No description available.

Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 49-59).

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: David R. Maidment. Vita. Includes bibliographical references. Also available from UMI.

Thesis (M.S.)--Ohio University, August, 2004. / Includes bibliographical references (p. 71-73).

Thesis (M.S.)--California Polytechnic State University, 2010. / Title from PDF title page; viewed on April 22, 2010. Major professor: Brian C. Ditterick, Ph.D., P.H. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Forestry Sciences." "March 2010." Includes bibliographical references (p. 101-109).

Thesis (M.S.)--Ohio University, August, 2004. / Title from PDF t.p. Includes bibliographical references (p. 71-73)

Thesis (M. En.)--Miami University, Institute of Environmental Sciences, 2006. / Title from first page of PDF document. Includes bibliographical references (p. 33-35).

656 pages / Livestock grazing and beaver trapping alter streams hydrologically and geomorphically leading to declines in the quality and extent of stream-riparian ecosystems. The influence of reductions in grazing pressure and fluctuating levels of beaver activity (treatments) on channel capacity was studied at I 08 channel cross-sections, located on eight headwater streams in Montana and Arizona. Cross-sections were surveyed two or three times over a two-to-five year period to determine annual rates of change as a function of treatment. Most cross-sections in the cattle and elk exclosures and grazed areas showed minimal changes in area(< 10 percent). Large decreases in cross-section area were observed in reaches with intact beaver dams, especially near the dams. The beaver ponds reduced channel capacity between 50 to I 00% in most reaches, compared to< 25% in reaches without beaver ponds. The ponds effectively restored the hydrologic connection between the stream and valley floor in less than one year. Upon dam failure, channel capacity increased within a year by 40 percent or more as the ponds drained and sediment eroded. A conceptual model describing geomorphic and hydrologic response of a drainage basin to the entry of beavers and then their removal or abandonment was developed, based on a literature review and field data. The model suggests that the simultaneous existence of discontinuous arroyos and wetlands, observed by Euro-American expeditions to the Southwest prior to settlement, may in fact reflect landscapes transforming due to recent beaver trapping rather than a recent climate shift. Beaver-dam failures would trigger channelization and thus greater flood magnitudes as water was more rapidly routed from upper to lower watersheds. The study suggests that Euro-American trapping and grazing, though temporally and spatially separated, combined with two recent periods of above-average precipitation to transform drainage networks in the West and increase stream ecosystem sensitivity to climatic variability. This transformation pre-dates the installation of stream gages and the data collection that forms the current basis of our understanding hydraulic geometry and fluvial processes. Consequently, current hydraulic geometry relationships and our understanding of stream sensitivity to climatic variability reflect highly disturbed watersheds and ecosystems, not intact systems. / Version has slight corrections to the original by the author, as specified in separately attached file Corrections_to_Fouty_2003_PhD_20181810.pdf

Channel instability has occurred in the Bell river, north eastern Cape, in the form of meander cutoffs, incipient meander cutoffs, channel straightening and general channel instability. Recent cutoffs occurred in 1974 and 1988. The study examines the spatial and temporal controls of channel form and pattern in the Bell river in order to assess the causes of channel instability. From the 17 km surveyed stretch, it was found that the main spatial controls of channel form were riparian vegetation density and channel bed material. Discharge as estimated in the field was not the main controlling variable of channel form. Two distinct groups of stream beds were identified from the survey; an upper gravel-bed stream and a lower sand-bed stream. These sites displayed distinct form ratios, channel gradients and bed material characteristics. The incidences of major channel instability were identified as being the transitional zone between the two reaches. Examination of temporal controls of channel form included climatic trend analysis and catchment sediment production analysis. Rainfall analysis indicated that no long term progressive trends in the annual or seasonal data existed. Distinct wet and dry cycles occur with peaks every 16 to 19 years. Wet cycles are the result of an increase in the frequency of daily events rather than in the magnitude of events. Flow record analysis demonstrated the relationship between regional discharge and upper catchment rainfall. Coincidence of peak flows and channel straightening were also noted. Soil erosion surveys showed that erosion had increased in the catchment and that accelerated erosion were probably the result of overstocking and poor veld management. It was concluded that channel changes in the Bell river are possibly the result of anthropogenic influence in catchment and channel processes. Increased sediment production to the channel resulted in channel aggradation with attendant instability. The plantation of riparian vegetation led to perimeter stability in the short term at flows less than bankfull discharge, but served to reduce cross-sectional area in the long term, thereby increasing the potential for flooding, meander cutoffs and channel change

Orientador: Archimedes Perez Filho / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-20T23:58:29Z (GMT). No. of bitstreams: 1 Silva_ViniciusdeAmorim_D.pdf: 9553562 bytes, checksum: 9936c995258ae48b043baf2e46be3e76 (MD5) Previous issue date: 2012 / Resumo: As alterações antropogênicas da morfologia dos subsistemas canal fluvial principal e delta permitiram interpretar as diversas dinâmicas que o sistema rio Jequitinhonha, está submetido, em seu baixo curso. A caracterização, identificação e análise no padrão de drenagem no canal principal e Delta foram possíveis investigando os parâmetros: índice de sinuosidade, morfologia do canal, migração de meandros do canal, vazão, datação por luminescência opticamente estimulada, descrição granulométrica, biológica e cromática dos sedimentos no Delta. Os resultados demonstraram que se identificou o aumento da complexidade sistêmica pela intervenção antropogênica no sistema hidrográfico. Dessa forma, sugere-se que a morfologia do delta, pode estar sendo modificada para que o rio estabeleça um novo equilíbrio geomorfológico em resposta à construção da barragem e retificação do canal fluvial principal. Sugere-se que ao passar do tempo a forma do delta vai se alterar como já está acontecendo, abandonando a sua configuração bifurcada e transformando-se em canal único em direção à sua margem esquerda, desaparecendo-se o canal localizado em na sua margem direita / Abstract: The anthropogenic changes of the morphology of the main river channel and delta allowed to interpret the diverse dynamics to which the Rio Jequitinhonha system was submitted, in its lower course. The drainage pattern characterization, identification and analysis in the main channel and Delta were possible investigating the parameters: sinuosity index, channel morphology, channel neighborhood migration, optically stimulated luminescence dating, granulometric, biological and chromatic description of the sediments in the outfall and Delta. The results showed the identification of the rising systemic complexity due to the anthropogenic intervention in the hydrographic system. So, it is suggested that the delta morphology may have been modified in order to the river to establish a new geomorphological balance, to respond to the construction of the barrage and main channel rectification. It is suggested that with time the form of the delta will be altered in the way it is happening now, abandoning its bisected configuration and transforming in a single channel directed to the left margin, with the disappearance of the channel located in its right margin / Doutorado / Análise Ambiental e Dinâmica Territorial / Doutor em Geografia