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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
291

Soil Erosion Risk Factors and the Impacts of Diversification on Organic Strawberry Farms along California’s Central Coast

Sterner, Kay 01 January 2017 (has links)
Soil erosion is a major issue that threatens to undermine our current system of agriculture. Due to the fact that this system is in turn the number one cause of erosion, agricultural practices in the United States need to be rethought. This study explores how traditional ideas of erosion risks are related to observed erosion on organic strawberry farms along California’s Central Coast. In addition, diversified farming systems are addressed as a possible solution for the current unsustainability of our farming practices. The data from this research suggest that diversity of crops on farms could be linked to less soil erosion. These results are promising for the future of diversification as a new framework for agriculture.
292

Photogrammetric techniques for across-scale soil erosion assessment

Eltner, Anette 01 November 2016 (has links) (PDF)
Soil erosion is a complex geomorphological process with varying influences of different impacts at different spatio-temporal scales. To date, measurement of soil erosion is predominantly realisable at specific scales, thereby detecting separate processes, e.g. interrill erosion contrary to rill erosion. It is difficult to survey soil surface changes at larger areal coverage such as field scale with high spatial resolution. Either net changes at the system outlet or remaining traces after the erosional event are usually measured. Thus, either quasi-point measurements are extrapolated to the corresponding area without knowing the actual sediment source as well as sediment storage behaviour on the plot or erosion rates are estimated disrupting the area of investigation during the data acquisition impeding multi-temporal assessment. Furthermore, established methods of soil erosion detection and quantification are typically only reliable for large event magnitudes, very labour and time intense, or inflexible. To better observe soil erosion processes at field scale and under natural conditions, the development of a method is necessary, which identifies and quantifies sediment sources and sinks at the hillslope with high spatial resolution and captures single precipitation events as well as allows for longer observation periods. Therefore, an approach is introduced, which measures soil surface changes for multi-spatio-temporal scales without disturbing the area of interest. Recent advances regarding techniques to capture high resolution topography (HiRT) data led to several promising tools for soil erosion measurement with corresponding advantages but also disadvantages. The necessity exists to evaluate those methods because they have been rarely utilised in soil surface studies. On the one hand, there is terrestrial laser scanning (TLS), which comprises high error reliability and retrieves 3D information directly. And on the other hand, there is unmanned aerial vehicle (UAV) technology in combination with structure from motion (SfM) algorithms resulting in UAV photogrammetry, which is very flexible in the field and depicts a beneficial perspective. Evaluation of the TLS feasibility reveals that this method implies a systematic error that is distance-related and temporal constant for the investigated device and can be corrected transferring calibration values retrieved from an estimated lookup table. However, TLS still reaches its application limits quickly due to an unfavourable (almost horizontal) scanning view at the soil surface resulting in a fast decrease of point density and increase of noise with increasing distance from the device. UAV photogrammetry allows for a better perspective (birds-eye view) onto the area of interest, but possesses more complex error behaviour, especially in regard to the systematic error of a DEM dome, which depends on the method for 3D reconstruction from 2D images (i.e. options for additional implementation of observations) and on the image network configuration (i.e. parallel-axes and control point configuration). Therefore, a procedure is developed that enables flexible usage of different cameras and software tools without the need of additional information or specific camera orientations and yet avoiding this dome error. Furthermore, the accuracy potential of UAV photogrammetry describing rough soil surfaces is assessed because so far corresponding data is missing. Both HiRT methods are used for multi-temporal measurement of soil erosion processes resulting in surface changes of low magnitudes, i.e. rill and especially interrill erosion. Thus, a reference with high accuracy and stability is a requirement. A local reference system with sub-cm and at its best 1 mm accuracy is setup and confirmed by control surveys. TLS and UAV photogrammetry data registration with these targets ensures that errors due to referencing are of minimal impact. Analysis of the multi-temporal performance of both HiRT methods affirms TLS to be suitable for the detection of erosion forms of larger magnitudes because of a level of detection (LoD) of 1.5 cm. UAV photogrammetry enables the quantification of even lower magnitude changes (LoD of 1 cm) and a reliable observation of the change of surface roughness, which is important for runoff processes, at field plots due to high spatial resolution (1 cm²). Synergetic data fusion as a subsequent post-processing step is necessary to exploit the advantages of both HiRT methods and potentially further increase the LoD. The unprecedented high level of information entails the need for automatic geomorphic feature extraction due to the large amount of novel content. Therefore, a method is developed, which allows for accurate rill extraction and rill parameter calculation with high resolution enabling new perspectives onto rill erosion that has not been possible before due to labour and area access limits. Erosion volume and cross sections are calculated for each rill revealing a dominant rill deepening. Furthermore, rill shifting in dependence of the rill orientation towards the dominant wind direction is revealed. Two field plots are installed at erosion prone positions in the Mediterranean (1,000 m²) and in the European loess belt (600 m²) to ensure the detection of surface changes, permitting the evaluation of the feasibility, potential and limits of TLS and UAV photogrammetry in soil erosion studies. Observations are made regarding sediment connectivity at the hillslope scale. Both HiRT methods enable the identification of local sediment sources and sinks, but still exhibiting some degree of uncertainty due to the comparable high LoD in regard to laminar accumulation and interrill erosion processes. At both field sites wheel tracks and erosion rills increase hydrological and sedimentological connectivity. However, at the Mediterranean field plot especially dis-connectivity is obvious. At the European loess belt case study a triggering event could be captured, which led to high erosion rates due to high soil moisture contents and yet further erosion increase due to rill amplification after rill incision. Estimated soil erosion rates range between 2.6 tha-1 and 121.5 tha-1 for single precipitation events and illustrate a large variability due to very different site specifications, although both case studies are located in fragile landscapes. However, the susceptibility to soil erosion has different primary causes, i.e. torrential precipitation at the Mediterranean site and high soil erodibility at the European loess belt site. The future capability of the HiRT methods is their potential to be applicable at yet larger scales. Hence, investigations of the importance of gullys for sediment connectivity between hillslopes and channels are possible as well as the possible explanation of different erosion rates observed at hillslope and at catchment scales because local sediment sink and sources can be quantified. In addition, HiRT data can be a great tool for calibrating, validating and enhancing soil erosion models due to the unprecedented level of detail and the flexible multi-spatio-temporal application.
293

The ecology of sodic sites in the Eastern Transvaal Lowveld

Chappell, Clive January 1992 (has links)
Submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg as a requirement for the Degree of Master of Science. Johannesburg, 1992. / The effect of sodium on clays dominates the formation and ecology of granitic eatenas in the Eastern Transvaal Lowveld. This study reviews the process involved and explains the soil, vegetation and erosion patterns in this landscape. Weathering parent rock gives rise to sodium in sufficient amounts to promote clay dispersion. Dispersed, mobile, clays respond to seasonal pulses of laterally moving soil water resulting in alternating zones of clay illuviation and clay deposition down hillslopes [Abbreviated Abstract. Open document to view full version] / AC2017
294

Conservação do solo e cana-de-açúcar: aspectos legais e bibliométricos e uma ferramenta de determinação do Fator C (RUSLE) / Soil conservation and sugarcane: legal and bibliometric outlook and a comprehensive C-Factor calculation tool (RUSLE)

Rocha, Gustavo Casoni da 08 March 2017 (has links)
A pressão por aumento da produção agrícola, seja por abertura de novas áreas, seja por aumento de produtividade, tem um impacto direto no uso e conservação do solo. A cana-de-açúcar, por ser uma cultura híbrida- alimentar e energética, tem grande relevância estratégica e seu sistema de produção muito ligado à agroindústria. Seu sistema de produção, portanto, tem pressão direta para uma maior eficiência (indústria), mas também para mecanismos ambientalmente mais sustentáveis (sociedade). O primeiro artigo apresentado foi uma sistematização da regulamentação legal e da produção científica na área de conservação de solo no Brasil e uma análise comparativa de ambos elementos: regulamentação e ciência. O arcabouço legal brasileiro sobre a conservação de solo reconhece sua importância, mas apresenta poucas ferramentas práticas efetivas. Existem políticas de incentivos econômicos à produção em nível federal e são observadas regulamentações para a penalização de danos causados ao solo, apenas em nível estadual (4 estados). Outros 4 estados preveem sistemas de PSA. No geral, a decisão de se conservar o solo é privada, não sendo direcionada ou induzida por um regulamento (salvo exceções). A produção científica tem uma abordagem predominantemente privada, contribuindo com soluções e compreensão dos impactos internos ao sistema agrícola. Os estudos que abordam as externalidades do processo erosivo, ou que possuem o entendimento da conservação de solo como um serviço ambiental, estão em menor número quando comparados aos estudos de abordagem privada. O estabelecimento de normatização que contemple os princípios básicos do direito ambiental (precaução, responsabilidade e poluidor-pagador) e os diferentes instrumentos (comando e controle e incentivos econômicos) é um caminho promissor para a regular o uso do solo de forma sustentável. Uma produção científica oriunda de linhas de pesquisa que contemplem as externalidades do processo erosivo pode contribuir para o estabelecimento destas normas de forma mais clara, viável e efetiva. A importância de modelos para estudo da erosão vem da dificuldade de montar experimentos de mensuração de perda de solo em campo. O Fator C (RUSLE) congrega a cobertura e o manejo das culturas. Dada a variabilidade de manejo da cana-de-açúcar, buscou-se no segundo capítulo compilar e analisar trabalhos que geraram ou citaram o valor de C. Levantou-se 39 trabalhos científicos, com valores que variam de 0.0012 a 0.5800. Este intervalo resulta em uma variação de mais de 480 vezes nos valores finais de perda de solo. Uma grande lacuna de valores de Fator C para variadas condições de manejo é observada, bem como a falta de clareza e critérios no uso de valores por modeladores e pesquisadores. Neste sentido, o terceiro artigo é uma contribuição para sintetizar o conhecimento local da cultura, na forma de uma ferramenta de cálculo do Fator C para a cultura. A ferramenta permite mais de 100 milhões de combinações e está em ambiente acessível e com interface simplificada (Excel). Os valores obtidos pela ferramenta são comparáveis aos desenvolvidos em campo. A amplitude máxima e mínima (0.5922 a 0.0351) observada reafirma a importância do conhecimento completo das condições de manejo da área de estudo para sua modelagem. A ferramenta é gratuita e está disponível para pesquisadores. / The pressure for increased agricultural production, either by opening new areas or by increasing productivity, has a direct impact in the soil use and conservation. Sugarcane, because it is a hybrid food and energy crop, has great strategic relevance and its production system closely linked to agroindustry. Its production system, therefore, has direct pressure for greater efficiency (industry), but also for more environmentally sustainable mechanisms (society). The first article presented was a systematization of legal regulation and scientific production in the area of soil conservation in Brazil and a comparative analysis of both elements: regulation and science. The Brazilian legal framework on soil conservation recognizes its importance, but presents few effective practical tools. There are policies of economic incentives for production at the federal level and regulations are observed to penalize damages to the soil, only at the state level (4 states). Another 4 states provide PSA systems. In general, the decision to conserve the soil is private, not being directed or induced by a regulation (with exceptions). Scientific production has a predominantly private approach, contributing with solutions and understanding of the internal impacts to the agricultural system. Studies that address the erosion process externalities, or that have the understanding of soil conservation as an environmental service, are less numerous when compared to the private approach studies. The establishment of standardization that contemplates the basic principles of environmental law (precaution, responsibility and polluter-payer) and the different instruments (command and control and economic incentives) is a promising way to regulate the use of the soil in a sustainable way. A scientific production derived from lines of research that contemplate the externalities of the erosive process can contribute to the establishment of these norms in a clearer, viable and effective way. The importance of models for the study of erosion comes from the difficulty of assembling soil loss measurement experiments in the field. C-Factor (RUSLE) brings together the coverage and management of crops. Considering the variability of sugarcane management, the second chapter compiled and analyzed works that generated or quoted the value of C. 39 scientific works, with values ranging from 0.0012 to 0.5800 were survey. This interval results in a variation of more than 480 times in the final values of soil loss. A large gap of C-Factor values for various management conditions is observed, as well as the lack of clarity and criteria in the use of values by modelers and researchers. In this sense, the third article is a contribution to synthesize local knowledge of culture, in the form of a tool for calculating C-Factor for culture. The tool allows more than 100 million combinations and is in an accessible environment with a simplified interface (Excel). The values obtained by the tool are comparable to those developed in the field. The maximum and minimum amplitude (0.5922 to 0.0351) observed reaffirms the importance of the complete knowledge of the management conditions of the study area for its modeling. The tool is free and available to researchers.
295

Aménagements hydroélectriques et conséquences environnementales dans le nord du Vietnam / Hydropower development and environmental consequences in northern Vietnam

Nguyen Van, Thiet 02 July 2015 (has links)
La thèse pose l’hypothèse que la construction des barrages hydroélectriques pourrait être un moteur de développement harmonieux entre montagnes et plaines. L’objectif serait de relier politiques de développement des barrages hydroélectriques et politiques agricoles en fonction des stratégies individuelles et des contraintes physiques et socio-économiques. Depuis les années 2000, dans toute l’Asie du Sud-Est, de nombreux projets de grands barrages hydroélectriques sont construits ou en construction pour répondre à la forte croissance de la demande en énergie, entraînant de grandes menaces sur la gestion de l’eau et l’environnement d’une part, et imposant d’importants déplacements de population d’autre part. Dans ces régions de montagne, les processus d’érosion représentent un risque majeur à la fois pour le comblement des lacs de barrage et pour la productivité agricole. Aussi grands investisseurs, pour la durée de vie des barrages hydroélectriques, et petits exploitants, pour leurs moyens de subsistance, se retrouvent également impactés. Le défi est de reformuler la relation entre la planification et la gestion des barrages hydroélectriques, et la planification et la gestion des terres agricoles des zones amont des barrages. Même si l’accompagnement socio-économique a été très largement amélioré de la part de l’Etat vietnamien, les agriculteurs déplacés et non-déplacés sont encore largement à subir les mutations sociospatiales régionales en cours. En effet, malgré des bonnes intentions gouvernementales et internationales, le manque de concertation au niveau local et le manque de connaissance en hydro-écologie restent les contraintes majeures pour le succès de la protection environnementale et l’équité entre les populations concernées, deux conditions obligatoires à la durabilité des projets de barrages hydroélectriques. Pour conclure, il semble que le succès d’implantation d’un grand barrage hydroélectrique soit lié à la capacité des décideurs à comprendre les interactions complexes entre systèmes écologiques et systèmes socio-économiques. / The thesis project assumes that the construction of hydropower dams could be a driven force for a harmonious economic development between mountains and plains. The aim would be to link policies for hydropower dam development, and policies for agriculture in mountains, within individual strategies, in relationship with physical and socio-economic constraints. Since 2000’s, throughout Southeast Asia, many projects of large hydropower dams are built or being built to meet the strong growth in demand for energy, causing great threats to water management and the environment on the one hand, and imposing important population displacement on the other hand. In these mountainous regions, the erosion process is a major risk for both the filling of reservoirs and agricultural soil productivity. Then major investors, for the lifespan of hydropower dams, and small farmers, for their livelihoods, are equally impacted. The challenge is to reformulate the relationship between planning and management of hydropower dams, and planning and management of agricultural uplands in upstream areas of dams. Although the socio-economic support has been very much improved from the Vietnamese State, displaced and non-displaced farmers are still largely undergoing regional socio-spatial changes on-going. In spite of good government and international intentions, the lack of consultation at local level and the lack of knowledge in hydro-ecology remain major constraints to the success of environmental protection and equity between the concerned populations, two mandatory conditions for sustainability of hydroelectric dam projects. In conclusion, it appears that the successful implantation of a large hydroelectric dam is related to the ability of policymakers to understand the complex interactions between ecological and socio-economic systems.
296

Conservação do solo e cana-de-açúcar: aspectos legais e bibliométricos e uma ferramenta de determinação do Fator C (RUSLE) / Soil conservation and sugarcane: legal and bibliometric outlook and a comprehensive C-Factor calculation tool (RUSLE)

Gustavo Casoni da Rocha 08 March 2017 (has links)
A pressão por aumento da produção agrícola, seja por abertura de novas áreas, seja por aumento de produtividade, tem um impacto direto no uso e conservação do solo. A cana-de-açúcar, por ser uma cultura híbrida- alimentar e energética, tem grande relevância estratégica e seu sistema de produção muito ligado à agroindústria. Seu sistema de produção, portanto, tem pressão direta para uma maior eficiência (indústria), mas também para mecanismos ambientalmente mais sustentáveis (sociedade). O primeiro artigo apresentado foi uma sistematização da regulamentação legal e da produção científica na área de conservação de solo no Brasil e uma análise comparativa de ambos elementos: regulamentação e ciência. O arcabouço legal brasileiro sobre a conservação de solo reconhece sua importância, mas apresenta poucas ferramentas práticas efetivas. Existem políticas de incentivos econômicos à produção em nível federal e são observadas regulamentações para a penalização de danos causados ao solo, apenas em nível estadual (4 estados). Outros 4 estados preveem sistemas de PSA. No geral, a decisão de se conservar o solo é privada, não sendo direcionada ou induzida por um regulamento (salvo exceções). A produção científica tem uma abordagem predominantemente privada, contribuindo com soluções e compreensão dos impactos internos ao sistema agrícola. Os estudos que abordam as externalidades do processo erosivo, ou que possuem o entendimento da conservação de solo como um serviço ambiental, estão em menor número quando comparados aos estudos de abordagem privada. O estabelecimento de normatização que contemple os princípios básicos do direito ambiental (precaução, responsabilidade e poluidor-pagador) e os diferentes instrumentos (comando e controle e incentivos econômicos) é um caminho promissor para a regular o uso do solo de forma sustentável. Uma produção científica oriunda de linhas de pesquisa que contemplem as externalidades do processo erosivo pode contribuir para o estabelecimento destas normas de forma mais clara, viável e efetiva. A importância de modelos para estudo da erosão vem da dificuldade de montar experimentos de mensuração de perda de solo em campo. O Fator C (RUSLE) congrega a cobertura e o manejo das culturas. Dada a variabilidade de manejo da cana-de-açúcar, buscou-se no segundo capítulo compilar e analisar trabalhos que geraram ou citaram o valor de C. Levantou-se 39 trabalhos científicos, com valores que variam de 0.0012 a 0.5800. Este intervalo resulta em uma variação de mais de 480 vezes nos valores finais de perda de solo. Uma grande lacuna de valores de Fator C para variadas condições de manejo é observada, bem como a falta de clareza e critérios no uso de valores por modeladores e pesquisadores. Neste sentido, o terceiro artigo é uma contribuição para sintetizar o conhecimento local da cultura, na forma de uma ferramenta de cálculo do Fator C para a cultura. A ferramenta permite mais de 100 milhões de combinações e está em ambiente acessível e com interface simplificada (Excel). Os valores obtidos pela ferramenta são comparáveis aos desenvolvidos em campo. A amplitude máxima e mínima (0.5922 a 0.0351) observada reafirma a importância do conhecimento completo das condições de manejo da área de estudo para sua modelagem. A ferramenta é gratuita e está disponível para pesquisadores. / The pressure for increased agricultural production, either by opening new areas or by increasing productivity, has a direct impact in the soil use and conservation. Sugarcane, because it is a hybrid food and energy crop, has great strategic relevance and its production system closely linked to agroindustry. Its production system, therefore, has direct pressure for greater efficiency (industry), but also for more environmentally sustainable mechanisms (society). The first article presented was a systematization of legal regulation and scientific production in the area of soil conservation in Brazil and a comparative analysis of both elements: regulation and science. The Brazilian legal framework on soil conservation recognizes its importance, but presents few effective practical tools. There are policies of economic incentives for production at the federal level and regulations are observed to penalize damages to the soil, only at the state level (4 states). Another 4 states provide PSA systems. In general, the decision to conserve the soil is private, not being directed or induced by a regulation (with exceptions). Scientific production has a predominantly private approach, contributing with solutions and understanding of the internal impacts to the agricultural system. Studies that address the erosion process externalities, or that have the understanding of soil conservation as an environmental service, are less numerous when compared to the private approach studies. The establishment of standardization that contemplates the basic principles of environmental law (precaution, responsibility and polluter-payer) and the different instruments (command and control and economic incentives) is a promising way to regulate the use of the soil in a sustainable way. A scientific production derived from lines of research that contemplate the externalities of the erosive process can contribute to the establishment of these norms in a clearer, viable and effective way. The importance of models for the study of erosion comes from the difficulty of assembling soil loss measurement experiments in the field. C-Factor (RUSLE) brings together the coverage and management of crops. Considering the variability of sugarcane management, the second chapter compiled and analyzed works that generated or quoted the value of C. 39 scientific works, with values ranging from 0.0012 to 0.5800 were survey. This interval results in a variation of more than 480 times in the final values of soil loss. A large gap of C-Factor values for various management conditions is observed, as well as the lack of clarity and criteria in the use of values by modelers and researchers. In this sense, the third article is a contribution to synthesize local knowledge of culture, in the form of a tool for calculating C-Factor for culture. The tool allows more than 100 million combinations and is in an accessible environment with a simplified interface (Excel). The values obtained by the tool are comparable to those developed in the field. The maximum and minimum amplitude (0.5922 to 0.0351) observed reaffirms the importance of the complete knowledge of the management conditions of the study area for its modeling. The tool is free and available to researchers.
297

Spatial analysis of soil depth variability and pedogenesis along toposequences in the Troodos Mountains, Cyprus

Robins, Colin R. 17 August 2004 (has links)
In unstable landscapes, modern pedological research explores the role of soils as products and indicators of geomorphologic change. Understanding the dynamics of hill slope pedogenesis is especially important in regions with limited, poor, or threatened soil resources. The island of Cyprus, situated in the eastern Mediterranean, is claimed by many authors to exhibit signs of severe soil degradation and is a prime site for comparative soil geomorphologic research. This study strove to 1) identify the controls of soil genesis and landscape stability within the Troodos Mountains of Cyprus using image and GIS analysis; 2) compare toposequence data to expected soil thickness trends from traditional models of xeric soil toposequences prevalent in current scientific literature; and 3) develop a predictive model for hillslope pedogenesis based on measured soil properties within the field area. Study soils within the Troodos are thin, weakly developed Lithic and Typic Xerorthents formed in colluvium derived from fractured, igneous bedrock. Soil thickness was measured at 368 sites in seven transects across three watersheds in the Troodos, using interpretations of field profiles and image analysis of digital soil-bedrock profiles in photographed road-cuts along forestry paths. Soil thickness was compared through GIS and statistical analysis to landscape attributes derived from a 25-m DEM and other map data. Results indicate that lithology is the only factor of several studied to have a significant relationship with the variability of soil-profile thickness in the Troodos, and that soil thickness does not vary in a predictable manner across toposequences. These results, combined with differences between measured soil data and values predicted by the landscape stability model SHALSTAB, suggest that soil genesis in the Troodos is best described only within the context of a weathering-limited geomorphological system. Short-term disruptive processes such as forest fires, land sliding, tree throw, and raindrop impact, combined with long-term processes such as tectonic uplift and stream incision, are the most likely driving forces behind the rapid erosion of hill slope sediments and the weak development of Troodos hill slope soils. These findings have important implications for DEM-based, predictive soil mapping in weathering-limited geomorphologic systems. / Graduation date: 2005
298

Ableitung von Blattflächenindex und Bedeckungsgrad aus Fernerkundungsdaten für das Erosionsmodell EROSION 3D

Klisch, Anja January 2003 (has links)
In den letzten Jahren wurden relativ komplexe Erosionsmodelle entwickelt, deren Teilprozesse immer mehr auf physikalisch begründeten Ansätzen beruhen. Damit verbunden ist eine höhere Anzahl aktueller Eingangsparameter, deren Bestimmung im Feld arbeits- und kostenaufwendig ist. Zudem werden die Parameter punktuell, also an bestimmten Stellen und nicht flächenhaft wie bei der Fernerkundung, erfasst. <br /> <br /> Im Rahmen dieser Arbeit wird gezeigt, wie Satellitendaten als relativ kostengünstige Ergänzung oder Alternative zur konventionellen Parametererhebung genutzt werden können. Dazu werden beispielhaft der Blattflächenindex (LAI) und der Bedeckungsgrad für das physikalisch begründete Erosionsmodell EROSION 3D abgeleitet. Im Mittelpunkt des Interesses steht dabei das Aufzeigen von existierenden Methoden, die die Basis für eine operationelle Bereitstellung solcher Größen nicht nur für Erosions- sondern allgemein für Prozessmodelle darstellen. Als Untersuchungsgebiet dient das primär landwirtschaftlich genutzte Einzugsgebiet des Mehltheuer Baches, das sich im Sächsischen Lößgefilde befindet und für das Simulationsrechnungen mit konventionell erhobenen Eingangsparametern für 29 Niederschlagsereignisse im Jahr 1999 vorliegen [MICHAEL et al. 2000].<br /> <br /> Die Fernerkundungsdatengrundlage bilden Landsat-5-TM-Daten vom 13.03.1999, 30.04.1999 und 19.07.1999. Da die Vegetationsparameter für alle Niederschlagsereignisse vorliegen sollen, werden sie basierend auf der Entwicklung des LAI zeitlich interpoliert. Dazu erfolgt zunächst die Ableitung des LAI für alle vorhandenen Fruchtarten nach den semi-empirischen Modellen von CLEVERS [1986] und BARET & GUYOT [1991] mit aus der Literatur entnommenen Koeffizienten. Des Weiteren wird eine Methode untersucht, nach der die Koeffizienten für das Clevers-Modell aus den TM-Daten und einem vereinfachten Wachstumsmodell bestimmt werden. Der Bedeckungsgrad wird nach ROSS [1981] aus dem LAI ermittelt. Die zeitliche Interpolation des LAI wird durch die schlagbezogene Anpassung eines vereinfachten Wachstumsmodells umgesetzt, das dem hydrologischen Modell SWIM [KRYSANOVA et al. 1999] entstammt und in das durchschnittliche Tagestemperaturen eingehen. Mit den genannten Methoden bleiben abgestorbene Pflanzenteile unberücksichtigt. Im Vergleich zur konventionellen terrestrischen Parametererhebung ermöglichen sie eine differenziertere Abbildung räumlicher Variabilitäten und des zeitlichen Verlaufes der Vegetationsparameter.<br /> <br /> Die Simulationsrechnungen werden sowohl mit den direkten Bedeckungsgraden aus den TM-Daten (pixelbezogen) als auch mit den zeitlich interpolierten Bedeckungsgraden für alle Ereignisse (schlagbezogen) durchgeführt. Bei beiden Vorgehensweisen wird im Vergleich zur bisherigen Abschätzung eine Verbesserung der räumlichen Verteilung der Parameter und somit eine räumliche Umverteilung von Erosions- und Depositionsflächen erreicht. Für die im Untersuchungsgebiet vorliegende räumliche Heterogenität (z. B. Schlaggröße) bieten Landsat-TM-Daten eine ausreichend genaue räumliche Auflösung. Damit wird nachgewiesen, dass die satellitengestützte Fernerkundung im Rahmen dieser Untersuchungen sinnvoll einsetzbar ist. Für eine operationelle Bereitstellung der Parameter mit einem vertretbaren Aufwand ist es erforderlich, die Methoden weiter zu validieren und möglichst weitestgehend zu automatisieren. / Soil erosion models become increasingly more complex and contain physically based components, resulting in changing requirements for their input parameters. The spatial and temporal dynamics of erosions forcing parameters thus produce high requirements on data availability (costs and manpower). Due to this fact, the use of complex erosion models for extensive regions is strongly limited by the high in-situ expense. Moreover, conventional measurement procedures provide parameters at certain points, while remote sensing is a two-dimensional retrieval method.<br /> <br /> This thesis demonstrates, how satellite data can be used as a cost-effective supplementation or alternative to conventional measurement procedures. Leaf area index (LAI) and soil cover percentage are examplarily derived for the EROSION 3D physically based soil erosion model. The main objective of this study is to summarise existing retrieval methods in order to operationally provide such paramaters for soil erosion models or for process models in general. The methods are applied to a catchment in the loess region in Saxony (Germany), that predominantly is agriculturally used. For comparison, simulations based on conventionally estimated parameters for 29 rainstorm events are available [MICHAEL et al. 2000]. <br /> <br /> The remote sensing parameters are derived from Landsat 5 TM data on the following dates: 13.03.1999, 30.04.1999, 19.07.1999. To get temporally continuous data for all events, they are interpolated between the acquisition dates based on the LAI development. Therefore, LAI is firstly calculated for all occurring crops by means of the semi-empirical models of CLEVERS [1986] and BARET & GUYOT [1991]. The coefficients appropriated to these models are taken from literature. Furthermore, a method is investigated that enables coefficient estimation for the Clevers model from Landsat data combined with a simplified growth model. Next, soil cover percentage is derived from LAI after ROSS [1981]. The LAI interpolation is performed by the simplified crop growth model from the SWIM hydrological model [Krysanova et al. 1999]. It has to be mentioned, that plant residue remains unconsidered by the used methods. In comparison to conventional measurement procedures, these methods supply a differentiated mapping of the spatial variability and temporal behaviour regarding the vegetation parameters.<br /> <br /> The simulations with EROSION 3D are carried out for the remotely sensed soil cover percentages, that are retrieved in two ways. Soil cover is directly derived from the remote sensing data for each pixel at the acquisition dates as well as estimated by means of the interpolation for each field on all rainstorm events. In comparison to conventionally determined soil cover, both methods provide an improved spatial allocation of this parameter and thus, a spatial reallocation of erosion and deposition areas. The used Landsat Data provide an adequate spatial resolution suitable for the spatial heterogeneity given in the test area (e. g. field size). These results show that satellite based remote sensing can be reasonably used within the scope of these investigations. In the future, operational retrieval of such remotely sensed parameters necessitates the validation of the proposed methods and in general the automation of involved sub-processes to the greatest possible extent
299

Identifying potential sedimentation sources through a remote sensing and GIS analysis of landuse/landcover for the Weeks Bay Watershed, Baldwin County, Alabama

Cartwright, John Harrison. January 2002 (has links)
Thesis (M.S.) -- Mississippi State University. Department of Geosciences. / Title from title screen. Includes bibliographical references.
300

The soil as a source material in archaeology. : Theoretical considerations and pragmatic applications.

Linderholm, Johan January 2010 (has links)
This thesis deals with questions on various applications using soils and sediments as sources of information in archaeological research. Human environmental impact on soils and sediments, in terms of pollution, is a well known phenomenon as the industrialisation intensified during historical times and onwards and has left strong pollutive marks. However, humans have always accumulated or emitted matter and various compounds in connection to their habitats for subsistence, but these earlier traces are not always detectable, depending on soil and sediment state of preservation. Bioessential elements are intimately linked to humans and their dwellings and especially phosphate has been evident in this respect. It was established already in the 1930s, that even Stone Age settlements could be located through elevated phosphate content in extensive soil phosphate mappings. This thesis is a compilation on results from several sites and excavations from the southern to the northern parts of Sweden. There is a wide variety of soil types and chronological setting in the material, from highly acid podzols to calcareous soils, and sediments dated to Younger Dryas to current top soils. Sites from the Mesolithic, Neolithic, Bronze Age, Early and Late Iron Age and Medieval are all represented. Methods that have been implemented are firstly various forms of analysis in regards to soil phosphate, magnetic susceptibility and organic matter. Furthermore, metal and non-metal elements have been considered, as well as lead isotopes. A multiproxy approach is applied in some examples where biological and chemical data is combined to interpret past events. In this thesis there are also five papers presented. The first paper deals with methodological issues concerning multi-element analyses of various soil samples (off-site to feature) from an archaeological excavation. The second paper is about the possibilities that may be used when analysing the soil organic phosphate in relation to prehistoric agriculture. Paper three and fourth are compilations of large scale contract archaeological project. These papers deal with theoretical, methodological and practical issues concerning environmental archaeology in relation to contract archaeology. Studies on landscape development and erosion are among the cases presented. The last paper deals with a late Mesolithic - early Neolithic settlement in Vuollerim, N. Sweden, and spatial dimensions on the human use of settlement (off-site to on-site) and house floors (intra-site), are discussed.

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