Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

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abstract: ABSTRACT The Phoenix Four Rivers Flora is an inventory of all the vascular plants growing along the Salt, Gila, New and Agua Fria Rivers, and their tributaries in the Phoenix Metropolitan Area during the years of the study (2009-2011). This floristic inventory documents the plant species and habitats that exist currently in the project area, which has changed dramatically from previous times. The data gathered by the flora project thus not only documents how the current flora has been altered by urbanization, but also will provide a baseline for future ecological studies. The Phoenix Metropolitan Area is a large urbanized region in the Sonoran Desert of Central Arizona, and its rivers are important for the region for many uses including flood control, waste water management, recreation, and gravel mining. The flora of the rivers and tributaries within the project area is extremely diverse; the heterogeneity of the systems being caused by urbanization, stream modification for flood control, gravel mining, and escaped exotic species. Hydrological changes include increased runoff in some areas because of impermeable surfaces (e.g. paved streets) and decreased runoff in other areas due to flood retention basins. The landscaping trade has introduced exotic plant species that have escaped into urban washes and riparian areas. Many of these have established with native species to form novel plant associations. / Dissertation/Thesis / M.S. Plant Biology 2011

Knowledge of habitats used by riverine fishes throughout their life history is important for management and conservation. Naturally occurring chemical markers in otoliths have recently been used to determine natal origins and environmental history of fishes in a variety of marine and freshwater environments. However, to our knowledge no studies have examined the applicability of this technique in large floodplain rivers in United States. We evaluated otolith microchemistry and stable isotopic composition as tools for determining origins of fishes in the upper and middle Mississippi and lower Illinois Rivers, their tributaries, and associated floodplain lakes. Fishes were collected from 21 sites during summer 2006 and 2 additional sites in spring 2007. Water samples were obtained from the same 23 sites plus three additional sites during summer and fall 2006 and spring 2007. Otoliths and water samples were analyzed for δ18O, and a suite of trace elements; otoliths were also analyzed for δ13C. Tributaries, floodplain lakes, and the Illinois and Mississippi Rivers had distinct isotopic and elemental signatures. Tributaries on the Missouri and Illinois sides of the middle Mississippi River could also be differentiated by their elemental and isotopic fingerprints. Otoliths reflected differences in water chemistry among habitats. Results indicate that otolith microchemistry and stable isotope analyses provide a potentially effective means of determining origins and environmental history of fishes in large river-floodplain systems.

xv, 137 p. : ill., maps. A print copy of this title is available through the UO Libraries under the call number: KNIGHT GB565.O7 H84 2008 / This study examines the role of floods in shaping the geomorphology of the multichannel, gravel-bed upper Umatilla River, northeastern Oregon, USA. Three parts are presented: (1) the development and application of an error-sensitive aerial photo-based planform channel-change detection and measurement methodology, (2) an examination of the occurrence, variability, and landform impacts of channel widening, straightening, and lateral movement during two mid-to-Iate 20th century flood periods, (3) an investigation of the effects of these floods on channel complexity, a proxy of habitat quality and indicator of ecological health in multi-channel rivers. Floods in 1964-5 (17- to 37-year recurrence interval) scoured, widened, and straightened the active channel in conjunction with large lateral movements, bar accretion, and capture of marginal vegetated areas by lateral scour. Following the flood, lateral movements were smaller, the channel narrowed, and bars, scoured areas, and vegetation lapsed from the channel. A similar flood in 1975 also scoured, widened, and straightened the channel; however, lateral channel movement and changes in channellandforrns were less in 1975 due to latent adjustment of the channel to the first flood. Migratory straightening, meander cutoffs, and avulsions dominated lateral movements during flood periods, whereas episodes of migratory (lateral) extension and (downstream) translation of meanders dominated lateral movement between flood periods. Channel changes were spatially variable and generally greater in reaches with wide floodplains. Floods reduced the overall complexity of the river channel, although the magnitude of change was highly variable and some areas increased in complexity in response to flooding. By contrast, channel complexity increased in the period between floods, particularly in laterally confined areas where complexity loss was high during the first flood period. Two key processes appear to most affect channel complexity: (a) lateral scour and avulsions, which capture vegetation into the channel, and (2) migrations of the main channel, which reflect bar accretion and dissection. Results of this study are broadly congruent with theories (and their corollaries) emphasizing adjustment of channel dimensions, increased rates of change, and reduced complexity in response to flood disturbance, but only partially consistent with theories emphasizing large geomorphic changes in structurally confined settings. This dissertation includes both previously published and co-authored material. / Committee in Charge: Dr. Patricia F. McDowell, Chair; Dr. W. Andrew Marcus; Dr. Patrick J. Bartlein; Dr. Joshua J. Roering

xv, 203 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Water and pumice accumulated behind a dam that, upon failure, scoured the c1aydominated floodplain and deposited pumice sands across the Sycan Valley. The pumice originated from the eruption of Mount Mazama (approximately 7660 ybp), and dam failure occurred very shortly afterwards. In response to the flood the lower Sycan River underwent episodes of channel aggradation and degradation. This study presents the history of channel evolution for the lower Sycan River from 11,000 years ago to present, based on floodplain stratigraphy and radiocarbon chronology. Seven primary periods of channel and floodplain development are identified: I. Early Holocene Dynamic Equilibrium; II: Sycan Outburst Flood; III. Initial Channel Formation; IV. Degradation & Widening; V. Aggradation & Lateral Migration; VI. (Secondary) Degradation & Widening; VII. Modern Dynamic Equilibrium. The active floodplain of the modern lower Sycan River is flanked by terraces of the rapidly abandoned Sycan Outburst Flood deposits. / Committee in Charge: Dr. Patricia McDowell, Chair; Dr. Jim E. O'Connor; Dr. Andrew Marcus

Wastewater treatment plants discharge effluents containing a number of constituents whose concentrations may negatively affect the receiving waters. Current research in mixing and transport between a point source discharge and the ambient environment attempts to reduce these effects through a better understanding of the physical processes involved and development of numerical models to better predict the fate of the effluents under different conditions. This thesis examined the mixing and transport of ammonia discharged from a multiport diffuser of a municipal wastewater treatment plant into the Ottawa River. The river reach was surveyed using an M9 acoustic Doppler current profiler to obtain spatially distributed measurements of depth and velocity. Water samples were collected at and downstream of the diffuser at multiple depths. The samples were analyzed for ammonia concentration and kinetics. The river reach was also simulated in the FLOW-3D model using available turbulence closure schemes. Comparisons were made between measured and modelled results, as well as some empirical and semi-empirical approximations. A combination of measured and modelled results helped describe (quantitatively and qualitatively) the mixing and transport between the discharged effluent and receiving river. Unionized ammonia was tested for regulatory compliance. Both measured and modelled results showed that although the regulatory end-of-pipe discharge concentrations were met, downstream regulations were not met.

This study investigates the relation between channel instability and sediment transport along an 80 km reach of lower Fraser River, British Columbia. The major processes governing instability, bank erosion and sedimentation were investigated by analyzing the patterns of morphologic change along the river over the last century. Morphologic changes were documented using historical maps and air photographs. The method of approach can be considered a "macroscopic" one since the investigation focused primarily on the gross patterns of change that occurred over periods of years to decades. It was found that this interval is the most appropriate time scale for investigating channel instability and sedimentation processes on a large stream such as the Fraser River. This is because the major features governing instability and sedimentation also develop over comparatively long time periods. Several examples are presented to illustrate how sequences of major channel instability have propagated along the river over periods of 10 to 30 years. These disturbances often initiated new patterns of sedimentation, local erosion and subsequent channel instability further downstream. The most common diagnostic feature associated with these travelling disturbances are relatively large, low amplitude, linguoidal-shaped "gravel sheets" that attach to more stable lateral bars and islands. These bars may cause strong flow impingement against previously stable banks and islands. As a result, rapid scour and erosion may be initiated even during periods of low discharge. Four different approaches were used to estimate the long term gravel transport rate along the river. These methods included direct measurements using trap samplers (carried out by Water Survey of Canada over a period of 12 years), a sediment budget calculation which related changes in transport through a reach to changes in the volume of sediment stored in the channel determined by surveys, a morphologic approach which used a simple model of sediment transfers through a reach, and finally theoretical bed load formulae. It was found that the sediment budget and the morphological model provided the most reliable and most generally applicable results. This was because the methods rely on observations of sediment movement over periods of years or decades. It was found that on Fraser River, the time scales of the major processes governing gravel bed load transport were also measured in years or decades. As a result, short term measurements such as from bed load trap samplers show only a poor correlation between transport rate and flow variables. Therefore, to estimate long term transport rates with these data, a very large number of observations is required to integrate the transport rates over time. / Arts, Faculty of / Geography, Department of / Graduate