No description available.

The prime challenge to those responsible for the management of South Africa’s estuaries is to maintain their viability in the face of ever increasing pressures. It is important that we learn to appreciate the value of estuaries and that we act wisely to manage them for sustainable use. Any operation must have the adequate resources to perform the duties and the correct processes must be followed. The purpose of this research is to determine whether the current inputs and processes needed for the monitoring and breaching of the Great Brak River Mouth system are sufficient to adhere to the output objectives of a healthy estuary together with safeguarding of properties. The research methodology for this study comprised the following steps: Firstly, a literature study was performed to identify the key elements of the operation management transformation model. Operations management deals with the output of any business, in other words the conversion of inputs to create certain outputs and they do this by a process of transformation. Secondly, extensive literature study was performed in order to access material regarding effective estuary and river mouth management. Thirdly, the current situation at Great Brak was assessed to determine whether the current inputs and processes are in place and if additional or altered inputs and processes are needed.

The stream pollution survey has become in the past decade a standard activity in the field of Sanitary Engineering. Both industry and municipality are now making wide use of the survey as one of the first steps in the determination of waste treatment requirements. / Master of Science

The planning and management of coastal and river structures such as breakwaters, groynes, jetties, bridges and tidal inlets require accurate predictions of equilibrium morphologies. Generally these types of situations are modelled numerically using process - based models, where wave, current and sediment transport modules are applied over a number of time - steps until a steady - state morphology is obtained. Two alternative methods have been developed and applied in this thesis, based on self - organisation and entropy approaches. The self - organisation - based method utilises a cellular automata model, where local rules produce a global stable pattern through positive and negative feedback. The entropy - based method is able to predict equilibrium morphologies directly. It compares different randomly generated morphologies using an objective function and optimisation, instead of moving to an equilibrium morphology through intermediate states. This avoids some potential problems associated with traditional models such as error propagation and reliance on accurate initial conditions. The models developed in this thesis have been applied to a number of case studies. It was found that the cellular automata model obtained a higher Brier Skill Score than a comparable process - based model when predicting the equilibrium morphology associated with a channel obstruction. The entropy - based method was able to predict a realistic erosional channel in a coastal lagoon, similar to field observations at the Murray River Mouth in South Australia. It had difficulties predicting the deposition pattern due to the bias of the objective function towards erosional environments. The entropy - based method outperformed a conventional model prediction of the equilibrium erosional channel associated with a laboratory - sized lagoon, but similar problems were observed with its deposition predictive ability. The modelling methods developed in this thesis are a first step into the use of non - traditional, entropy - and self - organisation - based models for the prediction of complex equilibrium morphologies. They have made use of non - conventional models in order to explore different objective function formulations or self - organisation rules and the sensitivity of these, and have compared the models to laboratory results. The work documented in this dissertation shows that it is possible to use self - organisation - and entropy - based modelling methods to predict stable, equilibrium morphologies in coastal and river environments. / Thesis (Ph.D.)--School of Civil and Environmental Engineering, 2006.

Seven streams, one of them permanent, were studied in western Oregon, USA. The research was designed to assess the value of summer-dry headwaters for conservation oriented landscape management. Streams were categorized primarily according to exposure (forest versus meadow sites) and secondarily according to flow duration (ephemeral = short-flow versus temporary = long-flow sites). Ephemeral streams have discontinuous flow and last less than three months annually. Temporary streams have continuous flow for more than five months each season. Ephemeral forest streams were highly efficient at filtering road-generated sediment. Uptake lengths for suspended sediment were short (36 m-105 m) at moderately elevated input concentrations. As a result of the filtration mechanism, filtration efficiency is expected to increase as annual flow duration decreases. Injection experiments yielded nitrate uptake rates of almost 1% per m of temporary stream channel. Exchange with subsurface flow was the most important route for nitrate removal from the water column. Biological uptake was insignificant in a light-limited forest stream, whereas a considerable amount of nitrate was retained by the biota a nutrient-limited meadow channel. At least 207 insect species were collected from the summer-dry streams. Species richness recorded from temporary forest streams exceeded that in an adjacent permanent headwater and there was high overlap between the fauna of the permanent and the temporary streams. Species richness in ephemeral channels was only 1/4 to 1/3 of that in long-flow forest streams. Multivariate analysis of community structure revealed flow duration and microhabitat pattern (riffle-pool) as the most important environmental factors determining faunal composition in temporary forest streams. Summer drought conditions at the sample sites also were important. By providing habitat and contributing to water quality in permanent downstream reaches, summer-dry streams have the potential to serve multiple purposes in conservation management. Their value from a conservation perspective is unexpectedly high. Landscape management therefore should be directed toward the preservation and protection of ephemeral and temporary streams. / Graduation date: 1993

Thesis (MS)--University of Montana, 2009. / Title from author supplied metadata. Includes bibliographical references.

Thesis (M.S.)--State University of New York at Binghamton, Department of Geological Sciences and Environmental Studies, 2009. / Includes bibliographical references.

Thesis (M. Sc.)--University of Hong Kong, 1998. / Includes bibliographical references (leaf 94-97).

Abstract In this thesis, I studied spatial and temporal variability of macroinvertebrate assemblages of boreal streams. The main objectives were (i) to characterize macroinvertebrate assemblage types across large geographical extents, and to assess the utility of assemblage types and landscape and stream type classifications as the basis of stream bioassessment and conservation programs (ii, iii). I also examined the relative roles of large-scale spatial trends and local environmental conditions in structuring macroinvertebrate assemblages (iv). Finally, I assessed (v) if assemblage classifications produce temporally stable and predictable assemblage types. Stream macroinvertebrate assemblage structure exhibited continuous variation instead of distinct assemblage types. Although ecoregions clearly accounted for a considerable amount of variation of macroinvertebrate assemblage characteristics, a combination of regional stratification and prediction from environmental factors would probably yield the most comprehensive framework for the characterizations of macroinvertebrate assemblages of boreal headwater streams. Differences in macroinvertebrate assemblage structure, as well as a group of effective indicator species for different stream types, suggest that landscape classifications could be used as a preliminary scheme for the conservation planning of running waters The strength of the relationship between assemblage structure and local environmental variables increased with decreasing extent, whereas assemblage variation related to spatially variables showed the opposite pattern. At the largest scale, spatial variation was related to latitudinal gradients, while spatial autocorrelation among neighbouring streams was the likely mechanism creating spatial structure within drainage systems. These results suggest that stream bioassessment should give due attention to spatial structuring of stream assemblage composition, considering that important assemblage gradients may not only be related to local environmental factors, but also to biogeographical constraints and neighbourhood dispersal processes. The classification strengths of macroinvertebrate assemblages based on data of three years were overall rather weak, and more importantly, the compositions of the site groups varied considerably from year to year. Such wide and continuous variation was also mirrored by low and inconsistent predictability of classifications from environmental variables. The observed level of temporal variation in assemblage structure may not be a serious problem for predictive approaches frequently used in bioassessment of freshwater ecosystems. For conservation purposes, however, alternative approaches (e.g. physical surrogates of biodiversity) need to be considered.

This report presents a study of the various mechanisms that may cause erosion of streambanks and the corresponding mitigation techniques used to combat them. The determination of each may depend upon a number of considerations. The source of the information comes from a variety of reports and papers, which are referenced in the text. Of all the mitigation techniques available to prevent streambank erosion, fabrics will generally offer the most cost effective method. Fabrics have had a good service record since their inception approximately 20 years ago. Further, as the technology continues to advance, it seems likely that fabric applications in this area will only increase. However, there are some concerns that need to be addressed. These include, assessment of geotextile performance in long term use under the different forces it will be subjected to, clogging potential of fabrics for various soil distributions, and the type of fabrics, woven or nonwoven, used in these applications. These factors should become more clearly defined as long term case study data becomes available. / M. Eng.