Browsing by Subject "Topography"

Now showing 1 - 4 of 4
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    C-29 Geologic Atlas of Clay County, Minnesota [Part A]
    (Minnesota Geological Survey, 2014) Bauer, Emily J.
    Surface and subsurface geology of Clay County, Mn., also includes data-base information, subsurface stratigraphy, bedrock topography, depth-to-bedrock and sand distribution models.
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    Numerical Simulation Of The Atmospheric Boundary Layer Over Complex Topography: A Modern Approach To A Classical Problem
    (2020-05) Andersen, Noah
    Numerical methods were developed and validated to simulate the atmospheric boundary layer (ABL) using large eddy simulation (LES). This framework captures the topography of the Earth’s surface rather than modeling it. To robustly simulate the ABL, four unique capabilities (temperature transport, topographic data, immersed boundary method with wall modeling, and turbulent inflow generation) were added to a traditional finite difference computational fluid dynamics code. The accuracy of each capability was analyzed individually using validation tests. Then, a full scale simulation of the ABL over a tidal inlet was conducted. It was found that the resolved topography of the Earth’s surface had a significant effect on the flow field. Furthermore, it was found that the results from LES are more accurate than mesoscale simulations. Lastly, it was found that the errors in the present simulation are a result of the roughness model used over the sea surface.
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    Seismic stratigraphy of Thunder Bay and the Isle Royale region of Lake Superior.
    (2010-08) Voytek, Emily Beach
    Glacial Lake Agassiz was the largest of the proglacial lakes to have formed in North America during retreat of the Laurentide Ice Sheet. The extent of Lake Agassiz was controlled by a combination of factors including topography, ice position and degree of isostatic rebound. Most changes in the outlet location of the lake involved a catastrophic release of water. Evidence for some of these catastrophic floods are visible in both terrestrial and sub‐lacustrine records. An influx of freshwater from Lake Agassiz to the North Atlantic from such floods has been suggested as a possible trigger for the initiation of the Younger Dryas cold interval. A series of airgun single‐channel seismic‐reflection profiles from Thunder Bay and the adjacent Isle Royal Trough of Lake Superior suggest that water from Glacial Lake Agassiz did not catastrophically release into Lake Superior at this locality, as has been previously suggested. Seismic surveys from a region further north within Lake Superior identified features of a younger catastrophic release of water. The features associated with the younger event include bedrock scour and large debris fans, neither of which are present in the Thunder Bay area. Given the similarity in geomorphic conditions at the two locations, similar features are expected if the same type of event occurred. Therefore, the absence of such features suggests that Lake Agassiz did not drain catastrophically through Thunder Bay. Instead of catastrophic outflow features in the seismic records, a thick package of distinct units occur in the Isle Royale trough, which suggest a complex history of ice retreat and readvance. Trough parallel profiles show a massive seismic package, which grades into more individually distinguishable units in the direction of general ice retreat.
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    Topography and flow model files for the Platte River, Nebraska, 2016-2017
    (2017-10-13) Limaye, Ajay B; aslimaye@umn.edu; Limaye, Ajay B
    Automated techniques for extracting channels from topography are well developed for convergent channel networks, and identify flow paths based on land-surface gradients. These techniques—even when they allow multiple flow paths—do not consistently capture channel networks with frequent bifurcations (e.g., in rivers, deltas, and alluvial fans). The project uses multithread rivers as a template to develop a new approach for channel extraction suitable for channel networks with divergences. This data set includes topography and flow model data used to demonstrate this new approach for automated identification of channels on planetary surfaces. The data set accompanies a 2017 publication in the Journal of Geophysical Research: Earth Surface.