Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 242-254).

The present thesis describes an experimental and theoretical investigation of the flow field and scour action of an offset jet. The hydraulic characteristics of the offset jet and the resulting scour developed in the bed were investigated in the laboratory. Tests were carried out using a fixed bed and a single offset ratio (height of jet above bed / jet thickness). Three flow rates were used. Velocity measurements in two directions, especially in the recirculating zone, were of help in understanding the flow field and in providing the necessary data for comparison with the theoretical results. The development of scour, on a uniform sand, was monitored at set time intervals, in most cases until the asymptotic state was reached. A new effective and simple method for measuring the scour profile, while the experiment was running, was devised. The experiments were conducted using four different offset ratios and several flow-rates. Results showed dependency of the scour characteristics on Froude number, time and especially the offset ratio. The findings of each experiment were combined dimensionlessly to produce relationships which describe the development of scour characteristics for the tested range of parameters. Scour profiles were found to be similar for a given offset ratio, but differed from one offset ratio to another. The second part of the work was concerned with developing a general integral method capable of the prediction of velocity fields of different flow situations, including those of offset jet impinging on rigidand eroded beds. The combination of strip integral method in a curvilinear system with the k-E and algebraic stress turbulence models provided such a method. Application of this method to a variety of selected test cases revealed the ability of the model to capture the main features of the flow within the considered range of interest. The algebraic stress model was found to give better results in curved and wall effected flows.

This study investigates channel bed scour and fill as a result of individual flood events in a gravel-bed channel. Given the complexity of interactions between hydraulic force, the texture and arrangement of bed material, and input of sediment to a particular point of the channel bed, study objectives were pursued with the view that bed material movement is a stochastic phenomenon. A two-year field program was conducted in Carnation Creek, a small gravel-bed stream draining 11 km2 on the west coast of Vancouver Island, British Columbia. In the 900 m study reach, an array of measurement techniques, including scour indicators, magnetically-tagged stones, and conventional survey, yielded information about the fluctuations of the channel bed elevation and movement of scoured material for individual flooding periods. Frequency distributions of scour and fill depths associated with individual flooding periods are adequately modeled by negative exponential functions over the range of flood peak magnitudes observed in Carnation Creek. Analysis of scour depths measured in streams on the Queen Charlotte Islands demonstrates the applicability of the exponential model to flooding periods and flood seasons. Further, exploratory analysis suggests that a regional scour depth model is possible. Power functions relating mean depths of scour and fill to flood peak discharge show that depth increases with an increase in peak magnitude. Observed maximum scour depths in flooding periods are linked, in general, to streambed conditions influenced by antecedent flow conditions. These patterns in scour and fill exist within an overall pattern of increasing variability in depths of scour and fill as peak discharge increases. Evaluation of a heuristic model for mean travel distance as a function of particle size proposed by Church and Hassan (1992) provides convincing evidence for its general merit. Mean travel distance decreases inversely with particle size as size increases beyond the median diameter of subsurface sediment. This trend is consistent in both individual flooding periods as well as flood seasons. The majority of material finer than the median diameter of surface sediment is supplied from subsurface material, which influences the travel distances of these finer fractions because of burial. Computation of volumetric transport rates of bed material, based on the active scour depth and width of the channel bed, the virtual velocity of particle movement, and sediment porosity, suggests the potential for building scale correlations with streamflow, which have usually been defined by bedload sampling during floods. Error analysis indicates that determination of active width contributes most significantly to the imprecision of transport rate estimates. Results underscore the stochastic nature of sediment transport in gravel-bed channels.

No description available.

As scouring around foundations is the most common cause of bridge failures, one of the most pressing questions of this research is to determine whether or not it is possible to predict the critical shear stress of different soil types using only soil property information. This report shows that it is possible to predict critical shear stress and determines the soil properties that are required to predict the critical shear stress based on soils from Georgia. Multiple methods to predict soil erodibility categories are developed based on the amount of soil information available to the researcher. The report shows how the methods to predict soil erodibility can be integrated with HYRISK, a scour risk assessment tool. In particular, the probabilities of bridge failures and expected economic losses are calculated for approximately 40 bridges in Georgia; soil erodibility characteristics for these bridges are calculated using the methods developed in this thesis. The goal of this thesis is to provide a faster and more cost-effective approach to calculate critical shear stress ranges likely to be encountered at a bridge foundation. Implementation of theses methodologies will help balance funding for new and existing bridges while simultaneously ensuring safe bridge foundation and minimizing economic consequences associated with overbuilding a bridge and/or having to retrofit or replace a bridge that has scour damage due to underbuilding it to withstand a major storm event.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (leaves 241-246).

Thesis(M.S.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.

Thesis (Ph.D.)--University of Western Australia, 2007.

Thesis (M.S.)--Auburn University, 2008. / Abstract. Includes bibliographical references (p. 187-189).

Thesis(M.S.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references (p.114).