Thesis (M.Env.Dev.) - University of KwaZulu-Natal, Pietermaritzburg, 2009. / Full text also available online. Scroll down for electronic link.

Thesis (Ph. D.)--Florida State University, 2006. / Advisor: James B. Elsner, Florida State University, College of Social Sciences, Dept. of Geography. Title and description from dissertation home page (Sept. 19, 2006). Document formatted into pages; contains x, 90 pages. Includes bibliographical references.

No description available.

Thesis (M.S.)--Oregon State University, 2001. / Typescript (photocopy). Includes bibliographical references (leaves 97-103). Also available via the World Wide Web.

Mountainous regions are ubiquitously dissected by river networks. These networks are the main drivers by which climate and tectonic signals are transmitted to the rest of the landscape, and control the response timescale of the landscape to these external forcings. Furthermore, river systems set the downslope boundary conditions for hillslope sediment transport, which controls landscape denudation. Therefore, understanding the controls on the organisation and structure of river networks in upland landscapes is an important goal in Earth surface processes research. The recent introduction of high-resolution topographic data, such as airborne lidar data, has revolutionised our ability to extract information from the topography, providing new opportunities for linking geomorphic process with landscape form. This thesis is focused on developing techniques for analysing high-resolution topographic data to quantify and understand controls on the structure of fiuvial systems in upland landscapes. Firstly, I develop and test new algorithms for objective feature extraction from lidar-derived digital elevation models (DEMs). I present a new method for identifying the upstream extent of channel processes by identifying scaling breaks in river long profiles. I then compare this new method to three existing methods of channel extraction, using field-mapped channel heads from four field sites in the US. I find that the new method presented here, along with another method of identifying channels based on valley geometry, most accurately reproduces the measured channel heads in all four field sites. I then present a new method for identifying floodplains and fiuvial terraces from DEMs based on two thresholds: local gradient, and elevation compared to the nearest channel. These thresholds are calculated statistically from the DEM using quantile-quantile plots and do not need to be set manually for each landscape in question. I test this new method against field-mapped floodplain initiation points, published flood hazard maps, and digitised terrace surfaces from eight field sites in both the US and the UK. This method provides a new tool for rapidly and objectively identifying floodplain and terrace features on a landscape scale, with applications including flood risk mapping, landscape evolution modelling, and quantification of sediment storage and routing. Finally, I apply these new algorithms to examine the density of channel networks across a range of mountainous landscapes, and explore implications for fluvial incision models. I compare the relationship between drainage density (Dd) and erosion rate (E) using both analytical solutions and numerical modelling, and find that varying the channel slope exponent (n) in detachment-limited fluvial incision models controls the relationship between Dd and E. Following on from this, I quantify Dd for five field sites throughout the US. For two of these field sites I compare Dd to cosmogenic radionuclide (CRN)-derived erosion rates, and for each site I use mean hilltop curvature as a proxy for erosion rate where CRN-derived erosion rates are not available. I find that there is a significant positive relationship between Dd, E, and hilltop curvature across four out of the five field sites. In contrast to assumptions made in many studies of fluvial incision, this positive relationship suggests that the channel slope exponent n is greater than unity for each of these landscapes, with fundamental implications for both landscape evolution and sediment transport.

It has been established that the impact of arsenic in irrigated agriculture has become a major environmental concern in Bangladesh. However, to date there is still a limited understanding of arsenic in Bangladeshi paddy soils at a landscape level. Besides, there is no data available for soil arsenic on its geographical distribution, geomorphic variations, and biogeochemical relationships across the landscape. In the present study, paddy (n = 1209) and adjacent nonpaddy (n = 235) soil samples across 10 different physiographic regions, comprising the Holocene floodplains and Pleistocene terraces, were collected, and analysed for arsenic and a suite of 16 other elements. The collected paddy soils were from fields irrigated with groundwater (n = 904) and surface waters (n = 281). Additionally, the soils could be categorised into 6 inundation land types. A set of 30 paddy soil samples from 6 physiographic regions were also studied using the diffusive gradients in thin-films (DGT) to assess the porewater dynamics of arsenic, and other geochemical elements in the soils. The paddy soils had generally 60 percent more arsenic than the matching non-paddy soils, perhaps due to the use of arsenic contaminated groundwater for paddy irrigation. Compared to the groundwater irrigated paddy soils, the surface water irrigated paddy soils had lower arsenic concentrations, but higher concentrations of most of the other elements. Within the topologically different inundation land types, the concentrations of arsenic and other elements, including the toxic metals, were found to be elevated in more deeply and prolonged flooded low-lying soils. The soils in the different physiographic regions had variability in arsenic concentrations as well as in their indigenous biogeochemical characteristics. The inherent concentrations and variability in arsenic and most other elements, including nutrients, were greater in the Holocene floodplain soils compared to the Pleistocene terrace soils. Paddy soils in Bangladesh have a high potential for arsenic resupply from soil solid phase to soil solution phase. In the physiographically different soils across the landscape, there is less difference in nutrient/ toxin bioavailability in the paddy soils than might be predicted based solely on the total concentrations in the soils. Therefore, distinctions of soils based just on total concentrations are perhaps misleading, particularly, when elements mobility under reducing paddy environment is concerned. While the bioavailable/ phytoavailable fractions of the elements in soils are of major concern with respect to the uptake by the growing plants, it is of utmost importance to consider the labile concentrations of elements in soil solution rather than the soil total concentrations. The present study substantiates that arsenic is simply associated with less well weathered/ leached soils and sediments, suggesting that it was either due to the geological newness of Holocene sediments or differences between the sources of sediments that gave rise to the arsenic problems in soils of Bangladesh. The inherent biogeochemical variability along with the complexity of the nature and properties of the soils at local and regional levels across the landscape of the dynamic sedimentary depositional environment in Bangladesh should be considered, in any future research on arsenic in the soil-water-crop systems in Bangladesh environment.

During the past decade, a series of record flood stages have occurred along the Tisza River, resulting in extensive damage and displacing the local floodplain population. Previous research on the Tisza River in Hungary showed increases in flood stages for fixed discharges (above bankfull). These results suggest that a loss of conveyance has taken place on the Tisza River, contributing to recent record flood levels. In order to assess the potential causes of flood conveyance losses, new hydrological and geospatial data were obtained from the Hungarian Federal Hydrological Authority (VITUKI) in order to develop hydrodynamic models for two reference conditions, 1979 and 1999, along two study reaches on the Middle Tisza River. In addition to these models of actual conditions at each time step (i.e., "retro-models"), four "scenario models" were developed in order to test the individual impacts of each of the hypothesized causal mechanisms: 1) channel geometry, 2) levees, 3) floodplain roughness (land cover), and (4) channel roughness. Comparison of the models for actual conditions ("retro-model") and the scenario models allows for quantitative assessments of the impacts of each of these parameters on flood conveyance. In addition to these four scenario models, an additional land cover scenario-model was created to further assess the impact of floodplain roughness on stage. Assessment of the two retro-models showed changes in flood stage along both study reaches over the 20-year time step. Along the upper study reach, changes in stage ranged between 0.64 and 1.64 m. On the lower study reach, changes in stage ranged from 0 to 1.75 m. These changes in stage were larger on average than changes in stage previously detected by Venzcel, 2008. Contributions from the channel geometry scenario model were significant on the upper study reach where channel geometry decreased flood stage by up to 0.58 m at Kisköre over the 20-year time step. This was attributed to the dam that was constructed immediately upstream from the Kisköre gauge on the upper study reach. Construction of a dam would cause incision downstream, and therefore, a decrease in flood stage over time due to channel geometry. On the lower study reach, change in stage due to channel geometry was negligible. Contributions from the levee scenario model were negligible on both the upper and lower study reach with a maximum change in stage over the 20-year time step at only 0.11 m. However, during the time step analyzed, no significant change in levee configuration occurred. Changes in stage due to changes in land cover were also negligible along both study reaches. An additional land cover scenario model was created to assess the impact of land cover change on modern flood levels. This scenario model set Manning's n values for floodplain roughness to 0.04, which approximates roughness for pasture and cropland. This scenario model showed that flood stages will decrease by 0.34-0.40 m, but only if the entire floodplain is converted from woodland to pasture/cropland. Channel roughness accounted for the majority of change in stage during the 20-year time step. Along the upper study reach, channel roughness accounted for an average of 1.51 m of change over the 20-year time step. On the lower study reach, channel roughness accounted for 1.03 m of change. Change in the stage/discharge relationship is the best explanation for changes in stage due to channel roughness. Most likely, the channel did not experience such a large change in roughness during the 20-year time step. Instead, the two flood years used in this analysis were different "types" of floods (with differing degrees of hysteresis), and the stage/discharge relationships could not be easily compared. Comparing these two floods may have exaggerated the total change in stage between the two retro-models. Backwater effects are a likely explanation for the change in hysteresis between the two flood years.

Made available in DSpace on 2016-01-13T13:26:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-09-23. Added 1 bitstream(s) on 2016-01-13T13:32:09Z : No. of bitstreams: 1 000856359.pdf: 4560575 bytes, checksum: ece5c5872e22934ad1d54a55ea859749 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação Araucária / A presença de vários níveis de terraços e depósitos sedimentares de idades e características distintas no alto rio Paraná sempre foi associada como registro de mudanças paleohidrológicas e paleoambientais em resposta às variações paleoclimáticas quaternárias. A área estudada está localizada no noroeste do Paraná, próximo a cidade de Querência do Norte, na margem esquerda do rio Paraná. Com base em dados de sensores remotos e de campo, que incluíram sondagens vibratórias e descrição de afloramentos, foi realizada a compartimentação e caracterização geomorfológica da área estudada com reconhecimento de terraços associados aos rios Paraná e Ivaí, planícies atuais de ambos os rios, lagoas de variados formatos e leques aluviais inativos formados por riachos que drenam terrenos situados a leste. Dados geomorfológicos, geológicos, datações absolutas (LOE e 14C) e interpretação de dados proxy como espículas de esponjas continentais, frústulas de diatomáceas e fitólitos permitiram reconstituir condições paleoambientais e paleoclimáticas. Datações revelaram idades de 150.900±32.400 e 50.300±7.900 anos AP para os terraços; 26.900±5.000 e 20.600±4.800 anos AP para as lagoas; e 7.540 anos AP para o leque aluvial. Os terraços da área estudada foram correlacionados com as unidades geomorfológicas Taquaruçu e Fazenda Boa Vista, no sudeste do Mato Grosso do Sul, e Terraço Ivaí, na margem direita do rio Ivaí, interpretados como extensões dessas unidades e produtos dos mesmos eventos paleoambientais/paleoclimáticos quaternários. A presença de espículas de esponjas em sedimentos lacustres descartou a contribuição de ambientes lóticos na gênese e evolução das lagoas. Foram identificadas gemoscleras correspondentes a quatro espécies de esponjas: a) Dosilia pydanieli; b) Radiospongilla amazonensis; c) Metania spinata, e d) Uruguaya corallioides; e frústulas de diatomáceas dos gêneros: a)... / Terraces levels and sedimentary deposits of different ages and characteristics in the upper Paraná River has been associated as a paleohydrological and paleoenvironmental record by Quaternary paleoclimatic changes. The study area is located in northwest of Paraná State (Brazil), near to Querência do Norte city, left bank of upper Paraná river. Based on remote sensing data and fieldworks, including vibro-core drilling and outcrops description, was held the study área geomorphological subdivision and caracterization, with recognition of terraces associated of Parana and Ivaí rivers, current plains of both rivers, various formats ponds and inactive alluvial fans formed by streams that drain high land. Geomorphology, geology, absolute dating (OSL and 14C) and interpretation of proxy records data as continental sponges spicules, diatoms frustules and phytoliths allowed to reconstruct paleoenvironmental and paleoclimatic conditions. Dating showed ages of 150,900 ± 32,400 and 50,300 ± 7900 years BP to terraces; 26,900 ± 5,000 and 20,600 ± 4800 years BP to ponds; and 7,540 years BP to aluvial fan. The terraces of the study area were correlated with the geomorphological units Taquaruçu and Fazenda Boa Vista, in southeastern Mato Grosso do Sul State (Brazil), and Ivaí Terrace on the right bank of the lower Ivaí river. The terraces were interpreted as extensions of these units and products of the same Quaternary paleoenvironmental / paleoclimatic changes events. The presence of sponge spicules in lake sediments show that lotic environments were not associated with the ponds genesis and evolution. Gemmoscleres were identified corresponding to four sponges species: a) Dosilia pydanieli; b) Radiospongilla amazonensis c) Metania spinata; and d) Uruguaya corallioides, as well two genus of diatoms frustules: a) Pinnularia sp. and b) Eunotia sp., which enabled the interpretation of paleoenvironmental change. The terraces degradation and ... / Fundação Araucária: 422/2009

Made available in DSpace on 2016-01-13T13:27:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-05-15. Added 1 bitstream(s) on 2016-01-13T13:33:03Z : No. of bitstreams: 1 000855512.pdf: 12106098 bytes, checksum: 81ded2faf8546e1221957a9d444d5d83 (MD5) / O crescimento desordenado das cidades brasileiras e as intensas atividades antrópicas não tem levado em consideração as condições do meio físico em seu território, tendo como consequências diversas catástrofes e perdas econômicas, sociais e ambientais. Nesse sentido, a Compartimentação de Terreno, por meio da abordagem fisiográfica ou integrada, surge como importante instrumento de Avaliação Ambiental. Com base neste cenário a pesquisa desenvolvida teve como objetivo principal a elaboração de uma Carta de Compartimentação Fisiográfica, na escala 1:50.000; individualizadas em 8 Unidades Básicas de Compartimentação (UBC's), homogêneas internamente, porém distintas em suas adjacências, relacionadas à fisiografia dos terrenos, utilizando técnicas de fotointerpretação em fotografias aéreas e geoprocessamento. Tais técnicas, em conjunto com dados indiretos (bibliografia) e diretos (trabalhos de campo) permitiram a elaboração de um produto cartográfico padronizado, de fácil manuseio e interpretação. Para a aplicação do método foi escolhida a Bacia do ribeirão de Araras, onde está localizado o município de Araras (SP). Verificou-se na área urbana, nas planícies fluviais, o risco de ocorrência de cheias, já nas áreas agrícolas apresentaram locais suscetíveis a processos erosivos e no noroeste da bacia foi verificada a ocorrência de um boçorocamento. Nesse sentido, a área deve ser objeto de adequado planejamento territorial, com o objetivo de evitar ou minimizar os impactos negativos. Nesse sentido, concluiu-se que o método utilizado, apesar de conter a variável geológica como preponderante, é passível de execução por profissionais de outras áreas, desde que possuam uma familiaridade com o técnicas e conceitos a serem utilizados. Espera-se ainda que a presente pesquisa possa dar suporte, tanto aos órgãos públicos, pesquisadores e a iniciativa privada, em relação a informações... / The uncontrolled growth of Brazilian cities and the intense human activities do not have adequate knowledge of the physical environment conditions in its territory, having as consequences many disasters and economic, social and environmental losses. In this context, the land subdivision, through the physiographic or integrated approaches, emerges as an important instrument for Environmental Assessment. Based on this scenario, the developed research had as main objective the development of a Charter of Physiographic subdivision, at the scale 1: 50,000; with individualization of 8 Basic Units of subdivision (UBC's) internally homogeneous but distinct in its surroundings, related to the Lands physiographies, using photointerpretation techniques in aerial photography and GIS. Such techniques in conjunction with indirect (bibliography) and direct (fieldwork) data allowed the development of a standardized cartographic product, easy handling and interpretation. For the application of the method, it was chosen the Basin of Ribeirão de Araras (SP), where it is located the city of Araras (SP). It was found in the urban area, in fluvial plains, the risk of floods, already in agricultural areas was presented susceptible to erosion and in the northeast basin was checked gully. Therefore, the area should be subject to appropriate territorial planning, in order to avoid or minimize the negative impacts. Under the conditions given, it was concluded that the method used, despite it contains the geological variable as predominant, it is open to other areas of professionals for implementation and not only those who have familiarity with geological issues. It is also expected that this research might support both public institutions, researchers and the private sector regarding physiographic information of the Basin of Ribeirão de Araras (SP)

Made available in DSpace on 2014-06-11T19:33:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-11-18Bitstream added on 2014-06-13T20:24:48Z : No. of bitstreams: 1 hardt_r_dr_rcla.pdf: 4572815 bytes, checksum: 0c1bd7aa44b19280926515147be7a636 (MD5) / L’existence de karsts dans les grès a été longtemps sujette à controverse, mais est de plus en plus acceptée depuis les dernières décennies par les karstologues. Le sous-sol d’une grande partie du territoire brésilien se constitue de grès et de métagrès. Des pluies abondantes, un couvert végétal et une matière organique abondante liés au climat tropical caractérisant majoritairement le pays, la présence d’oxydes de fer et de périodes d’érosion physicochimique prolongées ont favorisé l’altération chimique des quartz. Cette combinaison de facteurs a produit une grande variété de reliefs karstiques, ainsi que leur organisation sous la forme de systèmes karstiques gréseux. Quatre zones ont été étudiées en détail afin de comparer et de caractériser la morphologie karstique et les systèmes karstiques dans cette lithologie. Au Brésil, il s’agit de la Serra d’Itaqueri, de la Chapada dos Guimarães et de la région de Campos Gerais. En France, nous avons examiné les morphologies associées aux grès de la forêt de Fontainebleau. En outre, d'autres sites ont été visités afin de recueillir des données comparatives permettant une meilleure compréhension des processus morphogénétiques et de l'organisation des reliefs. Cette étude démontre la nature karstique des formes rencontrées et apporte une meilleure compréhension à leur intégration dans les paysages et leur intégration systémique. Les connaissances ainsi acquises autorisent la formulation d’une série d’hypothèses sur les processus impliqués dans la structuration de ces reliefs et des systèmes karstiques. L’influence de la végétation est soulignée, notamment comme... (Résumé complet accès életronique cidessous) / A carstificação dos arenitos já foi considerado um tema polêmico no passado, mas nas últimas décadas, vem sendo cada vez mais aceito pela comunidade de pesquisadores do carste. No Brasil, uma ampla área do território possui afloramentos de arenitos e meta-arenitos, e o clima tropical, com abundância de chuva e vegetação, associado a presença de matéria orgânica, óxidos de ferro, sais e longo tempo de exposição às intempéries, entre outros elementos, permitem uma aceleração do processo de intemperismo químico do quartzo, produzindo uma ampla variedade de formas cársticas, além de uma organização espacial, permitindo-se falar em Sistemas Cársticos em Arenitos. Visando a comparação e a caracterização da morfologia cárstica e dos sistemas cársticos nesta litologia, quatro áreas foram estudadas com maior grau de detalhamento, bem como outras áreas foram visitadas, com a ideia de fornecer subsídios comparativos na compreensão dos processos e organização, através do estudo das formas. As áreas estudadas foram a Serra de Itaqueri; a Chapada dos Guimarães, e a região dos Campos Gerais, no Brasil, e a região da Forêt de Fontainebleau, na França. Conseguiu-se, com isso, demonstrar a natureza cárstica das formas de relevo encontradas, entender a organização destas formas na paisagem e sua integração sistêmica, e fornecer subsídios para a formulação de hipóteses dos processos envolvidos na estruturação de tais formas e sistemas, sobretudo da importância da cobertura vegetal, como auxiliar na dissolução do quartzo, e do processo de “fantomização” da rocha (alteração “in situ”) e posterior remoção, por dissolução completa ou mecanicamente, da matéria alterada, resultando em formas e sistemas cársticos... / Karstification of sandstone was considered a controversial topic in the past, but has become increasingly accepted by karst researchers in recent decades. A large area of Brazil’s territory has sandstone and metasandstone outcrops. The country’s tropical climate, abundant rainfall and vegetation, allied to the presence of organic matter, iron oxides, salts and long weathering processes, among other factors, accelerate the chemical weathering of quartz. This combination of factors has produced a wide variety of karst landforms, as well as a spatial organization, that allows them to be referred to as Sandstone Karst Systems. Four areas were studied in great detail to compare and characterize the karst morphology and karst systems in this lithology. In addition, other areas were visited to collect comparative data to help shed further light on geological processes and the organization of landforms. The areas under study were Serra de Itaqueri, the Chapada dos Guimarães, and the region of Campos Gerais in Brazil, and the region of Forêt de Fontainebleau in France. This study allowed for the determination of the karst topography and an understanding of the organization of these landscape processes and their systemic integration. The knowledge thus gained served to underpin the formulation of hypotheses about the processes involved in the structuring of these landforms and systems, and above all the importance of vegetation as an aid for quartz dissolution, and about the process of rock phantomization (in situ alteration) and subsequent removal of modified material by complete dissolution or by mechanical means, resulting in karst landforms and systems. The aforementioned hypotheses served as the basis for a proposal to amend the definition of karst with respect to the term... (Complete abstract click electronic access below)