Both scores were considered when determining water quality impairment. The number and abundance of the different taxa and the number of biotopes present were considered as other measures of the river condition. The presence of numerous families of highly tolerant organisms (sludge worms and leeches) usually indicated poor water quality as represented in the Umlaas River, iSiphingo River, Tongati River, and the Ohlanga River. Several different types (or taxa) of stoneflies, mayflies and caddisflies (higher biodiversity) indicated a healthy site for example the iLovu River. Moderate river sites were characterized by declination in invertebrate diversity. Invertebrate diversity declines as the degradation of water quality increases. The manner in which SASS4 scores varied with "degree of anthropogenic impact" showed that the assessment does yield results, which follow water quality changes, provided that when SASS4 scores are less than 50, little attention is given to ASPT. At intermediate and high impacted sites ASPT did not follow habitat quality. However at low impacted water quality sites both SASS and ASPT tended to be greatest where habitat quality was the best. This study has identified that water quality "appears" to have a greater effect on macro invertebrate communities than the physical habitat and SASS distinguished sites with differing levels of water quality. This method was not designed to enable the exact nature of the disturbance to be determined, and it was intended that once an impairment of water quality had been established, it would be further assessed via intensive chemical and other studies. The use of more ecological indicators for example the inclusion of IHAS (version 2c) allowed a more comprehensive assessment of river health and more confidence could be linked to the outcome. / Thesis (M.Sc.Eng.)-University of Durban-Westville, 2002.

Presently within the scientific literature no terrestrial biogenic silica models exist that compare by magnitude, processes transporting silica. Change in vegetation type has the potential to alter dissolved concentrations of Si in rivers and ultimately the oceans. Diatoms greatly depend on Si concentrations for growth, and as a result land cover change may have influenced onset diatom radiation during the Cenozoic. To expand our understanding of this cycle, a terrestrial biogenic silica model is proposed. This model accounts for biogenic silica production, dissolution and leaching through soils, as well as providing estimates for annual silica soil storage. A case study performed using the constructed biogenic silica model, showed an increase in oceanic DSi concentration during the Miocene (period of diatom diversification). However, this increase does not appear to have been sufficient to trigger global diatom radiation, suggesting multiple geographically isolated locations for this diversification.

This dissertation is an analysis of the Quaternary fluvial history of central Northamptonshire. It uses new freshwater ostracod data which are interpreted using information on Quaternary and present day habitats and examines in detail associated patterns of environmental change in coarse sediments from which the ostracods were extracted. Stratigraphic, lithological and sedimentological data, supported by a study of geological maps, borehole logs and papers, are employed to produce a new hypothesis to explain the Quatemary development of the Milton River and the River Nene. The alignment of the Milton Formation Valley is established to have proceeded to the east of, but parallel with, the Nene Valley between Northampton and Higham Ferrers, where it turned to the south-east. It comprises locally derived deposits which are shown to be pre-Anglian Glaciation and, at the time of the deposition of the ostracods studied here, an interglacial environment prevailed. However, during a ‘cooling phase”, Milton Formation sediments were incised and the channel became partially infilled with fossiliferous boreal sediments. Further sedimentation continued to produce a non-fossiliferous, periglacial sand, which is typical of the Milton Formation. It is argued that this period of deposition was followed by two glacial episodes, the latter relating to the Lowestoft Formation. Stratigraphic, sedimentological and lithological evidence from the Nene valley shows vestigial terrace gravels exist between Northampton and Wellingborough. The oldest gravels of these features pre-date the Anglian age, sub-glacial tunnel valley” at Northampton, implying the Nene Valley existed prior to glaciation. Before glaciation it is suggested that the Milton River became confluent with the Nene at Northampton and, concurrently, diverted to the north-east at Higham Ferrers. This is believed to be associated with the simultaneous abandonment of the Milton Valley to the south-east of Higham Ferrers and the upstream stretch at Northampton. Evidence presented of downcutting, lateral migration, gravel reworking and changes in the ostracod assemblages in the Nene Valley confirm a history of several climatic oscillations which took place in the pre-Devensian, Devensian and Holocene. These oscillations are tentatively correlated with stages of deposition in the Nene established downstream at Peterborough. This revised fluvial history elaborates the course and age of the Milton River and establishes a pre-Devensian age for much of the Nene Valley sediment. The significance of this new understanding of the upper Nene Valley has been compared with that of the lower Nene Valley at Peterborough, Cambridgeshire. The combined evidence is used to produce a pattern of river development within the Quaternary which may be used as a model when reconstructing the palaeogeography of other rivers and their floodplains by means of their sedimentary structures and related fossils. This idea is explored to a small extent in the thesis, but is more applicable to future work. The new ostracod data throws new light on previous studies from other sites in England. Ostracod species new to the Pleistocene record are to be added to a worldwide data base

The Barren River was sampled twice monthly for one year to obtain data on aquatic yeasts. Sites upstream and downstream of the Bowling Green sewage plant, as well as the sewage effluent, were sampled to ascertain if the effluent had any effect on the yeast population of the river. Sporadic yeast counts were obtained which averaged 40 CFU/ml for the effluent, while the river averaged 15 CFU/ml. A total of 318 yeasts were isolated and identified during the study, including 16 different genera with Cryptococcus being the most common. Cryptococcus laurentii occurred most frequently of the 67 different species identified. The sewage effluent was not found to contribute significantly, either in number or in particular species, to the river yeast flora, although the effluent flora differed from the yeast flora in the river. Statistical analysis suggested relationships between yeast counts and several environmental parameters, particularly chlorine, turbidity, nitrate and phosphate levels. Some yeast pathogens of low virulence were isolated, but the probability of the river being a vector of mycotic disease was not found to be great. No seasonal variation was noted in yeast counts. The pathogenic yeast, Candida albicans, was not isolated. Two commercial yeast identification systems were tested. Neither system could be recommended for identifying aquatic yeasts.