The Meers Fault (Oklahoma) is one of few seismogenic structures with Holocene surface expression in the stable continental region of North America. Only the ~37 km-long southeastern section of the ~55 km long Meers Fault is interpreted to be Holocene-active. The ~17 km-long northwestern section is considered to be Quaternary-active (pre-Holocene); however, its low-relief geomorphic expression and anthropogenic alteration have presented difficulties in evaluating the fault length and style of Holocene deformation. We reevaluate surface expression and earthquake timing of the northwestern portion of the Meers Fault to improve fault characterization, earthquake rupture models, and seismic hazard evaluations based on fault length. We use a combination of airborne lidar (0.5--2 m-resolution), historical aerial photos, and new balloon-based photogrammetric (Structure from Motion) topography (0.25--0.5 m-resolution) collected in this study to analyze and characterize the fault scarp and local fault zone geomorphology. In the northwest, complex surface deformation includes fault splays, a left step, subtle monoclinal warping, and a minor change in fault strike. The fault is evident in the landscape as linear escarpments, incised channels on the up-thrown side of the scarp, and closed depressions on the downthrown side. I use topographic profiles, measured perpendicular to the fault scarp to show that the northwest scarp is characterized by decimeter surface offsets. Where the fault traverses the Post Oak Conglomerate the fault zone width rarely exceeds 25 m, in the Hennessey Shale I document an increase in fault zone width with deformation occurring over 20 m to 115 m. I further examined the northwest section of the fault in a paleoseismic excavation where weathered Permian Hennessey Shale and a ~1--2 m-thick veneer of Holocene alluvial deposits have been folded and warped during three surface-folding earthquakes. In an adjacent stream exposure these units are also faulted near the ground surface. Paleoearthquake age modeling (Oxcal) constrained by accelerated mass spectrometry (AMS) dating of detrital charcoal and optically stimulated luminescence (OSL) dating of sandy alluvial beds indicates two earthquakes occurred since ~6152-5550 cal. years BP and one possibly older event along the erosional unconformity along the Hennessey Shale bedrock. This analysis lengthens the Holocene extent of the Meers Fault by ~6 km, to ~43 km, and extends the paleoseismic record of the Meers Fault to ~9598 cal. years BP. These data will improve fault-rupture and earthquake recurrence models used for seismic hazard analysis of the Meers Fault.

Quantifying spatial and temporal patterns of rapid channelized erosion, on human time scales, is critical to understanding its processes and their consequences. This investigation utilized field observations, repeat terrestrial laser scanning (TLS), and Structure-from-Motion photogrammetry (SfM) to document the size and retreat rates of a knickpoint, defined as a localized near-vertical reach of a fluvial channel, and its contribution to erosion, in an urbanizing landscape with a loess substrate. The Bull Mountain area, in Washington County, southwest of Portland, Oregon, is an ideal study area, offering a measurable knickpoint that translates the response of the rapid erosion throughout this transient system. Previous urbanization there has increased peak flows in streams, potentially initiating rapid channel incision and associated slope instability and sediment pollution, affecting real property and infrastructure. Despite the documented increase in discharge, upstream migration rates of the knickpoint, as well as the overall channel erosion rate, were unknown. Sequential point cloud analysis quantified topographic changes in the landscape, in three dimensions, throughout time. The measured minimum knickpoint migration rates ranged from - 0.23 m/yr to - 2.45 m/yr with an average of - 1.52 m/yr and minimum of total volume eroded of 6.49 m3. The negative sign indicates the upstream direction. An extreme erosion event caused - 12.5 m of erosion in ~ 4.5 months. The interval including the extreme erosion event was recorded separately using traditional measurement techniques and resulted in an average retreat rate of - 4.31 m/yr. Analysis of patterns of erosion revealed four primary modes: exfoliation, large soil block failure, undercutting at the knickpoint base, and upper bank failure. Results from soil analyses indicate a layer of high bulk density (1.85 g/cm3) loess at the base of the upper channel may restrict the channelized incision for that reach and control the height and geometry of the knickpoint face, leading to a parallel mode of retreat. From the observed erosion rates a substrate specific average value of erodibility, or K value, of 0.01 m0.2 yr-1, was determined. As erosion forces the retreat of these knickpoints upstream, the effects of increasing urban runoff are felt throughout the watershed. The work presented here provides insight on the physical controls driving erosion and can serve as a prologue for future mitigation.

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: John C. Kraft, Dept. of Geology. Includes bibliographical references.

Graduation date: 1991

Thesis (Ph. D.)--University of Oregon, 2003. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 634-646). Also available for download via the World Wide Web; free to University of Oregon users.

Tropical Storm Debby affected the Gulf coast of Florida in late June, 2012. The storm's southerly approach temporarily reversed the annual net southward longshore sediment transport. The energetic conditions associated with Tropical Storm Debby can be seen in the wind, wave and tidal measurements taken from both onshore and offshore weather stations around the dual tidal inlets system of John's Pass and Blind Pass, approximately 25 kilometers north of the mouth of Tampa Bay. The energetic and persistent southerly forcing, in addition to higher storm induced water levels and wave heights, resulted in atypical beach erosion and sediment deposition on the ebb tidal deltas of the two inlets and the surrounding beaches. The John's Pass ebb delta gained 60,000 cubic meters of sediment and the Blind Pass ebb delta gained 9,000 cubic meters as a result of the storm. Shoreline position, beach profile and offshore bathymetric surveys conducted before and after Tropical Storm Debby illustrate the changes in the coastal morphology such as the development of an offshore bar south of Blind Pass and erosion of the dry beach north and south of John's Pass. The Coastal Modeling System (CMS) was used to simulate wave and tide-driven current fields during the passage of the storm. The modeled wave field qualitatively illustrated the shadowing effect of the Tampa Bay ebb delta in reducing the southerly approaching storm wave energy arriving at the study area during the storm. The tidal flow patterns through the inlets and over the ebb tidal deltas were considerably different during the storm, as compared to normal tidal cycles.

River regulation imposes direct changes on flow and sediment delivery, producing a suite of downstream responses in channel morphology. On the Peace River in northern British Columbia and Alberta, the W.A.C. Bennett hydroelectric dam has reduced peak flows while leaving sediment load effectively unchanged. My research aims to identify systematic, regulation-induced patterns of channel gradation in the mainstem Peace and its tributaries below the dam. The significance of regulation within the natural variability of basin hydrology is assessed by comparing actual regulated river flows to simulated flows based on reservoir level fluctuations. Mainstem bed elevation changes are assessed from repeatedly surveyed cross-sections and specific gauge records, supplemented by analysis of channel planform change. Results show degradation to be minimal, due to the naturally armoured gravel bed and elimination of competent flows. The predominant pattern in the upper regulated reaches is one of aggradation below tributary confluences and other sediment sources. In the long term, the Peace River may be raising its proximal bed to compensate for a loss of sediment transport capacity since regulation. Backchannel abandonment and other planform changes appear to be occurring more slowly, and may be less important to river slope adjustment. Data from the lower river are few and inconclusive. Tributary gradation was investigated by means of air photo, field surveys and dendrochronology of young floodplains. These methods reveal a range of responses to regulation, including degradation, aggradation and no apparent change. Degradation due to reduced tributary base level appears to attenuate downstream as the Peace River flood is restored by unregulated tributary flows, though this trend is complicated by other factors such as tributary sediment supply, flood timing between tributary and mainstem, and ice activity. Aggradation due to tributary fan growth may mitigate degradation; it is a less prominent response, though it appears to predominate in the lower Smoky River. Regulation is a secondary effect in the tributaries, and its influence on gradation has been limited. On the mainstem, however, it is a primary change, and the resulting channel gradation will take a long time to complete.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1990. / Includes bibliographical references (leaves 163-171) / Microfiche. / xi, 171 leaves, bound ill., maps 29 cm

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 43-46). Also available on the World Wide Web.

Sand ramps are widespread but understudied landforms which have the potential to provide detailed palaeoenvironmental information in dryland regions. This thesis investigates the utility of sand ramps as late Quaternary palaeoenvironmental archives by addressing two research questions: (1) What are the main controls on sand ramp formation in southern Africa? (2) What does the sand ramp record tell us about late Quaternary palaeoenvironments in southern Africa? The distribution of sand ramps in southern Africa was surveyed using Google Earth™ and 75 features were identified in southern Namibia. Ten of these sand ramps, and an additional feature from South Africa, were studied in the field. Sediments and morphology were mapped and a total of 64 OSL dates, 96 sediment samples, 10 heavy mineral assemblages and OSL sensitivity data from 8 samples were examined. The distribution of sand ramps suggests formation is dependent on (1) sediment supply, (2) accommodation space, (3) persistent unidirectional wind and (4) a variable semi-arid to arid climate. Chronologies and sediment analyses indicate individual sand ramp accumulation is locally controlled by sediment supply modulated by the availability, and nature, of the accommodation space. Comparison between the Namibian and South African sand ramps suggests considerable regional variation in the factors controlling sediment supply. The Namibian sand ramps show an affinity to local ephemeral river channels. Periods of dated sand ramp activity in multiple features are interpreted as periods of increased regional fluvial activity. Significant activity occurred at ~21-12 ka (with peaks at 21-18.5 ka and 14.5-12 ka), ~8.5-7.5 ka and ~2 ka. Some activity is also indicated at 85-65 ka and 45-35 ka. These results correspond well to regional records. Overall, this study demonstrates that sand ramps can provide palaeoclimatic information on both the local and regional scale but only if a number of caveats are taken into consideration.