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No description available.

The Brazos River, located predominantly within the state of Texas, has the highest water and sediment discharge of all rivers in the state, and ranks second behind the Mississippi River in terms of sediment load delivered to the Gulf of Mexico. This river is the only Texas river that consistently drains directly into the Gulf of Mexico forming a wave-dominated delta. The delta has experienced dramatic and rapid changes over the last 100-plus years. These changes have resulted from both natural and anthropogenic alterations to the coastal zone proximal to the river mouth and within the rivers watershed. By utilizing high-resolution geophysical data, sediment cores, water column data, and historic shoreline data this study investigated the mechanisms in which sediment is transported to the coastal ocean, the fate of that sediment as it becomes preserved in the modern geological record, and the evolution of a modern delta. Results from this study show that during for a majority of the time a salt-water intrusion in the lower river traps sediment, preventing export to the coastal ocean. The trapped sediment forms an ephemeral mud layer in the lower river that may be remobilized during increased river discharges. When river discharges increase above an observed threshold of 300 m^3/s the salt wedge is pushed seaward of the river mouth and sediment is exported via a buoyant plume. As export of sediment is episodic, accumulation of sediment on the subaqueous delta characterized as non steady-state, and resembles typical foreset delta attributes. These include physical stratification of sediment layers, episodic but relatively high rates of accumulation, and little bioturbation. Currently sediment is primarily accumulating west of the river mouth, and the majority of sediment is bypassing the system. Over the history of the delta, changes both anthropogenic and natural have shifted the relative balance of fluvial sediment supply and marine sediment dispersal. These changes have resulted in dramatic changes in the shoreline, and phases of activation and abandonment of deltaic lobes, which can be seen through historical data and imagery, and is preserved in the recent sedimentary record.

No description available.

No description available.

This study combined sedimentation, sediment chemistry and benthic community data from three Oncorhynchus mykiss cage farms in Ontario, along with a laboratory bioassay to examine the effects of aquaculture waste loading. Waste loading rates, as well as sediment TC, TN, TP and metal (Cu, Zn) concentrations were highest beneath the cage and decreased exponentially with distance. During the 21-day bioassay, Tubifex (Oligochaeta, Naididae), Chironomus (Diptera, Chironomidae) and Sphaerium (Bivalvia, Pisidiidae) were subjected to a gradient of waste loading. Survival and growth of Sphaerium simile was highest at intermediate levels of waste loading. Chironomus riparius growth increased with increasing waste addition. Tubifex tubifex growth increased with exposure to fish waste, compared with the control. Until this study, there were no predictions for thresholds of effect at freshwater cage farms in the literature. The proposed threshold of effect on freshwater benthos is 2.0 - 3.0 g C m-2 day-1.

In recent years, the study of rock glaciers has increased remarkably. Substantive progress has been made, particularly in understanding the formation of rock glaciers that have developed adjacent to existing or former valley or cirque glaciers, However, our understanding of valley-wall rock glaciers that are located at the base of talus slopes remains scant. Published work exhibits little consensus on the formation of valley-wall rock glaciers and several hypotheses remain under vigorous debate. The major objective of the research reported in this thesis has been to test the generality and feasibility of seven major models of valley-wall rock glacier formation using both empirical and theoretical evidence. The primary conclusion is that only one of these models, the segregation ice model, emerges as a general model of valley-wall rock glacier genesis. The model assumes that a thin layer or several thin layers of segregated ice are overlain by interstitially frozen sediments and an unfrozen mantle of coarse debris. A wide range of empirical and theoretical findings are shown to be consistent with the implications of the segregation ice model. Detailed observations on the morphology, sedimentology and distribution of active, inactive and relict valley-wall rock glaciers studied in Switzerland, northern Norway and Scotland provided a range of findings that support this model. Theoretical evidence was obtained by modelling a number of different density models that reflect different distribution of internal ice by applying a simple laminar flow equation to field measurements. Although only the segregation ice model appears to be valid at a general level, the possibility cannot be excluded of alternative modes of valley-wall rock glacier formation under particular circumstances. Snow avalanching, deformation of snowbank or matrix ice, and basal sliding under conditions of high hydrostatic pressure all constitute possible contributing mechanisms of formation and movement in particular cases.

A variety of moraine forms were deposited by glaciers during the Loch Lomond Stadial. Study of such moraines and related landforms provides a valuable source of data on patterns of landscape evolution and climatic change. This thesis presents detailed case-studies of moraines in geologically and topographically contrasting areas on the Island of Skye, Scotland. Geomorphological mapping, sedimentological analyses and mathematical modelling techniques were employed to determine the principal controls on moraine morphology, composition and distribution. Particular emphasis was placed on the provenance, transport and deposition of debris, and their spatial variation. The results were used to construct a summary model of glacial landform evolution, which relates different sediment-landform associations to spatial and temporal controls, particularly basin lithology and structure, topography, position of deposition and ice-margin activity. The initial stage of deglaciation in the study area was marked by a series of readvances and/or stillstands. During this stage, the lower-lying glaciers were more sensitive to climatic amelioration than the higher glaciers. The subsequent phase was characterised by more rapid deglaciation. Evidence for one instance of late-stage in situ glacier stagnation is described. The results indicate that landforms hitherto grouped as 'hummocky -moraine' formed by a variety of processes. Such moraines formed by (a) uneven deposition of supraglacially and/or -subglacially-derived debris at active ice margins, (b) deposition at the stagnant margins of otherwise active glaciers, and (c) deposition during uninterrupted glacier retreat or areal stagnation. Differentiation and analysis of so-called 'hummocky moraine' enables glacier behaviour, during the Lateglacial to be interpreted in great detail.

This study combined sedimentation, sediment chemistry and benthic community data from three Oncorhynchus mykiss cage farms in Ontario, along with a laboratory bioassay to examine the effects of aquaculture waste loading. Waste loading rates, as well as sediment TC, TN, TP and metal (Cu, Zn) concentrations were highest beneath the cage and decreased exponentially with distance. During the 21-day bioassay, Tubifex (Oligochaeta, Naididae), Chironomus (Diptera, Chironomidae) and Sphaerium (Bivalvia, Pisidiidae) were subjected to a gradient of waste loading. Survival and growth of Sphaerium simile was highest at intermediate levels of waste loading. Chironomus riparius growth increased with increasing waste addition. Tubifex tubifex growth increased with exposure to fish waste, compared with the control. Until this study, there were no predictions for thresholds of effect at freshwater cage farms in the literature. The proposed threshold of effect on freshwater benthos is 2.0 - 3.0 g C m-2 day-1.

For certain shellfish species, a mechanical harvester has the potential to greatly reduce harvesting costs. Traditionally, hand rakes are used in shellfish harvesting in British Columbia. In order to determine if it is environmentally feasible to use a mechanical harvester, an environmental assessment on mechanical harvesting and traditional harvesting needs to occur for comparison. In July 2008, a preliminary oceanographic assessment was conducted at three study sites in Baynes Sound. Each of the three study sites contained a mechanical and manual harvest plot and reference stations. Sampling stations were established at fixed positions within each plot and at four positions along a downstream transect (following the dominant current direction.) Surveys were conducted 24 hours pre-harvest, immediately post-harvest, and 24 hours post-harvest. Parameters included in situ sediment sulphides, eH (REDOX), sediment grain size (SGS), visual condition (digital imagery), sedimentation (silt flux) and sediment macro-fauna. Results show only localized environmental effects associated with each harvest approach; with no significant difference documented between the manual and mechanical harvesting methods on the study beaches. These results indicate the use of a mechanical shellfish harvester is as environmentally sound as the traditional method of hand harvesting, and poses no additional environmental risks. Introducing mechanization in shellfish harvesting will allow shellfish producers to reduce costs and increase profits, making the British Columbian shellfish industry more competitive with other suppliers. / Graduate