Scholarship & Research
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Item A spatial comparison of channel morphology between burn, timber and old growth areas within the Yellowstone ecosystem(Montana State University - Bozeman, College of Letters & Science, 1997) Myers, Stephen CharlesItem Effects of wildfire on first order stream channel morphology Yellowstone National Park, USA(Montana State University - Bozeman, College of Letters & Science, 1999) Ernstrom, Kim J.Item Sediment routing system response to tectonic activity in the Argentine Precordillera : Sierra Las Penas-Las Higueras(Montana State University - Bozeman, College of Letters & Science, 2010) Abrahamson, Ingrid Syverine; Chairperson, Graduate Committee: James G. SchmittAlluvial fan deposition in the Argentine Central Precordillera is part of a sediment routing system that changes along strike of an active thrust front. This study area is partitioned into erosional and depositional sectors for analysis. The erosional sector drainage basins are analyzed using topographic data from a digital elevation model, to see how morphology changes with fault displacement. Drainage basins become shorter with more displacement. The depositional sector alluvial fans are classified using spectral characteristics from satellite imagery. The fans are classified based on thermal, near infrared, and elevation parameters. Fans close to the thrust front are interpreted to be old sheetflood deposits, with younger fans more distal from the front in the foreland. In this setting, progressive fault displacement causes shortening of the erosional sector, increasing the efficiency of sediment evacuation from the range, and causing a progradation of sheetflood fans into the foreland basin. Remote sensing analysis techniques are useful for characterizing the sediment routing system of alluvial systems where field-based information (geodetic, seismic, structural and lithologic data) is not available.Item Fault segmentation control on alluvial fan and fan drainage basin morphometry, Lemhi Range, East-Central Idaho(Montana State University - Bozeman, College of Letters & Science, 2011) Carr, Christina Grace; Chairperson, Graduate Committee: James G. SchmittAlluvial fan and fan drainage basin morphometric parameters are proposed to vary as a function of distance from closest fault segment boundary along the Lemhi fault in east-central Idaho. Large normal faults are broken into segments along strike that have unique rupture histories. Since potential earthquake magnitude is related to rupture area and therefore segment rupture length, accurate delineation of segments can have implications for earthquake hazard assessment. Alluvial fans were mapped on airphotos, and drainage basins were extracted from digital elevation models (DEMs). Morphometric parameters calculated for each drainage basin/fan pair based on DEM-extracted data include: elongation ratio (measures basin roundness in map view), Melton ratio (relates absolute relief and basin area), fan area to drainage basin area ratio, and hypsometric integral. Hypsometric integral is the area under the hypsometric curve, which displays relative elevation as a function of relative area. Standard regressions compared variations in these parameters with distance to fault segment boundaries mapped by previous workers. Drainage basins closer to fault segment boundaries tend to have lower elongation ratios (more elongate shape), higher Melton ratios, higher fan area to drainage basin area ratios, higher hypsometric integrals, and straighter (less sinusoidal) hypsometric curves. No parameter is strongly correlated with distance to closest segment boundary, but the strongest correlation occurs with the Melton ratio. High Melton ratios have been associated with basins dominated by flows with higher sediment-to-water concentrations compared to basins with low Melton ratios. The observed along-strike morphometric variations can influence conceptual models of extensional footwall drainage development and hangingwall basin stratigraphic evolution. However, the relationships are not strong enough to inform seismic hazard or similar studies requiring a high degree of confidence and strong correlations. In agreement with previous studies, fan area and drainage basin area are directly correlated, fan slope and drainage basin area are inversely correlated, and drainage basin slope and area are also inversely correlated. This study recognizes differences between slope calculated conventionally and slope calculated using standard grid-based methodology. This observation requires future studies to consider which slope definition is most representative of gravity-driven hydrogeomorphic processes.