Numerous studies have addressed the role of stream geomorphology on vegetation distribution. These studies have shown that channel morphology, including depositional and erosional processes, influence vegetation colonization. However, few studies have addressed the impact of vegetation on the geomorphic processes of streams. Vegetation has the ability to stabilize channel banks and alter stream hydrology and stream power. Little research has addressed the impact of invasive vegetation and its ability to change river channel processes. My research addresses the impact of the highly invasive Phalaris arundinacea and quantifies its influence on the stream channel form of the Sprague River, Oregon. I conducted field research that included root density and root strength surveys to determine the below ground influences of vegetation in terms of added bank cohesion provided by the invasive and two similar native species: Eleocharis palustris and Carex vesicaria. To ascertain differences between the species above ground characteristics and influences, I measured stem density and elasticity to calculate their roughness (Manning's n) and determine their potential impact on stream velocity. Finally, I used these vegetation characteristics to model stream velocity, water depth, and bed shear stress within the 2-D model MD-SWMS. Differences in root size were significant with C. vesicaria having the largest root diameters, largest root area ratio, and largest bank cohesion provided by roots. This was followed by the invasive and then E. palustris. E. palustris had the highest stem density, followed by C. vesicaria and P. arundinacea. The invasive had the highest stem stiffness. E. palustris was associated with the highest roughness value, closely followed by the invasive and C. vesicaria. Using modeling I found the presence of the invasive increased velocity compared to E. palustris and increased bed shear stress compared to C. vesicaria. Therefore, changes in species composition, such as a shift from either of the natives to the invasive, could affect channel morphology over time. By comparing the impact of this invasive to that of native grasses and sedges, this research provides insight into how further spread of the invasive may affect the Sprague River and other riparian ecotones. / 2015-10-03

It has long been known that the presence of wood in rivers plays a vital biological and functional role and that a reciprocal relationship exists between woody material and the geomorphology of rivers. Fluvial wood studies, however, are rarely ongoing through time in order to ascertain long-term wood patterns within complete drainage networks. This dissertation addresses the temporal lag in fluvial wood patterns throughout four watersheds in the Oregon Coast Range by recreating a field dataset first collected in 1979 and then again in 1998. Statistical and spatial analysis of stream morphometric data at designated transects throughout the watersheds in addition to analysis of log step and log jam inventories provide insight into significant changes that have occurred over a thirty year interval at a multi-basin scale. These watersheds are located in areas that have been impacted by years of timber harvesting in the mid-twentieth century, however, clearcutting has been on the decline since the early 1980s. This research investigates the impacts that the legacy of clearcutting and subsequent afforestation has had on the abundance and volume of fluvial wood in the stream networks of these four watersheds. I digitized historical aerial imagery to determine the amounts of clearcutting in the basins over time. I integrated this variable with channel morphometric variables to assess predictors of wood abundance and volume through multiple regression analysis. Results show that the stream that has been the most affected by clearcutting has lower volumes of wood than measured in 1979 or 1998. Residence times of wood are short in these watersheds and wood abundance and volume was highly impacted by the debris flows that occurred during the Storm of 1996, prior to the 1998 data collection. There are statistically significant changes that have occurred in the stream morphology among the four watersheds. This dissertation also tests a method of detecting fluvial wood through airborne lidar analysis. This method provides an alternative to field surveys in areas of even the most extreme tree canopy cover.

Master of Science / Department of Biology / Martha E. Mather / Determining patterns and drivers of organismal distribution and abundance are fundamental and enduring challenges in ecology, especially for mobile organisms at a ‘scape scale. To address the problem presented by individuals whose distributions are dynamic across large geographic areas, here I tracked 59 acoustically-tagged migratory striped bass (Morone saxatilis) with an array of 26 stationary receivers in Plum Island Estuary (PIE), MA. Specifically, I asked (1) how these predators were distributed across the estuarine seascape, (2) if these fish used three types of geomorphic sites (exits, confluences, and non-confluences) differently, (3) if distinct types of individual distributional “types” existed, and (4) if fish within distinct distributional groups used geomorphic site types and regions differently. Based on three components of predator trajectories (site specific numbers of individuals, residence time, and number of movements), striped bass were not distributed evenly throughout PIE. Confluences attracted tagged striped bass although not all confluences or all parts of confluences were used equally. Use of non-confluences sites was more variable than exits or confluences. Thus, geomorphic drivers and regions link mobile organisms to physical conditions across the seascape. Based on spatial and spatial-temporal cluster analyses, these striped bass predators clustered into four seasonally-resident distributional types. These included the (1) Rowley River group (fish that primarily resided in the Rowley River), (2) Plum Island Sound group (fish that primarily resided in the Middle Sound region), (3) Extreme Fidelity group (fish that spent most of their time in PIE at a single receiver location), and (4) the Exploratory group (fish that showed no affiliation with any particular location). These distributional groups used geomorphic site types and regions differently. Thus, my data show a rare link between behavioral (i.e., individual animal personalities) and field ecology (seascape geomorphology) that can advance the understanding of field-based patterns and drivers of organismal distribution.

<p>Tidally-influenced sandwaves are common coastal features present in various settings, including shipping channels. The main shipping channel in Tampa Bay under the Bob Graham Sunshine Skyway Bridge (a.k.a. the Skyway Bridge) contains such sandwave bedforms. Between the years 2000 and 2017, these bedforms have been surveyed with multibeam echosounders (MBES) on 21 occasions with ranging coverage and quality of returns. Surveys between 2000 and 2009 used a 300 kHz Kongsberg EM3000; surveys between 2015 and 2017 used a 400 kHz Reson Seabat 7125. For comparable surveys, bathymetry, backscatter, slope, curvature, planform curvature, and profile curvature maps were created and analyzed. Spectral analyses were completed on the same cross-section for usable surveys, providing a period and amplitude for the bedforms. Sediment samples were taken in September 2015 using a Shipek grab. The sediment samples were analyzed for grain size and carbonate content. A bottom-mounted ADCP recorded velocity data semi-continuously over the same time period. These data were analyzed in an effort to investigate the forcing mechanisms that influence the bedform morphology. Mean grain sizes in the shipping channel under the Skyway Bridge range from 0.01 ? (0.99 mm, coarse sand) to 1.55 ? (0.34 mm, medium sand). Calcium carbonate content ranges from 25% to 87%. The sediment sample site most representative of the sandwave bedforms has a mean grain size of 0.01 ? and a calcium carbonate content of 87%. The calculated mean current velocity required to initiate transport of the D50 and D84 grain size percentile of the representative sediment sample site is 0.70 m/s and 1.05 m/s, respectively. Analysis of the ADCP-recorded velocity data shows that the calculated D50 critical velocity is frequently reached by peak flood and peak ebb currents except during neap tides, while the D84 critical velocity is reached only intermittently, mostly during spring tides. Analysis of MBES backscatter shows similar spatial patterns in two larger MBES surveys in 2004 and 2015. Bathymetric analysis of the sandwaves shows consistent characteristics through time. Wave crest analysis reveals that bedforms migrate in both the ebb and flood directions. Spectral analysis shows primary wave spatial frequencies range from 0.13 m-1 to 0.22 m-1, and primary wave periods range from 4.5 m to 6.0 m. The predominant wavelength of sandwaves within the study area is about 5 m, with an average wave height of 0.47 m. The maximum wave height along the axial cross-section analyzed is 0.8 m, observed in April 2017. The sediments comprising the sandwave bedforms are likely winnowed by tidal currents resulting in larger grain size and carbonate content than other areas of the shipping channel and surrounding bay. Consistent patterns in MBES backscatter over time indicate that the sediment distribution pattern in the study area have not significantly changed. The size and shape of the bedforms in the shipping channel beneath the Skyway Bridge are have been in a quasi-dynamic equilibrium over the past 13 years. The bedforms are shown to migrate in both the ebb and flood directions despite an average faster ebb current velocity than a flood current velocity. More frequent and consistent MBES surveys as well as more continuous ADCP data availability would allow for better understanding of sediment transport via bedform migration in tidally-influenced environments.

Orientador: Archimedes Perez Filho / Banca: Iandara Alves Mendes / Banca: Cleide Rodrigues / Resumo: O estudo dos padrões de canal fluvial permitiu decifrar as diversas dinâmicas fluviais que o Rio Mogi Guaçu está submetido. A identificação e caracterização dos padrões de canal foram possíveis investigando os parâmetros: largura da planície fluvial, índice de sinuosidade, morfologia do canal, relevo das planícies, largura do canal, profundidade do canal, vazão e velocidade do fluxo. Para o Rio Mogi Guaçu foram encontrados sete padrões: Alto curso; Contato Serra-Depressão; Meandros de Conchal; Meandros de Leme; Boqueirão de Porto Ferreira; Meandros de Jataí; e, Foz do Mogi. A formação destes padrões está ligada a mudanças do gradiente, das estruturas e litologias no perfil longitudinal. Foi possível concluir que o desenvolvimento e a distribuição dos padrões de canal e das planícies fluviais são o resultado do inter-relacionamento das variáveis e fatores do sistema fluvial. Para o Rio Mogi Guaçu estas combinações modificam-se ao longo de todo o curso fluvial condicionando a formação de trechos com distintos padrões e dinâmicas. / Abstract: The study of fluvial channel patterns allowed to decipher various fluvial dynamics that Mogi Guaçu River is submitted. The channel patterns identification and characterization were possible investigating the parameters: floodplain width, sinuosity index, channel morphology, floodplains landform, channel width, channel depth, discharge and flow velocity. For Mogi Guaçu River were met seven channels patterns: Alto curso; Contato Serra-Depressão; Meandros de Conchal; Meandros de Leme; Boqueirão de Porto Ferreira; Meandros de Jataí; e, Foz do Mogi. The formation of these channels patterns is jointed move of gradient, geologic structures and lithologies in the longitudinal profile. It was possible to conclude that the development and the distribution of channel patterns and the floodplains are the effected of the interrelation of the variables and factors system fluvial. For Mogi Guaçu River these combinations modify all along the stream flow conditioning the formation of the intervals with distinct channel patterns and dynamics. / Mestre

Resumo: O trabalho aqui apresentado tem como cenário de estudo a "Serra do Calcário", posicionada no município de Cocalinho (MT), e teve por objetivo caracterizar geomorfologicamente o relevo cárstico ali observado, propor um modelo explicativo da sua evolução e, conseqüentemente, fornecer subsídios para a compreensão do relevo cárstico desenvolvido na região Centro-Oeste do Brasil. A fundamentação teórica que norteou esta pesquisa foi a abordagem sistêmica, mais precisamente a ótica do sistema aberto do tipo processo-resposta. Neste contexto seguiu-se a orientação de Scheidegger, segundo a qual a paisagem pode ser entendida como um sistema dinâmico composto pela inter-relação de cinco princípios: Antagonismo, Instabilidade, Catena, Seleção e Controle Estrutural. Com base nesta fundamentação teórica e em trabalhos de campo e de gabinete, onde se destacam a interpretação de imagens de Satélite e Radar, foi possível a identificação de duas zonas e de cinco unidades geomorfológicas, bem como a proposição de uma seqüência evolutiva para o relevo da área em apreço. / Abstract: This thesis is based on a study conducted in the "Serra do Calcário"(Limestone Mountain Range), located in the county of Cocalinho in the state of Mato Grosso; it was designed to provide a description of the geomorphology of the karst features observed and propose a model to explain its development, in an attempt to promote the understanding of the karst features found in the central-western part of Brazil. The theoretical background orienting the research was a systemic approach, specifically that of an open system of a process-response type. In the process-response open system approach adopted, the work of Scheidegger suggests that such features can be understood as part of a dynamic system based on the interrelationship of 5 principles: Antagonism, Instability, Catena, Selection and Structural Control. Based on this theoretical foundation, as well as work in the field and laboratory interpretation of satellite and radar images, it was possible to identify two zones and 5 geomorphologic features, as well as proposing a developmental sequence for the surface features of the area in question. / Orientador: Iandara Alves Mendes / Coorientador: Augusto Sarreiro Auler / Banca: Chisato Oka Fiori / Banca: Nádia Regina do Nascimento / Mestre

<p> Wood dynamics that store, transport, break down, and ultimately export wood pieces through watershed networks are key elements of stream complexity and ecosystem health. Efforts to quantify wood processes are advancing rapidly as technological innovations in field data collection, remotely sensed data acquisition, and data analyses become increasingly sophisticated. The ability to extend the temporal and spatial scales of wood data acquisition has been particularly useful to the investigations presented herein. The primary contributions of this dissertation are focused on two aspects of wood dynamics: watershed-scale wood export processes as identified using the depositional environment of a mountain reservoir, and wood deposition mechanisms in a bedrock-dominated mountain river. Three chapters present this work: </p><p> In Chapter 1, continuous video monitoring of wood in transport revealed seasonal and diurnal hydrologic cycle influences on the variable rates at which wood transports. This effort supports the efficacy of utilizing continuous data collection methods for wood transport studies. Annual wood export data were collected via field efforts and aerial image analyses from New Bullards Bar Reservoir on the North Yuba River, Sierra Nevada, California. Examination of data revealed linkages between decadal-scale climatic patterns, large flood events, and episodic wood export quantities. A watershed-specific relation between wood export quantities and annual peak discharge contributes to the notion that peak discharge is a primary control on wood export, and yielded prediction of annual wood export quantities where no data were available. Linkages between seasonality, climatic components, and hydrologic events that exert variable control on watershed scale wood responses are presented as a functional framework. An accompanying conceptual model supports the framework presumption that wood responses are influenced by seasonal variations in Mediterranean-montane climate conditions and accompanying hydrologic responses. </p><p> Chapter 2 contains development of new theory in support of the introduction of multiplicative coefficients, categorized by water year type, that were used to predict wood export quantities via utilization of an existing discharge-based theoretical equation. This new theory was the product of continued investigations into watershed-scale factors in search of explanation of observed variation of wood export rates into New Bullards Bar Reservoir. The gap between known variability and the attribution of wood export to one hydrologic relation continues to be a persistent issue, as the hierarchical and stochastic temporal and spatial nature of wood budget components remain difficult to quantify. The development of &ldquo;watershed processes&rdquo; coefficients was specifically focused on a generalized, parsimonious approach using water year type categories, with validation exercises supporting the approach. In dry years, predictions more closely represented observed wood export quantities, whereas the previously derived annual peak discharge relation yielded large over-predictions. Additional data are needed to continue development of these watershed-specific coefficients. This new approach to wood export prediction may be beneficial in regulated river systems for planning purposes, and its efficacy could be tested in other watersheds. </p><p> Chapter 3 presents the results of an investigation into wood deposition mechanisms in a 12.2 km segment of the confined, bedrock-dominated South Yuba River watershed. Inclusion of coarse wood particles in the analyses was essential in recognizing depositional patterns, thus supporting the value of utilizing a wider wood-size range. A near-census data collection effort yielded myriad data, of which topographic wetted width and bed elevation data, developed for an observed 4.5-year flood event, were standardized in 10-m intervals and then univariate and linked values were ordered into landform classifications using decision tree analyses. Digital imagery collected via kite-blimp was mosaicked into a geographic information system and all resolvable wood pieces greater then 2.5 cm in one dimension were delineated and categorized into piece count density classes. Visual imagery was also key in identifying two river corridor terrains: bedrock outcrops and cobble-boulder-vegetation patches. A conceptual model framed an investigation into how topographic variability and structural elements might influence observed wood deposition dynamics. Forage ratio test results that quantified wood piece utilization versus interval availability revealed that high-density wood deposition patterns were most significantly co-located with five discrete bedrock outcrops that dominated small portions of the river corridor in high flow conditions. Topographic variations and cobble-boulder-vegetation patches were found to be subordinate factors in wood deposition patterns. Bedrock outcrops with specific structural components were the primary depositional environments that acted as floodplain extents for coarse wood deposition, with mechanisms such as topographic steering, eddying, trapping, stranding, backwater effects, and lateral roughness features inferred to be responsible for observed wood deposition patterns.</p><p>

M.Sc. / This study concentrates, not only on the physical origin of the pans, but also attempts to define certain guidelines which will contribute to an improved urban environment in the future. The series of pans on the East Rand form part of the greater Highveld pans, which extends in an easterly direction to eventually link up with the Lake Chrissie pan series. The study is however limited to those pans appearing on the 1: 50 000 topographical map 2628 AB Benoni ...

M.A. / Pan are naturally occurring depressions or closed basins and play a very important role in ecosystems. The East Rand is characterized by more than one hundred pans dotting its landscape. The impact of urbanisation on these pans is significant. To determine exactly how the characteristics of the pans on the East Rand has changed, a comparison was done between the characteristics and utilization of the pans in 1992, as then described by Le Grange (1992) and the current situation in 2003. Water samples were also collected over a period of three months and analysed in the laboratories of Rand Water. The current utilization of the pans leaves much to be desired. Informal settlements, industries, residential areas and mine dumps are all found on the pan floors. Large waste dumping sites are developing at five out of the 19 pans in the study area. This has severely negatively affected the water quality within the pans, and the quality of bird life at thee pans. Continuous research is needed from government and private organisations on the pans found on the East Rand to improve their current quality and condition. Responsibility and proper management strategies must be implemented to protect the pans from negative human impacts.

I seek to reconstruct the balance between sediment storage and yield across multiple drainage basin scales in a large (1 230 km2) watershed in the Northern Cascade range, British Columbia and Washington. Chilliwack Valley and surrounding area has been the site of numerous studies that have detailed much of its Quaternary sedimentary history. In the present study this information is supplemented by reconstruction of the morphodynamic trajectory of the river valley though the Holocene Epoch, and development of a sediment transfer model that describes the relaxation from the Fraser glaciation. The total Holocene sediment yield is estimated from basins across several scales using field and remotely sensed evidence to constrain the historical mass balance of delivery to higher order tributary basins. Rates of hillslope erosion are estimated using a diffusion-based relation for open slopes and delimitating the volume evacuated from major gully sources. Digital terrain models of paleo-surfaces are constructed to calculate total sediment erosion and deposition from tributary valleys and the mainstem. Chilliwack Lake has effectively trapped the entire post-glacial sediment load from the upper catchment (area = 334 km2), allowing to compare this "nested" system with the larger catchment. Rates of lake sediment accumulation are estimated using sediment cores and paleomagnetism. These are compared with accumulation rates in the terminal fan inferred from radiocarbon dating of fossil material, obtained by sonic drilling in the apex gravels. A sediment budget framework is then used to summarize the net transfer of weathered material and glacial sediments from the hillslope scale to the mainstem. The long-term average sediment yield from the upper basin is 62 +/- 9 t/km2/yr; contemporary yield is approximately 30 t/km2/yr. It is found that only 10-15% of the material eroded from the hillslopes is delivered to mouths of the major tributaries; the remaining material is stored at the base of footslopes and within the fluvial sedimentary system. Since the retreat of Fraser Ice from the mouth of the valley, Chilliwack River delivered over 1.8 +/- 0.21 km3 of gravel and sand to Vedder Fan in the Fraser Valley. In the sediment budget developed here, roughly 85% of that material is attributed to glacial sources, notably the Ryder Uplands and glacial valley fills deposited along the mainstem, upstream of Tamihi Creek. In tributary valleys, local base-level has fallen, leading to the evacuation of deep glacial sedimentary fills. Many of the lower reaches of major tributaries in upper Chilliwack Valley (e.g. Centre and Nesakwatch Creeks) remain primarily sediment sinks for slope-derived inputs, since base-level fall has not been initiated. In distal tributaries (Liumchen, Tamihi and Slesse creeks), paraglacial fans have been incised or completely eroded, entrained by laterally active channels. A transition from transport-limited to supply-limited conditions has been effected in many of these reaches. Slesse Creek has struck an intermediate balance, as it continues to remobilize its considerable sediment stores. It functions today as the sedimentary headwaters of Chilliwack Valley. Using grain size data and fine-sediment geochemical data gathered from Chilliwack River over the course of several field seasons, a simple finite-difference, surface-based sediment transport model is proposed. The aim of the model is to integrate the sediment-balance information, as inferred from estimates of hillslope erosion and valley storage, and physical principles of sediment transport dynamics to reproduce the key characteristics of a system undergoing base-level fall and reworking its considerable valley fill during degradation. Such characteristics include the river long profile, the river grain-size fining gradient, the percentage of substrate sand, and the diminution of headwater granite lithology in the active load. The model is able to reproduce many of the characteristics, but is not able to satisfy all criteria simultaneously. There is inevitably some ambiguity as to the set of parameters that produce the "right" result, however the model provides good insight into long-term interactions among parameters such as dominant discharge, grain size specifications, abrasion rates, initial topography, hiding functions, and hydraulic parameters. / Arts, Faculty of / Geography, Department of / Graduate