Browsing by Subject "Debris flow"
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Item A Geomorphological Assessment of Armored Deposits Along the Southern Flanks of Grand Mesa, CO, USA(2011-08-08) Brunk, Timothy J.A series of deposits, located along the southern flanks of Grand Mesa, Colorado, and extending to the south, are problematic, and the processes related to emplacement are not understood. The overall area is dominated by two landform systems, Grand Mesa, which supported a Pleistocene ice cap, and the North Fork Gunnison River drainage. Thus, one has to ask: Are these deposits the result of the melting of the ice cap or are they fluvial terraces associated with the evolution of the ancestral Gunnison River? The goal of this research was to map the areal extent of the deposits and to interpret the formation and climatic significance in understanding the evolution of the Pleistocene landscape in the region. An extensive exposure, parallel to State Highway 65 near Cory Grade, was used for detailed description and sampling. Three additional exposures, ~10 to 20 km (~6 to 12 mi) were used to extend the areal extent of sampling. The study area was mapped using aerial photography and traditional field mapping aided by GPS. From the field work, a detailed stratigraphic column, including lithology and erodability, was constructed. Vertical exposures of the deposits were described, mapped, and recorded in the field and using detailed photo mosaics. Samples were collected from each stratum of the deposits for grain-size, shape, and sorting analyses. Five distinct depositional facies were identified. Sieve analysis on collected samples shows that four distinct grain-sizes occur in the outcrops; coarse sand, very-coarse sand, granule, and pebble and boulder. Mean grain-sizes range from 0.0722 to 0.9617, -0.0948 to -0.9456, -1.0566 to -1.9053, and -2.0050 to -3.4643, respectively. Glacio-fluvial depositional environments were identified and supported with observations of sedimentary structures and clast composition. Two major environments of deposition are recorded in the deposits; fluvial deposits from glacial outburst floods, and debris flow deposits. Imbrication of clasts in the strata suggests the flow came from the direction of Grand Mesa to the north. Facies and subsequent sequences were constructed to portray evidence that supports the glacio-fluvial mode of deposition.Item Modeling of debris flows and induced phenomena with non-Newtonian fluid models(2015-12) Jeon, Chan-Hoo; Hodges, Ben R.; McKinney, Daene C; Liljestrand, Howard M; Moser, Robert D; Sepehrnoori, KamyDebris flows contain inhomogeneous distributions of solids within a liquid. By considering a mixture of solid and liquid forming debris flows as a non-Newtonian continuous liquid, the viscosity term for rheological models is simply constructed in the Navier-Stokes equations. Time-independent models (e.g. Herschel-Bulkely) for viscosity have been widely used, but there is an open question as to whether time-dependent models might provide improved results. In this work, both time-dependent and time-independent non-Newtonian fluid models are taken into account in simulation. Since debris flow induced phenomena include two or more interfaces, the level set method for multiple materials is applied as the interface tracking method. The numerical model is applied to two-dimensional test cases to validate this approach and analyze the relative importance of the viscosity model. The simulation results for the two models show reasonable agreement with available experimental data in most cases, however, time-dependent model only shows good correlation with experimental measurements for special case. It indicates that debris flows and induced phenomena could be simulated by the approach of this research and the time-dependent model is more adequate for representing real debris flows than time-independent models.