Dissertations / Theses on the topic 'Wind erosion'

Mestrado em Engenharia do Ambiente
Biochar application to soils has been reported in the scientific community as a possible means of improving agricultural productivity and, at the same time, as a powerful tool for carbon sequestration and climate change mitigation. However, current knowledge of biochar effects on soil functions and possible environmental threats is still not enough for a full-scale implementation. Erosion is one of the most serious and irreversible threats to soil and there is still no information if biochar may increase or decrease soil erosion rates. Soil erosion by wind is of particular interest for biochar, because of the low particle density and potential human exposure. The purpose of this study was to fill this knowledge gap by investigating the wind erosion potential of biochar-amended soil with a focus on the effect of soil moisture content, using a laboratory wind tunnel. Firstly, experimental tests were implemented in the DAO wind tunnel to define a robust wind erosion methodology in a facility only used for smoke studies. Sediment collecting methods, dust fraction analysis and wind velocity range were the main factors that required investigation. The erosion of biochar-amended soil (10% m m-1) and control soil (sandy soil) was simulated by positioning a tray divided in a sample area and an area for creeping particles, inside the test section of the wind tunnel. To determine the effect of soil moisture content on the erosion potential, four moisture contents were used: 0.2%, 1.7%, 4% and 8% (gravimetric). The wind tunnel simulations were performed with the duration of 15 minutes at a wind velocity of 7 m s-1. The samples of collected sediment were oven-dried and weighed to give the sediment loss as consequence of the erosion event. Results on the erosion simulations for control and biochar-amended soil with the wind flow velocity of 7 m s-1 (small erosion event) indicated that only biochar particles were displaced. Erosion of biochar-amended soil was similar for 0.2%, 1.7% and 4.0% and despite a sediment loss reduction of 50% from 4% MC to the higher MC, 8%, this latter was not identified as the threshold MC for the moment when erosion ceases to exist. As for mineral particles, after 4% MC there was no sediment collected indicating this MC as the threshold, even though a reduced mass of particles eroded for the smaller MCs. Further future tests are needed to build a more comprehensive understanding of wind erosion of biochar-amended soils. Relevant factors to include are: higher wind velocities representative of medium and high erosion events, as well as higher MCs to identify when erosion of biochar particles will stop completely. Secondly, based on the results found in the present study, other soil types and biochar types warrant further investigation. Studies like this contribute for the understanding of the effects of biochar application to soil functions, as well as the behaviour and fate of this material, which are indispensable for the development of adequate biochar regulations and policies.
A aplicação de biochar no solo tem sido referida na comunidade científica como um possível meio para melhorar a produtividade agrícola e, ao mesmo tempo, como um instrumento para sequestro de carbono e mitigação de alterações climáticas. Contudo, o conhecimento actual sobre os efeitos do biochar nas funções do solo e possíveis ameaças ambientais não é, ainda, suficiente para uma implementação em larga escala. A erosão é uma das mais sérias e irreversíveis ameaças ao solo e não existe, ainda, informação se o biochar pode aumentar ou reduzir os níveis de erosão. A erosão do solo pelo vento é de particular interesse para o biochar, devido à reduzida densidade das partículas e à potencial exposição humana. O objectivo deste trabalho foi preencher esta falha ao investigar o potencial de erosão do solo melhorado com biochar com enfoque no efeito do teor de humidade, usando um túnel de vento. Primeiramente, testes experimentais foram implementados no túnel de vento do DAO para definir uma metodologia robusta de erosão eólica numa estrutura, até então, apenas usada para estudos de dispersão de poluentes. A colecta do sedimento, análise de fracção de poeiras e a gama de velocidades foram os factores principais que necessitaram de investigação. A erosão de solo com biochar (10% m m-1) e de solo de controle (solo arenoso) foi simulada posicionando um tabuleiro dividido em área de amostra e área para partículas de rolamento, dentro da secção de teste do túnel de vento. Para determinar o efeito do teor de humidade do solo no potencial de erosão, quatro teores de humidade foram usados: 0.2%, 1.7%, 4% and 8% (gravimétricos). As simulações no túnel de vento foram realizadas com a duração de 15 minutos a uma velocidade do vento de 7 m s-1. As amostras de sedimento colectado foram secas e pesadas para fornecerem a perda de sedimento como consequência do evento de erosão. Os resultados das simulações de erosão para o controle e o solo melhorado com biochar, com a velocidade de 7 m s-1 (reduzido evento de erosão) indicaram que apenas partículas de biochar foram movidas. Erosão de solo com biochar foi semelhante para 0.2%, 1.7% and 4.0% e, apesar da redução da perda de sedimento em 50% do teor de 4% para para o teor mais alto, 8%, este último não foi identificado como sendo o limiar para o momento em que a erosão deixa de existir. Relativamente às partículas minerais, após o teor de 4% não houve sedimento colectado indicando este teor de humidade como o limiar, ainda que uma massa reduzida de partículas tenha sofrido erosão para teores mais reduzidos. Testes futuros são necessários para gerar um melhor conhecimento acerca de erosão de solo com biochar pelo vento. Factores relevantes a incluir são: maiores velocidades do vento, representativas de eventos de erosão médios e elevados, tal como maiores teores de humidade para identificar quando a erosão de partículas de biochar pára por completo. Em segundo lugar, com base nos resultados observados neste estudo, outro tipos de solo e biochar impõe mais investigação.Estudos como este contribuem para perceber os efeitos da aplicação de biochar nos solos, bem como o comportamento e destino deste material, que são indispensáveis para o desenvolvimento de regulamentos e políticas adequadas sobre biochar.

La poussière minérale atmosphérique résultant de l’érosion éolienne des sols affecte le système terrestre. La distribution en taille (PSD) de cette poussière joue un rôle clé dans le bilan radiatif et la chimie atmosphérique, la formation des nuages et la productivité des écosystèmes terrestres et marins. Néanmoins les modèles climatiques peinent à reproduire précisément la PSD de la poussière émise. Ceci vient de la représentation imparfaite des mécanismes d’émission de poussières et des vitesses de vent de surface associées. C’est particulièrement vrai en présence d’éléments de rugosité de surface comme la végétation en régions semi-arides. Cette thèse vise à améliorer la compréhension de l’émission de poussière en environnements semi-arides, caractérisé par des surfaces hétérogènes liées à la végétation saisonnière éparse. A cette fin, une combinaison d’expériences numériques et de terrain a été employée, en partant d’un sol nu érodable à des surfaces couvertes de végétation éparse.Une revue des schémas existants a montré des ambiguïtés dans la paramétrisation des processus influençant l’émission de poussières. Une analyse de sensibilité utilisant un modèle 1D de dispersion de poussière a démontré l’importance (i) de la PSD de la poussière à la surface et de la paramétrisation de la cohésion interparticules qui affectent la PSD de la poussière émise, et (ii) des processus de dépôt qui influencent la PSD du flux net de poussière dans la couche de surface atmosphérique. A partir de cette analyse, un nouveau schéma d’émission a été incorporé à un modèle 3D d’érosion, couplé à un modèle turbulent Large Eddy Simulation (LES), et évalué d’abord sur une surface nue sur la base de l’expérimentation WIND-O-V 2017 en Tunisie. Le modèle a ainsi été capable de reproduire la dissimilarité entre les transports turbulents de poussière et de quantité de mouvement dans la couche de surface, observée durant l’expérience. Cela signifie que poussière et quantité de mouvement ne sont pas toujours transportées par les mêmes tourbillons. Le modèle a démontré que la cause principale de cette dissimilarité est l’intermittence de l’émission de poussières, qui varie avec l’intensité du vent et le fetch.L’impact de la végétation éparse sur le flux net de poussière émis a ensuite été étudié sur la base de l’expérimentation WIND-O-V 2018, conduite sur le même site que celle de 2017. Les mesures ont été utilisées pour évaluer le modèle 3D d’érosion incluant les caractéristiques de la végétation. La comparaison entre les expérimentations 2017 et 2018 a confirmé que la végétation éparse réduit l’émission en augmentant la vitesse de frottement seuil de l’érosion, qui dépend des caractéristiques de la végétation et de la direction du vent. Au cours de l’expérimentation 2018, nous avons observé que la PSD du flux net de poussière émis variait, contrairement à 2017, avec un appauvrissement progressif en grosses particules (1.50 µm). Il s’est avéré que cet appauvrissement n’était pas lié à la présence de végétation, mais à l'épuisement du sol en grosses particules en raison de périodes d’émission plus longues sans modification de la surface, comparé à 2017. Cette absence d’influence de la végétation a été validée par la similarité entre la PSD du flux de poussière au début de l’expérimentation 2018, quand la végétation était à sa hauteur maximum, et celle de 2017 sans végétation. Et elle a été confirmée par nos simulations qui montrent (i) une re-déposition négligeable des grosses particules sur la végétation durant les émissions, et (ii) un effet négligeable de la turbulence induite par la végétation sur la PSD du flux net de poussière émis.Notre modèle 3D d’érosion apparaît comme un outil prometteur pour caractériser les émissions de poussière sur des surfaces hétérogènes représentatives des régions semi-arides et pour établir des schémas d’émission de poussières pour les modèles climatiques en fonction des propriétés de rugosité de la surface
Atmospheric mineral dust resulting from aeolian soil erosion affects the Earth system. Their size-distribution (PSD) plays a key role on atmospheric radiation balance, cloud formation, atmospheric chemistry, and the productivity of terrestrial and marine ecosystems. However, climate models still fail to reproduce accurately the suspended dust PSD. This is explained by the poor representation of the dust emission mechanisms and the associated surface wind speed in these large-scale models. This is particularly true in the presence of surface roughnesses such as vegetation in semiarid regions. This thesis aims at improving the understanding of dust emission in semi-arid environments, characterized by heterogeneous surfaces with sparse seasonal vegetation. To this end, a combination of numerical and field experiments was employed, with investigations progressing from a bare erodible soil to surfaces with sparse vegetation.A review of the existing dust emission schemes showed ambiguities in the parametrization of the processes influencing the emitted dust. A sensitivity analysis, using a 1D dust dispersal model, demonstrated (i) the importance of surface dust PSD and inter-particle cohesive bond parametrization on the emitted dust PSD, and (ii) the importance of the deposition process on the net dust flux PSD. Based on this analysis, a new emission scheme was incorporated into a 3D erosion model, coupled with a Large Eddy Simulation (LES) airflow model, and evaluated first on a bare surface against the WIND-O-V’s 2017 field experiment in Tunisia. The model was able to reproduce the near-surface turbulent transport dissimilarity between dust and momentum observed during the experiment. This means that momentum and dust are not always transported by the same turbulent eddies. The model demonstrated that the main cause of this dissimilarity is the dust emission intermittency, which varies as a function of wind intensity and fetch.The role of sparse vegetation on the net emitted dust flux was then explored using the WIND-O-V’s 2018 experiment, conducted at the same site as the 2017 experiment. The resulting field measurements were used to evaluate the 3D erosion model, including vegetation characteristics. A comparison between the 2017 and 2018 experiments confirmed that sparse vegetation reduces dust emission by increasing the erosion threshold friction velocity, which depends on vegetation characteristics and wind direction relative to the vegetation arrangement. During the 2018 experiment, the net emitted dust flux PSD varied continuously, unlike the 2017 experiment, with a progressive impoverishment in coarse particles (1.50 μm). This impoverishment was found independent of the vegetation, and resulted from the depletion of coarse particles at the surface due to longer emission periods in 2018 without surface tillage or precipitation. This non-influence of vegetation on the dust flux PSD was validated by the similarity of the dust flux PSD at the beginning of the 2018 experiment, when the vegetation was at its maximum height, with the one of the 2017 experiment without vegetation. It was further confirmed by the simulations that demonstrated (i) negligible re-deposition of coarse particles on to vegetation during emission events, and (ii) negligible effect of the turbulence induced by the vegetation on the PSD of the net emitted dust flux.Our 3D erosion model appears as a promising tool for characterizing dust emissions over heterogeneous surfaces typical of semi-arid regions and for deriving dust emission schemes for climate models as a function of surface roughness properties

While some of the properties of turbulence have long been measured under laboratory conditions, current instruments are not suitable for use in the sand-blasting conditions that arise during wind erosion. This thesis describes the design and construction of a new instrument for such conditions. The instrument measures three components of wind velocity using pressure techniques. The thesis presents background material regarding the characterisation of turbulent and eroding flows, the design of pressure probes, and the modelling of pressure propagation in tubes. A mathematical model is developed to allow compensation for the complex effect of the tubing systems. This permits measurement of turbulent velocity fluctuations of the order of 100Hz. Algorithms for real-time signal processing are described. The results of calibration and testing of the instrument are discussed.

Wind erosion is a global issue and affecting millions of people in drylands by causing environmental issues (acceleration of snow melting), public health concerns (respiratory diseases), and socioeconomic problems (costs of damages and cleaning public properties after dust storms). Disturbances in drylands can be irreversible, thus leading to natural disasters such as the 1930s Dust Bowl. With increasing attention on aeolian studies, many studies have been conducted using ground-based measurements or wind tunnel studies. Ground-based measurements are important for validating model predictions and testing the effect and interactions of different factors known to affect wind erosion. Here, a machine-learning model (random forest) was used to describe sediment flux as a function of wind speed, soil moisture, precipitation, soil roughness, soil crusts, and soil texture. Model performance was compared to previous results before analyzing four new years of sediment flux data and including estimates of soil moisture to the model. The random forest model provided a better result than a regression tree with a higher variance explained (7.5% improvement). With additional soil moisture data, the model performance increased by 13.13%. With full dataset, the model provided an increase of 30.50% in total performance compared to the previous study. This research was one of the rare studies which represented a large-scale network of BSNEs and a long time series of data to quantify seasonal sediment flux under different soil covers in southern Utah. The results will also be helpful to the managers for controlling the effects on wind erosion, scientists to choose variables for further modeling or local people to increase the public awareness about the effects of wind erosion.

L’érosion éolienne est un phénomène complexe avec des interactions entre la couche limite atmosphérique, le transport des particules et la déformation des dunes. Dans cette thèse des simulations numériques de transport de particules solides sur des dunes fixes ou déformables sont effectuées. L’écoulement turbulent est calculé par des simulations des grandes échelles (LES) couplée avec une méthode de frontières immergées. Les particules solides sont tractées par une approche Lagrangienne. L’entraînement des particules, leur interaction avec la surface et leur dépôt sont pris en compte par des modèles physiques complets d’érosion. D’un point de vue numérique, une méthode de frontières immergées a été introduite pour simuler les écoulements turbulents sur des frontières mouvantes. Le nouveau solveur a été validé en effectuant des comparaison avec les résultats expérimentaux de Simoens et al. (2015) dans le cas d’une colline Gaussienne. D’un point de vue physique, des modèles complets ont été développés pour l’érosion éolienne en se basant sur les forces agissant sur les particules. Des modèles instantanés pour l’envol, le roulement et le glissement des particules sont développés pour initier le mouvement des particules. Leur rebond et le splash sont également pris en compte. Des équations Lagrangiennes sont utilisées pour simuler la trajectoire des particules solides dans l’air. Une équation de transport d’un lit de particules a également été développée pour les cas de glissement et de roulement des particules sur la surface. La déformation de la dune est effectuée en faisant le bilan des particules qui s’envolent et se déposent. Ces modèles ont été validés en comparant les résultats de simulation avec les résultats expérimentaux de Simoens et al. (2015) sur les profils de concentration autour d’une colline Gaussienne. Enfin, des simulations numériques d’une dune sinusoïdale déformable sont effectuées. La forme de la dune simulée est comparée avec les résultats expérimentaux de Ferreira and Fino (2012). Un bon agrément est obtenu a t = 2.0 min, par contre la hauteur de la dune est sous-estimée entre 4.0 min et 6.0 min. Les résultats numériques montrent que la zone de recirculation diminue progressivement quand la dune se déforme. L’érosion, due à l’envol et au splash, est important a l’avant de la dune tandis que les particules se déposent a l’arrière de la dune. Le modèle de splash a été modifié pour prendre en compte l’effet de la pente, ce qui a permis une meilleure estimation de la hauteur de la dune a t = 4.0 min
Wind erosion is a complex dynamic process consisting in an atmospheric boundary layer, aeolian particle transport, sand dune deformation and their intricate interactions. This thesis undertakes this problems by conducting three-dimensional numerical simulations of solid particle transport over a fixed or deformable sand dune. Turbulent flow is calculated by a developed numerical solver (Large-eddy simulation (LES) coupled with immersed boundary method (IBM)). Solid particle trajectories are tracked by a Lagrangian approach. Particle entrainment, particle-surface interactions and particle deposition are taken into account by physical comprehensive wind erosion models. Firstly, a new numerical solver has been developed to simulate turbulent flows over moving boundaries by introducing the IBM into LES. Two canonical simulation cases of a turbulent boundary layer flow over a Gaussian dune and over a sinusoidal dune are performed to examine the accuracy of the developed solver. Recirculation region characteristics, mean streamwise velocity profiles, Reynolds stress profiles as well as the friction velocity over the dune are presented. In the Gaussian case, a good agreement between experimental data and simulated results demonstrates the numerical ability of the improved solver. In the sinusoidal case, the developed solver with wall modeling over the immersed boundary shows a better performance than the pure one, when a relatively coarse grid is used. Secondly, physical comprehensive modeling of wind erosion is described in detail, based on the forces acting an individual particle. An instantaneous entrainment model for both lifting and rolling-sliding modes is proposed to initialize particle incipient motions. Lagrangian governing equations of aeolian particle motion are presented and used to simulate the trajectories of solid particles. Particularly, Lagrangian governing equations of bed-load particle motion are originally deduced and applied to model the particle rolling-sliding movement on the bed surface. In addition, particle-surface interactions are taken into account by probabilistic rebound/splash models. Thirdly, numerical simulations of particle transport over a fixed Gaussian dune and over a deformable sinusoidal dune are carried out. In the fixed Gaussian case, an overall good agreement on the particle concentration profiles over the dune between the simulated results and the experimental data of Simoens et al. (2015) preliminarily validates the ability and accuracy of the developed numerical solver coupled with physical comprehensive wind erosion models. In the deformable sinusoidal case, the simulated dune shapes are compared with the experimental ones of Ferreira and Fino (2012). A good agreement between them is observed at t = 2.0 min and an obvious underestimate of the dune shape is shown at t = 4.0 min and t = 6.0 min. By analyzing the simulated results, it is shown that the recirculation zone behind the dune is gradually reduced as the dune deforms and that windward erosion and lee side deposition is observed. It is also shown after testing that the splash entrainment is important for the lee side erosion. Moreover, a preliminary attempt is presented to apply an improved splash model with accounting for the bed slope effect to the simulation of sand dune deformation. A better performance on the simulated dune shape is achieved at t = 4.0 min in comparison with the experimental one

Doctor of Philosophy
Biological & Agricultural Engineering
Mark E. Casada
Ronaldo G. Maghirang
Wind erosion is an important problem in many locations, including the Great Plains, that needs to be controlled to protect soil and land resources. This research was conducted to assess the effectiveness of vegetation (specifically, standing vegetation and tree barriers) as controls for wind erosion. Specific objectives were to: (1) measure sand transport and abrasion on artificial standing vegetation, (2) determine porosity and drag of a single row of Osage orange (Maclura pomifera) barrier, (3) assess effectiveness of Osage orange barriers in reducing dust, (4) predict airflow through standing vegetation, and (5) predict airflow and particle collection through Osage orange barriers. Wind tunnel tests were conducted to measure wind speed profiles, relative abrasion energies, and sand discharge rates for bare sand and for two vegetation heights (150 and 220 mm) at various densities of vegetation. Results showed that vegetation density was directly related to threshold velocity and inversely related to sand discharge. The coefficient of abrasion was adversely affected by saltation discharge but did not depend on wind speed. Field tests measured the aerodynamic and optical porosities of Osage orange trees using wind profiles and image analysis, respectively, and an empirical relationship between the two porosities was derived. Vertical wind profiles were also used to estimate drag coefficients. Optical porosity correlated well with the drag coefficient. Field measurements also showed a row of Osage orange barrier resulted in particulate concentration reduction of 15 to 54% for PM2.5 and 23 to 65% for PM10. A computational fluid dynamics (CFD) software (OpenFOAM) was used to predict airflow in a wind tunnel with artificial standing vegetation. Predicted wind speeds differed slightly from the measured values, possibly due to oscillatory motions of the standing vegetation not accounted for in the CFD simulation. OpenFOAM was also used to simulate airflow and particle transport through a row of Osage orange barrier. Predicted and measured wind speeds agreed well. Measured dust concentration reduction at two points (upwind and downwind) were also similar to the predicted results.

Bibliography: pages 122-129.
Soil erosion is regarded as a serious problem throughout the world. Erosion is caused by both water and wind. Although the two usually occur together, wind erosion has received little attention with the exception of the problems associated with croplands. Wind erosion can, however, also be a serious problem in natural grazing lands. In this research project an attempt is made to determine the areas of potential wind erosion in the Cape Province through the use of two different models. The models used were developed and applied in semi-arid areas and thus were considered to be applicable in South Africa. The models used are: The Wind Erosion Equation developed by Chepil, Woodruff and Siddoway in the United States; and Lynch and Edward's Model for the Analysis of Limited Climatic Data, developed in Australia. There are two aspects to soil erosion by wind - the erodibility of the soil as determined by moisture, grains size, aggregates, plant cover and surface topography; and soil erosivity as determined by wind strength and duration. Methods to control wind erosion are based on decreasing erosivity through the establishment of shelterbelts and by decreasing erodibility through improving plant cover, aggregate stability and moisture retention properties. Efforts at wind erosion measurement are generally ineffective. A number of models have been developed to overcome these difficulties and to allow for prediction of soil loss. Two of these models are applied to conditions in the Cape Province. This area covers a wind range of climatic, soil and agricultural conditions and as such provides an appropriate area for their application. It is, however, concluded that neither of these models can be directly applied to conditions in the Cape Province. The seasonal rainfall distribution and the uneven distribution of the data points contribute to the ineffectiveness of the models. The greatest problem, however, is the importance of management in determining whether or not wind erosion occurs. As a result, although the models illustrate the general climatic trends affecting the susceptibility of an area to wind erosion, the lack of a management factor accounts for the lack of detail.

In der vorliegenden Studie wird einerseits die Winderosion und der damit verbundene Sedimenttransport hinter ausgedehnten Waldgebieten, die in ihrer Zusammensetzung typisch für den Nordraum von Leipzig sind, und hinter schmalen Gehölzschutzstreifen untersucht. Als Ergebnis dieser Analyse lassen sich Empfehlungen für die günstigsten Eigenschaften von Windschutzanpflanzungen hinsichtlich einer maximalen Schutzwirkung vor Sedimenttransport ableiten. Andererseits wird die Häufigkeit möglicher erosiver Ereignisse am Beispiel einer für das Untersuchungsgebiet repräsentativen meteorologischen Station geprüft. Kritische meteorologische Randbedingungen für erosive Prozesse treten entsprechend einer statistischen Datenanalyse zweimal pro Jahr auf
On the one hand, the wind erosion and the associated sediment transport behind extensive forest areas, which are typically for the northern area of Leipzig, and behind narrow shelterbelts were examined in this study. Recommendations for the favourable properties of such protective arrangements with reference to the maximal shelter effect against sediment transport follow from this analyses. On the other hand, the :frequency of the potential occurrence of erosion will be proofed by data of a representatively meteorological station. Critically meteorological conditions appear two times per year corresponding to the statistical analyses

Wind erosion is recognised as an important issue globally. It is of importance in Australia due to a large proportion of the continent being classed as arid to semi-arid. With increases in land use and projected increases in the frequency and intensity of drought periods in Australia, wind erosion may be seen to increase, intensify and expand across the continent. Additionally, increases in the severity of annual to inter-annual climate systems (such as the El Niño Southern Oscillation (ENSO), the Southern Annual Mode (SAM), the Indian Ocean Dipole (IOD)) and even in overarching decadal to inter-decadal climate systems (such as the Interdecadal Pacific Oscillation (IPO) and the Pacific Decadal Oscillation (PDO)) will result in the spatial and temporal impacts of wind erosion being altered over time. Variations in drought and climate systems are recognised to affect wind erosion in Australia due to their influences on precipitation and erosive wind systems. Literature in the field of drought, wind erosion and climate systems was reviewed with respect to framing the need for this dissertation. It was identified that although a detailed understanding of drought has been developed over time (including definitions, impacts and influences) there are still challenges associated with the lack of uniform definition and with measures of severity, scale and overall prediction. Few wind erosion studies have focused on the impact that drought may have (and its flow-on effects to other wind erosion variables such as vegetation), particularly with respect to changes in response to climate. Climate systems research presents another layer of complexity to measuring or predicting wind erosion in Australia. This dissertation explores the role of drought and climate systems in wind erosion in eastern Australia (over the past 100 years), comparing a calculation of the potential for wind erosion with actual wind erosion (AWE) measures. It selects and adapts a drought index suitable for use in wind erosion studies and estimates the wind erosion potential (WEP) of eight drought periods, incorporating measures of soil erodibility and wind erosivity. It also evaluates why actual wind erosion rates (according to three different measures) differ to results produced by the WEP and examines how climate systems (the ENSO, SAM and IOD) and synoptic-scale systems influence wind erosion during the drought periods. Two drought indices (rainfall deciles (RD) and the Standardized Precipitation Index (SPI)) were assessed according to seven criteria developed to evaluate the favourability of indices for use in wind erosion studies. The SPI was selected as the most favourable due to its ability to identify the start and end dates of drought, provide measures of drought intensity, magnitude and severity and best capture wind erosion activity. The SPI was adapted and enhanced for the calculation of WEP using established factors of drought, erodibility (vegetation cover) and erosivity (wind speed) and applied to historical data (over 100 years from the consolidation of 63 observer stations into 22 stations in eastern Australia. Differences in results were evident for northeastern Australia (NEA) and southeastern Australia (SEA), reflecting varying short and longer term climatic influences. At a localised level wind severity, vegetative cover types and geomorphological features were able to explain differences. Specific climate systems phases (negative ENSO, negative SAM and positive IOD) occurring drought periods were found to favour wind erosion activity (both in NEA and SEA). A combination lock of climate system phase and wind erosion risk was developed to provide a conceptual understanding of the influence of climate systems on wind erosion during drought periods in Australia. This conceptual approach is unique to this dissertation, constituting an original innovation in the field of wind erosion research during drought and climate system studies in general. Combinations of climate system phases and associated wind erosion risk were presented for eight combinatoric scenarios, with highest wind erosion risk associated with negative ENSO, negative SAM and positive IOD. These combinations were demonstrated to have differing impacts according to location on the Australian continent due to differing synoptic-scale system dominance (trough systems in the north and cold fronts in the south). This dissertation has confirmed the important role that climate systems have on wind erosion during drought periods in eastern Australia. Its results have new implications for research in the field of wind erosion. It demonstrates a method of measuring drought from a wind erosion perspective and develops a way of both estimating wind erosion potential risk and investigating wind erosion activity from the lens of climate systems. The combination lock approach to climate systems and wind erosion during drought periods provides a conceptual advance in the climatological and meteorological understanding of wind erosion activity (spatially and temporally). Furthermore, at a time when the future impacts of drought and climate systems are predicted to intensify in severity and spatial scale, this research could provide a way for aeolian geomorphologists and land managers to predict the risk of wind erosion occurrence.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text

In this thesis, an integrated wind erosion assessment and prediction system has been developed. This system couples a physically based dust emission scheme, a high resolution limited area weather prediction model, a dust transport model, and a high resolution GIS (Geographic Information System) database. A simple expression for particle threshold velocity has been derived by considering the force balance of a single particle resting on the surface. Theoretical analyses have been performed to confirm that the main mechanism for dust uplifting is sand saltation bombardment rather than direct aerodynamic entrainment. A new model for dust emission by saltation bombardment is proposed and validated against experimental data. Preliminary sensitivity tests for the new dust emission model have been carried out by examining the dependence of dust emission rate on a range of parameters. The transport of airborne dust is modelled by using the particle mean concentration equation. The time-dependent advection terms are discretized and solved numerically by a multi-dimensional wave-propagation slope-limiter scheme. Some computational features of the integrated model are discussed in terms of its coupling, module decomposition, data handling and efficiency. A systematic sub-grid treatment is designed to extract soil surface parameters from the GIS database for large scale modelling. The integrated system is applied to investigate the February 1996 dust storms over the Australia continent. The simulated wind erosion pattern and intensity are in good agreement with available meteorological records and satellite images. It reveals that the system can be used to identify areas and periods under wind erosion threat as well as the responsible environmental factors.

Wind turbine blade damage, particularly leading edge erosion, is a signifcant problem faced by the renewable energy industry. Wind turbines are subject to a wide range of environmental factors during a 20+ year lifespan, with hailstones often touted as a key contributor to the deterioration of blade profile. The consequences of blade damage are exhibited in terms of cost of component repair but, perhaps more seriously, in the reduced performance and thus annual energy production (AEP) of the turbine. This thesis firstly presents the likelihood of hail events with respect to wind turbine locations, from an investigation of UK meteorological data. Three datasets were obtained: surface observations from UK-wide MIDAS stations, detailing back to 1949; as well as precipitation individual measurements from instruments located at CFARR and NERC facilities, also located in the UK. The prevalence of hail incidents is related to both onshore and offshore wind turbine operation. Particular attention was paid to the rotational speed of the wind turbine blades, which was determined to be a fundamental component of the energy associated with hail impact. From these impressions, an experimental campaign was carried out to investigate the effects on of repeated impact of simulated hail ice (SHI) on composite materials. Hailstones at four different diameters (5 mm, 10 mm, 15mm and 20mm) were fired at a range of velocities and for different numbers of impacts. Samples used for experimentation were manufactured from triaxial stitched glass fibre (0º, -45º, +45º) and epoxy resin. Damage was analysed qualitatively using scanning electron microscopy. A computational model was developed to compare the simulated damage of a singular hailstone impact to that of the experimental findings and examine other parameters not available in a practical setting. A survey of calculation methods was undertaken, to determine the elastic properties of the composite required prior to simulation. Threshold velocities were obtained for the onset of damage caused by singular impact of the different diameters of SHI.

The coastal population is growing, putting extra stress on coastal sediments and protection features, such as beach dunes. Moreover, global warming will increase the frequency of storms, and coastal dunes and other defense infrastructure will be subjected to increased erosion and scouring, endangering the people they are meant to protect. Understanding soil dynamics and fluid interaction is crucial to predict the effects of sand erosion. In particular, the study of wind erosion of sands in coastal dunes is essential due to the protective role these earthen structures have during storm events. One of the challenges about predicting wind erosion in coastal dunes is its extended spatial scale and the associated economic and logistics costs of sampling and characterizing the sediments. Because of this, in-situ testing for sediment characterization is essential. In particular, the usage of free-fall penetrometers (FFP) is appealing due to their portability and robustness. The sediment properties obtained with this type of testing can later be used to assess wind erosion susceptibility by determining, for example, the wind velocity to initiate the erosion process. FFP testing involves dropping an instrumented probe that impacts the soil and measures the kinematics or kinetics during the penetration process. For example, deceleration measurements are used to compute an equivalent quasi-static failure, which is not in line with the dynamic process characteristic of FFP testing. This preassumed failure mechanism is used to back-calculate the sand's geomechanical properties. However, soil behavior is highly complex under rapid loading, and incorporating this behavior into FFP sediment characterization models is challenging. Advanced numerical modeling can improve the understanding of the physics behind FFP testing. This thesis presents various advancements in numerical modeling and erosion models to bridge FFP in-situ testing with predicting the initiation of wind erosion of sands. First, improvements oriented to the Material Point Method (MPM) for modeling in-situ FFP testing are proposed. The numerical results show that the simulation of FFP deployment in sands is affected by strain localization and highlight the importance of considering constitutive models sensitive to different loading rates. Because of the importance of rate effects in soil behavior, the second aspect of this thesis proposes a novel consistency framework. Two constitutive models are adapted to study strain-rate sensitive non-cohesive materials: i) a strain-softening Mohr-Coulomb, and ii) a NorSand model. In addition to increased strength, the proposed framework captures increased dilatation, an early peak deviatoric stress, and relaxation. Finally, a novel sand erosion model is derived using a continuum approximation and limit equilibrium analysis. The erosion law considers geotechnical parameters, the effects of slope, and moisture suction, in a combined manner. The proposed model is theoretically consistent with existing expressions in the literature. It covers a wide range of environmental and geometrical conditions and helps to reconcile the results from FFP testing with the prediction of the initiation of wind erosion. The model was validated in a wind tunnel and is demonstrated to be a viable alternative for predicting sand erosion initiation. This thesis opens up new research prospects, such as improving the soil characterization models or the direct prediction of sand erosion using rapid, reliable, and efficient in-situ testing methods.
Doctor of Philosophy
With global warming and climate change, it is expected that the frequency and intensity of storms will increase. This increment will put extra stress on coastal sediments such as beach sand and coastal dunes, making them prone to erosion. Coastal dunes lose their ability to withstand storms as they erode, potentially making coastal flooding more frequent. In light of this, all stakeholders involved in the protection against coastal disasters must have the tools to predict, prepare for, and mitigate for situations like the ones stated above. An essential aspect of the prediction component is dependent on a successful sediment characterization, for example, determining how much wind the sand can withstand before it erodes. Free-fall penetrometers (FFP) are devices designed to conduct the characterization mentioned above. However, the procedures used to perform this characterization are mainly based on empirical or semi-empirical expressions. Computer models, capable of simulating the physics behind FFP testing, can bring more insight into the process of interaction between FFP devices, sands, and water and can be the basis to improve the characterization methods. The latter results can be utilized for instance to predict wind erosion, including several properties of the sand, such as its mineralogy and shape. This study contributes to developing the computer simulations of FFP deployment and the wind erosion prediction models. Eventually, these developments can help engineers and coastal managers to anticipate and prepare for more frequent coastal hazards.

This study uses a very high resolution numerical weather prediction (NWP) model to investigate the complex structure and behaviour of cold fronts along the New South Wales coast during the warmer months of the year, the complex interaction between the wind flow and coastlines and elevated areas as well as the lee-trough effect, particularly the way it affects waters off the east coast of Tasmania, The study also investigates the utility of the higher resolution NWP model to better predict wind fields compared to a lower resolution model. The University of New South Wales very high resolution model (HIRES), nested in the Australian Bureau of Meteorology's coarse NWP model (GASP), was run at various horizontal resolutions (from 15 to 25km) in order to investigate the above-mentioned features. It was found to bave very good skill in resolving the features and was also found to be very accurate in the prediction of surface wind fields for various yacht race events out to at least four days ahead. It can be concluded that there is considerable skill in the ability of high-resolution NWP models such as HIRES, to predict the major features of the wind fields over the ocean out to several days ahead. Moreover, it was also able to more accurately simulate the complex structure of the summer-time cool change as it progressed along the NSW coast than the lower resolution model runs. The influence of coastlines, particularly ones with complex topographical features, on the wind flow was demonstrated to a limited extent throughout the study. Finally the following concepts were also verified as a result of the study: - air flow takes the path of least resistance - the shape of topography can help generate local turbulence - the orientation of the wind flow to a mountain range is important in determining turbulent effects. - under certain airflow and stability situations, standing wave activity and a lee trough can be observed in the lee of mountains, hills or even high coastal cliffs.

Wind erosion is widespread across the world’s drylands and includes the arid and semi-arid rangelands of Australia. An estimated 110 Mt of dust is eroded by wind from the Australian land surface each year, most of which originates from the arid and semi-arid rangelands. Livestock production is known to increase the susceptibility of the rangelands to wind erosion, and produce accelerated erosion, by reducing vegetation cover and modifying surface soil stability. Extended episodes of wind erosion have been reportedly caused by overgrazing notably in Australia in the 1940’s and 1960s. However, research is yet to fully understand and quantify the impacts of pastoral activities on the wind erosion of the rangelands. Better understanding of the impact of pastoral managements (e.g. stocking rates, land conditions) on wind erosion and information on how these impacts change through time and space are required. This should offer the possibility to better understand and estimate the impact of pastoral activities on wind erosion and provide information to land managers in order to reduce grazing impacts on wind erosion.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Wind erosion and associated dust emissions play a fundamental role in many ecological processes, yet most ecological studies do not explicitly consider dust-driven processes despite the growing body of evidence suggesting that wind erosion is a key driver of land surface dynamics and many other environmentally relevant processes such as desertification. This study provides explicit support for a pervasive underlying but untested desertification hypothesis by showing that at the vegetation patch scale shrubs are significantly more efficient at capturing wind-blown sediment and other resources such as nutrients than grasses and that this difference is amplified following disturbance. At the landscape scale, the spacing and shape of woody plants were found to be a major determinant of dryland aeolian sediment transport processes in grasslands, shrublands, woodlands and forests, particularly following disturbance. This study also found that disturbance such as fire can have a significant influence on background dust emissions, which can have important consequences for many basic ecological and hydrological processes. Potential interactions between aeolian and fluvial processes were also evaluated in this study, and a new conceptual framework was developed that highlights important differences and similarities between the two processes as a function of scale-dependencies, mean annual precipitation, and disturbance. This study also explicitly evaluates the effect of climatic extremes and alternate land management practices on the absolute and relative magnitudes of wind and water erosion. Notably, results indicate that wet/dry climatic extremes and grazing can increase the wind-to-water erosion ratio, whereas burning disproportionally increases water erosion relative to wind erosion.

In der vorliegenden Studie wird einerseits die Winderosion und der damit verbundene Sedimenttransport hinter ausgedehnten Waldgebieten, die in ihrer Zusammensetzung typisch für den Nordraum von Leipzig sind, und hinter schmalen Gehölzschutzstreifen untersucht. Als Ergebnis dieser Analyse lassen sich Empfehlungen für die günstigsten Eigenschaften von Windschutzanpflanzungen hinsichtlich einer maximalen Schutzwirkung vor Sedimenttransport ableiten. Andererseits wird die Häufigkeit möglicher erosiver Ereignisse am Beispiel einer für das Untersuchungsgebiet repräsentativen meteorologischen Station geprüft. Kritische meteorologische Randbedingungen für erosive Prozesse treten entsprechend einer statistischen Datenanalyse zweimal pro Jahr auf.
On the one hand, the wind erosion and the associated sediment transport behind extensive forest areas, which are typically for the northern area of Leipzig, and behind narrow shelterbelts were examined in this study. Recommendations for the favourable properties of such protective arrangements with reference to the maximal shelter effect against sediment transport follow from this analyses. On the other hand, the :frequency of the potential occurrence of erosion will be proofed by data of a representatively meteorological station. Critically meteorological conditions appear two times per year corresponding to the statistical analyses.

Master of Science
Department of Agronomy
DeAnn R. Presley
Through the 2007 Energy Independence and Security Act, the U.S. government has set goals to decrease fossil fuel use and sustainably produce ethanol from biomass, rather than existing corn grain-based ethanol. In southwest Kansas, crop residues are necessary to protect soil from erosion and to contribute to soil organic carbon (SOC) levels, a key factor in most desirable characteristics of soil quality, and are positively related to soil and crop productivity. Our objective was to quantify the effect of different residue management treatments (residue continuously retained, residue continuously removed, and alternating year residue removal) on soil physical properties, chemical properties, and corn yield. For 2.5 years, measurements and samples were collected from a Hugoton loam (L) and Bigbow fine sandy loam (FSL) in southwest Kansas. Residue continuously removed decreased water stable aggregates ≥ 0.25 mm and mean weight diameter of aggregates in contrast to residue continuously retained treatments following two winter seasons at the Bigbow FSL site. In residue continuously removed treatment for the Bigbow FSL, dry aggregate size distribution (ASD) measurements at the soil surface in the fine sandy loam had higher levels of soil % < 0.84 mm (wind erodible fraction) during the winter season of 2008-2009 and 2009-2010 by 6% and 15%, respectively. No significant differences in wet aggregate stability and ASD were measured at the Hugoton L site. Soil temperature and moisture levels monitored during the winter season showed a higher frequency of freeze-thaw cycles, which can be destructive to aggregates, in residue continuously removed plots. During the winter seasons of 2008-2009 and 2009-2010, the residue continuously removed treatments experienced three more freeze-thaw cycles than the residue continuously retained treatments in the Bigbow FSL soil. Bulk density measurements were variable, and no significant differences due to residue treatment were observed in both the loam and fine sandy loam. Total C, N, and exchangeable K were significantly different in residue continuously retained and removed plots due to residue treatment following 1 year of establishment of the study in the FSL. Total C was 14 g kg-1 and 8.7 g kg-1 in the residue continuously retained and removed treatments, respectively. Total N was 0.3 g kg-1 higher in the residue continuously retained versus the residue continuously removed treatment in the FSL. Irrigated continuous corn in southwest Kansas produces a lot of biomass, and has been reported to create emergence problems in the past. Corn emergence was slightly higher in residue continuously removed treatments in both the spring of 2009 and 2010, but differences were insignificant. No significant treatment effects on corn grain yield were observed in the duration of the study.

O manuseio de matéria-prima bruta utilizada na indústria pode gerar emissões durante o seu transporte, armazenamento e eventual mistura. A atuação dos ventos em pátios abertos de armazenamento de carvão que existem em termelétricas, siderúrgicas e zonas de mineração pode acarretar no transporte e dispersão de partículas de carvão a grandes distâncias e a alturas consideráveis. É desejável reduzir a emissão do poluente sem interferir na atividade operacional destes pátios de carvão, de forma a se obter ganhos ambientais e econômicos. Os efeitos da utilização de telas de proteção para reduzir o transporte eólico de partículas de carvão foram estudados através de ensaios em túnel de vento, medindo-se as distribuições das pressões médias e flutuantes sobre a superfície de um modelo reduzido, em escala 1/125, de uma pilha representativa de um pátio real de estocagem de carvão.Distintas porosidades de tela (68%, 53%, 37% e 0%), em três distintas configurações, dois afastamentos e a duas diferentes alturas foram testadas. Além das medidas de pressões, o campo de velocidades sobre a superfície e entorno das pilhas foi obtido através de medições com sistema de anemometria de fio quente. Percebe-se claramente que as velocidades médias do vento são mais altas próximo ao topo da pilha, e que a presença das telas causa uma redução destas velocidades nas regiões mais críticas. As telas com porosidades intermediárias mostraram-se mais eficazes em minorar os efeitos nocivos provocados pela combinação das sucções na superfície com as velocidades tangenciais de arrasto. Verificou-se que a redução da porosidade implica em uma redução na velocidade do vento atuante na pilha. Quando posicionada a barlavento, a tela com porosidade 0% (placa) causou um aumento da zona de recirculação atrás da mesma, aumentando, portanto, as sucções sobre a superfície da pilha. Entretanto, quando posicionada a sotavento, a placa sólida implicou em reduções significativas das pressões médias sobre a pilha. De uma forma geral, as telas com porosidades variando de 53% a 68% foram mais eficazes em reduzir as flutuações de pressão na face a barlavento da pilha, sem aumentar significativamente as pressões médias. Entretanto, as telas com porosidade em torno de 37% foram as mais eficientes em reduzir os picos de pressão que se desenvolvem a partir de incidências oblíquas do vento.
The effects of using wind fences to reduce wind-blown coal dust were studied through wind tunnel tests. The mean and fluctuating pressure distributions over the surface of reduced coal pile models were measured. The tests were performed at a 1/125 scaled model of a typical coal pile. Different fence porosities (68%, 53%, 37%, 0%) as well as different fence positions and heights were tested. Further to the pressure measurements, the field velocities over the surface and surroundings of the piles were obtained through hot-wire anemometry measurements. The fence with no porosity (0%) caused and increase in the re-circulating zone behind the fence, therefore increasing the negative pressures over the pile surface, being soon disregarded. The fences with porosities ranging from 53% to 68% were most effective in reducing the pressure fluctuations on the windward face of the pile, without increasing significantly the mean pressures over it. These pressures are closely related to the dust emissions from the surface, directly affecting the surrounding environment. Although most effective for reducing pressure fluctuations, the best combined effect together with the drag surface velocities were found for the fences with intermediate porosities. The 37% porosity fence was the most effective in reducing the oblique wind induced peak pressures.

Leading edge erosion of modern wind turbine blades is a growing and developing issue within the wind industry, effecting blade performance and efficiency. Little is known, researched or published on the phenomenon and there are currently no apparent full-proof material solutions for the issue. The research presented here looks to develop a fuller understanding of the issue of leading edge erosion, through first reviewing the literature (both within and outwith wind energy) on the topic to put the issues in context, and then subsequently further exploring and investigating the key damage mechanisms associated rain droplet and hailstone impact on the blade leading edge; identified as two of the most erosive types of environmental exposure. Both numerical (finite element) and experimental methods are employed to identify the key damage mechanisms associated with each form of impact in the different possible blade material coating and substrate systems. It is found that for rain exposure, surface degradation and erosion is a real risk for classical gelcoat coating systems. Whereas, for newer flexible and more erosive resistant materials, interface damage and debonding from the substrate is the most likely form of damage creation. Hailstone impact is found to pose a heightened erosive threat in comparison to rain, based on individual impact damage creation; although it is recognised that hailstorms are far more infrequent than rain showers in most regions. However, it is predicted that for extreme hailstones of sufficient mass, significant substrate composite damage could also be created through impact on the leading edge. Future work and further research development aimed at further understanding the issues of blade leading edge erosion are also identified and discussed.

Master of Science
Department of Biological & Agricultural Engineering
Ronaldo G. Maghirang
Large cattle feedlots emit considerable amounts of particulate matter (PM), including TSP (total suspended particulates), PM[subscript]10 (PM with equivalent aerodynamic diameter of 10 μm or less), and PM[subscript]2.5 (PM with equivalent aerodynamic diameter of 2.5 μm or less). Particulate emissions result from pen surface disturbance by cattle hoof action, vehicle traffic on unpaved roads and alleyways, and wind erosion. Research is needed to determine concentrations of various size fractions, size distribution, and emission rates from various sources in feedlots. This research was conducted to measure particle size distribution using laser diffraction method and estimate emissions from unpaved roads and wind erosion. Particle size distribution and concentrations of PM[subscript]10 and PM[subscript]2.5 at a commercial cattle feedlot in Kansas (Feedlot 1) were measured over a 2-yr period. The feedlot had a capacity of 30,000 head and total pen area of 50 ha and was equipped with a sprinkler system for dust control. Collocated low-volume samplers for TSP, PM[subscript]10, and PM[subscript]2.5 were used to measure concentrations of TSP, PM[subscript]10, and PM[subscript]2.5 at the upwind and downwind edges of the feedlot. Dust samples that were collected by TSP samplers were analyzed with a laser diffraction analyzer to determine particle size distribution. Particle size distribution at the downwind edge of the feedlot was also measured with micro-orifice uniform deposit impactor (MOUDI). The laser diffraction method and MOUDI did not differ significantly in mean geometric mean diameter (13.7 vs. 13.0 μm) but differed in mean geometric standard deviation (2.9 vs. 2.3). From laser diffraction and TSP data, PM[subscript]10 and PM[subscript]2.5 concentrations were also calculated and were not significantly different from those measured by low-volume PM[subscript]10 and PM[subscript]2.5 samplers (122 vs. 131 μg/m[superscript]3 for PM[subscript]10; 26 vs. 35 μg/m[superscript]3 for PM[subscript]2.5). Both PM[subscript]10 and PM[subscript]2.5 fractions decreased as pen surface moisture contents increased, while the PM[subscript]2.5/PM[subscript]10 ratio did not change much with pen surface moisture content. Published emission models were used to estimate PM[subscript]10 emissions from unpaved roads and wind erosion at Feedlot 1 and another nearby feedlot (Feedlot 2). Feedlot 2 had a capacity of 30,000 head, total pen surface area of 59 ha, and used water trucks for dust control. Estimated PM[subscript]10 emissions from unpaved roads and wind erosion were less than 20% of total PM[subscript]10 emissions obtained from inverse dispersion modeling. Further research is needed to establish the applicability of published emission estimation models for cattle feedlots.

Tidal systems are subjected to a variety of internal and external drivers whose interplay and feedbacks affect the shape and the morphological evolution of typical tidal landforms such as channel networks, salt marshes and tidal flats. Several studies have been carried out describing the various processes that drive the evolution of tidal landforms (e.g., the hydrodynamic circulation, the consequences of tidal currents and wind waves on sediment dynamics, vertical and horizontal dynamics of salt marshes, sea level rise and human interferences). Understanding the positive feedbacks existing between salt-marsh erosion, tidal-flat widening and deepening and more energetic wave generation by means of observational evidence and numerical models is a critical step to predict the response of tidal landforms to future environmental changes. With this aim we first improved current our knowledge on the ancient configurations of the Venice lagoon through the bathymetric reconstruction of the oldest map, dating back to 1611, providing a realistic representation of its morphological features. This furthermore allowed us to gain new insights on the hydrodynamic changes occurred in the last four centuries. We then compared different existing model approaches, in order to unravel the implications of different assumptions and formulations used to model wave dynamics in shallow tidal basins. Subsequently, we analysed the effects of wave action on marsh boundaries and how the wave field has changed in the last four centuries with the aim of further emphasizing the feedbacks existing between the overall erosion of the Venice Lagoon and the increase in wave power density. Finally, we analysed the bottom shear stress distribution obtained for different configurations of the Venice Lagoon, in order to support the possibility of describing wind-wave induced bottom erosion as a marked Poisson process. The main results from this work highlighted that: I) the most important mophodynamic changes in the Venice Lagoon have started in the last century and were mainly triggered by human interferences; II) the assumptions adopted in different modelling framework strongly influence the computation of the bottom shear stress induced by waves, in particular when very shallow water depths are considered; III) the salt-marsh erosion rate is linearly related to the mean wave power density; IV) the erosive trend of the Venice Lagoon during the last four centuries can be explained also by the increase in wave power density and by the analysis of bottom shear stress distribution; V) wind-wave induced erosion processes over tidal flats can be described as marked Poisson processes for all the past and current lagoon configurations, thus leading important consequences for the prediction of future scenarios and implications for the long-term morphodynamic modelling of tidal environments.
I sistemi mareali sono soggetti ad innumerevoli forzanti interne ed esterne, le cui interazioni e feedbacks influenzano l’evoluzione morfologica delle principali strutture morfologiche che caratterizzano gli ambienti a marea:i canali, le barene e i bassifondi. Sono stati svolti innumerevoli studi che descrivono i diversi processi che determinano l’evoluzione degli ambienti lagunari (e.g., l’idrodinamica dei canali a marea, le conseguenze delle correnti di marea e delle onde da vento sulla dinamica dei sedimenti, i meccanismi di evoluzione laterale e orizzontale delle barene, l’incremento del livello del medio mare, gli interventi antropici). Capire i meccanismi di feedback positivi esistenti tra l’erosione delle barene, l’allargamento e approfondimento dei bassifondi e la generazione di moto ondoso più energetico con l’aiuto di dati di campo e di modelli numerici risulta un passo fondamentale per prevedere la risposta delle strutture morfologiche degli ambienti a marea ai futuri cambiamenti ambientali. Al fine di raggiungere questo obiettivo, abbiamo, in primo luogo, ampliato la nostra conoscenza delle configurazioni storiche della Laguna di Venezia attraverso la ricostruzione batimetrica della più antica mappa, risalente al 1611, che forniva una rappresentazione realistica delle strutture morfologiche lagunari. Questo ha consentito di conseguenza di approfondire l’analisi dei cambiamenti idrodinamici che si sono verificati negli ultimi quattro secoli. Abbiamo in seguito confrontato diversi approcci adottati in modelli esistenti, al fine di investigare e comprendere le implicazioni delle diverse assunzioni e formulazioni utilizzate per modellare la dinamica delle onde da vento in bacini a marea poco profondi. Di seguito, abbiamo analizzato gli effetti dell’azione delle onde da vento sui bordi delle barene e il cambiamento del campo di moto ondoso negli ultimi quattro secoli, allo scopo di enfatizzare ulteriormente i feedbacks esistenti tra l’erosione generale della Laguna di Venezia e l’aumento della potenza delle onde. Infine, abbiamo analizzato gli sforzi di attrito al fondo ottenuti per diverse configurazioni della Laguna di Venezia, in modo da supportare la possibilità di descrivere l’erosione del fondo indotta da onde da vento come un processo di Poisson marcato. I principali risultati di questo lavoro hanno evidenziato che: I) i più gravosi cambiamenti morfodinamici nella Laguna di Venezia sono iniziati nell’ultimo secolo e sono stati innescati principalmente dagli interventi antropici; II) le assunzioni adottate in diversi approcci modellistici fortemente influenzano il calcolo dello sforzo di attrito al fondo dovuto alle onde da vento, in particolare quando si considerano profondità molto ridotte; III) il tasso di erosione delle barene è linearmente correlato alla potenza generata dalle onde da vento; IV) la tendenza erosiva della Laguna di Venezia negli ultimi quattro secoli può essere spiegata dall’aumento della potenza media e dall’analisi della distribuzione dello sforzo di attrito al fondo; V) i processi erosivi dovuti alle onde da vento in sistemi lagunari possono essere descritti come processi di Poisson marcato in tutte le configurazioni passate e per quella attuale, questo produce importanti conseguenze per quanto riguarda la previsione di scenari futuri e implicazioni per la modellazione morfodinamica a lungo termine degli ambienti a marea.

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第15421号
農博第1806号
新制||農||979(附属図書館)
学位論文||H22||N4520(農学部図書室)
27899
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 舟川 晋也, 教授 縄田 栄治, 教授 間藤 徹
学位規則第4条第1項該当

This study examines wind generated waves during winter storms, their transformation/attenuation near the marsh edge, and the resulting saltmarsh edge erosion. A simple numerical model for wave generation, transmission and marsh edge erosion was developed and validated against observations from Lake Borgne, Louisiana. Results suggest that meteorological conditions modify the local water depth via wind or wave setup and atmospheric pressure, thus exerting a first order control on the location of wave attack, which in turn determines the type of wave forces (shear vs. impact) that dominate the erosion process. Scarp failure follows, at a location determined by water level, creating multiple erosive scarps and terraces. High measured erosion, likely due to marsh edge destabilization followed by subsequent frontal passage forces differential marsh erosion, exposing underlying substrate to further erosion. A conceptual model for marsh edge retreat is developed using these observations and supported further by model predictions.

Most of the early wind erosion research undertaken in Australia, concentrated on how wind erosion affects cultivated farm land. However, in the 1990's the focus of wind erosion research in Australia started to shift to include rangeland environments. Initially these rangeland experiments used experimental configurations that were developed for cultivated fields. This meant that in most cases a sampler was set up in the middle of a field and it was assumed that the data collected was representative of the field as a whole. It was also assumed that temporal changes in dust fluxes/concentration reflect overall changes in the land type erodibility and wind erosivity. However, recent experiments and field observations within the rangelands, of the Channel Country suggest that this assumption is not valid. These experiments and observations suggest that there are substantial spatial and temporal variations in erodibility within individual land types. Such variations complicate the interpretation of temporal and spatial erosion trends. In particular, this variability implies that it is difficult to compare sampler data between different wind erosion events. To begin quantifying and comparing sampler data between events within the rangeland environments, the Dust Source Interaction Simulation Model (DSism) was developed to simulate the effect that physical processes and spatial variations in erodibility have upon observed dust concentration pro- files. The modelling/simulation approach used is closely linked to experimental data via the extensive use of sensitivity testing. Another key feature of the DSism approach, is its flexibility in allowing different dust source areas to have particle emission characteristics. This combined sensitivity testing and simulation approach has provided new insights into the wind erosion processes. By using DSism, it has been possible to identify several key features of the wind erosion process within rangeland environments. The first observation is that spatial and temporal changes in erodibility produce distinct changes in both the vertical and crosswind dust concentration profiles. Further investigations, indicate that the dispersion processes in operation vary from event to event. In particular, the results presented here indicate that surface heating plays an important role in some wind erosion events. These results also suggest that even small variations in the vertical dust concentration profile can reflect temporal and spatial changes in processes and erodibility. Finally the simulation results show that the particle size distribution of a vertical dust concentration profile depends on (a) the processes in operation during a given event and (b) the spatial variation in the particle size emission characteristics of the various source areas. These findings have several important implications. In particular, they indicate that both the crosswind and vertical dust concentration profiles can be viewed as amalgamation of several distinct plumes from different dust source areas and that dust concentration profiles contain significant information about both the spatial distribution of sources and the processes in operation during any given event. Most field studies have used regression models to describe the variation in dust concentration with height. A problem with this approach is that it assumes that the variation in dust concentration with height, always has a given functional form (or shape) and that dust concentration always decreases with height. Field observations, indicate that this assumption is only valid for some events within rangeland environments and that dust concentration does not always decrease with height in these environments. In most cases, such variations from the regression fit have been assumed to be the result of experimental 'noise' (error) or spatial variations in erodibility. This thesis presents, modelling and field evidence, which suggests that such variations, are the result of a combination of spatial variations in erodibility and changes in thermal conditions.

In many arid and semiarid regions worldwide, high levels of soil salinity is a key driver of land degradation, as well as a key impediment to re-establishing plant cover. Combating land degradation and erosion associated with soil salinity requires experimental determination of plant species that can grow in soils with high levels of salinity and can be used to re-establish plant cover. Herein, we evaluated the responses of untested candidate cultivars of two halophytic grass species to high soil salinity: alkali sacaton (Sporobolus airoides Torr.) and seashore paspalum (Paspalum vaginatum Swartz). We evaluated the growth responses of both species in a greenhouse under control (no-salt) and various levels of NaCl salinity (EC 8, 16, 24, 32, 40, and 48dSm(-1)) using Hoagland solution in a hydroponics system in a randomized complete block design trial. At all salinity levels, sacaton grass had a greater shoot height, shorter root length, lower shoot fresh and dry weights, and poorer color and general quality compared to seashore paspalum. The shoot fresh and dry weights of both grasses were greatest at the low to medium levels of salinity, with the greatest response observed at EC 16dSm(-1). At the highest level, salinity significantly reduced shoot fresh and dry weights of both grasses. Because growth of both halophytic species exhibited high tolerance to salinity stress and were stimulated under low to medium levels of salinity, both species could be considered suitable candidates for re-establishing plant cover in drylands to combat desertification and land degradation associated with high levels of soil salinity.

Most of the early wind erosion research undertaken in Australia, concentrated on how wind erosion affects cultivated farm land. However, in the 1990's the focus of wind erosion research in Australia started to shift to include rangeland environments. Initially these rangeland experiments used experimental configurations that were developed for cultivated fields. This meant that in most cases a sampler was set up in the middle of a field and it was assumed that the data collected was representative of the field as a whole. It was also assumed that temporal changes in dust fluxes/concentration reflect overall changes in the land type erodibility and wind erosivity. However, recent experiments and field observations within the rangelands, of the Channel Country suggest that this assumption is not valid. These experiments and observations suggest that there are substantial spatial and temporal variations in erodibility within individual land types. Such variations complicate the interpretation of temporal and spatial erosion trends. In particular, this variability implies that it is difficult to compare sampler data between different wind erosion events. To begin quantifying and comparing sampler data between events within the rangeland environments, the Dust Source Interaction Simulation Model (DSism) was developed to simulate the effect that physical processes and spatial variations in erodibility have upon observed dust concentration pro- files. The modelling/simulation approach used is closely linked to experimental data via the extensive use of sensitivity testing. Another key feature of the DSism approach, is its flexibility in allowing different dust source areas to have particle emission characteristics. This combined sensitivity testing and simulation approach has provided new insights into the wind erosion processes. By using DSism, it has been possible to identify several key features of the wind erosion process within rangeland environments. The first observation is that spatial and temporal changes in erodibility produce distinct changes in both the vertical and crosswind dust concentration profiles. Further investigations, indicate that the dispersion processes in operation vary from event to event. In particular, the results presented here indicate that surface heating plays an important role in some wind erosion events. These results also suggest that even small variations in the vertical dust concentration profile can reflect temporal and spatial changes in processes and erodibility. Finally the simulation results show that the particle size distribution of a vertical dust concentration profile depends on (a) the processes in operation during a given event and (b) the spatial variation in the particle size emission characteristics of the various source areas. These findings have several important implications. In particular, they indicate that both the crosswind and vertical dust concentration profiles can be viewed as amalgamation of several distinct plumes from different dust source areas and that dust concentration profiles contain significant information about both the spatial distribution of sources and the processes in operation during any given event. Most field studies have used regression models to describe the variation in dust concentration with height. A problem with this approach is that it assumes that the variation in dust concentration with height, always has a given functional form (or shape) and that dust concentration always decreases with height. Field observations, indicate that this assumption is only valid for some events within rangeland environments and that dust concentration does not always decrease with height in these environments. In most cases, such variations from the regression fit have been assumed to be the result of experimental 'noise' (error) or spatial variations in erodibility. This thesis presents, modelling and field evidence, which suggests that such variations, are the result of a combination of spatial variations in erodibility and changes in thermal conditions.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Australian Environmental Studies
Full Text

Doctor of Philosophy
Agronomy
DeAnn R. Presley
Crop residue removal for livestock feeding and biofuel production at large scales must be evaluated to assess impacts on soil productivity and properties. Among all the potential negative impacts, wind erosion is a major concern in the central Great Plains. We conducted an on-farm study from 2011 to 2013 by removing crop residue at five levels (0, 25, 50, 75, and 100%) to determine the effects of crop residue removal on soil wind erosion parameters such as dry aggregate size distribution including soil wind erodible fraction (EF <0.84 mm aggregates), geometric mean diameter (GMD) and geometric standard deviation (GSD), dry aggregate stability, and soil surface roughness. The sub-model of Wind Erosion Prediction System (WEPS) developed by the USDA-ARS, Single-event Wind Erosion Evaluation Program (SWEEP) is a stand-alone companion software package that can be applied to simulate soil loss and dust emission from a single windstorm event. We applied measured data (i.e. EF, GMD, GSD, and roughness) to SWEEP for predicting wind velocity that can initiate wind erosion and soil loss under each crop residue removal condition with wind velocity at 13 m sˉ¹. The threshold wind velocity to initiate wind erosion generally decreased with increase in crop residue removal levels, particularly for residue removal >75%. The total amount of soil loss in 3 hours ranged from about 0.2 to 2.5 kg mˉ² and depends on soil condition and crop residue cover. On the other hand, high-yielding crops can produce abundant crop residue, which then raises the question that if a farmer wants to reduce residue, what could they do without removing it? The application of fertilizer on crop residue to stimulate microbial activity and subsequent decomposition of the residue is often debated. We conducted wheat straw decomposition field experiments under different fertilizer rates and combinations at three locations in western Kansas following wheat harvest in 2011 and 2012. A double shear box apparatus instrumented with a load cell measured the shear stress required to cut wheat straw and photomicrography was used to measure the cross-sectional area of wheat straw after shearing. Total C and N were also analyzed. The fertilizer rate and timing of application during summer 2012 and Fall 2013 at the Hays site had impacts on wheat straw shear stress at break point. Across site years, earlier (fall) fertilizer application generally resulted in lower remaining aboveground biomass as compared to a spring application. Multivariate and linear regressions suggested that N and C:N ratio partially explain the results observed with respect to treatment effects on winter wheat residue decomposition.

L'érosion éolienne des matières granulaires (minerais, charbons,. . . ) est un des facteurs influençant grandement la qualité de l'air dans l'environnement proche de nombreux sites industriels. L'objectif principal de ce travail est l'amélioration des méthodologies de quantification des émissions des sources diffuses, notamment à partir d'une meilleure prise en compte de l'exposition éolienne des sources que sont les tas de stockage et des répartitions granulométriques des matières présentes sur les sites de stockage. Les observations sur sites industriels montrent que les régions proches des tas de stockage de matières granulaires sont chargées de particules de granulométries plutôt fines. Celles-ci sont susceptibles d'être remises en suspension par les structures tourbillonnaires générées par le vent incident. Ainsi, ces zones d'envol potentiel ont fait l'objet d'analyses afin de quantifier leur contribution aux émissions globales. Une technique de visualisation d'écoulement pariétal, associée à des simulations numériques tridimensionnelles, ont été mises en oeuvre pour mieux comprendre ces structures de l'écoulement. Les matières granulaires sont un mélange de particules érodibles et non-érodibles. Le caractère érodible étant lié aux propriétés des particules (principalement granulométrie et masse volumique), ainsi qu'à la vitesse du vent incident. Dans ce cadre, deux types d'études ont été menées: des essais expérimentaux d'envol de particules dans une soufflerie et des simulations numériques tridimensionnelles avec un logiciel open-source de mécanique des fluides (Code_Saturne). Une technique originale a ainsi été développée pour quantifier, par une pesée en continue, l'influence des particules non-érodibles sur le flux massique envolé. En parallèle, le comportement des particules sur la surface est analysé à l'aide de clichés photographiques. L'analyse de l'effet des particules non-érodibles au niveau local est réalisée grâce à des simulations numériques pour des configurations polydispersées. Les résultats présentés dans ce mémoire constituent de premiers éléments pouvant possiblement contribuer à l'amélioration des modèles actuels de quantification des émissions de particules par une meilleure intégration et pris en compte de la présence de particules non-érodibles pour les matières présentant de larges spectres granulométriques.

Le processus d'érosion éolienne peut entraîner plusieurs conséquences environnementales: la désertification, la dégradation des sols, la pollution de l'air, etc. Cette dernière est liée aux émissions de particules de matériaux granulaires couramment trouvés sur des sites industriels tels que le minerai et le charbon. La distribution granulométrique de ces matériaux consiste habituellement en un mélange d'une large gamme de diamètres, qui comprennent des particules plus grosses qui ne sont pas érodables même avec de fortes rafales de vent. Les particules non érodables jouent un rôle protecteur pour les particules érodables, en recouvrant la surface et en réduisant ses émissions. L'objectif principal de cette thèse est d'estimer plus précisément les émissions dues à l'érosion éolienne compte tenu de l'influence du pavage causée par des particules non érodables. Un modèle analytique a été proposé pour quantifier les émissions des lits de particules et des tas de stockage avec une large distribution granulométrique. Les effets du processus de pavage sont incorporés dans le modèle par la diminution de la vitesse de frottement moyenne sur la surface érodable puisque les particules non érodables s'accumulent. Des travaux antérieurs ont défini une relation mathématique entre l'évolution de la vitesse de frottement sur la surface érodable et la géométrie des éléments de rugosité. Néanmoins, l’equation n'est valable que pour des taux de couverture de particules non érodables limités. Des simulations numériques ont été effectuées dans ce travail pour étendre cette relation afin d'inclure d'autres cas rencontrés dans des situations réelles (avec de plus grandes quantités de particules non érodables). Le modèle d'émission proposé décrit la relation entre la valeur minimale de la vitesse de frottement (à laquelle les émissions cessent), en tirant parti des résultats numériques, et la profondeur finale érodée du lit, qui fournit à son tour la masse émise. Des expériences en soufflerie ont été réalisées afin de mieux comprendre le phénomène de pavage et estimer les émissions d'un lit de particules contenant une distribution de taille bimodale. Les résultats expérimentaux ont également été utilisés pour valider la modélisation, y compris la masse émise globale et les caractéristiques finales de la surface du lit. Un bon accord a été trouvé entre les résultats expérimentaux et modélisés pour les émissions globales et la profondeur de lit érodé. Le modèle d'érosion a été étendu pour l'application dans les tas de stockage. Dans ce cas, l'érodabilité des particules est plus complexe, puisque la vitesse de frottement et les conditions de seuil ne sont pas spatialement homogènes. L'idée du modèle était de subdiviser le tas en isosurfaces dans lesquelles les conditions de seuil et la vitesse de frottement sont constantes, et traiter chacune de ces zones comme une source différente où le modèle d'émission peut être appliqué. Des expériences en soufflerie ont été réalisées afin d'estimer les émissions d'un tas de sable contenant une distribution de taille bimodale. Les résultats modélisés et expérimentaux ont été comparés pour la configuration d'un tas isolé et un bon accord a été trouvé entre la masse émise estimée et mesurée. L'impact de la présence d'un bâtiment et d'un tas de stockage parallèle successif sur l'émission globale de particules a également été évalué. Des expériences en soufflerie et des simulations numériques ont été effectuées pour plusieurs configurations, en évaluant les effets de: (i) l'orientation du vent, (ii) la vitesse du vent, (iii) la distance entre l'obstacles et (iv) la quantité de particules non érodables. Il a été constaté que les interférences de l'écoulement entre les obstacles augmentent les émissions. Par conséquent, toutes les perturbations du vent ont un impact significatif et doivent être prises en compte dans l'estimation et la modélisation des émissions de poussières
Wind erosion process can lead to several environmental consequences: desertification, land degradation, air pollution, etc. This last one is related to particulate matter emissions from granular materials commonly found on industrial sites, such as ore and coal. The particle size distribution of these granular materials usually consist of a mixture of a wide range of diameters, which include larger particles that are non-erodible even with strong gusts of wind. The non-erodible particles play a protective role for erodible particles, paving the surface and reducing emissions. The main objective of this thesis is to estimate more accurately emissions due to wind erosion considering the influence of the pavement caused by non-erodible particles. An analytical model was proposed to quantify emissions from particle beds and stockpiles with a wide size distribution. The effects of pavement process are incorporated in the model through the decrease of the mean friction velocity on the erodible surface as the non-erodible particles accumulate. Previous works have defined a mathematical relation between the evolution of the friction velocity over the erodible surface and the geometry of the roughness elements. Nonetheless, the formulation was only valid to limited cover rates of non-erodible particles. Numerical simulations were carried out in this work to extend the formulation in order to include other cases encountered in real situations (with larger amounts of non-erodible particles). The proposed emission model describes the relationship between the minimum value of friction velocity (at which emissions cease), taking advantage of the numerical findings, and the final eroded depth of the bed, which in turn, provides the emitted mass. Wind tunnel experiments were carried out in order to better understand the pavement phenomenon and estimate emissions from a bed of particles containing a bimodal size distribution. The experimental results were also used to validate the modeling, including the global emitted mass and the final characteristics of the bed surface. A good agreement was found between experimental and modeled results for the global emissions and the bed eroded depth. The erosion model was extended for application in stockpiles. In this case, the erodibility of the particles is more complex as the friction velocity and the threshold conditions are not spatially homogeneous. The idea of the model was to subdivide the pile in isosurfaces in which the threshold conditions and the friction velocity are constant and then treat each one of these areas as a different source where the emission model can be applied. Wind tunnel experiments were carried out in order to estimate emissions from a sand pile containing a bimodal size distribution. The modeled and the experimental results were compared for the configuration of an isolated stockpile and a good agreement was found between the estimated and the measured emitted mass. The impact of the presence of a building and a successive parallel stockpiles on the overall particles emission was also evaluated. Wind tunnel experiments and numerical simulations were carried out for several configurations evaluating the effects of: (i) main wind flow orientation, (ii) wind flow velocity, (iii) gap between the obstacle and (iv) amount of non-erodible particles. It was found that the flow interferences between the obstacles increase emissions. Therefore, all wind perturbations have a significant impact and have to be accounted in dust emission estimation and modeling
O processo de erosão eólica pode levar a várias consequências ambientais: desertificação, degradação da terra, poluição do ar, etc. Esta última está relacionada com as emissões de partículas provenientes de materiais granulares comumente encontrados em indústrias, como minério e carvão. A distribuição granulométrica destes materiais normalmente consiste em uma mistura com uma ampla gama de tamanhos, incluindo partículas maiores que não são erodíveis mesmo com fortes rajadas de vento. As partículas não erodíveis desempenham um papel protetor para as partículas erodíveis, pavimentando a superfície e reduzindo as emissões. O objetivo principal desta tese é estimar com maior acurácia as emissões devidas à erosão eólica considerando a influência da pavimentação causada pelas partículas não-erodíveis. Um modelo analítico foi proposto para quantificar as emissões de leitos de partículas e pilhas com ampla distribuição granulométrica. Os efeitos do processo da pavimentação são incorporados no modelo por meio da diminuição da velocidade de fricção média na superfície erodível à medida que as partículas nãoerodíveis se acumulam. Trabalhos anteriores definiram uma relação matemática entre a evolução da velocidade de fricção na superfície erodível e a geometria dos elementos rugosos. No entanto, a formulação é válida apenas para limitadas taxas de cobertura de partículas não-erodíveis (< 12%). Simulações numéricas foram realizadas neste trabalho para estender a formulação de modo a incluir outros casos encontrados em situações reais (com maiores quantidades de partículas nãoerodíveis). O modelo de emissão proposto descreve a relação entre o valor mínimo da velocidade de fricção (para qual as emissões cessam), utilizando os resultados numéricos, e a profundidade final erodida do leito, que, por sua vez, fornece a massa emitida. Experimentos em túnel de vento foram realizados para melhor compreender o fenômeno da pavimentação e estimar as emissões de um leito de partículas contendo uma distribuição granulométrica bimodal. Os resultados experimentais foram também utilizados para validar a modelagem, incluindo a massa global emitida e as características finais da superfície do leito. Uma boa concordância foi encontrada entre os resultados experimentais e modelados para as emissões globais e a profundidade erodida do leito. O modelo de erosão foi estendido para aplicação em pilhas de estocagem. Neste caso, a erodibilidade das partículas é mais complexa, uma vez que a velocidade de fricção e as condições de limiar não são espacialmente homogêneas. A ideia do modelo é subdividir a pilha em isosuperfícies em que as condições de limiar e a velocidade de fricção são constantes e, em seguida, tratar cada uma dessas áreas como uma fonte diferente onde o modelo de emissão pode ser aplicado. Foram realizados ensaios experimentais em túnel de vento para estimar as emissões de uma pilha de areia contendo uma distribuição de tamanho bimodal. Os resultados experimentais e modelados foram comparados para a configuração de uma pilha isolada (orientada 60 e 90° em relação a direção do escoamento) e uma boa concordância foi encontrada entre a massa estimada e a emitida. O impacto na emissão da presença de um edifício e de uma pilha de estocagem sucessiva também foi avaliado. Experimentos em túnel de vento e simulações numéricas foram realizados para várias configurações avaliando os efeitos de: (i) orientação do vento, (ii) velocidade do vento, (iii) espaçamento entre os obstáculos e (iv) quantidade de partículas não erodíveis. Verificou-se que as interferências do escoamento entre os obstáculos aumentam as emissões. Portanto, todas as perturbações no escoamento têm um impacto significativo e devem ser contabilizadas na estimativa e modelagem de emissões de partículas

Aeolian sediment transport threshold is commonly defined as the minimum wind speed (or shear stress) necessary for wind-driven sediment transport. Threshold is a core parameter in most models of aeolian transport. Recent advances in methodology for field-based measurement of threshold show promise for improving parameterizations; however, investigators have varied in choice of method and sensor. The impacts of modifying measurement system configuration are unknown. To address this, two field tests were performed: (i) comparison of four piezoelectric sediment transport sensors, and (ii) comparison of four calculation methods. Data from both comparisons suggest that threshold measurements are non-negligibly modified by measurement system configuration and are incomparable. A poor understanding of natural sediment transport dynamics suggests that development of calibration methods could be difficult. Development of technical standards was explored to improve commensurability of measurements. Standards could assist future researchers with data syntheses and integration.
xi, 108 leaves : ill. ; 29 cm

Thesis (MSc (Earth Sciences))--Stellenbosch University, 2008.
This study aims to provide a practical tool for the prediction and management of dust generated by the activities of an opencast mining operation. The study was conducted on opencast gypsum mines in the semi-arid environment of the Bushmanland, 90 km north of Loeriesfontein in the Northern Cape Province from April 2000 to October 2007. The vertical and horizontal components of wind transported sediment were sampled and a dust settling model was designed to predict the settling pattern of dust generated by opencast mining operations. The model was applied to soil samples collected from an area surrounding a mine. The influence sphere of the mining operation was predicted by the application of the model and then mapped. Once the influence sphere is mapped, the dust influence can be managed with the aid of an onsite weather station. By further applying the predictions based on climatic data, the influence sphere can be modelled. The model is not only applicable to the planning phase of an opencast mine to plan the position of dust sensitive areas like the living quarters, office buildings and workshops etc., but also to indicate the historical impact that a mining operation had once a quarry on an active mine is worked out and rehabilitated or a mine is closed. The model application can also aid with the explanation and visual or graphic representation of the predicted impact of planned mining operations on communities or neighbouring activities to them and thus avoid later penalties.

Sediment resuspension and deposition are key processes governing intertidal morphodynamics and are crucially influenced both by physical and biological factors. The present thesis addresses two important aspects of sediment trans- port processes in intertidal areas. The first topic concerns the quantitative analysis of suspended sediment concentration and wind forcing to provide estimates of sediment properties, such as settling velocity and the critical shear stress for erosion, valid at a spatial scale which is relevant for the overall morphodynamics of the system. The first part of the thesis thus develops and describes a method to evaluate sediment properties based on the solution of a sediment mass conser- vation equation in the water column accounting for the effects of wind-induced and current-induced bottom shear stress. The method is applied by using data from a network of in situ sensors in the Venice lagoon and provides estimates which compare favorably with observations in the same shallow tidal areas, and are in line with what is expected for sandy-silt sediments. The proposed estimation method is direct and quantitative, it does not interfere with the local system physical and biological status, and lends itself to the monitoring of sed- iment parameters on a seasonal basis and for long periods of time with limited operational effort. The second, related, topic treated here concerns the labora- tory study of the impact of mats of Ulva intestinalis on sediment stability and flow dynamic in shallow tidal areas. Macroalgae are a controlling factor of flow and sediment stability, as they act to inhibit sediment erosion due to waves or currents and promote sedimentation. Algal mats are increasingly more frequent and extended in many coastal and estuarine intertidal habitats and it is thus important to quantitatively characterize their impact on the flow field and on sediment stability, in order to better understand ongoing degradation of coastal lagoons and to develop suitable mitigation and restoration measures. The second part of the thesis thus describes and analyzes a series of experiments performed in a large open-channel flume (the Total Environment Simulator - TES- facility at University of Hull, UK), set up with a bed of fine sand, partially covered by strands of U. intestinalis. The experiments allowed the accurate measurement, both in space and time, of flow velocity distributions, water levels, bed levels, and suspended sediment concentration. The presence of macroalgae was found to influence both the velocity distribution near the sediment bed, and the Reynolds shear stress acting on it. Direct inspection during the experiments and data analysis suggest that macroalgae exert a significant bio-stabilizing effect.
La risospensione e la deposizione dei sedimenti sono processi chiave nel governo della morfodinamica a marea e sono influenzate in modo cruciale sia da fattori fisici che biologici. La presente tesi affronta due importanti aspetti dei processi di trasporto dei sedimenti negli ambienti a marea. Il primo argomento riguarda l’analisi quantitativa della concentrazione del sedimento in sospensione e della forzante vento per produrre delle stime delle proprietà del sedimento, quali la velocità di sedimentazione e lo sforzo tangenziale critico per l’erosione, a scale spaziali rilevanti per la generale dinamica morfologica del sistema. La prima parte della tesi pertanto sviluppa e descrive un metodo per valutare le proprietà del sedimento sulla base della soluzione di una equazione di conservazione del sedimento nella colonna d’acqua che tiene conto degli effetti dello sforzo tangenziale al fondo dovuto al vento e alle correnti di marea. Il metodo è applicato utilizzando osservazioni da una rete di sensori nella laguna di Venezia e produce stime in buon accordo con osservazioni puntuali negli stessi siti e allineate con i valori attesi per sedimenti sabbiosi- limosi. L’analisi è stata effettuata attraverso serie temporali relative a intensità del vento, fornite da stazioni anemometriche, a misure di torbidità, fornite da sensori torbidimetrici ed a serie temporali relative a livelli di marea acquisite dalla rete telemareografica; tutte le stazioni operano simultaneamente, sono dis- poste in prossimit`a l’un l’altra e ricoprono grossomodo l’intera area lagunare. Per calcolare gli sforzi dovuti all’azione del moto ondoso è stato implementato un modello puntuale forzato dal vento sotto l’ipotesi di fetch illimitato, in cui gli sforzi sono stati calcolati in funzione del coefficiente di attrito, della densità dell’acqua e della velocità orbitale massima al fondo. La velocità orbitale massima al fondo è stata espressa in funzione dell’altezza d’onda ed il periodo d’onda che è stato calcolato in funzione di parametri adimensionalizzati e seguendo la legge di potenza i cui parametri di fitting sono stati adattati alle osservazioni in laguna. L’altezza d’onda è stata calcolata secondo un bilancio energetico in cui si è trascurata la componente advettiva dell’energia dell’onda. Con il modello forzato dalla marea si sono calcolati gli sforzi in funzione del coefficiente di attrito, della densità dell’acqua e della velocità della corrente di marea. Una volta calcolati gli sforzi tangenziali al fondo è stata implementata l’equazione di conservazione della massa di sedimenti assumendo concentrazione dei sedimenti spazialmente uniforme (divergenza del flusso nulla e continuità della massa d’acqua), in cui la variazione nel tempo del prodotto tra il tirante e la concentrazione (la concentrazione viene espressa come differenza tra la concentrazione effettivamente acquisita dai torbidimetri ed una concentrazione residua che rimane sempre in sospensione in laguna) è data dalla somma tra il flusso di erosione ed il flusso di sedimentazione. Nel caso di processo di sedimentazione, il flusso erosivo è stato trascurato, ed i parametri ws (velocità di settling) e Co (concentrazione residua) sono stati calcolati risolvendo un fitting lineare. Una volta calcolati i valori di velocità di deposizione compresi tra 2.7 · 10-4 e 6.3 · 10−4 m/s e la concentrazione residua compresa tra 6.7 e 16.2 mg/l, si sono successivamente calcolati la velocità di erosione, sulla base della quale si è risolto l’algoritmo del simplesso per ottenere la curva di regressione dei valori medi di velocità di erosione. Dalla regressione si sono ottenuti i valori dello sforzo critico di erosione compresi tra 0.1 e 0.5 Pa e del parametro di erosione compresi tra 2 · 10−6 e 3 · 10−4 kg/sm2. E’ stata compiuta inoltre un’analisi stagionale dopo aver suddiviso le serie temporale in stagioni secondo la suddivisione astronomica. I risultati si sono dimostrati in generale in soddisfacente accordo con i valori misurati in situ attraverso le tradizionali strumentazioni, Sea Carousel e Mini Flume. La metodologia implementata ha il vantaggio di stimare i parametri dei sedimenti senza interferire con gli effetti di bio-stabilizzazione operati dai microrganismi e di fornire una stima parzialmente integrata delle soglie di erosione e della velocità di sedimentazione. Si può in definitiva concludere che il metodo di stima proposto è diretto e quantitativo, non interferisce con lo stato fisico e biologico locale del sistema e si presta ad attività di monitoraggio delle proprietà dei sedimenti su base stagionale e per lunghi periodi, con limitato sforzo operativo. Il secondo, correlato, argomento riguarda lo studio di laboratorio dell’impatto della macroalga Ulva intestinalis, sulla stabilità del sedimento e sul campo di velocità in aree a marea. Le macroalghe, infatti, esercitano un controllo importante sulla distribuzione della velocità e sul trasporto di sedimenti, poichè inibiscono l’erosione del sedimento dovuta a onde o correnti e promuovono la sedimentazione. Larghe estensioni di macroalghe sono sempre più frequenti in molti habitat intertidali estuarini e costieri ed è dunque importante caratterizzare quantitativamente il loro impatto sul campo di moto e la stabilità del sedimento, per una migliore comprensione dell’attuale degrado di lagune costiere e per sviluppare adatte misure di mitigazione e ricostruzione ambientale. La seconda parte della tesi, dunque, descrive e analizza una serie di esperimenti condotti in una canaletta di grandi dimensioni (il Total Environment Simulator - TES- presso l’Università di Hull, UK), con sedimento costituito da sabbia fine, parzialmente coperto da individui di U. intestinalis. L’attività sperimentale è stata indirizzata a quantificare l’effetto delle macroalghe sulla dinamica della struttura del campo di moto indotto da correnti e moto ondoso. L’apparato strumentale utilizzato è costituito da una canaletta di 11 metri di lunghezza e 2 di larghezza, su cui è disposto uno strato di sedimenti artificiali non coesivi (sabbia fine: 135μm di diametro). L’apparato è fornito di generatore di flusso ed onde. Attraverso una completa strumentazione costituita da ADV (Acoustic Doppler Profiler), PIV (Particle Image Velocimetry), ABS (Acoustic BackScat- ter) si sono fornite informazioni su: andamento temporale del vettore velocità, evoluzione temporale della superficie del fondo, andamento temporale della concentrazione dei sedimenti sospesi. Si sono infine utilizzate trappole di sedimento posizionate all’uscita del flusso di corrente dalla canaletta per fornire l’integrale della massa solida trasportata. Sono stati compiuti 12 test simulando diverse condizioni idrodinamiche: corrente ed onde per diversi livelli di tirante (0.21 m; 0.31 m; 0.25 m) dapprima in presenza di macroalghe e successivamente su fondo nudo. Le alghe dopo essere state prelevate presso la Riserva Naturale Nazionale di Budle Bay, sulla costa nord-orientale dell’Inghilterra, sono state ripiantate nello strato di sedimenti della canaletta in modo da seguire una disposizione su linee trasversali sfalsate ricoprendo tutta la superficie della canaletta con una densità di circa 12 unità /m2. Con l’obiettivo di quantificare le osservazioni raccolte durante ciascun test ed in particolare al fine di determinare l’intervallo di tempo entro cui calcolare il valor medio delle velocità turbolente, si è inizialmente calcolata la funzione di autocorrelazione della componente longitudinale della velocità di fluttuazione. Dalla funzione di autocorrelazione si sono calcolate la microscala e la macroscala temporale per i diversi esperimenti. Al fine di calcolare la velocità di attrito ed il parametro di scabrezza di Nikuradse, si è implementata la legge universale logaritmica delle velocità media per paretri scabre. Per ottenere questi parametri, si è realizzato il fitting lineare dei dati sperimentali: dalla stima della pendenza ed intercetta si sono ottenuti la velocità di attrito ed il parametro di scabrezza. Al fine di determinare l’esistenza di una relazione statisticamente significativa tra le rette di regressione (fitting lineare per i quattro ADV nelle 4 posizioni in cui sono stati disposti gli strumenti), si è calcolato l’errore standard per la pendenza e l’intercetta da cui si sono de- terminati i relativi intervalli di confidenza al 95 %. Sia la velocità di attrito sia il parametro di scabrezza sono risultati maggiori nei test con macroalghe piuttosto che nei test senza macroalghe, confermando quanto riscontrato in letteratura sul ruolo bio-stabilizzatore delle macroalghe. Sulla base degli sforzi di Reynolds e del gradiente di velocità media si è poi calcolato il profilo verticale degli sforzi tangenziali, i quali hanno dimostrato comportamenti differenti tra i test con e senza macroalghe. Nel primo caso gli sforzi aumentano dal fondo fino ai primi centimetri per poi diminuire quasi linearmente fino alla superficie, mentre nel secondo caso diminuiscono linearmente dal fondo alla superficie. Infine con l’obiettivo di studiare la struttura della turbolenza, si è calcolato lo spettro monodimensionale dell’energia nel tempo, caratterizzato principalmente dalla presenza di vortici di piccole dimensioni corrispondenti alle alte frequenze. Per visualizzare il trend decrescente della densità di energia è stato calcolato il valor medio dell’energia (binning) nell’intervallo inerziale. Si è calcolato il fitting lineare da cui si è ottenuto il valore della pendenza. Dal confronto delle pendenze per i diversi test, si sono ottenuti valori minori per i test con macroalghe che per i test senza macroalghe, poichè si ritiene che queste ultime agiscano interferendo sulla struttura della turbolenza del campo di energia. Attraverso l’ipotesi di Taylor si è calcolata la macroscala spaziale sulla base delle fluttuazioni temporali precedentemente calcolate, in modo da produrre lo spetto monodimensionale dell’energia nello spazio. Anche in questo caso la pendenza nel test con macroalghe è risultata minore rispetto alla pendenza nei test senza macroalghe. Dall’osservazione diretta compiuta durante gli esperimenti e dai risultati ottenuti dall’elaborazione dei dati di velocità acquisiti dagli ADV, si conferma quanto riscontrato in letteratura riguardo al ruolo bio-stabilizzatore delle macroalghe, a cui si associa riduzione del campo di moto in prossimità del fondo, forme di fondo di dimensioni inferiori, minor quantità di materiale solido trasportato sia di fondo sia in sospensione.

Master of Science
Department of Biological and Agricultural Engineering
Ronaldo G. Maghirang
Military installations in the United States may be large sources of fugitive dust emissions. Off-road vehicle training can contribute to air quality degradation resulting from increased wind erosion events as a result of soil disruption; however, limited information exists regarding the impacts of off-road vehicle maneuvering. This study was conducted to determine the effects of soil texture and intensity of training with off-road vehicles on fugitive dust emission potential due to wind erosion at military training installations. Multi-pass trafficking experiments, involving wheeled and tracked military vehicles (i.e., M1A1 Abrams tank, M925A1 water tanker and various HMMWV models), were conducted at three military training facilities with different climate and soil texture (i.e., Fort Riley, KS; Fort Benning, GA; and Yakima Training Center, WA). Dust emissions were measured on site using a Portable In-Situ Wind Erosion Laboratory (PI-SWERL) coupled with a DustTrak™ dust monitor. In addition, a top layer of soil was collected in trays and tested in a laboratory wind tunnel for dust emission potential. In wind tunnel testing, the amount of emitted dust was measured using glass-fiber filters through high-volume samplers. Also, the particle size distribution and concentration of the emitted dust were measured using a GRIMM aerosol spectrometer. Comparison of the PI-SWERL (with DustTrak™ dust monitor) and wind tunnel test (with GRIMM aerosol spectrometer) results showed significant difference and little correlation. Also, comparison of the filter and GRIMM aerosol spectrometer data showed significant difference but high correlation. The dust emission potential (as measured with the GRIMM spectrometer) was significantly influenced by soil texture, vehicle type and number of passes. For the light-wheeled vehicle, total dust emissions increased from 66 mg m-2 for undisturbed soil to 304 mg m-2 (357%) and 643 mg m-2 (868%) for 10 and 50 passes, respectively. For the tracked vehicle, an average increase in total dust emission of 569% was observed between undisturbed conditions and 1 pass, with no significant increase in emissions potential beyond 1 pass. For the heavy-wheeled vehicle, emissions increased from 75 mg m-2 for undisturbed soil to 1,652 mg m-2 (1,369%) and 4,023 mg m-2 (5,276%) for 10 and 20 passes, respectively. Soil texture also played an important role in dust emission potential. For all treatment effects, there was a 1,369% difference in emissions between silty clay loam soil and loamy sand soil.

Master of Science
Department of Biological & Agricultural Engineering
Ronaldo G. Maghirang
Military training lands can be significant sources of fugitive dust emissions due to wind erosion. This study was conducted to determine dust emission potential of soils due to wind erosion as affected by off-road military vehicle disturbance. Multi-pass traffic experiments using two types of vehicles (i.e., wheeled and tracked) were conducted on six soil textures at four military training facilities: Fort Riley, KS; Fort Benning, GA; Yakima Training Center, WA; and White Sands Missile Range (WSMR), NM. Prior to and after the preselected number of vehicle passes, soil samples at three locations were collected with minimum disturbance into trays. Adjacent to the location where tray samples were collected, a Portable In-Situ Wind Erosion Lab (PI-SWERL) was used to measure dust emission potential. The tray samples were tested in a laboratory wind tunnel (with sand abrader) for dust emission potential using a GRIMM aerosol spectrometer and gravimetric method with filters. Comparison of the PI-SWERL (with DustTrak™ dust monitor) and wind tunnel (with GRIMM aerosol spectrometer) measurement results showed significant difference in measured values but high correlation, particularly for soils with high sand content. Wind tunnel tests results showed that sampling locations significantly affected dust emissions for the tracked vehicles but not for the light-wheeled and heavy-wheeled vehicles. Also, soil texture, number of vehicle passes, and vehicle type significantly affected dust emissions. For the light-wheeled vehicles, dust emissions increased as the number of vehicle passes increased. From undisturbed conditions to 10 vehicle passes, there was a significant (P<0.05) increase in dust emissions (297%) on average for all light-wheeled vehicle tests. From 10 to 25 passes and 25 to 50 passes, an additional 52% and 62% increments were observed. For the tracked vehicle, for the straight section sampling location, dust emission increased as the number of vehicle passes increased. However, for the curve section, dust emissions at any level of pass were significantly higher than initial condition; beyond the first pass, no significant increase was observed.

Erozija predstavlja vrlo složen fizički proces u kome pod dejstvom atmosferskih sila nastaju destruktivne promene na površinskom sloju zemljišta. Kada je osnovni agens pokretanja čestica zemljišta vetar, govori se o eroziji vetrom ili eolskoj eroziji. Eolska erozija je specifičan proces koji se odvija u izrazito složenim okolnostima uzajamnog delovanja brojnih prirodnih i antropogenih faktora uglavnom stohastičkog karaktera, zbog čega je njeno istraživanje kompleksan naučno-istraživački problem.Osnovni cilj sprovedenih istraživanja je bio da se na izabranim lokalitetima Deliblatske peščare, najvećeg i najznačajnijeg područja takve vrste u Evropi, uspostavi praćenje stanja procesa eolske erozije, odnosno neposrednim, sistematskim merenjima u terenskim uslovima ustanove količine eolskog nanosa – pronos nanosa, odrede dominantni pravci njegovog kretanja, definiše njegova unutargodišnja raspodela i utvrdi efekat vegetacije na smanjenje intenziteta eolske erozije. U toku četvorogodišnjeg perioda su po prvi put na ovim prostorima, na istom lokalitetu, sprovedena uporedna istraživanja eolske erozije primenom mehaničkih hvatača nanosa i metoda zasnovanih na praćenju aktivnosti radionuklida veštačkog porekla 137Cs u zemljištu, čije količine služe da se posebnim teorijskim modelima pretvore u gubitke zemljišta.Praćenje procesa eolske erozije je vršeno od 2006. do 2009. godine na lokalitetu Cvjićev vis, koji je izabran kao karakterističan, jer je pored centralne pozicije na Deliblatskoj peščari, obrađivani površinski sloj zemljišta bio bez zaštite od vetra. Paralelno sa ovim merenjima, na lokalitetu Dragićev hat – rasadnik, praćenje procesa eolske erozije vršeno je na dva merna mesta u periodu od maja 2006. godine do aprila 2007. godine u uslovima postojanja zaštitne uloge vegetacionog pokrivača i/ili vegetacionog pojasa. Merenje intenziteta eolske erozije je realizovano statičnim hvatačima nanosa tipa deflametar (dimanzija ulaznog otvora 10 x 10 cm) orijentisanih prema određenim pravacima (N, NE, E, SE, S, SW, W, NW) da bi potpuno definisali procese eolske erozije u vektorskom smislu. Kvantifikacija eolskog nanosa statičnim hvatačima stalno usmerenim prema određenim pravcima duvanja vetrova, omogućila je da se posebno evidentiraju i razlikuju „sumarna” produkcija eolskog nanosa (aritmetički zbir zahvaćenih količina nanosa iz svih hvatača) i „rezultujuća” količina eolskog nanosa (vektorski zbir), jer te veličine određuju pored ukupno pokrenute količine eolskog nanosa (produkcija nanosa) i delove nanosa koji se transportuju van granica erozionog polja (gubitak zemljišta), generalni pravac i smer njegovog kretanja.Merenja eolske erozije na lokalitetu Cvijićev vis za period 2006-2009. godine su ukazala na značajne procese eolske erozije koji su definisani srednjim godišnjim pronosom nanosa od 4,48 kg m-1. Ustanovljeno je da su ukupno zahvaćene količine nanosa na 8 hvatača bile Σ = 25,94, 20,92, 52,98 i 43,47 kg m-1 god-1, a pronosi nanosa Σ' (Σ/8) = 3,24, 2,61, 6,62 i 5,43 kg m-1 god-1 u 2006., 2007., 2008. i 2009. godini respektivno.Pronosi nanosa za period od maja 2006. do aprila 2007. godine su pokazali da je nalokalitetu Cvijićev vis koga karakterišu neobraslost i otvorenost površine zabeležen najveći intenzitet eolske erozije na godišnjem nivou koji je 4 puta veći u odnosu na lokalitet Dragićev hat – rasadnik I koga karakterišu neobraslost i zaštićenost površine i 30,2 puta veći u odnosu na Dragićev hat – rasadnik II koga karakterišu obraslost i zaštićenost zemljišta. Na lokalitetu Dragićev hat – rasadnik I intenzitet eolske erozije na godišnjem nivou je 7,5 puta veći od onog na lokalitetu Dragićev hat – rasadnik II.Gubici zemljišta izraženi preko rezultujućih mesečnih pronosa nanosa (vektorski zbir)iznosili su 5,13, 2,04, 4,31 i 11,94 kg m-1 u 2006., 2007., 2008. i 2009. godini respektivno, a procentualni udeo godišnjih gubitaka zemljišta u odnosu na ukupnu produkciju nanosa (aritmetički zbir) se kretao od 8,1% do 27,5. Rezultujući pravac kretanja eolskog nanosa u toku perioda istraživanja bio je jugoistok - severozapad (SE-NW) pod uticajem dominantnog jugoistočng vetra „Košava”.Iako se najpouzdanije determinisanje eolske erozije i njenih efekata postiže na osnovu neposrednih sistematskih merenja u realnim terenskim uslovima, počev od kraja prošlog veka se sve više primenuju i metode praćenja radionuklida iz radioaktivnih padavina, posebno 137Cs, u cilju procene gubitaka zemljišta i prostornog rasporeda eolskog nanosa.Ukupan broj uzetih uzoraka za metodu praćenja količina 137Cs je iznosio 149, od kojih je bilo 9 inicijalnih uzoraka (3 profila po 3 uzorka), 14 osnovnih uzoraka (2 profila po 7 uzoraka), 32 ostala uzorka (8 profila po 4 uzorka), 36 referentnih uzoraka (9 profila po 4 uzorka) i 58 uzoraka uzetih zrakasto po određenim pravcima (N, NE, E, SE, S, SW, W, NW).Osnovni uzorak na neobrađenom zemljištu sa detektovanom količinom 137Cs od 10.603,57 Bq m-2 predstavlja uporednu vrednost, tj. lokalni padavinski ulaz 137Cs za modele pretvaranja količina 137Cs u količine izgubljenog zemljišta. Ovaj uzorak odslikava sredinu na kojoj su sprovedena istraživanja i predstavlja uporednu vrednost koja može korektno da definiše procese eolske erozije.Za pretvaranje izmerenih količina 137Cs u količine izgubljenog zemljišta po modelima Walling-a korišćen je najjednostavniji proporcionalni model (PM) za obrađena zemljišta, a najprimenjeniji model profilne distribucije (PDM) za neobrađena zemljišta u okviru najnovije verzije PC-kompatibilnog softverskog paketa u Microsoft Excel Add-Ins varijanti. Modelom profilne distribucije (PDM) za sve uzorake uzete na eksperimentalnom području dobijeni su prosečni gubici zemljišta od 207,06 t ha-1 god-1 i 2,10 cm. Model Basher & Webb je dao prosečne gubitke zemljišta od 212,18 t ha-1 god-1 i 2,09 cm. Gubici zemljišta dobijeni modelima pretvaranja količina 137Cs u količine izgubljenog zemljišta ukazuju na značajne procese eolske erozije definisane jakom i ekscesivnom eolskom erozijom.Za 58 uzoraka zemljišta uzetih na tačkama raspoređenih zrakasto po određenim pravcima (N, NE, E, SE, S, SW, W, NW), pored koncentracija i količina 137Cs i 210Pbex, određene su prostorne koordinate X i Y i nadmorske visine uzetih uzoraka. Prostorne distribucije koncentracija 137Cs i 210Pbex izražene su izolinijama, a kreiranani su i 3D prikazi u procentima odstupanja 137Cs i 210Pbex od lokalnog padavinskog ulaza 137Cs i 210Pbex. U oba slučaja je primetan dominantan uticaj pravca jugoistok - severozapad (SE-NW), odnosno jugoistočnog vetra „Košava”.Komparativna analiza ovih metoda je ukazala na validnost u kvantifikaciji procesa eolske erozije i mogućnost njihove primene u budućnosti, a dobijeni rezultati produkcije eolskog nanosa i gubitaka zemljišta su dali doprinos oceni stanja degradacije zemljišta i ugroženosti Deliblatske peščare.  
Erosion is a very complex physical process which, under the impact of atmospheric forces, creates destructive changes on the soil surface layer. In case the primary agent of particle movement is wind, we talk about wind or aeolian erosion. Aeolian erosion is a specific process which occurs in extremely complex situations of mutual interaction of numerous natural and anthropogenic factors of mainly stochastic properties making its research a complex scientific-research problem.The main goal of conducted research was to monitor the process of aeolian erosion at the chosen localities of Deliblato Sands, the largest and the most important area of the kind in Europe. In other words, the goal is to determine the quantities of aeolian sediment – sediment transport by direct systematic measurements in field conditions, determine dominant direction of sediment transport, define its annual distribution and determine the effect of vegetation on reducing the intensity of aeolian erosion. During a four-year period, for the first time in this area, i.e. at the same locality, a comparative research of aeolian erosion have been conducted using the mechanical sediment trap and activities based on 137Cs radioisotope tracing technique for estimating soil losses using special theoretical models.The monitoring of aeolian erosion processes was conducted during the period 2006 – 2009 at Cvijićev vis which was chosen as a typical locality since it was, apart from the central position on Deliblato Sands, a cultivated surface without any wind protection. Alongside with these measurements, at Dragićev hat – nursery garden, the monitoring of aeolian erosion was conducted on two measurement points during the period May 2006 – April 2007 in areas with the protective vegetative covers and/or vegetative belts. Aeolian erosion intensity measurement was performed by static sediment traps of the type “deflametre” (dimension of entry opening 10 x 10 cm) oriented on certain directions (N, NE, E, SE, S, SW, W, NW) in order to define the aeolian erosion processes in vector terms. The quantification of aeolian sediment using static traps constantly facing certain wind blowing directions enabled to log and differentiate “summary” yield of aeolian sediment (arithmetic sum of all sediment quantities from all traps) and “resulting” quantity of aeolian sediment (vector sum), since those quantities determine not only the entire amount of transported aeolian sediment (sediment yield) but also the sediment transported outside the areas of erosion field (soil loss), bur also the general direction of its transport.Aeolian erosion measurement on Cvijićev vis for the period 2006 – 2009 indicated thesignificant aeolian erosion processes which were defined by medium annual edimenttransport of 4.48 kg m-1. It has been determined that the total quantities of movedsediment were 25.94, 20.92, 52.98 and 43.47 kg m-1 year-1, and sediment transport 3.24, 2.61, 6.62 and 5.43 kg m-1 year-1 in 2006, 2007, 2008 and 2009 respectively.Sediment transport for the period May 2006 – April 2007 showed that on Cvijićev vis which is characterized by bareness and openness there was the biggest aeolian erosion – four times bigger compared to Dragićev hat – nursery garden I characterized by bareness and protectiveness and 30.2 times bigger compared to Dragićev hat – nursery garden II characterized by overgrown condition and protectiveness of erosive field. At the locality Dragićev hat – nursery garden I the aeolian erosion was recorded 7.5 times bigger compared to the one recorded on Dragićev hat – nursery garden II.Soil loses expressed through the resulting monthly sediment transport (vector sum)equalled 5.13, 2.04, 4.31 and 11.94 kg m-1 in 2006, 2007, 2008 and 2009 respectively, and the percentage share of annual soil losses compared to total sediment yield (arithmetical sum) varied between 8.1% and 27.5%. The resulting aeolian sediment movement direction was SE-NW under the influence of the dominant southeast wind “Koshava”.Even though the most reliable determination of aeolian erosion and its effects is based on direct systematic measurements in real time conditions in the field, starting from the end of the last century the methods of tracking radionuclide from radioactive precipitation, especially 137Cs, for the purposes of estimating the soil loss and spatial distribution of aeolian sediment, have been used increasingly.The total number of samples taken for the method of monitoring the quantity of 137Cs was 149, 9 of which were initial samples (3 profiles with 3 samples each), 14 main samples (2 profiles with 7 samples each), 32 remaining samples (8 profiles with 4 samples each), 36 reference samples (9 profiles with 4 samples each) and 58 samples taken radially on certain directions (N, NE, E, SE, S, SW, W, NW).The main sample taken from the uncultivated land with the detected quantity of 137Cs of 10,603.57 Bq m-2 represents the comparative value, i.e. local precipitation input of 137Cs for the models of 137Cs quantities conversion into the quantities of lost soil. This sample depicts the area where the research was conducted and represents the comparative value which can properly define the aeolian erosion processes.For converting the measured quantities of 137Cs into the quantities of lost soil using Walling model the simplest proportional model (PM) for cultivated land was used and the most appropriate profile distribution model (PDM) for uncultivated soil with the newest version of PC compatible software package in Microsoft Excel Add-Ins. Using the profile distribution model (PDM) on all samples taken from the experimental area the quantities of average soil loss obtained were 207.06 t ha-1 year-1 and 2.10 cm. Basher & Webb model gave the average soil loss of 212.18 t ha-1 year-1 and 2.09 cm. Soil loss calculated using the conversion of 137Cs quantities into the soil loss quantities indicate the significant aeolian processes defined by strong and excessive aeolian erosion.For 58 soil samples taken from areas radially distributed on certain directions (N, NE, E, SE, S, SW, W, NW), apart from 137Cs and 210Pbex concentrations and quantities, spatial coordinates X and Y were determined as well as the altitude of taken samples. Spatial distribution of 137Cs and 210Pbex quantities are represented by isolines, and also 3D demonstrations were created showing the percentage of deviation of 137Cs and 210Pbex from the local precipitation input of 137Cs and 210Pbex. In both cases, the dominant direction SENW was noticeable, i.e. the southeast wind “Koshava”.The comparative analysis of these methods indicated the validity in the quantification of aeolian erosion process and the possibility of its application in the future and the obtained results of aeolian sediment yield and soil loss contributed to determining the state of soil degradation and vulnerability of Deliblato Sands.

Les écosystèmes sahéliens, et tout particulièrement ceux qui se développent sur des sols sableux, réagissent très vite et très intensément aux moindres changements climatiques. Dans cette zone semi-aride, l'érosion éolienne qui affecte essentiellement les surfaces cultivées met en péril l'exploitation durable des ressources en terre. Par ailleurs, l'explosion démographique de ces dernières décennies et les grandes crises climatiques à l'origine des sécheresses du vingtième siècle ont eu d'importantes répercussions sur le milieu. Pour gérer au mieux ce milieu fragile, il importe d'abord de bien comprendre son fonctionnement. Ce travail de thèse s'est donc inscrit dans le programme de recherche AMMA (Analyse Multidisciplinaire de la Mousson africaine) et se situe au coeur du programme CORUS2 (Coopération pour la Recherche Universitaire et Scientifique) concernant essentiellement l'étude de la dynamique éolienne des sols sableux cultivés de la région de Niamey. La stratégie suivie au cours de cette étude a été de s'appuyer sur un important dispositif de mesures expérimentales pour comprendre au mieux et quantifier le fonctionnement actuel du milieu essentiellement vis-à-vis de l'érosion éolienne. Ces mesures expérimentales ont permis d'interpréter les changements que nous avons pu mettre en évidence sur un ensemble de terroirs proches de Niamey qui constituent les bassins versants de deux lacs permanents récents : Bangou Bi et Bangou Kirey (13,51° N - 2,21° E). Les enregistrements sédimentaires recueillis dans ces lacs ont ensuite été analysés en regard de l'évolution de leur bassin versant. Au cours de cette étude nous avons mis en évidence le rôle majeur des résidus de culture dans les champs traditionnels et montré que même à des taux de recouvrement extrêmement bas, ils constituent une protection pour les sols. Cependant leur efficacité chute en deçà d'un seuil de 2% et l'érosion éolienne déplace alors des quantités considérables de terres (130 t/an en moyenne) et participe activement à l'encroûtement des sols. Il est probable qu'à la faveur combinée de la mise en culture de l'ensemble des versant avant 1975 et de la sécheresse de 1985, un tel processus d'érosion et d'encroûtement s'est mis en place expliquant ainsi la dégradation considérable du milieu que nous avons mise en évidence entre 1975 et 2009 à partir d'enquêtes auprès des population et par la cartographie diachronique des petits bassins versant étudiés. A partir de l'étude des sédiments collectés dans les lacs, nous avons pu proposer un modèle de mise en place de ces sédiments qui suggère une intensification de l'érosion à partir du milieu des années 80.

Suite aux changements climatiques, de nouveaux paysages reflétant les interactions entre les processus naturels et les activités humaines inappropriées sont apparus en Tunisie Méridionale. L’érosion éolienne en est l’une des manifestations les plus remarquables. Au cours de cette thèse, une méthodologie opérationnelle et validée (méthode du transect permanent) a été mise au point pour la caractérisation des états de surfaces éolisés et la quantification du bilan sédimentaire d’un transect d’environ 500m de longueur sur une période de deux ans. A l’échelle spatiale, la cartographie des Unités Eoliennes : zones de départ, transit et dépôt de sable a été élaborée. Un essai de caractérisation radiométrique des zones de dépôt ensablées a été ensuite tenté pour l’analyse diachronique des changements survenus durant plus de 35 ans. A l’échelle stationnelle, la méthode du transect permanent permet le calcul diachronique des bilans sédimentaires et la comparaison simultanée des changements des Complexes d’Etat de Surface. La seule observation des états de surface éolisés est insuffisante pour déterminer le fonctionnement éolien précis d’une région, elle induit à des erreurs d’interprétation sur les processus sédimentaires en cours.A l’échelle spatiale, les cartes des Unités Eoliennes permettent de déterminer la vulnérabilité du milieu face aux processus de déflation, transport et dépôt. De plus, la caractérisation des zones ensablées par des indices radiométriques n’est pas évidente avec des images de 30 m de résolution. Les analyses statistiques effectuées ont montré que l’indice de couleur est le plus indiqué pour ce genre d’étude. Le calcul des taux de changement entre deux images de dates successives permet d’estimer l’évolution temporelle des espaces ensablés et la distribution spatiale des zones nouvellement ensablées sur plus de 35 ans
Under the effect of climate change, new landscapes reflecting the interactions between natural processes and human inappropriate activities appeared in Southern Tunisia. Wind erosion is one of the most important events. In this thesis, operational and validated methodology (the permanent transect method) has been developed for the characterization of Surfaces States and quantification of the sediment balance of a 500 m length transect over a period of two years. On spatial scale, mapping of the Aeolian units of deflation, transit and sand deposit was developed. Radiometric characterization of sand accumulations was then tried for the detection of changes that occurred within more than 35 years.At the site level, the permanent transect method enabeled the diachronic sedimentary balance calculation and the comparison of the Surface states changes. The single observation of these areas is insufficient to determine the real eolian process of a region ; moreover it induces to errors of interpretation on the sedimentary process.At the spatial scale, maps of the Aeolian units enabeled to determine the vulnerability of the environment to the process of deflation, transport and deposition. In addition, the characterization of sand accumulations by radiometric indices is not obvious within 30 m resolution images. The statistical analyses have shown that Color Index is the most indicated for this type of study. The calculation of the rates of change between two successive dates images allows to estimate the sandy spaces evolution and their spatial distribution for more than 35 years

Esta pesquisa teve como objetivo verificar a alteração do campo de vento na área de estudo, decorrente da alteração de gabarito quanto à ventilação natural, e avaliar o impacto nas condições de conforto dos pedestres. A verificação das condições de ventilação natural nas cidades, com estudos em modelos, auxilia na elaboração de projetos arquitetônicos, ou de planejamento, possibilitando uma análise da influência do efeito do vento em determinados locais da área em análise. O objeto de estudo da tese é a relação entre a alteração de gabarito (altura dos edifícios) e as mudanças ocasionadas na ventilação natural em espaços urbanos na área entre o Canal 1 e 2 (Bairro Pompéia) na cidade de Santos/SP. Partiu-se da hipótese que a ventilação natural em áreas urbanas depende da altura dos edifícios, da direção e velocidade dos ventos. Foi utilizado método experimental com simulação da configuração urbana em túnel de vento, medidas in loco para a verificação das condições climáticas, simulação com software CFD (Computer Fluids Dynamics) e a aplicação de um índice de neutralidade térmica. Trata-se de uma tese de caráter experimental e exploratório, onde os métodos utilizados demonstraram ser aplicáveis para o entendimento das condições de ventilação natural em meio urbano.
The objective of this research is to verify alterations of the wind pattern in the study area, stemming from changes to the grids natural ventilation, and evaluate the impact to the pedestrians comfort conditions. The verification of natural ventilation conditions in cities, with the study of models, aids in the creation of architectural or planning - designs, enabling an analysis of the influence of the effects of wind in certain points of the area in study. This thesis object of study is the relation between changes to the framework (building height) and changes to the natural ventilation in urban environments in the area between Canal 1 and 2 (Bairro Pompéia), in the city of Santos/SP. The hypothesis is that natural ventilation in urban areas depends on the height of buildings, direction and velocity of winds. The study involved an experimental method, with wind-tunnel simulation of the urban grid, in loco measurements of the climate conditions, simulation with CFD software and application of a thermal neutrality index. This thesis is experimental and exploratory in its character, and the methods used proved applicable to the understanding of the natural ventilation conditions in an urban environment.