Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    Historical Shoreline Changes in Response to Environmental Conditions in West Delaware Bay
    (1990) French, Gregory T.; Leatherman, Stephen
    This study quantified historical changes in the coastline of the west shore of Delaware Bay. Shoreline changes were measured through the compilation of historical maps and photographs utilizing the Metric Mapping technique. These changes were correlated with various environmental conditions and with human influences. The results portray a 135 year pattern of overall erosion, with long-term rates averaging -4.5 ftjyr, which is considerably greater than the u.s. Atlantic coast average. Coastal engineering (e.g., groins, jetties and beach nourishment) were locally effective in reducing erosion rates and in some cases promoting limited accretion. Perhaps more importantly, there were few associated negative effects alongshore suggesting that various forms of coastal engineering can be effective in a low-energy environment, even when done in a somewhat unorganized fashion. A correlation was found between erosion rates and underlying Pleistocene morphology. Where pre-Holocene sediments were exposed in the nearshore, erosion rates were lower. However, erosion rates were substantially higher along marshy shorelines. This erosion is not continuous either spatially or temporally, but instead is largely storm-driven. Periods of relative quiescence corresponded with lowered rates of average annual shoreline recession. With the exception of the northernmost marshy areas, severe erosion occurs along all shorelines, regardless of morphology, in response to major coastal storms.
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    Scales of Bank Roughness and Their Relationship to Bank Erosion Processes
    (2009) Hankin, Erik Ravnholt; Prestegaard, Karen L; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Stream bank erosion rates and the stabilization of channel width are poorly understood processes. There have been two distinct approaches to the study and prediction of bank erosion rates in natural streams. In order to predict bank shear stresses, scientists either define a reach as being meandering or straight, even though most river channels are neither meandering nor straight but a combination of the two. This thesis aims to determine if river segments can be divided into straight reaches and curved reaches with different bank erosion prediction approaches applied to each as well as investigating the role of bank roughness element size and spacing in bank erosion. The results show that straight reaches are affected by upstream curvature and that large isolated bank protrusions that are widely spaced generate erosion-causing, stable, macroturbulent eddies. The thesis has implications for stream restoration practices regarding bank stability and erosion.