Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 84-88). Also available on the Internet.

Thesis (Ph. D.)--University of Idaho, 2005. / Also available online in PDF format. Abstract. "August 2005." Includes bibliographical references.

Thesis (M.Sc.)(Geography)--University of Pretoria, 2005. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

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abstract: Numerous studies have examined the interplay of climate, tectonics, biota and erosion and found that these variables are intertwined in a complicated system of feedbacks and as a result, some of these factors are often oversimplified or simply neglected. To understand the interplay of these factors one must understand the processes that transport or inhibit transport of soil. This study uses the short-lived, fallout-derived, radionuclides 137Cs and 210Pb to identify soil transport processes and to quantify soil transport using the profile distribution model for 137Cs. Using five field sites in the San Gabriel Mountains of California, I address four questions: (1) Is there a process transition between high and low gradient slopes observable with short-lived isotopes? (2) Do convex hilltops reflect short-term equilibrium erosion rates? (3) Do linear transects of pits accurately characterize hillslope averaged erosion rates? and (4) What role does fire play on short-term soil transport and isotope distribution? I find no evidence supporting a process transition from low gradient to high gradient slopes but also find that significant spatial variability of erosion rates exist. This spatial variability is the result of sensitivity of the method to small scale variations in isotopes and indicates that small scale processes may dominate broader scale trends. I find that short-term erosion rates are not at equilibrium on a convex hilltop and suggest the possibility of a headward incision signal. Data from a post-fire landscape indicates that fires may create complications in 137Cs and 210Pb distribution that current models for erosion calculation do not account for. I also find that across all my field sites soil transport processes can be identified and quantified using short-lived isotopes and I suggest high resolution grid sampling be used instead of linear transects so that small scale variability can be averaged out. / Dissertation/Thesis / M.S. Geological Sciences 2011

O solo é um recurso natural e fundamental para toda a vida terrestre e a questão da degradação do solo assume importância não apenas ambiental, mas também de ordem social e econômica. A erosão pela água da chuva é o mais severo tipo de erosão, podendo ser encontradas diversas feições erosivas resultantes desse processo tais como erosão laminar, em sulcos ou em voçorocas. Ainda, são encontradas as feições erosivas subsuperficiais (pipes), que embora sejam menos estudadas e difíceis de quantificar, provocam perdas de solo que podem ultrapassar as quantias advindas dos processos erosivos mais tradicionalmente estudados. O objetivo deste trabalho foi o de entender a gênese das feições erosivas superficiais e subsuperficiais através da análise dos atributos físico-hídricos do solo e do relevo. Foi efetuado o mapeamento subsuperficial de pipes e a caracterização dos materiais de subsuperfície por meio da técnica geofísica da eletrorresistividade. Aliado a isso, utilizou-se a técnica da dendrogeomorfologia como ferramenta para datação, quantificação e reconstrução da dinâmica dos processos erosivos ocorrentes na área de estudo. Os resultados demonstraram que a gênese e desencadeamento dos pipes da área de estudo foi governada por fatores concorrentes, dada a complexidade da área de estudo, tais como gradiente de atributos físicos entre horizontes do solo (textura, estrutura, porosidade), estrutura e composição geológica, e gradientes topográficos. Fatores neotectônicos e morfoestruturais também poderiam estar afetando, entretanto devem ser melhor estudados. O método da eletrorresistividade foi eficiente na caracterização da geometria dos materiais em subsuperfície e na deteccção da presença de pipes, colapsados e ainda não colapsados, sendo importante para não subestimar os processos subsuperficiais. Os resultados obtidos também demonstraram o potencial da espécie Esenbeckia leiocarpa para estudos dendrogeomorfológicos, uma vez que as mudanças nos padrões de crescimento após a exposição das raízes possibilitaram datar o primeiro ano de exposição. A técnica da dendrogromorfologia se mostrou eficaz em entender a dinâmica do processo de sistemas complexos, tais como a abertura de voçorocas e voçorocas efêmeras e que a subsidência da superfície do solo causada pelos pipings é responsável pela formação e evolução das voçorocas efêmeras e pela ramificação da voçoroca principal. / Soil is a natural and fundamental resource for all terrestrial life and the question of soil degradation assumes not only environmental but also social and economic importance. Erosion by rainwater is the most severe type of erosion, and several erosive forms resulting from this process can be found such as sheet erosion, ephemeral gullies or gullies. Also, subsurface erosive forms (pipes) are found, although they are less studied and difficult to quantify, they cause soil losses that exceed the amounts coming from the more traditionally studied superficial erosive processes. The objective of this work was to understand the genesis of superficial and subsurface erosive forms from the perspective of soil and relief properties. Subsurface pipe mapping and the characterization of subsurface materials using the geophysical technique of electroresistivity, was performed. The dating, quantification and reconstruction of the dynamics of the erosive processes occurring in the study area were done using dendrogeomorphology as a tool. The results demonstrated that the genesis and the initiation of pipes in the study area was governed by competing factors, due to the complexity of the study area, such as the gradient of physical attributes between soil horizons (texture, structure, porosity), structure and geological composition, and topographic gradients. Neotectonic and morphostructural factors could also be affecting, however they should be better studied. The electroresistivity method was efficient in characterizing the geometry of the materials in subsurface and in detecting the presence of pipes, collapsed and not yet collapsed, aiding in avoiding the underestimation of the subsurface erosive processes. The results obtained demonstrated the potential of the species Esenbeckia leiocarpa for dendrogeomorphological studies, since the changes in the patterns of root growth after exposure allowed to date the first year of exposure. Dendrogromorphology also proved effective in understanding the process dynamics of complex systems, such as the opening of gullies and ephemeral gullies, and that the subsidence of the soil surface caused by pipings is responsible for the formation and evolution of ephemeral gullies and the branching of the main gully.

Le contrôle de la sûreté des ouvrages hydrauliques est l’une des grandes priorité dans le domaine du génie civil et de l’ingénierie hydraulique. Durant sa vie, un ouvrage est soumis à des sollicitations variables hydromécaniques, physicochimiques et climatiques qui contribuent à son éventuelle détérioration. Parmi les phénomènes qui en résultent, l’érosion des sols sous toutes ses formes représente un enjeu majeur à comprendre, maîtriser et empêcher. L’objectif de ce travail est d’étudier l’érosion des sols par le Jet Erosion Test. La première partie est consacrée à la description des dispositifs expérimentaux, surtout le Jet Erosion Test (JET) développé à l’Ecole Centrale Paris permettant de mesurer directement quelques paramètres d’érosion. A partir des résultats du JET, à l’aide d’une loi d’érosion empirique, nous déduisons la contrainte de cisaillement critique, le coefficient d’érosion, la profondeur d’érosion d’équilibre. La deuxième partie du travail est consacrée à l’étude de l’influence des paramètres de compactage sur l’infiltration de l’eau et la résistance du sol, en utilisant le pénétromètre. Dans les troisième et quatrième parties, nous étudions l’influence des propriétés géotechniques du sol et celle des paramètres d’essai sur les paramètres d’érosion du sol. Les résultats obtenus montrent que les paramètres d’érosion sont influencés non seulement par les propriétés géotechniques du sol mais aussi par les paramètres d’essai. La dernière partie présente la synthèse entre les résultats des essais de pénétromètre et ceux des essai de JET, et tente de relier les paramètres d’érosion avec les propriétés géotechniques du sol. / Control of the safety of hydraulic structures is a major priority in the field of civil and hydraulic engineering. During its life, the hydraulic structure is submitted to variable hydromechanical, physicochemical and climatic loads that may contribute to its possible failure. Among the resulting phenomena, soil erosion under all its forms is a major challenge which it is important to understand, control and prevent. The objective of this work is to study soil erosion by the Jet Erosion Test. The first part is devoted to the description of the experimental devices, especially the Jet Erosion Test (JET) developed at the Ecole Centrale Paris to directly measure some erosion parameters. From the results of JET, using an empirical erosion law, we deduce the critical shear stress, the erosion coefficient, the equilibrium scour depth. The second part of this work is devoted to the study of the influence of compaction parameters on water infiltration and soil strength, using the penetrometer. In the third and fourth parts, we study the influence of the geotechnical properties of soil and of the test parameters on the erosion parameters of soil. The obtained results show that the erosion parameters are influenced not only by the geotechnical properties of soil but also by the test parameters. The final section presents a synthesis of the results of penetrometer tests and JET tests, and attempts to link the erosion parameters with the geotechnical properties of soil.

Land and water degradations are serious environmental concerns facing South Africa. One of the major causes is human-induced soil erosion due to intensified land uses and environmental degradation caused by bad agricultural practices and inappropriate land uses. Soil erosion is a typical and important example of land degradation that the LandCare program intends to address. In order to evaluate the success of LandCare project in addressing soil erosion evaluation tools which can be applied during the project monitoring and evaluation process. Several soil loss models and field assessment methods were theoretically evaluated on criteria such as the scientific principles, availability and the impact of data requirements of the models. Soil loss models, SLEMSA (Soil Loss Estimation for Southern Africa) and RUSLE (Revised Universal Soil Loss Estimation) and the ACED (Assessment of Current Erosion Damage) method were selected to be tested in a study area that is naturally susceptible to erosion. The soil loss as predicted by RUSLE and SLEMSA and that resulting from visible damage as accounted by ACED method is not comparable. The SLEMSA and RUSLE models vary considerably in extent and approach compared with the field assessment method, ACED. ACED can be used as a participatory learning erosion tool and to identify critical areas on hillslopes. SLEMSA and RUSLE had predictive advantage over ACED and could predict soil loss before and after the LandCare project. Therefore, the models were considered valuable tools to guide decision-making based on the management and use of the natural resources on farmland or by the community. Soil loss models that require readily available input data, such as RUSLE and SLEMSA, are suitable evaluation tools for monitoring and evaluation of soil erosion in LandCare project. Based on the results of the scenario prediction study, it was found that RUSLE could simulate the impact of different agricultural practices much better than SLEMSA. However, the reliability of SLEMSA and RUSLE should be verified with measured data from erosion plots as RUSLE also underestimate the erodibility of the Escourt soil. / Dissertation (MSc (Agriculture))--University of Pretoria, 2006. / Plant Production and Soil Science / unrestricted

Under the threat of global warming it is vital to determine the impact that future changes in climate may have on the environment and to what extent any adverse effects can be mitigated. In this research an assessment was carried out on the impact that climate trends may have on soil erosion and contaminant transport in India and examined the potential for top soil management practices to improve or maintain soil quality. Historical rainfall data from 50-135 years and extreme temperature data for 103 years were analysed and long term trends were assessed for various aspects of Indian climates using suitable statistical techniques. Results indicated that intra-region variability for extreme monsoon seasonal rainfall is large and mostly exhibited a negative tendency leading to increasing frequency and magnitude of monsoon rainfall deficit and decreasing frequency and magnitude of monsoon rainfall excess everywhere in India except in the peninsular Indian region. This is further exacerbated by increased and more variable extreme temperatures. Intra-region rainfall variability in India is linked to the pacific Southern Oscillation, where the associations of monsoon drought and El-Niño Southern Oscillation (ENSO) in the regions near to coast are greatest. 50-years high resolution daily gridded rainfall data was analysed to set up certain indices for the extreme daily rainfalls to assess their changes for the six gridded regions of Kerala, the extreme south western state of India where monsoon rainfall initiates every year. This was also done for two study sites, namely Bhoj wetland area of west central India and Sukinda chromite mining site of central north east India. Significant decrease was found in monsoon and spring rainfall extremes and increase in winter and autumn rainfall extremes in Kerala that would affect the tendency of change in seasonal total rainfall as well. Decrease in monsoon rainfall in Kerala also indicate that monsoon rainfall is decreasing in India as a whole, increased occurrence of floods is expected in winter and autumn seasons, together with water scarcity are expected to be felt both in spring and monsoon seasons with a delaying monsoon onset in Kerala. Soil erosion studies were conducted for two northern most gridded regions of Kerala as an extended work of the related MPhil study, and contaminant transport with eroded sediments was looked at for the Bhoj and Sukinda sites using RUSLE2 model software and other suitable numerical methods. It was found that soil erosion depended on a complex interaction of climate, soil properties, topography, and cover management. An assessment on extreme climate patterns for Bhoj and Sukinda showed an increasing tendency of seasonal and annual rainfall extremes and temperatures leading to an increasing pattern of soil erosion at both the sites. However, a certain consensus was difficult to reach because of the complex interaction of climate and soil carbon that is a very important deciding factor for soil erosion potential. Vegetative cover and plant residue was found providing essential soil nutrients, enhancing soil properties and retarding rainfall impact on bare top soil leading to reduction of soil erosion. Therefore, a soil erosion and contaminant transport prevention plan should take care of the top soil such that it is not kept bare especially when rainfall intensity is high in a given year. This work as a whole has highlighted the importance of regional climatological analysis with the large scale spatial averages especially at local decision making level, which is very useful for the broad scenarios such as climatological and ecological risk management.