Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 174-185). Also available in electronic version. Access restricted to campus users.

This dissertation examines how turbidity currents interact with submarine channels. Turbidity currents display exaggerated super-elevation at the outer banks of channel bends, because they have low excess densities relative to the ambient sea-water. Low-velocity zones form where flows separate from the inner banks. In a high-resolution seismic volume, I mapped 226 inclined surfaces associated with bank-attached bars in 16 channel bends of 2 buried sinuous channels. Position and geometries of bars indicate construction from suspended sediment in flow separation zones. Concave-bank benches, first identified in rivers where they are built from fully-suspended sediment deposited within flow separation zones in channel bends, comprise approximately 19% of this dataset. Bars have high median slopes (10°-11°) and occupy less than 30% of channel width. Associated channels migrated a median distance of less than 70% of the channel width and incised 20-30% of the channel depth. These bars are therefore interpreted to have formed during sediment bypass or weak erosion. I have analyzed the sedimentology and stratigraphy of a well-exposed channel complex, in the Permian Brushy Canyon Formation, west Texas. A steeply-inclined set of fine-grained sandstone beds (median dip=10°) at the margin of the channel complex is interpreted as deposits of a bank-attached bar. Beds are characterized by sub- to super-critically climbing ripple-lamination, planar stratification and trough cross-stratification. Paleo-transport directions are at high angles, 20-120°, to the dip azimuths of interpreted bar surfaces. Geometries of bounding surfaces, sedimentation styles and grain-size data were used to construct a facies model for suspension-dominated, bank-attached bars, built within flow-separation zones in submarine channels. I designed physical experiments to examine how erosional turbidity currents evolve channel- bend topography. Time-lapse bathymetry maps capture the evolution of raised benches tied to sedimentation within flow separation zones and erosion outside of separation zones. Erosional currents showed sensitivity to local conditions. The pattern of erosion was connected to roughness elements such as bend curvature and scours on the bed. Turbidity current run-up at the outside of bends produced a greater aerial extent of side-wall erosion than is commonly seen in incisional rivers.

No description available.

Filter-to-waste infrastructure is now commonly incorporated in recently constructed treatment plants and is required by many jurisdictions, including the Nova Scotia Standard for Surface Water Treatment. In the absence of filter-to-waste, operational backwash procedures, such as filter resting, decreased backwash duration, and extended terminal subfluidization wash (ETSW), have shown promise for decreasing ripening time and intensity. Halifax Water’s J.D. Kline Water Supply Plant (JDKWSP) is not equipped with filter-to-waste. Due to the high cost associated with implementing this infrastructure an assessment of filter ripening was performed at this facility to determine if filter-to-waste was needed. The assessment consisted of four studies, including microbial monitoring during filter ripening, testing backwash procedural concepts and backwash water chemistry concepts, and an analysis of the current full-scale procedure.

Eutrophication is a major problem in the Baltic Sea, as a result of increased loading of nitrogen and phosphorus. In the coastal parts of Östergötland the soil largely consists of clay and contains high levels of phosphorus bound to clay particles. Erosion of the soil in agricultural areas makes the water turbid and transports phosphorus to the Baltic Sea. The aim of this project was to examine the relationship between phosphorus and turbidity in the coastal streams of Östergötland. The aim was also to evaluate the possibility to use turbidity as a surrogate measure for phosphorus. Water samples from 41 streams along the coast of Östergötland were collected once from each location 7 – 11 of April 2014. Variables examined were turbidity, total phosphorus, molybdate reactive phosphorus and water color (absorbance 420 nm). On average, particulate phosphorus made up 80 % of total phosphorus. The study showed a significant correlation between total phosphorus and turbidity (R2adj=0.879, P<0.01, linear regression). Water color was not correlated with total phosphorus. A multiple regression with turbidity and water color as independent variables resulted in a slightly improved model (R2adj = 0,886), but was regarded as not meaningful considering the additional efforts. The conclusion of the project is that is it possible to use turbidity as a surrogate measure in these streams. / Övergödning av Östersjön är ett stort problem orsakat av ett överskott av kväve och fosfor. I de östra delarna av Östergötland består jordarna till stor del av lera och innehåller rikligt med fosfor bundet till lerpartiklarna. Vid erosion från jordarna grumlas kustmynnande vattendrag och fosfor transporteras ut till Östersjön. Syftet med projektet var att undersöka om mätning av turbiditet kan användas för att uppskatta koncentrationen av totalfosfor i Östergötlands kustmynnande vattendrag. En fältstudie genomfördes där 41 vattendrag provtogs en gång per lokal den 7 - 11 april 2014. Vattenprover från lokalerna analyserades med avseende på totalfosfor, molybdatreaktiv fosfor, turbiditet och färg (absorbans 420 nm). I genomsnitt så bestod 80 % av totalfosfor av partikulärt bunden fosfor. Det fanns ett signifikant samband mellan totalfosfor och turbiditet (R2 adj =0,879, P<0,01, linjär regression) men inte mellan färg och totalfosfor. Vid multipel regression med turbiditet och färg som oberoende variabler förbättras förklaringsgraden så marginellt (R2adj=0,886) att det inte motiverar analys av färg, då det ger en ökad arbetsinsats. Projektet visar att turbiditet går att använda som ersättningsmått för totalfosforhalt i kustmynnande vattendrag i Östergötland.

The Chattahoochee River is the most utilized surface water in Georgia, and it and Utoy Creek are receiving waters for Atlanta stormwater and wastewater effluent. Population growth and record-breaking rainfall in 2013 has led to potential stress from stormwater runoff and nonpoint source loading. The goals of this research are to examine spatial and temporal variations in E. coli and the bacteriophage MS2 and relationships with DO, turbidity, rainfall, and riverflow; to determine if E. coli in water is correlated with E. coli in sediment; and to determine if wastewater effluent discharges influence downstream sample sites. Water samples were collected at fifteen sample sites and two outfall sites in the Chattachoochee, and ten sites in Utoy Creek. No significant spatial variation in E. coli was found for the Chattahoochee, although there was significant temporal variation in mean E. coli concentrations. The lowest mean DO values and the highest mean turbidity levels both occurred on the date of the highest mean E. coli concentrations. Effluent from the two outfalls did not contaminate downstream sample sites. In Utoy Creek, E. coli concentrations showed spatial and temporal variation in water samples, but not for sediment samples. Turbidity was found to be positively correlated with both E. coli in sediment and MS2. These findings suggest that nonpoint source loading is a potential cause of contamination. Since DO, turbidity, and rainfall were correlated with E. coli and MS2, these parameters could be used as indicators of pollution for future monitoring of the Chattahoochee River and Utoy Creek.

Thesis supervisor: Jerald L. Schnoor. Thesis supervisor: Craig L. Just. Includes bibliographic references (p. 186-196).

Thesis (M.S.)--Oregon State University, 1993. / Typescript (photocopy). Includes bibliographical references (leaves 85-87). Also available on the World Wide Web.

Turbidity currents, both continuous flow and surge-type, have been detected with acoustic sounders operating at 42.5, 107 and 200, kHz. The turbidity currents are associated with the discharge of mine tailing into Rupert Inlet. A linear relation is obtained between the backscattered acoustic signal at 200 kHz and the one-half power of suspended particulate concentration from 10 to 1000 mg 1⁻¹. This relation is consistent with Rayleigh scattering theory in form and (relative to a standard target) amplitude, and is used to generate a cross-sectional profile of sediment concentration in the discharge plume. Estimates of surge speeds from the acoustic records based on a universal shape for density current heads range from 30 to 120 cm s⁻¹. The excess density of one surge was estimated from the reverberation amplitude to be 0.12 g cm⁻³. The additional attenuation of sound waves by suspended particles is important in turbidity currents and may be used to estimate suspended particulate concentration. Thermal processes contribute very little to the additional attenuation by particles with the grain densities of common minerals. A leveed submarine channel extended from the point of the tailing discharge (outfall) over the surface of the tailing deposit as early as 1974. The upper reach of this system was buried in 1978, and by late 1979 a new channel had developed. In 1976-77, the original channel consisted of: (1) a left-hooking upper reach with an average slope of 2.2°, (2) a middle reach (1° slope) with pronounced meanders (700-1100 m wavelengths) "increasing in curvature with distance downstream and (3) a straight lower reach (0.5° slope). The cross-sectional area of the channel decreased with distance downstream, excepting an increase in the first 100-200 m, until the channel disappeared about 5.5 km from the outfall. Acoustic records of the discharge plume in bends indicate overspill from the outer bank and an upward tilt of the upper interface away from the centre of bend curvature. The interfacial slope is steeper than indicated by the cross-channel difference in levee heights. These records together with observed tidal currents suggest that the left hook in the upper reach is caused by a mechanism similar to that which has been suggested for deep-sea channels. Turbidites in gravity cores from the levees are present as layers of vertically-graded, Cu-rich and Fe-poor sand and silt, some of which have load-casted flame-structures or load-pockets at their basai contacts. These layers comprise more of the sediment column with distance down-channel, suggesting that levee-building by overbank spillage from continuous flow becomes less important, and that most of the material transported through the lower reach is carried by turbidity surges. Surge recurrence intervals of 2-5 d are obtained from the number turbidites per core and the local deposition rate. The latter ranged from 0.3-4 m yr⁻¹, as given by changes in water depth, in tailing thickness from seismic reflection surveys, and in diatom frustule abundance in the cores. A model of continuous turbidity flow in submarine channels including entrainment is applied to the Rupert Inlet channel. Results are consistent with a sediment budget based on changes in the tailing deposit volume, and with turbidity surge recurrence intervals. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

A consequence of stirring sea bottoms within construction sites is that suspended particles are being released. Pollutants such as heavy metals are often bonded to suspended particles which can spread over long distances. Analyzing the levels of particles in the water can either be made in a laboratory, or by measuring turbidity. Turbidity is a measure of the water’s ability to diffuse light and is used to determine the content of suspended material. This thesis is made in collaboration with AFRY who is preforming water sampling during a construction of a new quay area in Kallholmsfjärden, Skellefteå. The purpose of this study has been to investigate if, and how, suspended substances are being spread during water-based constructions that causes stirring of the sea bottom. The study was carried out by analyzing data sampled from Kallholmsfjärden. In summary, the result indicate that water-based constructions may result in suspended substances being spread into the water. Suspended material is correlating with turbidity, which means that turbidity can be used as an indicator for suspended materials. The kind of operation preformed during construction, affects the turbidity and dredging leads to higher particle scattering than padding. The result underlines the importance of taking preventive measures that reduce particle scattering, and one way of doing that is by using silt curtains. According to the result, silt curtains fulfill its purpose by preventing particle scattering. Finally, there is no difference in suspended material between dissimilar depths. The result of this theses is relevant when planning similar projects.