This research experimentally shows the effect of sediment roughness characteristics on the acoustic reflection coefficient. This information is useful when trying to classify various types of sediment over an area. This research was conducted in an indoor laboratory tank at Applied Research Laboratories (ARL) at the University of Texas at Austin. A single beam echo-sounder (SBES) system was developed to project and receive a wideband (3 kHz to 30 kHz) acoustic pulse. A method was developed using the system transfer function to create a custom pulse that would minimize the dynamic range over the wide frequency band. A matched filtering and data processing algorithm was developed to analyze data over the full frequency bandwidth and over smaller frequency bands. Analysis over the smaller frequency bands showed the effect of the roughness on the reflection coefficient with respect to frequency. It was found that the reflection coefficient is significantly lower at the higher frequencies (above 20 kHz) than at the lower frequenices [sic] due to off specular scattering. It was also found that the variability of the reflection coefficient was significantly higher for the rough sediment than for the smooth sediment. / text

This thesis investigates how benthic fluxes of phosphorus (P), nitrogen (N), and silicon (Si) change upon oxygenation of anoxic soft bottoms in the brackish, eutrophicated Baltic Sea. Direct measurements in situ by benthic landers demonstrated that fluxes of dissolved inorganic P (DIP) from anoxic bottom sediments in the Eastern Gotland Basin are higher than previously thought (Paper I). It is argued that the benthic DIP flux has a much larger influence on the DIP inventory in the Baltic proper than the external sources. Similarly, benthic fluxes of DIP and dissolved inorganic N (DIN) from anoxic sediment in the coastal Kanholmsfjärden Basin, Stockholm archipelago, were sufficiently high to renew the pools of these nutrients below the upper mixed layer in roughly one year (Paper II). A natural inflow of oxygen rich water into the deep, and previously long-term anoxic part of Kanholmsfjärden Basin, increased the P content in the sediment by 65% and lowered DIP and dissolved silica (DSi) concentrations in the pore water. These changes, as well as the large increases in benthic effluxes of these solutes following de-oxygenation of the bottom water, suggest that they are influenced similarly by changing oxygen conditions. Experimental results in papers III and IV show that common benthic macrofauna species in the Baltic Sea can stimulate benthic release of DIN and DSi, as well as dissolved organic and particulate bound nutrients. Thus, if benthic oxygen conditions would improve in the Baltic, initial effects on benthic–pelagic nutrient coupling will change due to animal colonisation of currently azoic soft bottoms. A new box corer was designed (Paper V) which can be used to obtain highly needed virtually undisturbed samples from soft bottom sediments – if lowered slowly and straight into the bottom strata – as demonstrated by in situ videography and turbidimetry. The commonly used USNEL box corer caused severe biasing during sediment collection. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript.</p> / Baltic oxygenation project

Bedload transport studies are essential in the understanding of river forms, functions and processes. These studies have been done using various methods over the past century. In recent years Radio Frequency Identification Technology (RFID) has become popular with researchers to track bedload particles. However, no standard operating procedures are used in the implementation of this technology. Methods used for tagging, seeding and tracking RFID tracers (RFID transponders inserted into a bedload particle) can introduce variability in their detection. In this study, RFID tracers were used to study four sites in Laurel Creek in Waterloo, Ontario. Two hundred RFID tracers were seeded in each of the four sites. Following three major storm events, the tracers were tracked with an antenna and their locations surveyed. The tracers were able to be detected to a precision of 1 m as a transponder used can be detected at a maximum of this distance. Practical tracking in the field highlighted the need for the understanding of how precisely the tag location can be identified. Laboratory experiments were designed and carried out to determine the effects of factors (tracer orientation, antenna orientation, tracer size, clustering of multiple tracers, burial depth, saturation and submergence of the soil matrix) that possibly confounded detection. Of these factors, tracer orientation, clustering and burial depths were determined to be the ones that affected detection distances the most. A transponder in a vertical orientation was found to have as much as 40% larger range of detection than a transponder in a horizontal orientation (i.e., they could be detected from further away). Additionally, “skip zones” were identified during laboratory and field experiments. These are zones of gaps in the electromagnetic field of the transponder that occur directly over the transponder. These zones were experimentally determined to extend to approximately 10 cm on each side of the transponder. Therefore, by identifying the skip zones, the tracers can be located to a precision of 10 cm; this is an order of magnitude smaller than the published detection limit of the transponder. The precision of detection can also be improved by the reduction of the effects of confounding factors. However, the improvement in the precision of detection is a tradeoff with the ease of detection. A tagging, seeding and tracking protocol is recommended to counter the effects of confounding factors.

The Tibbitt-to-Contwoyto Winter Ice Road (TCWR) is the sole overland route servicing diamond mines north of Yellowknife, Northwest Territories (NWT), Canada. The road is 568 km long, 85% of which extends over frozen lakes. As such, its operational season is highly dependent upon the length of the winter season. This was exemplified in 2006, when an El Niño event caused an unusually short ice road season and resulted in a costly reduction of shipments to the mines. For future use and development of the TCWR, a comprehensive understanding of past regional climate variability is required. This study is an integral component of a larger-scale study designed to develop a comprehensive database of high-resolution paleoclimate data for the NWT, using a variety of proxies. As part of the larger study, freeze cores were taken from numerous lakes along the TCWR and sliced at 1-mm intervals using a custom-designed sledge microtome. Bulk 13C and 15N isotope analysis was completed at preliminary 1-cm intervals through the cores of two lakes on opposite sides of the tree line. Results from this analysis show clear trends with distinct transitions in both cores, whose closely-matched timing suggests regional-scale climate events. These results indicate that the Early Holocene was warm and dry, with a sudden shift to wetter conditions around 7200-6900 cal yr BP. Another shift to cooler conditions occurred at 4000 cal yr BP, and a final transition to even cooler temperatures occurred around 755-715 cal yr BP, coinciding with the Little Ice Age. Additionally, a modern lake survey was completed using surface sediments of numerous lakes throughout the Arctic and Subarctic. This survey verifies the strong influence of boreal forest vs. tundra conditions in affecting various environmental properties within lakes, including carbon and nitrogen isotopes. Lastly, time-series analysis was completed on two sections of Danny’s Lake core at high resolution (up to 2 mm), in order to determine short-term climate cycles. These results highlight specific climate frequencies which may be related to the Pacific Decadal Oscillation. These results offer insight to short-term climate phenomena in the Northwest Territories which will allow future climate modellers to make more accurate predictions of future climate and its impact on the ice road.

There are only a few detailed measurements of the cross-shore variation in the net sediment transport and beach evolution for single or multiple swash events, and no data showing the influence of long waves and wave groups on swash zone morphology. Novel laboratory experiments and numerical modeling have been performed to study the influence of long waves and bichromatic wave groups on sediment transport and beach morphodynamics in the swash zone. Due to complex processes, difficulties in measuring, and very significant difficulties in isolating the morphodynamic processes induced by long waves and wave groups on natural beaches, a laboratory study was designed to measure in very high detail the bathymetric evolution of model sand beaches under monochromatic waves, long wave and short wave composites (free long waves), and bichromatic wave groups (forced long waves). Net sediment transport, Q(x), and beach morphology changes under the monochromatic waves were analyzed and compared to conditions with and without the free long waves, and then compared with the bichromatic wave groups. A range of wave conditions, e.g., high energy, moderate energy, and low energy waves, were used to obtain beach evolution ranging from accretionary to erosive, and including intermediate beach states. Hydrodynamics parameters, e.g., instantaneous water depths, wave amplitudes, run-up and rundown, were also measured to study and test a sediment transport model for the swash zone, based on modifying the energetic-bedload based sediment transport equations with suspended sediment. The experimental data clearly demonstrate that for the monochromatic wave conditions, beach evolution develops erosion for high steepness waves and accretion for lower steepness waves. The model beach profile evolutions are similar to natural beaches, and form and develop bars and berms over time. Adding a free long wave to the short wave in the composite wave results in changes to the overall trend of erosion/accretion of the beach profile, but the net transport pattern does not change significantly. The short wave strongly dominates beach behavior and the net transport rate, instead of the free long wave in the composite wave. The free long wave, however, carries more water and sediment onshore, leading to an increase in shoreline motion and wave run-up further landward. The long wave influences the structure and position of the swash bar/berm, which generally tends to move onshore and forms a larger swash bar/berm for higher long wave amplitudes. The free long wave also increases overall onshore sediment transport, and reduces offshore transport for erosive conditions. The long wave tends to protect the beach face and enhances onshore transport for accretive conditions, especially in the swash zone. In contrast, for bichromatic wave groups having the same mean energy flux as their corresponding monochromatic wave, the influence on sediment transports is generally offshore in both the surf and swash zone instead of onshore. The swash berm is, however, formed further landward compared with the berm of the corresponding monochromatic wave. The sediment transport patterns (erosion or accretion) generated by the bichromatic wave group or corresponding monochromatic wave are similar, but differ in magnitude. The numerical model, starting in the inner surf zone to reduce the effect of poor breaker description in the non-linear shallow water equations, can produce a good match between observed data and the modeled hydrodynamics parameters in the SZ. The sediment transport model shows the important role of suspended sediment in the swash zone. In contrast with the observed data, energetic-based bed-load models predict offshore sediment transport for most wave conditions because of negative skewness. The modified sediment transport model, with added suspended sediment terms and optimized coefficients, produces a good match between model results and observed data for each wave condition, especially for low frequency monochromatic waves. The optimized coefficient set corresponding to particular monochromatic wave conditions can be used to predict the net sediment transport quite well for some composite wave conditions. Overall, the same optimized coefficient sets can be applied to predict the correct overall trend of net transport for most composite wave conditions. However, the predicted net transport for the bichromatic wave groups does not match well with the overall net transport patterns. There is no set of single transport coefficients that can be used to predict sediment transport for all wave conditions. This suggests that the present sediment transport models cannot predict evolution correctly, even for conditions which represent only perturbation from those for which they were calibrated.

There are only a few detailed measurements of the cross-shore variation in the net sediment transport and beach evolution for single or multiple swash events, and no data showing the influence of long waves and wave groups on swash zone morphology. Novel laboratory experiments and numerical modeling have been performed to study the influence of long waves and bichromatic wave groups on sediment transport and beach morphodynamics in the swash zone. Due to complex processes, difficulties in measuring, and very significant difficulties in isolating the morphodynamic processes induced by long waves and wave groups on natural beaches, a laboratory study was designed to measure in very high detail the bathymetric evolution of model sand beaches under monochromatic waves, long wave and short wave composites (free long waves), and bichromatic wave groups (forced long waves). Net sediment transport, Q(x), and beach morphology changes under the monochromatic waves were analyzed and compared to conditions with and without the free long waves, and then compared with the bichromatic wave groups. A range of wave conditions, e.g., high energy, moderate energy, and low energy waves, were used to obtain beach evolution ranging from accretionary to erosive, and including intermediate beach states. Hydrodynamics parameters, e.g., instantaneous water depths, wave amplitudes, run-up and rundown, were also measured to study and test a sediment transport model for the swash zone, based on modifying the energetic-bedload based sediment transport equations with suspended sediment. The experimental data clearly demonstrate that for the monochromatic wave conditions, beach evolution develops erosion for high steepness waves and accretion for lower steepness waves. The model beach profile evolutions are similar to natural beaches, and form and develop bars and berms over time. Adding a free long wave to the short wave in the composite wave results in changes to the overall trend of erosion/accretion of the beach profile, but the net transport pattern does not change significantly. The short wave strongly dominates beach behavior and the net transport rate, instead of the free long wave in the composite wave. The free long wave, however, carries more water and sediment onshore, leading to an increase in shoreline motion and wave run-up further landward. The long wave influences the structure and position of the swash bar/berm, which generally tends to move onshore and forms a larger swash bar/berm for higher long wave amplitudes. The free long wave also increases overall onshore sediment transport, and reduces offshore transport for erosive conditions. The long wave tends to protect the beach face and enhances onshore transport for accretive conditions, especially in the swash zone. In contrast, for bichromatic wave groups having the same mean energy flux as their corresponding monochromatic wave, the influence on sediment transports is generally offshore in both the surf and swash zone instead of onshore. The swash berm is, however, formed further landward compared with the berm of the corresponding monochromatic wave. The sediment transport patterns (erosion or accretion) generated by the bichromatic wave group or corresponding monochromatic wave are similar, but differ in magnitude. The numerical model, starting in the inner surf zone to reduce the effect of poor breaker description in the non-linear shallow water equations, can produce a good match between observed data and the modeled hydrodynamics parameters in the SZ. The sediment transport model shows the important role of suspended sediment in the swash zone. In contrast with the observed data, energetic-based bed-load models predict offshore sediment transport for most wave conditions because of negative skewness. The modified sediment transport model, with added suspended sediment terms and optimized coefficients, produces a good match between model results and observed data for each wave condition, especially for low frequency monochromatic waves. The optimized coefficient set corresponding to particular monochromatic wave conditions can be used to predict the net sediment transport quite well for some composite wave conditions. Overall, the same optimized coefficient sets can be applied to predict the correct overall trend of net transport for most composite wave conditions. However, the predicted net transport for the bichromatic wave groups does not match well with the overall net transport patterns. There is no set of single transport coefficients that can be used to predict sediment transport for all wave conditions. This suggests that the present sediment transport models cannot predict evolution correctly, even for conditions which represent only perturbation from those for which they were calibrated.

Thesis (Ph.D.). / Written for the Dept. of Natural Resource Sciences, Macdonald College of McGill University. Title from title page of PDF (viewed 2008/07/24). Includes bibliographical references.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 91-98). Also available via the Internet.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [122]-141).

Thesis (M.S.)--University of North Carolina Wilmington, 2008. / Title from PDF title page (viewed September 22, 2008) Includes bibliographical references (p. 60-62)