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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.
1

Modeling the Evolution of Rill Networks, Debris Fans, and Cinder Cones: Connections between Sediment Transport Processes and Landscape Development

McGuire, Luke January 2013 (has links)
Landscapes evolve through a number of processes in response to a wide range of forcing mechanisms. Many of the processes that drive landscape evolution occur at the interface between fluid and sediment. Sediment transport leads to changes in topography that, in turn, influence fluid flow. Feedback mechanisms between topography and fluid flow can lead to the formation of patterns, such as sand ripples, dune fields, parallel channel networks, and periodically spaced valleys. In many cases, the development and evolution of patterns within landscapes are heavily influenced by environmental conditions. Therefore, given relationships between landform features and the underlying processes, present-day landscapes have the potential to be used to infer a record of climatic conditions over the course of their development. An inability to make direct observations over geologically relevant timescales makes it difficult to study the processes that influence landscape evolution. Mathematical models provide a means of quantitatively linking natural patterns and landscape features with physical processes. Patterns in landscapes also provide a simple means of testing quantitative representations of geomorphic processes. In this work, we develop landscape evolution models to study the development of debris-flow-dominated hillslopes, rill networks, and cinder cones. Through a combination of theoretical modeling, analysis of experimental data, and remote sensing data, we attempt to better understand each of these three systems. While each system is interesting in isolation, these and similar studies add to our knowledge of the mathematical representations of processes that are used more generally within the study of landscape evolution.
2

Erodibilidade em sulcos e tensão cisalhante crítica de latossolos com diferentes teores de óxidos de ferro / Rill erodibility and critical shear stress of latosols with different iron oxides

Alcantara, Grenda Hingrid 11 July 2018 (has links)
Submitted by GRENDA HINGRID ALCANTARA (grendaalcantara@outlook.com) on 2018-10-04T10:38:02Z No. of bitstreams: 1 Dissertação Grenda.pdf: 1551203 bytes, checksum: b29f515793930c19d42450e6fb2bd2c6 (MD5) / Rejected by Neli Silvia Pereira null (nelisps@fcav.unesp.br), reason: Solicitamos que realize correções na submissão seguindo as orientações abaixo: 1 - A ficha catalográfica e o certificado de aprovação estão em ordem invertida. Primeiro vem a ficha e depois o certificado. 2- Está faltando o resumo em inglês no repositório. Agradecemos a compreensão. on 2018-10-04T14:53:32Z (GMT) / Submitted by GRENDA HINGRID ALCANTARA (grendaalcantara@outlook.com) on 2018-10-04T22:12:52Z No. of bitstreams: 1 Dissertação Grenda imprimir .pdf: 1550980 bytes, checksum: 54ea8cf2c739e50badf9194898503dba (MD5) / Approved for entry into archive by Neli Silvia Pereira null (nelisps@fcav.unesp.br) on 2018-10-08T17:15:49Z (GMT) No. of bitstreams: 1 alcantara_gh_me_jabo.pdf: 1550980 bytes, checksum: 54ea8cf2c739e50badf9194898503dba (MD5) / Made available in DSpace on 2018-10-08T17:15:49Z (GMT). No. of bitstreams: 1 alcantara_gh_me_jabo.pdf: 1550980 bytes, checksum: 54ea8cf2c739e50badf9194898503dba (MD5) Previous issue date: 2018-07-11 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Em modelos de predição da erosão, caso do Water Erosion Prediction Project – WEPP, há a necessidade da determinação de propriedades do solo relativas à sua resistência à erosão. Deste modo, o objetivo deste trabalho foi determinar a erodibilidade em sulcos (Kr) e a tensão cisalhante crítica (tc) em Latossolos com diferentes teores de óxidos de ferro na região nordeste do Estado de São Paulo. A erosão em sulcos foi avaliada com chuva simulada de intensidade média de 65 mm h-1 aplicada por 65 minutos, além de fluxos adicionais de água (11, 39 e 64 L min-1), em seis sulcos pré-formados, em cada Latossolo, com 9,0 m de comprimento, 0,10 m de profundidade e 0,25 m de largura em cada solo. Os valores Kr para os Latossolos foram de 0,0094 s m-1 a 0,0035 s m-1. Os Latossolos mais cauliníticos apresentaram os maiores valores de Kr. Já os valores de tc foram de 2,915 N m-2 a 2,514 N m-2. A razão Ct/(Ct+Gb) explicou 90% das variações na erodibilidade em sulcos e 94% das observadas para a tensão cisalhante crítica nos quatro Latossolos. / In erosion prediction models, in the case of the Water Erosion Prediction Project (WEPP), it is necessary to determine the soil properties related to its erosion resistance. Thus, the objective of this work was to determine the RILL erodibility (Kr) and critical shear stress (tc) in Oxisols with different levels of iron oxides in the northeastern region of the State of São Paulo. Furrow erosion was evaluated with simulated rain of 65 mm h-1 mean intensity applied for 65 minutes, as well as additional water flows (11, 39 and 64 L min-1) in six preformed grooves in each Latosol, 9.0 m in length, 0.10 m in depth and 0.25 m in width in each soil. The Kr values for the Oxisols were 0.0094 s m-1 to 0.0035 s m-1. The most kaolinitic Oxisols presented the highest values of Kr. The values of tc were 2.915 N m-2 to 2.514 N m-2. The Ct/(Ct + Gb) ratio explained 90% of the variations in erodibility in grooves and 94% of those observed for critical shear stress in the four Oxisols. / CNPQ 143683/2016-0
3

Predicting Soil Erosion in the Santa Rosa Creek Watershed Using RUSLE2 and Geographic Information Systems

Smith, Stacey Carol 01 June 2011 (has links) (PDF)
The Santa Rosa Creek watershed is one of the most pristine watersheds on California’s Central Coast. Preserving this watershed is of great interest because it provides rich soils for agriculture, vast rangelands for cattle, and flowing streams for federally threatened species such as steelhead trout. Soil erosion could impact these resources. Using prediction tools, it is possible to study the erosion that could be occurring in a watershed and identify locations which could contribute the highest amounts of sediment. The objectives of this study were to use RUSLE2 and Geographic Information Systems (GIS) to predict soil erosion rates for each soil map unit in every drainage of the upper Santa Rosa Creek watershed and to determine areas where soil erosion could surpass a soil development rates. Environmental and anthropogenic factors that influence soil erosion such as topography, climate, soil, geology, vegetation, and land use, were described for the entire watershed to provide supplementary data used in the RUSLE2 model and to explain erosion in highly erosive areas. Predicted soil erosion rates were studied to determine if correlations exist between other factors such as slope, existing erosion features, and vegetation. Predicted soil erosion rates calculated using RUSLE2 confirmed that the watershed is healthy and that 98 percent of the drainages are within sustainable soil erosion rates (five tons/acre/year). There were 37 soil map units totaling 1,617 acres (5.6 percent of the entire upper watershed area) with predicted soil erosion rates above a sustainable rate. In Perry Creek watershed, these sites were located on steep slopes tangent to streams. Along the main-stem of Santa Rosa Creek these sites were found in the headwaters where on average slopes are steep, soils are shallow, and rock outcrops exist. There appeared to be no relationship between predicted high soil erosion rates and mapped upland erosion sites, however upland erosion features could not be identified where vegetation canopy restricted view of the soil surface. Additionally, RUSLE2 predicts rill and interrill erosion while upland erosion sites identified using GIS identified larger erosion features, such as gullies. Correlations between predicted soil erosion rates and vegetation formations were confirmed with shrub and tree formations having the highest average predicted soil erosion values. In addition, there was a moderate positive correlation between slope percent and predicted soil erosion (r=0.76), affirming that predicted soil erosion rates increased with increasing slopes.
4

Abordagem física do WEPP na erosão em solos em ambiente semiárido

SOUZA, Waldemir Pereira de 18 September 2015 (has links)
Submitted by Mario BC (mario@bc.ufrpe.br) on 2016-08-15T15:18:46Z No. of bitstreams: 1 Waldemir Pereira de Souza.pdf: 2049790 bytes, checksum: cfb86b171794e47f98d211aa32854b10 (MD5) / Made available in DSpace on 2016-08-15T15:18:46Z (GMT). No. of bitstreams: 1 Waldemir Pereira de Souza.pdf: 2049790 bytes, checksum: cfb86b171794e47f98d211aa32854b10 (MD5) Previous issue date: 2015-09-18 / Soil erosion is an irreversible phenomenon that causes soil degradation and deterioration of water quality, therefore, models such as water erosion prediction project (WEPP) physical base can be increasingly used to assess erosion rill in semiarid environment. The objective was to quantify the rill erosion with relationships the WEPP and evaluate the hydraulic conditions of runoff under conditions of rill preformed. The experiment was conducted in the exu watershed in Serra Talhada, semiarid region of Pernambuco where was prepared 16 rill preformed who underwent different flow levels: 5.87 L min-1, 12.10 L min-1, 20.33 L min-1 and 27.57 L min-1 in Entisol fluvent. With the performance of the concentration of runoff in rill experimental produced flow regimes slow turbulent in the largest flows applied characterizing the characterizing the occurrence of erosion in rill. The erodibility values in rill (Kr)was 0.0011 kgN-1s-1 and critical shear corresponds to 1.91 Pa. The values of soil losses to erosion rill were considered high for Entisol fluvent behaving smaller particle size composition with a higher percentage of sand. / A erosão do solo é um fenômeno irreversível que causa a degradação do solo e a deterioração da qualidade da água, dessa forma, modelos como o Projeto de Predição de Erosão Hídrica (WEPP) de base física podem ser cada vez mais utilizados na avaliação da erosão do solo em sulcos em ambiente semiárido. Objetivou-se quantificar a erosão em sulcos com as relações de erosão do WEPP e avaliar as condições hidráulicas do escoamento superficial sob condições de sulcos pré-formados. O experimento foi realizado na Bacia do Riacho Exu, no município de Serra Talhada, região semiárida de Pernambuco onde foram preparadas parcelas experimentais que consistiram em 16 sulcos pré-formados que foram submetidos a aplicação de diferentes níveis de vazão: 5,87 Lmin-1, 12,10 Lmin-1, 20,33 Lmin-1 e 27,57 Lmin-1 em Neossolo Flúvico. Com a atuação da concentração do escoamento superficial nos sulcos experimentais produziram regimes de escoamento na faixa de turbulento lento nos maiores fluxos aplicados caracterizando a ocorrência da erosão em sulcos. Os valores de erodibilidade em sulcos (Kr) foi de 0,0011 KgN-1s-1 e a tensão crítica de cisalhamento corresponde a 1,91 Pa. Os valores das perdas de solo para a erosão em sulcos foram consideradas altas para um Neossolo Flúvico comportando menor composição granulométrica com maior percentagem de areia.
5

Hemlig dataavläsning och Europakonventionen : Den svenska lagen om hemlig dataavläsning i förhållande till rätten till privatlivenligt artikel 8 Europakonventionen

Delfin, Henrik January 2022 (has links)
Article 8 of the European Convention on Human Rights prescribes that everyone has the right to respect for his or her private life. A restriction of this right presupposes that the law of the Contracting State achieves certain requirements which include the need for the restrictive measure to be necessary in a democratic society. This thesis examines the case law of the European Court of Human Rights regarding secret surveillance. The thesis concludes that the European Court has established further requirements regarding these particularly intrusive measures, which consist of various minimum safeguards concerning the substantive national law. Sweden introduced a new method of secret surveillance, hemlig dataavläsning, in April 2020. This new covert surveillance measure enables the authorities to breach the systems of different types of technical equipment, to retrieve stored personal information within. The main purpose of this thesis is to analyse and determine if the Swedish law of secret data interception meets the requirement set out in the case law. The thesis concludes that the Swedish law does not meet all the requirements set out by the European Court of Human Rights. The Swedish law does not with sufficient clarity define the offences which justifies the application of the covert surveillance. The law also prescribes an authorization procedure which lack sufficient safeguards regarding the independence of the decision-making authority. Furthermore, the law does not regulate the technology and methods used for the action, and there is no legal requirement for the national court to take these into account in its decision-making. Lastly, the Swedish legislation stipulates that the individual does not need to be notified about the surveillance if there is any confidentiality regarding the information about the surveillance one year after the preliminary investigation. In these cases, the supervisory authority must safeguard the interests of the individual, which due to the lack of legally binding decisions, are not sufficient. Finally, the thesis outlines various solutions to address these problems, which consist of inter alia: that the Swedish law should set higher requirements for the severity of crimes that can justify the use of the secret coercive measure; the removal of the interim decisions of prosecutors; a legal requirement that the court in its assessment must consider and decide on the technology used to execute the surveillance; and lastly, a legal requirement that the individual should be notified about the surveillance as soon as this is possible, or alternatively, an increase of power to the supervisory authority.
6

Experimentelle Untersuchungen zum Einfluss physikalischer Bodeneigenschaften auf die Rillenerosion

Hieke, Falk 29 January 2010 (has links)
Der Einfluss bodenspezifischer Größen auf die Rillenerosion wurde in Überströmungsversuchen in einem eigens dafür konstruiertem Kleingerinne untersucht. Die Neigung des 2 m langen und 0,1 m breiten Gerinnes wurde dafür zwischen 2, 4 und 6 % variiert. Im Gerinne wurden zum einen natürliche Böden, zum anderen künstliche, aus Schluff und Sand gemischte Substrate mit 0,060 l*s-1, 0,125 l*s-1 und 0,300 l*s-1 überströmt. Die Körnung der natürlichen Böden reichte von stark schluffig bis sandig-lehmig, die der künstlichen Substrate von stark schluffig bis sandig. Die künstlichen Substrate wiesen im Gegensatz zu den natürlichen Böden keine Aggregierung auf und waren frei von organischer Substanz. Zu Beginn der Versuche wird der Boden zunächst flächig überströmt. Währenddessen bilden sich Mikrorillen auf der Gerinnesohle aus. Selektiver Sedimenttransport bewirkt die Akkumulation der nicht transportablen Fraktion auf der Bodenoberfläche, wodurch sich Rippel bilden. Über den Rippeln formen sich stehende Wellen im Abfluss. Die stehenden Wellen erzeugen Sohlschubspannungsspitzen auf die Gerinnesohle, welche zu verstärkter lokaler Erosion, zur Ausbildung von Mikrodepressionen und im weiteren zur Entstehung von Rillenköpfen führen. Die Rillenköpfe wandern entgegen dem Gefälle und hinterlassen Rillen, in denen sich der Abfluss konzentriert. In den Rillen können weitere Rillenköpfe entstehen. Anhand des Beginns der Rillenerosion, der Rillenkopfneubildungsrate, dem Erosionsfortschritt der Rillenköpfe, der Bestandsdauer der Rillenköpfe und der Sedimentkonzentration im Abfluss kann das Phänomen „Rillenerosion“ erfasst und quantifiziert werden. Diese erosionsspezifischen Kennwerte zeigen sich dabei in Abhängigkeit von bodenspezifischen Größen, wie der Lagerungsdichte, der Korngrößenzusammensetzung sowie der Aggregatgrößenverteilung und –stabilität. Aus den Korrelationsanalysen zwischen den bodenspezifischen Größen und den spezifischen Kennwerten der Rillenerosion leiten sich empirische Beziehungen ab. Diese Beziehungen sind nicht-linearerer und nicht-stetiger Natur. Parallel zu den Versuchen im Kleingerinne wurden Überströmungs- und Beregnungsversuche in einem Großgerinne durchgeführt. Die Projektion der laborativen Ergebnisse des Kleingerinnes auf das naturnahere Großgerinne zeigte dabei Parallelen.
7

Experimentelle Untersuchungen zum Einfluss physikalischer Bodeneigenschaften auf die Rillenerosion / Experimental research on the influence of soil physical properties on rill erosion

Hieke, Falk 17 February 2010 (has links) (PDF)
Der Einfluss bodenspezifischer Größen auf die Rillenerosion wurde in Überströmungsversuchen in einem eigens dafür konstruiertem Kleingerinne untersucht. Die Neigung des 2 m langen und 0,1 m breiten Gerinnes wurde dafür zwischen 2, 4 und 6 % variiert. Im Gerinne wurden zum einen natürliche Böden, zum anderen künstliche, aus Schluff und Sand gemischte Substrate mit 0,060 l*s-1, 0,125 l*s-1 und 0,300 l*s-1 überströmt. Die Körnung der natürlichen Böden reichte von stark schluffig bis sandig-lehmig, die der künstlichen Substrate von stark schluffig bis sandig. Die künstlichen Substrate wiesen im Gegensatz zu den natürlichen Böden keine Aggregierung auf und waren frei von organischer Substanz. Zu Beginn der Versuche wird der Boden zunächst flächig überströmt. Währenddessen bilden sich Mikrorillen auf der Gerinnesohle aus. Selektiver Sedimenttransport bewirkt die Akkumulation der nicht transportablen Fraktion auf der Bodenoberfläche, wodurch sich Rippel bilden. Über den Rippeln formen sich stehende Wellen im Abfluss. Die stehenden Wellen erzeugen Sohlschubspannungsspitzen auf die Gerinnesohle, welche zu verstärkter lokaler Erosion, zur Ausbildung von Mikrodepressionen und im weiteren zur Entstehung von Rillenköpfen führen. Die Rillenköpfe wandern entgegen dem Gefälle und hinterlassen Rillen, in denen sich der Abfluss konzentriert. In den Rillen können weitere Rillenköpfe entstehen. Anhand des Beginns der Rillenerosion, der Rillenkopfneubildungsrate, dem Erosionsfortschritt der Rillenköpfe, der Bestandsdauer der Rillenköpfe und der Sedimentkonzentration im Abfluss kann das Phänomen „Rillenerosion“ erfasst und quantifiziert werden. Diese erosionsspezifischen Kennwerte zeigen sich dabei in Abhängigkeit von bodenspezifischen Größen, wie der Lagerungsdichte, der Korngrößenzusammensetzung sowie der Aggregatgrößenverteilung und –stabilität. Aus den Korrelationsanalysen zwischen den bodenspezifischen Größen und den spezifischen Kennwerten der Rillenerosion leiten sich empirische Beziehungen ab. Diese Beziehungen sind nicht-linearerer und nicht-stetiger Natur. Parallel zu den Versuchen im Kleingerinne wurden Überströmungs- und Beregnungsversuche in einem Großgerinne durchgeführt. Die Projektion der laborativen Ergebnisse des Kleingerinnes auf das naturnahere Großgerinne zeigte dabei Parallelen.
8

Mapping rill soil erosion in agricultural fields with UAV-borne remote sensing data

Malinowski, Radek, Heckrath, Goswin, Rybicki, Marcin, Eltner, Anette 27 February 2024 (has links)
Soil erosion by water is a main form of land degradation worldwide. The problem has been addressed, among others, in the United Nations Sustainability Goals. However, for mitigation of erosion consequences and adequate management of affected areas, reliable information on the magnitude and spatial patterns of erosion is needed. Although such need is often addressed by erosion modelling, precise erosion monitoring is necessary for the calibration and validation of erosion models and to study erosion patterns in landscapes. Conventional methods for quantification of rill erosion are based on labour-intensive field measurements. In contrast, remote sensing techniques promise fast, non-invasive, systematic and larger-scale surveying. Thus, the main objective of this study was to develop and evaluate automated and transferable methodologies for mapping the spatial extent of erosion rills from a single acquisition of remote sensing data. Data collected by an uncrewed aerial vehicle was used to deliver a highly detailed digital elevation model (DEM) of the analysed area. Rills were classified by two methods with different settings. One approach was based on a series of decision rules applied on DEM-derived geomorphological terrain attributes. The second approach utilized the random forest machine learning algorithm. The methods were tested on three agricultural fields representing different erosion patterns and vegetation covers. Our study showed that the proposed methods can ensure recognition of rills with accuracies between 80 and 90% depending on rill characteristics. In some cases, however, the methods were sensitive to very small rill incisions and to similar geometry of rills to other features. Additionally, their performance was influenced by the vegetation structure and cover. Besides these challenges, the introduced approach was capable of mapping rills fully automatically at the field scale and can, therefore, support a fast and flexible assessment of erosion magnitudes.
9

Numerical Investigation of Rock Support Arches

Rentzelos, Theofanis January 2019 (has links)
The Garpenberg mine, owned by the Boliden Mining group, has established a trial area at Dammsjön orebody in order to examine the possibility of increasing the productivity of the mine. The mine uses the rill mining method with a current rill height of 15 m. In order to increase the productivity, the mine is examining the possibility of increasing the height of the rill. The trial area is located at 882 m depth surrounded by dolomite on the hangingwall and quartzitic rock on the footwall side. Rock support arches have been installed, in addition to the regular support pattern, to test their effectiveness on stabilizing the ground around the drifts. The arches have been installed in every 6 m and every 3 m in different parts of the test area. Rock samples from the trial area were brought to the university laboratory for testing. The data gathered from the laboratory tests along with the data from the monitoring of the trial area were used to develop a calibrated numerical model. A three-dimensional (3-D) model was therefore created, by using the FLAC3D numerical code. After the calibration of the model a parametric study was conducted for different rill heights and different arch spacing to investigate the performance of the arches. Specifically, the case of no arch installation along with the cases of an installed arch every 6 m and 3 m were tested, for the rill heights of 15 m, 20 m, 25 m and 30 m. The study concluded that the arches assisted in reducing the ground convergence in the production drift. The results also showed that the total height of the rill bench yields regardless of its height. After the yielding, the rockmass can no longer support itself and caves under its own weight. The larger the rill height, the larger the volume of loose rock that has to be supported and thus, higher the convergence. Furthermore, it was also observed that, significant amount of convergence in the production drift occurred during the drifting of the top drive and less during the stoping of the rill bench. This indicates that, the timely installation of the arches is an important criterion for their performance.
10

A Sediment Yield Equation from an Erosion Simulation Model

Shirley, E. D., Lane, L. J. 15 April 1978 (has links)
From the Proceedings of the 1978 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 14-15, 1978, Flagstaff, Arizona / Sediment is widely recognized as a significant pollutant affecting water quality. To assess the impact of land use and management practices upon sediment yield from upland areas, it is necessary to predict erosion and sediment yield as functions of runoff, soil characteristics such as erodibility, and watershed characteristics. The combined runoff-erosion process on upland areas was modeled as overland flow on a plane, with rill and interrill erosion. Solutions to the model were previously obtained for sediment concentration in overland flow, and the combined runoff-erosion model was tested using observed runoff and sediment data. In this paper, the equations are integrated to produce a relationship between volume of runoff and total sediment yield for a given storm. The sediment yield equation is linear in runoff volume, but nonlinear in distance and, thus, watershed area. Parameters of the sediment yield equation include the hydraulic resistance parameter, rill and interrill erodibility terms, and flow depth-detachment coefficient and exponent.

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