Thesis (M.Sc.(Hons.))--Victoria University of Wellington, 2009. / Includes bibliographical references.

A digital model based on a random walk was used in an experiment to determine how well such a model is able to simulate alluvial-fan deposition. The model is in three dimensions and is dynamic with respect to both time and space. Two principal stochastic events were employed, (1) a relative uplift of the mountain area that is the source of the fan sediments, and (2) a storm event of sufficient magnitude to result in the deposition of material on the fan. These two events are assumed to follow independent Poisson processes with exponentially distributed interoccurrence times. The pattern of deposition is determined by a random walk from the canyon mouth at the mountain front, and each depositional event is assumed to occur instantaneously. The direction that each step in the walk takes is determined probabilistically by the gradient in the direction of flow, the momentum of flow, and the boundary conditions stipulated in the model. The type of flow, whether a depositing debris or water flow, or eroding water flow, depends upon the thickness of erodible material in the source basin. Deposition is assumed to occur over the entire route of flow either as a bed tapered in the direction of flow or as a bed of uniform thickness. The particle-size distribution of the water-flow deposits is governed by the slope in the direction of flow. Erosion is considered negative deposition and results from the exponential decline in elevation of the main stream channel at the fan apex during periods of no uplift, or from water flows containing little basin sediment. Results from the computer runs were printed as geologic maps of the fan surface, and geologic sections through the deposits; these indicate that, at least qualitatively, a random-walk model provides a reasonable basis for simulating alluvial-fan deposition.

Thesis (Ph. D.)--University of Washington, 1988. / Vita. Bibliography: leaves [236]-254.

Thesis (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: James G. Schmitt. Includes bibliographical references (leaves 110-122).

This thesis adopts a geoarchaeological approach to palaeoenvironmental research in the Konya basin of South-Central Turkey. It involves the analysis of sediment sequencesth rough cultural and alluvial depositsa crossa broad alluvial fan which has developed on the southern edge of the basin since the beginning of the Holocene. Sediments have been analysed by mineral magnetics, particle size, carbonate and organic matter content, and grouping into lithological units has been aided by statistical techniques including principal components analysis and discriminant analysis. Resultso f the analysis have shown a complex sequenceo f deposition across the alluvial fan throughout the Holocene, and within the sequences a number of archaeological sites ranging in date from the Early Neolithic to the Byzantine periods have been identified as being established on various land surfaces. During the early to mid Holocene, the predominant alluvial deposit across the fan was a fine-grained, heavy backswamp clay, deposition of which was time transgressive, i. e. area of deposition changed over this period as the course of the depositing river migrated laterally, and up/down fan. Evidence from the largest and earliest site studied, I; atalh6yiik, where archaeological excavation has recently recommenced, shows that the site was established during the Early Neolithic in an actively flooding alluvial environment. This has implications, not only for the populations inhabiting the site, but also for the wider reasoning behind the establishment of early agricultural settlements in the Near East. Other sites in the area up to the Early Bronze Age have also been seen to have been established in actively depositing alluvial settings. Shortly before c. 4000 BP there was a permanent change in the nature of alluvial deposition, with the heavy backswamp clay being replaced by a less fine-grained deposit of different origin. This initial change was concurrent with an apparent depopulation of the alluvial fan and a relationship between the two phenomena is possible. More importantly, there appear to have been major population changes and increased human influence on the environment of both the fan catchment and the wider region subsequent to these phenomena. Such changes appear to have had a long-term effect on the fan environment as the nature of the alluvial deposition remained relatively unaltered between these events and intensive irrigation schemes which restricted alluvial deposition in the early twentieth century.

No description available.

This thesis attempts to determine to what extent fluvial allogenic factors affect the development of vegetation in the Lillooet Valley, north-west of Pemberton, B.C. Microenvironments exist within the floodplain, based on height, flood frequency, drainage conditions, tree cover and soil development. The area is in a constant state of flux with respect to the change of species over time and the associated nature of the river channels that cause new areas to become available while constantly destroying other vegetated areas. The major hypothesis that vegetation, both individual species and species groups, can be spatially related to elevation differences as a measure of flood frequencies, cannot be proved in isolation from other hypotheses. Mo species were found to be solely related to the elevation factor. Although six species were found to be significantly related to height, they can only be used in very general terms to estimate flood frequency, however, as it is the rare 15 to 50 year event that determines the major vegetation pattern. Pioneer, scrub and young deciduous forests on the lower elevations and the understorys of the mature forests are entirely destroyed by such an event, thus changing the direction and pace of the development of many sites markedly. The second hypothesis was that sediment type as a measure of drainage conditions is important in differentiating species distribution, especially at the pioneer stage. It has been successfully demonstrated that during initial species invasion sediment type is important. This initial spatial differentiation causes major species variation in young forests and these differences may still be noticeable in mature coniferous forests. Finally, the importance of time and associated autogenic processes was noted to be of importance. It has been shown that there are several species groups existing within the field area that reflect the age of the sediment surface, and that the sites must be discussed within the age groups for meaningful results. / Arts, Faculty of / Geography, Department of / Graduate

No description available.

No description available.

A tilting bed flume study was made to examine the relationships between velocity, suspended sediment and infiltration rate in alluvial channels for velocities from 2 to 5 feet per second and suspended sediment up to 0.6 percent. Preliminary experiments using samples from Rhllito Creek near Tucson, Arizona to define limits for the flume study included mechanical analyses of bed sediments, permeability and infiltration tests, and analyses of suspended sediment in flood waters. Flume experiments using bed materials from Rillito Creek were made with constant velocity and variable suspended sediment content, then with constant suspended sediment and variable velocity. Considerable variability was found in the mechanical analyses, permeability and infiltration tests, and suspended sediment content for samples from different locations. The flume studies indicated a direct relationship between velocity and infiltration rate and an inverse relationship between the suspended sediment content and infiltration rate in the ranges tested. Very poor correlation was found between the preliminary permeability and infiltration tests and the flume infiltration rates, but good correlation was obtained for the flume results with the flow losses and natural recharge occurring in the river channels in the Tucson area.