Thesis (M.S.)--Oregon State University, 2005. / Printout. Includes bibliographical references (leaves 45-48). Also available via the World Wide Web.

Thesis (M.S.) -- University of Tennessee, Knoxville, 2005. / Title from title page screen (viewed on July 5, 2005). Thesis advisor: John S. Schwartz. Document formatted into pages (x, 146 p. : col. ill., maps (some col.)). Vita. Includes bibliographical references (p. 84-89).

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 108-113).

Thesis (M.S.)--Oregon State University, 2004. / Typescript (photocopy). Includes bibliographical references (leaves 58-61). Also available via the World Wide Web.

Thesis (Ph.D.)--University of Washington, 1995. / Vita. Includes bibliographical references (leaves [163]-173).

Thesis (Ph. D.)--University of California, Santa Cruz, 1993. / Typescript. Includes bibliographical references (leaves 162-172).

Magister Scientiae - MSc / The primary origin of this project is due to a high demand for freshwater supply in the Berg Water Management Area (WMA). Most of the Berg WMA`s freshwater supply does not live up to the high ecological standards. This is mainly due to high sediments loading in the Berg River which is one of the water supplies to the Berg WMA. The project was conducted on a small-scale catchment at Langgewens experimental farms in Swartland district. The focus of this study was to address some of the hydrological processes active in the research catchment: infiltration, run-off and sediment mobilization on different soil types under wheat and canola vegetation cover. This was done to investigate the origin of sediments in the Berg River. Considering the results, one might conclude that the decayed root systems from the canola and wheat vegetation covers, organic matter content, soil cracks, slope orientation, and soil composition, all played a major role in influencing the ability of the soil to absorb the simulated rainfall. Because the infiltration was calculated using the difference between the incoming simulated rainfall and the measured run-off, there was an inverse relationship between run-off and infiltration. When run-off was low, the infiltration was high and vice versa. iv Factors that governed sediment mobilisation within the ring area are micro topography within the ring area, the slope gradient and vegetation covers. Considering the results, vegetation cover played a pivotal role and it must be maintained at all times. It is advisable that the land users leave crop residual cover behind after the annual harvest and not expose the land surface in bare form for too long as this will generate more run-off and increase sediment mobilisation. The analyses showed that wheat crop protects the soil from rain drop impact than on canola crop.

Erosion is a natural process that occurs when soil particles are detached from one site and transported to another by water or wind, and can occur naturally or be accelerated by humans. Sediment can cause direct mortality or reduce growth of fish and other aquatic resources, particularly larval fish and eggs. Three treatments consisting of compost and jute netting, crimped straw with native seeds, and jute netting and vegetation filter strip were used to evaluate loss of runoff water and sediment on steep slopes. Erosion plots were built on slopes of 27 percent and filled with soil. The treatments were applied in triplicate and irrigated at 14-day intervals. Each erosion plot was irrigated with approximately 79 gallons of water for 10 hours and runoff was collected in pre-weighed containers during each period. After each collection, runoff from each plot was measured and recorded by subtracting the weight of each empty container from the combined weight of water and sediment. Turbidity, pH, and electrical conductivity were measured, and the separate weights of runoff and dry sediment were determined. The combination of jute netting over a layer of commercially available compost was over 99 percent effective at reducing runoff and sediment loss as compared to the untreated control erosion plots. Jute netting combined with a vegetative filter strip of creeping wild rye was over 94 percent and 99 percent effective at reducing runoff and sediment loss when compared to the untreated control erosion plots, respectively. Runoff and sediment loss from plots treated with crimped straw and native seeds was significantly greater than that of the other treatments, yet this treatment was over still 80 percent effective at reducing runoff and nearly 97 percent effective at reducing sediment loss. The cost-effectiveness of each treatment was evaluated based on the cost of the total treatment compared to the amount of water each treatment prevented from leaving the site, using the control plots as a baseline. The combination of jute and vegetation filter strip cost approximately $0.47 per liter of water prevented from leaving the site and was almost as effective at reducing runoff and sediment loss as was jute combined with compost, which cost $1.04 per liter. While each of the three treatments significantly reduced runoff and sediment loss when compared to the barren control plots, the jute and filter strip treatment was the most cost-effective of the three treatments. All treatments were effective at decreasing runoff and sediment loss when compared to the control, though no significant difference in runoff was observed between the control and any of the treatments after ten weeks. Thus, erosion control BMPs should be implemented well before the first storm causing runoff in order to be most effective.

Although sediment is a natural component of stream ecosystems, excess sediment presents a threat to natural freshwater ecosystems. Sediment management is complicated because sediment can be dissolved in the water column, suspended as particles in the water column, or rest on the bottom of the stream bed, and can move between these forms (e.g. bedded sediment can be resuspended). Each form of sediment affects aquatic life in a specific way. To manage stream sediment in a way that protects aquatic life, we need to understand the ways different forms of sediment affect living things, and we need to be able to predict how sediment changes form under different stream conditions (for example, during high water events). To improve our understanding of these things, the studies in this dissertation set out to: (1) identify how often sediment is specifically mentioned as the primary pollutant “stressor” of the benthic macroinvertebrate community (primarily aquatic insects); (2) determine which forms of sediment have the largest negative impacts on aquatic insects in Virginia and what levels of sediment may cause harm; and (3) measure the changes of sediment between suspended and bedded forms in a small stream to provide information needed to restore the health of stream ecosystems. An inventory of published US Clean Water Act Total Maximum Daily Load (TMDL) reports, which states write to identify their impaired waters and their plans to improve those waters, revealed that sediment is an important stressor in over 70% of waters that have altered aquatic insect communities. If the language used to describe how waters are evaluated and what is causing the impairments were standardized among states, data collected under the Clean Water Act could be more broadly used to help understand water quality issues and ways to address them. Analysis of 10 years of Virginia Department of Environmental Quality sediment and aquatic insect community data collected within 5 ecoregions of the state indicates that a combination of 9 sediment parameters reflecting dissolved, suspended, and bedded forms explains between 20.2% and 76.4% of the variability in the health of the aquatic insect community within these regions. Embeddedness, which measures how much larger particles such as gravel and cobble are buried by finer particles like sand; and conductivity, which is a measure of dissolved salts in the water column, both have substantial impacts on the aquatic insect community. Sensitivity thresholds for embeddedness and conductivity indicate the levels of these parameters above which 5% of insect families are absent from a stream; therefore, these levels are considered protective of 95% of the insect community. Thresholds for embeddedness are 68% for the 5 combined ecoregions, 65% for the Mountain bioregion (comprised of Central Appalachian, Ridge and Valley, and Blue Ridge ecoregions), and 88% for the Piedmont bioregion (comprised of Northern Piedmont and Piedmont ecoregions). Thresholds for conductivity are 366 µS/cm for combined ecoregions, 391 µS/cm for the Mountain bioregion, and 136 µS/cm for the Piedmont bioregion. These thresholds can be used by water quality professionals to identify waters with sediment impairments and can be used to help identify appropriate stream restoration goals. A study of sediment movement within the channel of a small stream indicated average transport speeds of ~ 0.21 m/s during floods with peak flows of ~ 55 L/s. The use of rare earth elements (REE) to trace sediment particles revealed individual particle transport distances ranging from 0 m to >850 m. Deposition on a unit area basis was greater in the stream channel than on the floodplain, and the movement of sediment from the stream bed to the water column and back again during sequential floods was evident. Approximately 80% of the tracer was deposited within the first 66 m of the reach. This information can aid the development of models that predict the impact of stream restoration practices on in-stream habitat and improve predictions on the time it will take between the initiation of stream restoration projects and when we see improvements in the biological community. / PHD

Free-fall penetrometers (FFP) are useful instruments for the rapid characterization of seabed sediments. However, the interpretation of FFP data remains largely a skilled task. In order to increase the reliability of results obtained using these instruments, in both expert and non-expert hands, it is advantageous to establish well defined and repeatable procedures for instrument use and data interpretation. The purpose of this research was therefore to develop and refine methods for the interpretation of FFP data. Data were gathered with the FFP Nimrod during two surveys following dredging in Sydney Harbour, Nova Scotia. The challenge of interpreting the data from these two surveys in an efficient and consistent manner was the basis of this work and led to the development of new techniques for improving resolution of the mud-line, identifying areas of erosion and deposition, and qualitatively evaluating the consolidation state of cohesive marine sediments. The method developed for improving the resolution of the mud-line simply describes a procedure of combining the data from different accelerometers with different accuracies and ranges to more clearly define the point of impact with the sea-floor. The method developed to evaluate in-situ sediment consolidation state combines theories of self-weight consolidation and ultimate bearing capacity to predict a range of potential bearing capacities for normally consolidated cohesive sediments. Finally, by combining the previous two methods a third method is proposed for locating areas of potential erosion and deposition. / Master of Science