acase@tulane.edu / Though rivers are inextricably linked in our minds with an intermittently flooded overbank environment, surprisingly little is known about the sedimentary processes that operate there, or how they interact with those of the river. The knowledge gap is acute in deltas, where dense populations often necessitate tightly engineered control over flow patterns, leading to disconnected overbank environments that no longer receive input from the main channel. However, the need to understand sedimentary function in the overbank is also acute in deltas, as rising relative sea levels create an urgent need to manage water and sediment resources. This dissertation is presented as three primary chapters, each of which examines a different aspect of the hydrodynamic and sedimentary connection between a river’s channel and its overbank environment. In Chapter 2, my coauthors and I ask which factors enhance overbank sediment retention, and what retention rates might be considered typical in deltas. We compare the sediments stored in a crevasse splay to those transported by the river and conclude that retention rates approaching 100% might be achievable in settings that are not exposed to coastal processes. Chapter 4 is also concerned with spatial patterns of sedimentation on a delta. In it we use physical experiments to examine the influence that floods play in mobilizing sediments from the channel and storing them in the overbank environment. We find, counterintuitively, that an experiment whose input included floods has a lower proportion of floodplain to channel deposits preserved than an experiment with a constant input. Chapter 3 is focused on water and sediment dynamics in the channel in a region where significant flow is lost to the overbank environment. Here we present measurements from channel networks in the Mississippi River’s Birdsfoot Delta and show that flow loss along the channels is a critical control on channel function that causes channels of disparate sizes to behave similarly. We use our field results to inform a numerical model of channel bed evolution in a region with flow losses, and conclude that the modern flood control system in the Lower Mississippi River may have significantly changed the bed morphology. / 1 / Christopher R. Esposito

Thesis (MScIng)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 141-160).

Thesis (Ph. D.)--Texas State University--San Marcos, 2009. / Vita. Appendices: leaves 132-141. Includes bibliographical references (leaves 142-152). Also available on microfilm.

Thesis (M.S.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains viii, 152 p. : ill. (some col.), maps. Includes abstract. Includes bibliographical references (p. 62-64).

Thesis (M.S.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2005. / Includes bibliographical references (p. 57-58).

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 228-237).

The question posed in this study is why alluvial soil on a floodplain is finer than the bed material of the river that supplied the sediments deposited to form the floodplain. A schematic, simplified river/floodplain system is used in an approximate analysis to find the size distribution of the floodplain soil. It is assumed that the stable limiting condition is a suspended load in the floodplain flow of the same concentration and composition as the sediment load in that portion of the river channel flow above the level of the floodplain. It was found that floodplain soil should be finer than the channel bed material; how much finer depending on the bank height, and to a lesser degree the width of the floodplain.

Thesis (M.S.)--University of Tennessee, Knoxville, 2003. / Title from title page screen (viewed Sept., 24, 2003). Thesis advisor: Randall W. Gentry. Document formatted into pages (viii, 164 p. : ill. (some col., col. maps)). Vita. Includes bibliographical references (p. 117-122).

The purpose of this thesis was to develop a methodology that could be used by local communities to evaluate the cost-effectiveness of their floodplain management programs. The methodology (i.e.: model) was designed to be usable by communities without requiring computer capability. The model looks at cost-effectiveness in terms of minimizing the average annual flood damages and the costs of programs implemented by the community to reduce flood damages. The Cities of Decatur, Elkhart, and Kokomo were selected to field test the model to illustrate current conditions in these communities. The City of Decatur was used as an example to show how alternative program scenarios could be developed, incorporated into the model, and used to determine the most cost-effective combination of average annual damages and program costs. The model was run to illustrate its method of operation and not to determine the cost-effectiveness of the floodplain management programs in the Cities of Decatur, Elkhart, and Kokomo. / Department of Urban Planning