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1
Duncan, S. "Ion erosion in surface analysis." Thesis, Loughborough University, 1985. https://dspace.lboro.ac.uk/2134/28023.
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Low energy ion bombardment is a process used in surface analysis and in the electronics and telecommunications industries. Techniques such as Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS) and Secondary Ion Mass Spectroscopy (SIMS) employ ion bombardment for surface cleaning and for the provision of composition-depth profiles.
2
Wheeler, David William. "Solid particle erosion of CVD diamond coatings." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342748.
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3
Menaa, Merouane. "Performance of surface structures subjected to subsurface soil erosion." Mémoire, École de technologie supérieure, 2008. http://espace.etsmtl.ca/148/1/MENAA_Merouane.pdf.
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Plusieurs infrastructures geotechniques (ex. chaussees, dalles, fondations) exercent une
pression a travers leurs surfaces de contact avec le sol. Le dimensionnement de ces
structures suppose un contact parfait tout au long de la vie de service de celles-ci. Par
ailleurs, I'erosion des sols sous-jacents est un mecanisme qui pent contribuer au
developpement de cavites souterraines et par consequent a une perte locale de contact entre
la structure et le sol, caracterisee par un vide sous la structure.
La performance des structures telles que les chaussees en beton, les dalles ainsi que les
trottoirs sujettes a I'erosion souterraine est etudiee experimentalement et numeriquement
dans ce memoire. Les experiences ont ete menees dans un caisson en acier rigide contenant
du sable ou I'erosion souterraine a ete cree artificiellement; le tout supportant une plaque en
acier rigide. Les deformations de la surface ainsi que les pressions de contact a I'interface
plaque-sol ont ete mesurees afin de quantifier les effets de I'erosion souterraine sur les
contraintes developpees dans la structure. L'etude numerique a ete conduite en utilisant un
modele elastoplastique a 2 dimensions. Le modele a ete calibre avec les resultats
experimentaux et divers scenarios ont ete envisages. Des parametres tels que le volume du
sol erode, sa localisation ainsi que les chargements appliques sur la dalle de beton ont ete
varies. Les resultats de cette recherche ont montre que lorsque le vide est centre directement
sous la dalle, les contraintes de traction developpees dans celle-ci augmentent avec la taille
du vide provoquant ainsi la rupture de la dalle. II a egalement ete conclu que lorsque le vide
est excentre, le sol au voisinage de celui-ci est susceptible de subir une rupture avant que
des contraintes de traction excessives ne se developpent dans la fibre la plus tendue de la
dalle en beton.
4
Bao, Ruotian. "Effect of Microbial Induced Carbonate Precipitation on Surface Erosion." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1498471342771954.
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5
Macgregor, Duncan S. "Surface seepage and sub-surface destructive processes as controls on the distribution of giant oilfields." Thesis, University of Aberdeen, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363645.
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Study of a database of 350 giant oilfields show these to be dynamic short lived phenomena, with a median age of 35 Ma. A third show evidence of post-entrapment destructive processes, particularly erosion, fault leakage and gas flushing. Biodegradation is a destructive process most active during oil entrapment. Re-entrapment of oil released from spilling or breached traps is common. These processes are illustrated with case examples from SE Asia and throughout the world. The main controls on oilfield preservation are post-entrapment tectonism and seal type, with temperature and hydrodynamic regimes being secondary factors. Destructive processes are concentrated in shallow and deep zones and in seepage-prone traps such as compressional anticlines. Such factors strongly influence the distribution of preserved light oilfields, with preservation potential maximised in tectonically quiescent basins with evaporite or thick mudstone seals e.g. the Middle East and the Permian Basin, or in basin centres distant from inverted or uplifted zones e.g. Central Sumatra. More attention is required in prospect and regional evaluations to models involving post-entrapment leakage and re-migration.
6
Villanueva, Evelyn. "Risk assessment of rock surface spillway erosion using parametric studies." Master's thesis, Mississippi State : Mississippi State University, 2007. http://library.msstate.edu/etd/show.asp?etd=etd-07022007-155027.
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Zalewsky, Brian J. "Use of the Water Erosion Prediction Project (WEPP) Model to Predict Road Surface Erosion in Mountain Rangeland Areas." DigitalCommons@USU, 1998. https://digitalcommons.usu.edu/etd/3655.
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A significant source of sediment in many watersheds is that associated with the layout, construction, and maintenance of roadways. Much work has been done in more mesic forested environments with little or none in semiarid systems. Acc urate estimation of runoff and sediment yield from native surfaced roads located in semiarid mountainous ecosystems is important to both private and public regulatory agencies. The Watershed Erosion Prediction Project (WEPP) model represents the most current erosion prediction technology. WEPP has been applied to the problems of logging road erosion in more mesic forests but has not been tested or evaluated on roadways located in semiarid mountainous ecosystems.
Six rainfall simulation experiments were conducted to measure runoff and sediment yield off three separate plots located on Tickville Road, located on Camp W.G. Williams, a National Guard Training Center in Utah . These data were compared with runoff and erosion estimates produced by the WEPP model. WEPP cropland and rangeland erodibility equations were used to predict rill erodibility (Kr), interrill erodibility (Ki), and critical shear (TAUc). These were tested for their effectiveness in predicting road erodibilities in these environments. A sensitivity analysis was performed on those parameters that were suspected of having a substantial impact on model output and accuracy.
There was an excellent correlation between predicted and observed total runoff volumes for all simulations (R2= 0.96). The differences were greater than 10% only for plot 2 wet; otherwise, the average difference for all six simulations was 4.9%. When using Kr, K.i , and TAUc as predicted by rangeland methods, predicted sediment yields differed from those measured, on average, by 82%. Predicted sediment yields differed by only 22% compared to calculated sediment yields, when using the cropland erodibility equations to predict Kr, K.i , and TAUc. A sensitivity analysis showed that percent slope, slope length, days since last tillage, and ridge roughness all had a significant impact on WEPP predicted sediment yields. Results show the effectiveness of the WEPP model in predicting runoff and erosion off native surfaced roads in these semiarid mountainous regions.
8
Beyer, Portner Niki. "Erosion des bassins versant [sic] alpins suisses par ruissellement de surface /." [S.l.] : [s.n.], 1998. http://library.epfl.ch/theses/?nr=1815.
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9
Downward, Kenneth. "Relationships between surface crusts and erosion in the Tabernas Badlands, Almeria, S.E. Spain." Thesis, University of Wolverhampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325975.
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10
Karagianna, Anthoula. "Changes in the surface chemistry of enamel exposed to acid : a surface study of caries and erosion." Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/3237/.
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Dental caries is a result of acid production by plaque bacteria and manifests with mineral loss and hard tissue dissolution. Dental erosion is the irreversible loss of dental hard tissue caused by acidic agents without bacterial involvement. Numerous techniques have been described for the early detection of dental caries and erosion. However, they all rely on detecting already lost tissue, suggesting that the disease process has been operating for some time. Recent research suggests that uptake of protons from bacterial or dietary acids precedes hard tissue dissolution. The aim of this research project was to examine whether protonation of sound and carious sterile and non-sterile human primary tooth surfaces which have been subjected to acids of known pH occurs and can be detected in vitro and in situ with a simple and clinically applicable technique. A total of 219 human primary tooth surfaces were investigated in vitro. Of these, 110 sound and carious sterile and non-sterile tooth surfaces were examined at baseline and 109 after an acidic challenge. Universal pH indicator solution was used to assess the protonation state of the tooth surfaces. Significantly more tooth surfaces were found protonated after the acidic challenge compared to baseline for all the groups of teeth (p<0.01) with the exception of non-sterile tooth surfaces with caries into dentine (p=0.467). This was probably because the tooth surfaces were already protonated at baseline as a result of the carious process. The in situ study involved five participants and thirty sound enamel slabs. The enamel slabs were obtained from human primary teeth and were incorporated into mandibular removable appliances. The appliances were placed intra-orally for 48 hours to allow plaque accumulation. After removal from the mouth, the enamel slabs were subjected to 10% w/v sucrose rinse. The protonation state of the tooth surface was assessed with universal pH indicator solution. The proportion of protonated tooth surfaces was significantly higher compared to the proportion of non-protonated tooth surfaces (p<0.001). The results of these studies suggest that protonation of human primary tooth surfaces after an acidic challenge occurs and can be detected with a clinically applicable technique both in vitro and in situ. Measuring the degree of protonation can be a novel means to detect tooth surfaces that are at increased risk of caries and erosion at a very early stage before any irreversible change of the hard tissue structure.
11
Andermann, Christoff. "Climate, topography and erosion in the Nepal Himalayas." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2012. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-86385.
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This thesis deals with the role of precipitation on erosion and landscape formation in the Nepal Himalayas. I investigate all successive steps involved in the erosion process: 1) Starting from the evaluation of precipitation datasets, 2) the transfer of precipitation to river discharge, 3) the mobilization and transport of material out of the mountain range, 4) and finally, erosion constrains over longer time-scales. I show that the dataset derived from the interpolation of rain gauge data performs best in the Himalayas. I demonstrate the importance of an until now unconsidered, major compartment of the Himalayan discharge cycle, which I identify as a fractured basement aquifer, and estimate the snow and ice melt contribution to the Himalayan rivers. Erosion rates calculated from suspended sediment fluxes and cosmogenic nuclide analysis range between 0.1 and 4 mm/yr. The rivers in the Nepal Himalayas are supply limited and the hillslopes as contributing source are transport limited. Last I show that over several thousand years erosion is not related with precipitation, but with reliefCette thèse porte sur le rôle des précipitations sur l’érosion et la formation des reliefs dans l’Himalaya Népalais. J’étudie chaque étape du processus d’érosion : 1) Evaluation des bases de données de précipitations, 2) Transfert des précipitations au débit fluvial, 3) Mobilisation et transport du matériel dans le bassin versant, et enfin 4) Mécanismes d’érosion sur de longues échelles de temps. Je montre que la base de données de précipitations obtenue par interpolation de données pluviométriques est la plus performante pour la région de l\'Himalaya. Je démontre l’importance d’une composante majeure, jusqu’alors ignorée, du cycle de débit de l’Himalaya que j’identifie comme étant les aquifères de sous-sol fracturé, et j’évalue la contribution de la fonte des neiges et glaces aux rivières Himalayennes. Les taux d’érosion calculés à partir des flux de sédiments en suspension et des analyses de nucléides cosmogéniques varient de 0.1 à 4 mm/a. Les rivières au Népal sont limitées par l’apport sédimentaire alors que les versants, en tant que source de sédiments, sont limités par le transport. Enfin, je montre que l’érosion sur des milliers d’années ne dépend des précipitations mais du relief
Die vorliegende Arbeit beschäftigt sich mit der Rolle des Niederschlag bei Erosions- und Oberflächenprozessen im nepalesischen Himalaja. Ich untersuche die Abfolge der Erosionspsozesse im Himalaja: 1) Ausgehend von der Bewertung von Niederschlagsdatensätzen, 2) die Prozesse der Abflussbildung in Flüssen, 3) die Mobilisierung und Transport von Material, 4) und Erosionsraten über längere Zeiträume. Ich zeige, dass interpolierte Niederschlagsdaten die beste Qualität im Himalaya haben. Ich zeige auf, wie wichtig der bislang unberücksichtigt Grundwasserzwischenspeicher für die Abflussbildung im Himalaya ist und schätze den Anteil der Schnee-und Eisschmelze an dem Gesamtabfluss der Flüssen im Himalaja. Erosionsraten die mittels Schwebestofffracht und der Analyse kosmogener Nukluide berechnet wurden, liegen zwischen 0,1 und 4 mm pro Jahr. Der Sedimenttransport in den Flüssen in Nepal ist limitiert durch die Verfügbarkeit von transportierbarem Material, während der Transport und die Mobilisierung auf den Hängen durch die Verfügbarkeit von Wasser limitiert ist. Zudem sind die Erosionsraten über mehrere Jahrhundert nicht von der Niederschlagsverteilung abhängig sondern vom Relief
12
Glotzbach, Christoph. "Low-temperature thermochronology from tunnel and surface samples in the Central and Western Alps." [S.l. : s.n.], 2008.
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13
Wong, Stephanie Tomita. "Computer-aided modeling of controlled release through surface erosion with and without microencapsulation." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002206.
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14
Woodun, Jayashree Khanta. "Surface crusting of soils from the South Downs in relation to soil erosion." Thesis, University of Sussex, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270498.
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15
Finke, Manuela. "Studying food-related demineralisation of teeth with atomic force microscopy (AFM) and nanoindentation." Thesis, University of Bristol, 2001. http://hdl.handle.net/1983/8d6de76b-d940-47ad-b0f6-095f56ddf54e.
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16
Кирилів, Ярослав Богданович, Володимир Іванович Кирилів, Богдан Романович Ціж, and Максимів Ольга Володимирівна. "Resistance of surface nanocrystalline and ultrafine-grained structures to wear and cavitation erosion damage." Thesis, LLC «Computer-publishing, information center», Kiev, Ukraine, 2020. http://hdl.handle.net/123456789/6943.
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17
Kilic, Arif Nesimi 1963. "A multi-region transient erosion model for concrete with time-dependent surface heat flux." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/290695.
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A multi-region, transient concrete ablation and decomposition model is developed. The model consists of four regions of concrete containing a thermally affected region, a dry (evaporated and chemically dehydrated) region, and a gas-free (decarboxylated) region with ablated concrete at the melt/concrete interface. Each region has an interface where the latent heat of local decomposition reactions is taken into account as heat sinks due to endothermic characteristics of the reactions. The time dependent temperature profiles, and depth and growth rate of the regions are evaluated by use of the heat balance integral method. Solutions are obtained for surface heat fluxes in forms of constant, e ⁻(λ)ᵗ, t⁻(λ) and -At to analyze various melt cooldown schemes. The erosion front progresses with a constant rate proportional to the surface heat flux in case of constant heat flux, and terminates at a finite erosion depth that is logarithmically proportional to the cooldown rate for surface heat flux in forms of ⁻(λ)ᵗ and t⁻(λ). Sensitivity analyses are performed to investigate the effects of important thermophysical parameters. Larger erosion depth and rate is observed for higher thermal conductivity. Decomposition temperatures are found to be significant in ablation. Model results were compared with previous experiments and models, and determined to be valid and accurate for different types of melt/concrete interaction. The model presented in this study is simple yet very detailed and accurate in simulating the actual molten core/concrete interaction (MCCI) phenomena, and in investigating the concrete reaction to the molten core. It not only can be embodied into the MCCI codes currently being developed, but also can be used to determine the containment integrity, and fission products released into the environment and to the public as a stand alone code.
18
Bontrager, Austin. "Estimation of agricultural soil erosion and surface water quality trends in the Cheney Lake watershed." Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/13182.
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Master of ScienceDepartment of Agronomy
Nathan Nelson
Phosphorus and sediment runoff are the primary cause of eutrophication in Cheney Lake, the primary water source for Wichita, Kansas. Best Management Practices (BMPs) such as no-till farming practices and nutrient management can be implemented to reduce phosphorus runoff on high-risk agricultural fields. Past efforts have established BMP use in this watershed, although the effectiveness of these efforts has not been evaluated. The goals of this project were to identify any existing water quality trends in the Cheney Lake watershed, estimate the current distribution of erosion in the watershed, and evaluate the placement of BMPs with regards to field-scale erosion risk. Parametric, multi-linear regression and non-parametric, seasonal Mann-Kendall analyses were used to identify trends in the Total Suspended Solids (TSS) and Total Phosphorus (TP) of grab samples from the North Fork Ninnescah River. A Geographic Information System (GIS) model based on the Revised Universal Soil Loss Equation (RUSLE) was used to estimate watershed-scale erosion, prioritize agricultural land for BMP placement, and evaluate existing placement of BMPs within the Cheney Lake watershed. No detectible trends were identified in the water quality data due to stream variability, frequency of sampling, or absence of actual improvement in water quality. Additional sampling must be done to detect any trends in the future. BMPs were implemented on 13% of prioritized field area, and 11% of non-prioritized field area. Conservation Reserve Program (CRP) fields were placed on 14% of prioritized field area, and 5% of non-prioritized field area. No-till practices were implemented on 13% of prioritized field area, and 18% of non-prioritized field area. The top 20% eroding fields were identified given current conditions, and account for approximately 56% of the watershed-wide erosion. The GIS method has demonstrated utility in evaluating past erosion control measures for the watershed and in informing future decisions concerning BMP placement.
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Alistoun, Judith Robyn. "The origin of endorheic pans on the African erosion surface North of Grahamstown, South Africa." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1011048.
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Pans on the African Erosion Surface near Grahamstown are small features, which, perhaps due to their small size have been neglected by researchers. From the outset the striking difference of these pans relative to other pans in southern Africa, is that the host rock is silcrete, a highly resistant rock well known as being associated with deeply weathered plateaus. The dominant origin theory for pans in southern Africa was developed by Goudie and Thomas (1985), and focuses on mechanisms relating to erosion and deflation. This model does not fit in well with the pans that have formed on substrate that has largely been unaffected by erosion in recent geological history (thousands to 10 000 years). As such this study examined the role of prolonged chemical weathering of Dwyka Tillite, that has led to the formation of silcrete. The hypothesis was that such deep weathering is responsible for local scale volume changes, which have in turn led to the formation of a depression. The centre of the pan indicated the highest concentration of Al₂O₃ and kaolinite at mid depths, and their concentrations decreased vertically away from these depths, and laterally towards the margins of the pan. Similar results were noted for SiO₂, while CaO and MgO (and calcite and dolomite) were highest at mid depths along the margins of the pan, and decreased laterally toward the centre of the pan. Results indicated that there was a positive relationship in the centre of the pan between: - the degree of chemical weathering and volume losses, - relative elevation of the pan and volume changes. Geochemically and mineralogically, there was a link between the high concentrations of Ca and Mg carbonates and volume gains in the margin of the pans. It is proposed that transpiration of vegetation along the margin of the pan caused the lateral movement of solutes, and the selective exclusion of these solutes by plants was associated with carbonate precipitation, leading to the creation of local relief. These results provide evidence to suggest that weathering and precipitation processes occurring over geological time scales are responsible for minor scale relief features, whose origin has been mistakenly attributed to deflation processes occurring over hundreds to thousands of years.
20
Enriquez, Adriana Gomez. "Erodibilidade e tensão crítica de cisalhamento no canal de uma estrada não pavimentada situada em um Latossolo Vermelho-Amarelo." Universidade Federal de Viçosa, 2012. http://locus.ufv.br/handle/123456789/3628.
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Previous issue date: 2012-05-23The erosion in unpaved roads associated with the runoff has negative implication in social, economic and environmental development of a region. Therefore the incorporation of techniques for prevention and control of erosion on these roads is important. The techniques developed for this purpose require knowledge of the indices of soil resistance to erosion, principally the soil erodibility and critical shear stress. In this context, the aim of this study was to determine the erodibility and critical shear stress in the channel of an unpaved road implanted in an Oxisol horizons B and C. Study was conducted on an unpaved road in Viçosa-MG, Brazil, where the indices were obtained using a runoff simulator installed on the channel road, which allows to estimate soil loss associated with different shear stress. The results obtained in each test was adjusted using simple linear regression models and, the models identity test proceeded to obtain a representative value of the indices for the study site, and to obtain the confidence interval associated with the erodibility, considering 95% of probability. The erodibility value determined for the horizon B was 0.0044 g cm-2 min-1 Pa-1, and its associated confidence interval with 95% probability was 0.0035 to 0.0053 g cm-2 min-1 Pa-1. The critical shear stress determined for this horizon was 7.61 Pa. The horizon C erodibility value determined was 0.0347 g cm-2 min-1 Pa-1, and its xv associated confidence interval with 95% probability was 0.0288 to 0.0406 g cm-2 min-1 Pa-1. The critical shear stress value for this horizon was 8.16 Pa.
A erosão em estradas não pavimentadas associada ao escoamento superficial interfere negativamente no desenvolvimento social, econômico e ambiental de uma região. Por isso é importante a incorporação de técnicas que visem a prevenção e o controle da erosão nestas estradas. As diferentes técnicas desenvolvidas para este fim requerem o conhecimento dos índices de resistência do solo ao processo erosivo, sendo a erodibilidade e a tensão crítica de cisalhamento os índices de maior importância. Neste sentido, objetivou-se com a realização deste trabalho, determinar a erodibilidade e a tensão crítica de cisalhamento no canal de uma estrada não pavimentada implantada nos horizontes B e C de um Latossolo Vermelho-Amarelo. O estudo foi realizado em uma estrada não pavimentada do município de Viçosa- MG, onde os índices foram obtidos utilizando um método de determinação direta com o uso de um simulador de escoamento instalado no canal da estrada, que permitiu estimar as perdas de solo associadas a diferentes tensões cisalhantes. Aos resultados obtidos em cada teste foi ajustado um modelo de regressão linear simples e, posteriormente, se aplicou a técnica de teste de identidade de modelos, a fim de obter um valor representativo destes índices para o local de estudo, além de obter o intervalo de confiança associado à erodibilidade com um nível de confiança de 95%. O valor de erodibilidade determinado para o horizonte B, foi de 0,0044 g cm-2 min-1 Pa-1, sendo a ele associado um intervalo de confiança com 95% de probabilidade de 0,0035 a 0,0053 g cm-2 min-1 Pa-1. A tensão crítica de cisalhamento determinada para este horizonte foi de 7,61 Pa. Para o horizonte C o valor de erodibilidade determinado foi de 0,0347 g cm-2 min-1 Pa-1, sendo a ele associado um intervalo de confiança com 95% de probabilidade de 0,0288 a 0,0406 g cm-2 min-1 Pa-1. A tensão crítica de cisalhamento determinada para este horizonte foi de 8,16 Pa.
21
Devauchelle, Olivier. "Ecoulements de surface et érosion." Paris 6, 2007. https://hal.archives-ouvertes.fr/tel-01499527.
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L'écoulement laminaire d'un liquide sur un lit granulaire conduit à la formation de divers motifs d'érosion (bancs, méandres, tresses et rides) rencontrés en Géomorphologie fluviale, où les écoulements sont turbulents. En se fondant sur des modèles simples (équations de Saint-Venant, transport par charriage), la présente étude aborde ces systèmes par des méthodes analytiques et numériques. Un modèle de berges érodables est établi pour des micro-rivières. L'étude de leur stabilité éclaire différents phénomènes pour lesquels l'influence des conditions aux bords est cruciale. L'évolution non-linéaire de l'instabilité de banc conduit à l'apparition de fronts d'érosion en forme de chevrons. Le développement des rides est succinctement abordé. Enfin, la théorie de la lubrification est mise en oeuvre pour établir l'existence d'une ligne de contact mobile sur un solide poreux extrait d'un liquide, et sa disparition au profit d'un film de Landau-Levich-Derjagin, au-delà d'une vitesse critique.
22
Andermann, Christoff. "Climate, topography and erosion in the Nepal Himalayas." Doctoral thesis, Rennes 1, 2011. https://tubaf.qucosa.de/id/qucosa%3A22808.
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This thesis deals with the role of precipitation on erosion and landscape formation in the Nepal Himalayas. I investigate all successive steps involved in the erosion process: 1) Starting from the evaluation of precipitation datasets, 2) the transfer of precipitation to river discharge, 3) the mobilization and transport of material out of the mountain range, 4) and finally, erosion constrains over longer time-scales. I show that the dataset derived from the interpolation of rain gauge data performs best in the Himalayas. I demonstrate the importance of an until now unconsidered, major compartment of the Himalayan discharge cycle, which I identify as a fractured basement aquifer, and estimate the snow and ice melt contribution to the Himalayan rivers. Erosion rates calculated from suspended sediment fluxes and cosmogenic nuclide analysis range between 0.1 and 4 mm/yr. The rivers in the Nepal Himalayas are supply limited and the hillslopes as contributing source are transport limited. Last I show that over several thousand years erosion is not related with precipitation, but with relief.Cette thèse porte sur le rôle des précipitations sur l’érosion et la formation des reliefs dans l’Himalaya Népalais. J’étudie chaque étape du processus d’érosion : 1) Evaluation des bases de données de précipitations, 2) Transfert des précipitations au débit fluvial, 3) Mobilisation et transport du matériel dans le bassin versant, et enfin 4) Mécanismes d’érosion sur de longues échelles de temps. Je montre que la base de données de précipitations obtenue par interpolation de données pluviométriques est la plus performante pour la région de l\'Himalaya. Je démontre l’importance d’une composante majeure, jusqu’alors ignorée, du cycle de débit de l’Himalaya que j’identifie comme étant les aquifères de sous-sol fracturé, et j’évalue la contribution de la fonte des neiges et glaces aux rivières Himalayennes. Les taux d’érosion calculés à partir des flux de sédiments en suspension et des analyses de nucléides cosmogéniques varient de 0.1 à 4 mm/a. Les rivières au Népal sont limitées par l’apport sédimentaire alors que les versants, en tant que source de sédiments, sont limités par le transport. Enfin, je montre que l’érosion sur des milliers d’années ne dépend des précipitations mais du relief.
Die vorliegende Arbeit beschäftigt sich mit der Rolle des Niederschlag bei Erosions- und Oberflächenprozessen im nepalesischen Himalaja. Ich untersuche die Abfolge der Erosionspsozesse im Himalaja: 1) Ausgehend von der Bewertung von Niederschlagsdatensätzen, 2) die Prozesse der Abflussbildung in Flüssen, 3) die Mobilisierung und Transport von Material, 4) und Erosionsraten über längere Zeiträume. Ich zeige, dass interpolierte Niederschlagsdaten die beste Qualität im Himalaya haben. Ich zeige auf, wie wichtig der bislang unberücksichtigt Grundwasserzwischenspeicher für die Abflussbildung im Himalaya ist und schätze den Anteil der Schnee-und Eisschmelze an dem Gesamtabfluss der Flüssen im Himalaja. Erosionsraten die mittels Schwebestofffracht und der Analyse kosmogener Nukluide berechnet wurden, liegen zwischen 0,1 und 4 mm pro Jahr. Der Sedimenttransport in den Flüssen in Nepal ist limitiert durch die Verfügbarkeit von transportierbarem Material, während der Transport und die Mobilisierung auf den Hängen durch die Verfügbarkeit von Wasser limitiert ist. Zudem sind die Erosionsraten über mehrere Jahrhundert nicht von der Niederschlagsverteilung abhängig sondern vom Relief.
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King, David. "Sonochemical analysis of the output of ultrasonic dental descalers." Thesis, University of Bath, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538276.
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Ultrasonic descalers are used in dentistry to remove calculus and other contaminants from teeth. One mechanism which may assist in the cleaning is cavitation generated in cooling water around the descaler. The spatial distribution of cavitation around three designs of descaler tips and under three load conditions has been observed using sonochemiluminescence from a luminol solution and compared with the vibratory motion of the tips in a water bath, characterised by scanning laser vibrometry. The type of cavitation was confirmed by acoustic emission analysed by a ‘Cavimeter’ supplied by NPL. Surface profilometry and SEM of eroded hydroxyapatite pellets was performed to quantitatively study the erosion caused by a descaler tip in both contact and non-contact modes. Densitometry was used to study the erosion of black ink from a glass microscope slide, and determined that under the majority of conditions, no erosion was demonstrated via cavitation, by descalers operating in non-contact mode, although significant erosion was demonstrated with the tip in contact with the slide.
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Andermann, Cristoff. "Climate, topography and erosion in the Nepal Himalayas." Phd thesis, Université Rennes 1, 2011. http://tel.archives-ouvertes.fr/tel-00674919.
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Cette thèse porte sur le rôle des précipitations sur l'érosion et la formation des reliefs dans l'Himalaya Népalais. J'étudie chaque étape du processus d'érosion : 1) Evaluation des bases de données de précipitations, 2) Transfert des précipitations au débit fluvial, 3) Mobilisation et transport du matériel dans le bassin versant, et enfin 4) Mécanismes d'érosion sur de longues échelles de temps. Je montre que la base de données de précipitations obtenue par interpolation de données pluviométriques est la plus performante pour la région de l'Himalaya. Je démontre l'importance d'une composante majeure, jusqu'alors ignorée, du cycle de débit de l'Himalaya que j'identifie comme étant les aquifères de sous-sol fracturé, et j'évalue la contribution de la fonte des neiges et glaces aux rivières Himalayennes. Les taux d'érosion calculés à partir des flux de sédiments en suspension et des analyses de nucléides cosmogéniques varient de 0.1 à 4 mm/a. Les rivières au Népal sont limitées par l'apport sédimentaire alors que les versants, en tant que source de sédiments, sont limités par le transport. Enfin, je montre que l'érosion sur des milliers d'années ne dépend des précipitations mais du relief.
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Jess, Scott. "Resolving the timing of major erosion events along the West Greenland-Baffin-Bylot continental margins." Thesis, University of Aberdeen, 2018. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=239479.
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Continental passive margins exhibit high elevation topography in many localities across the globe. The source and age of much of this topography remains a subject of great debate within the wider community, with numerous theories being presented, including significant post-rift uplift and isostatically preserved rift anks. Establishing the mechanisms that generate topography and the onshore evolution across passive margins is vital in understanding regional geological histories and their wider development. The passive margins of the NW Atlantic realm exhibit high elevation topography topped with low relief summits. The origin of this topography is debated, with both 3 km of uplift in the post-rift stage and the isostatic preservation of Cretaceous rift anks being suggested within the literature. The work of this thesis aims to resolve this debate by establishing the timing and source of uplift across the region and determining the onshore evolution prior to, during and after rifting with the application of apatite low temperature thermochronology. Contemporary analytical and modelling techniques are utilised to generate thermal histories from across both central West Greenland and SE Baffin Island, helping to de ne how the modern landscape has formed. Results from this work outline an onshore history dominated by uplift in the Cretaceous and exhumation throughout the Cenozoic. Basement samples from SW Greenland exhibit protracted cooling throughout the Mesozoic and Cenozoic, implying low rates of exhumation have been apparent throughout. Within the Nuussuaq Basin, centralWest Greenland, thermal histories display reheating i through the Late Cretaceous/Palaeogene and cooling to present, consistent with events outlined in the basin's stratigraphy and implying uplift of the topography is likely the result of extrusive volcanism and an isostatic response to the unroo ng of the lithosphere. Spatial trends in data and thermal histories across SE Ba n Island imply much of the landscape is shaped by rift ank uplift along its SE coastline, driving exhumation of the region throughout the Cenozoic. Collectively these results suggest the elevated topography of the NW Atlantic realm is the result of rift related uplift in the Cretaceous, magmatism and widespread exhumation throughout the Cenozoic, preserved by isostatic exure. This interpretation of the region's onshore history contributes greatly to our understanding of the NW Atlantic's geological evolution. The results highlight the role of extensional tectonism, exhumation and isostasy in shaping both margin's landscapes and helps to determine the principal characteristics of the wider extensional system and the evolution of the o shore domain. Moreover, these conclusions have a wider relevance to the evolution of passive margins across the North Atlantic, improving our understanding of how topography across other margins, such as of East Greenland, Norway and the UK, has formed.
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Albright, Amy N. "An Analysis of Slope Erosion and Surface Changes on Off-Road Vehicle Trails in Southeastern Ohio." Ohio University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1276715617.
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Casas-Apayco, Leslie, Vanessa Manzini Dreibi, Ana Carolina Hipólito, Márcia Sirlene Zardin Graeff, Daniela Rios, Ana Carolina Magalhaes, Marília Afonso Rabelo Buzalaf, and Linda Wang. "Erosive cola-based drinks affect the bonding to enamel surface: an in vitro study." Faculdade De Odontologia De Bauru - USP, 2014. http://hdl.handle.net/10757/324186.
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Objective: This study aimed to assess the impact of in vitro erosion provoked by different cola-based drinks (Coke types), associated or not with toothbrushing, to bonding to enamel. Material and methods: Forty-six bovine enamel specimens were prepared and randomly assigned into seven groups (N=8): C- Control (neither eroded nor abraded), ERO-RC: 3x/1-minute immersion in Regular Coke (RC), ERO-LC: 3x/1-minute immersion in Light Coke (LC), ERO-ZC: 3x/1-minute immersion in Zero Coke (ZC) and three other eroded groups, subsequently abraded for 1-minute toothbrushing (EROAB-RC, EROAB-LC and EROAB-ZC, respectively). After challenges, they were stored overnight in artificial saliva for a total of 24 hours and restored with Adper Single Bond 2/Filtek Z350. Buildup coronal surfaces were cut in 1 mm2-specimens and subjected to a microtensile test. Data were statistically analyzed by two-way ANOVA/Bonferroni tests (a=0.05). Failure modes were assessed by optical microscopy (X40). The Interface of the restorations were observed using Confocal Laser Scanning Microscopy (CLSM). Results: All tested cola-based drinks significantly reduced the bond strength, which was also observed in the analyses of interfaces. Toothbrushing did not have any impact on the bond strength. CLSM showed that except for Zero Coke, all eroded specimens resulted in irregular hybrid layer formation. Conclusions: All cola-based drinks reduced the bond strength. Different patterns of hybrid layers were obtained revealing their impact, except for ZC.This study was supported in part by grants given by the São Paulo Research Foundation (FAPESP), Process no. 2009/14986-0, and the National Council for Scientific and Technological Development (CNPq), Process no. 480038/2007-4. In Addition, this study was performed by V.D.M. and A.C.H. as fulfillment of their graduation research, which was supported by FAPESP (Processes no. 2009/01376-9 and 2009/01377-5, respectively). The authors are also grateful to Oral B and SDI, which donated the materials used in the study.
Revisión por pares
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Mounirou, Lawani A. "Etude du ruissellement et de l’érosion à différentes échelles spatiales sur le bassin versant de Tougou en zone sahélienne du Burkina Faso : quantification et transposition des données." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20039/document.
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La variabilité spatio-temporelle du ruissellement et de l'érosion hydrique n'est pas un fait nouveau. Leurs caractéristiques s'estiment généralement avec une marge raisonnable sur des parcelles d'un à quelques dizaines de m². Avec l'accroissement de la surface, l'hétérogénéité du milieu croît ce qui induit un effet d'échelle. Le passage de la parcelle au bassin versant n'est pas totalement maîtrisé compte tenu de la complexité et de la variabilité des facteurs mis en jeu. L'objectif de cette thèse est de comprendre les processus de ruissellement et de l'érosion dans différents environnements et à différentes échelles spatiales, d'identifier les sources de variation, puis de développer une méthodologie de transposition des résultats de l'échelle parcellaire à l'exutoire du bassin versant. À cet effet, un réseau de dix-huit parcelles expérimentales de différentes tailles, de deux unités hydrologiques ont permis de quantifier le ruissellement et les pertes en terre sur les principaux états de surface du bassin versant de Tougou.Les résultats obtenus sur les micro-parcelles de 1m², les parcelles de 50 et 150m², les unités hydrologiques de 6 et 34 ha et le bassin versant de 37km², montrent que, tant sur sols cultivés que sur sols dénudés, la lame ruisselée ainsi que les pertes en terres diminuent lorsque la superficie augmente, pour une même pluie et dans des conditions comparables d'humidité préalable des sols. Ce phénomène d'effet d'échelle de la superficie sur l'écoulement et l'érosion est connu des hydrologues qui se heurtent toujours à l'écueil de l'extrapolation des résultats obtenus sur petites superficies à des superficies plus grandes. Nos résultats montrent que l'effet d'échelle observé sur le ruissellement et l'érosion est dû principalement à l'hétérogénéité spatiale des sols (propriétés hydrodynamiques, microrelief) et à sa variabilité (état des variables) et que la dynamique temporelle de l'intensité de la pluie ne fait que l'amplifier.Les résultats obtenus lors des essais de transposition permettent de soutenir avec raison qu'une meilleure extrapolation des données de l'échelle parcellaire à l'échelle du bassin viendra de la prise en compte des questions de la connectivité hydrologique.En définitive, cette étude met en avant l'intérêt d'effectuer des mesures de ruissellement et d'érosion sur des unités homogènes en termes d'occupation du sol qui peuvent représenter une mosaïque hétérogène de surfaces homogènes. La localisation sur le bassin versant et le taux de connectivité de ces unités hydrologiques à l'intérieur desquelles les processus dominants du ruissellement et d'érosion se manifestent peuvent permettre d'approcher la résolution du problème de transfert d'échelleThe spatio-temporal variability of runoff and erosion is not new fact. Their characteristics are generally estimated with a reasonable margin on plots of a few tens of square meters. With the increase of the surface, the heterogeneity of environment increases which induces a scale effect. The passage of the plot to the catchment is not totally controlled because of the complexity and variability of factors come into play. The objective of this thesis is to understand the processes of runoff and erosion in different environments and at different spatial scales, to identify the sources of variation, and to develop a methodology for implementation of the results of field scale to the basin outlet. To this end, a network of eighteen plots of different sizes, two hydrological units were used to quantify runoff and soil loss on the main surface features Watershed Tougou.The results obtained on micro-plots of 1 m², plots of 50 and 150 m², hydrologic units of 6 and 34 ha and the catchment area of 37 km², show that, both in cultivated soils and on bare soils, the runoff excess decreases as the area increases, for the same rain and prior comparable humidity conditions of the soil. This phenomenon of the scale effect of the area on runoff is known to hydrologists who still face the challenge of extrapolating results obtained on small areas to larger areas. Our results show that the scale effect observed on the runoff is mainly due to the spatial heterogeneity of soils (hydraulic properties, microrelief) and its variability (state of the variables) and that temporal dynamics of the intensity of rain just amplifies it. The results obtained in tests of transposition can maintain with reason that a better extrapolation of data from the field scale across the pond comes from the consideration of the issues of hydrologic connectivity.Ultimately, this study highlights the value of measurements of runoff on homogeneous units in terms of land use that may represent a heterogeneous mosaic of homogeneous areas. The location on the watershed and the rate of connectivity of the hydrologic units within which the dominant processes of runoff occur can allow approach the solution of the problem of scale transfer
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Matzke, Jeffrey Alan. "Geophysical investigation of the stone zone and loamy mantle on the Iowan surface." Thesis, University of Iowa, 2013. https://ir.uiowa.edu/etd/5022.
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The processes that generated the distinctive landscape of the Iowa Erosion Surface (IES) of northeastern Iowa have been debated for over a century. A number of researchers have concluded that the IES experienced a periglacial environment and was underlain by continuous permafrost during the last glacial maximum. Ubiquitous throughout the IES is a stone zone that lies 60-100cm below the surface. Several explanations for the genesis of the stone zone have been proposed, including a lag concentrate, biomantle processes, and cryogenesis. We utilized a combination of coring and trenching, ground penetrating radar and resistivity to investigate the 3D distribution of the stone zone, overlying "pedisediment" and the underlying contact with dense till across a 100m2 area on a typical IES hillslope in east-central Iowa .
Our preliminary results indicate that the stone zone occurs in the basal few decimeters of pedisediment that rests uncomformably and abruptly on eroded, dense till. Ice wedge casts extend from the stone zone into the underlying till. The depth of the stone zone below the modern surface increases downslope and the stone zone dissipates and eventually is replaced by relatively thick loamy sand beneath the footslope. These relationships argue against the stone zone being of biogenic origin. The occurrence of ice wedge casts associated with the stone zone and systematic changes in the thickness and texture of the pedisediment suggest to us that stone zone on the IES was formed by a combination of cryogenic and active zone erosive processes during the full glacial period.
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Xu, Hanchang. "An assessment of corrosion and erosion-corrosion behaviour of austenitic cast iron and surface coatings for pump applications." Thesis, Heriot-Watt University, 2001. http://hdl.handle.net/10399/1159.
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Dryden, Garri A. "Optimum gravel size for use as a soil surface cover for the prevention of soil erosion by water." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280469.
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Eleven series of replicated tests were conducted using 38.1 mm, 15.9 mm, and 9.5 mm gravel to determine the most effective soil surface cover to prevent soil erosion from rainfall. A sediment tray one meter square in size with an integrated rainfall simulator was used to generate data after initial trial runs had established test procedures. Various size gravels and a control with no cover were tested in a laboratory using simulated rainfall to evaluate their effectiveness in preventing erosion. Through thirty-three experiments, signature traits of specific rock sizes were identified. Experiments on 38.1 mm gravel indicated the usefulness of rock mulches in soil erosion prevention. Evaluations with 9.5 mm material indicated that erosion prevention varies inversely with particle size. Experiments with 15.9 mm gravel suggested that this material could increase erosion. This study reflects the ambivalence in the literature and points to the complexity of micro-interactions and erosion potential as influenced by gravel size. Six mechanisms governing rock mulch erosion were proposed.
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Henderson, Marc Bryson. "Changes in Streambank Erodibility and Critical Shear Stress Due to Surface Subaerial Processes." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/33114.
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Previous studies have shown that soil erodibility and critical shear stress are highly influenced by weathering processes such as freeze-thaw cycling and wet-dry cycling. Despite over forty years of research attributing changes in soil properties over time to climate-dependent variables, little quantitative information is available on the relationships between streambank erodibility and critical shear stress and environmental conditions and processes that enhance streambank erosion potential. The goal of this study was to investigate temporal changes in streambank erodibility and critical shear stress due to surface weathering.
Soil erodibility and critical shear stress were measured monthly in situ using a multi-angle submerged jet test device. Environmental and soil data were also collected directly at the streambank surface to determine freeze-thaw cycles, soil moisture, soil temperature, bulk density, soil erodibility, critical shear stress, and other atmospheric conditions that could impact bank erosion potential. Statistical tests, including a nonparametric alternative to ANOVA and multiple comparison tests, were used to determine if temporal changes in soil erosion potential were greater than spatial differences. Regression analyses were also utilized to identify the factors contributing to possible changes in soil erodibility, critical shear stress, and bulk density.
The nonparametric alternative to ANOVA in combination with Dunnâ s nonparametric multiple comparison test showed soil erodibility was significantly higher (p=0.024) during the winter (November - March) and the spring/fall (April - May, September - October). Regression analyses showed 70 percent of soil erodibility variance was attributed to freeze-thaw cycling alone. Study results also indicated that bulk density is highly influenced by climate changes since gravimetric water content and freeze-thaw cycles combined explain as much as 86 percent of the variance in bulk density measurements.
Results of this study show significant amounts of variation in the resistance of streambank soils to fluvial erosion can be attributed to subaerial processes, specifically changes in soil moisture and temperature. These results have potential implications for streambank modeling and restoration projects that assume constant values for soil erodibility. Watershed models and restoration designs should consider the implications of changing soil erodibility during the year in model development and stream restoration designs.Master of Science
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Beggy, Holly M., and Jeffrey S. Fehmi. "Effect of surface roughness and mulch on semi-arid revegetation success, soil chemistry and soil movement." ELSEVIER SCIENCE BV, 2016. http://hdl.handle.net/10150/616986.
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For the successful reclamation of disturbed land, the reduction of initial erosion risk must be balanced with later vegetation establishment. A combination of erosion control and revegetation practices was researched using commercial (full-sized) equipment on a semi-desert grassland site in southern Arizona, USA. Two soils with different parent materials were used to add a 30 cm cap on sites at two elevations: 1646 and 1403 m asl. There were two surface roughness treatments: smooth and rough. Three straw mulch treatments were applied: no mulch, mulch incorporated into the surface soil, and mulch tackified onto the surface. Plots were planted with a 10 species native mix dominated by perennial grasses. After two growing seasons, the incorporated mulch treatment resulted in significantly more seeded grass aboveground biomass than the no mulch treatment while the no mulch treatment had more forb and volunteer biomass than the surface mulch treatment. There was significantly higher erosion on the rough surface treatment compared to the smooth surface. Increasing perennial grass biomass was correlated with reduced erosion while forb and volunteer biomass showed no relationship with erosion. The smooth surface with surface mulch best established perennial grasses, minimized weeds, and reduced erosion. This combination of practices both minimized erosion as well as maximized vegetation establishment. (C) 2016 The Authors. Published by Elsevier B.V.
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NUNES, Francisco Miquéias Sousa. "Avaliação hidrossedimentologica de uma Bacia sem dados de vazão utilizando o modelo SWAT." Universidade Federal de Campina Grande, 2018. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/382.
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Capes
O crescimento populacional desordenado juntamente com a intensificação das atividades humanas estão acelerando as modificações dos ecossistemas naturais acarretando vários problemas ambientais, em particular , aos recursos hídricos. A necessidade da humanidade por esse recurso vem crescendo de forma rápida e incompatível com a capacidade de recuperação da natureza, causando a escassez e prejuízo na sua qualidade. Além disso, as diversas finalidades para as quais esses recursos são utilizados têm gerado um grande número de conflitos do uso e também degradação qualitativa e quantitativa dos corpos hídricos.No semiárido brasileiro, a situação de escassez hídrica compromete o desenvolvimento econômico e social da região. Assim, torna-se necessário desenvolver ferramentas adequadas para apoiar a tomada de decisão quanto ao uso dos recursos hídricos. Alterações no uso e na ocupação do solo afetam o comportamento do escoamento superficial, e a análise das tendências na vazão dos cursos d’água é importante para o planejamento do uso dos recursos hídricos e do solo. As variações no regime pluviométrico devido às mudanças climáticas também afetam a disponibilidade hídrica nas bacias hidrográficas.Este trabalho tem por objetivomodelar os processos de geração de escoamento superficial, erosão do solo e a recarga potencial subterrânea na bacia do Rio Sucuru a jusante da barragem de Sumé-PB utilizando o modelo SWAT. Foram utilizados dados de precipitação, temperatura, do período de 1994 a 2015, além de mapas de tipos de solo, uso e ocupação do solo com as mudanças observadas no período.Os parâmetros CANMAX, GWQMN, GW_REVAP, ESCO, EPCO e CN foram identificados como os mais influentes sobre o processo de geração de escoamento superficial. O valor do parâmetro GWQMN foi fixado em 2000 mm, pois nenhuma sondagem realizada na bacia indica uma profundidade do solo maior que 2,0 m. Os parâmetros CANMX, ESCO, EPCO e CN se mostraram muito influentes, pois qualquer pequena alteração para mais ou para menos, provocava uma superestimação e/ou subestimação da lâmina escoada, necessitando assim de muitas tentativas antes de obter seus valores finais. Os resultados demosntram a eficiência do modelo SWAT em quantificar e avaliar comparativamente os processos hidrossedimentologicos na região do cariri paraibano. A contribuição deste trabalho se dá pela formulação de uma metodologia para a realização de estudos hidrossedimentologicos em regiões onde não existem dados de escoamento superficial ou de produção de sedimento pela erosão.
Disorganized population growth coupled with the intensification of human activities is accelerating changes in natural ecosystems, leading to a number of environmental problems, in particular water resources. The need of mankind for this resource has been growing rapidly and incompatible with nature's capacity for recovery, causing scarcity and damage in its quality. In addition, the various purposes for which these resources are used have generated a large number of use conflicts and also qualitative and quantitative degradation of water bodies. In the Brazilian semi-arid, the situation of water scarcity compromises the economic and social development of the region. Thus, it is necessary to develop adequate tools to support the decision making regarding the use of water resources. Changes in soil use and occupation affect the behavior of surface runoff, and the analysis of trends in water flow is important for planning the use of water resources and soil. Variations in pluviometric regime due to climate change also affect water availability in river basins. This work aims to model the processes of generation of runoff, soil erosion and potential underground recharge in the Sucuru River basin downstream of the Sumé-PB dam using the SWAT model. Precipitation and temperature data were used from 1994 to 2015, as well as maps of soil types, land use and occupation with changes observed in the period. The parameters CANMAX, GWQMN, GW_REVAP, ESCO, EPCO and CN were identified as the most influential on the process of generation of surface runoff. The value of the GWQMN parameter was set at 2000 mm, since no survey conducted in the basin indicates a soil depth greater than 2.0 m. The parameters CANMX, ESCO, EPCO and CN were very influential, because any small changes for more or less, caused an overestimation and / or underestimation of the drained sheet, thus requiring many attempts before obtaining their final values. The results demonstrate the efficiency of the SWAT model in quantifying and comparing the hydrosedimentological processes in the Paraíba region. The contribution of this work is given by the formulation of a methodology for the realization of hydrosedimentological studies in regions where there is no data of surface runoff or sediment production.
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Nguyen, Hong Quang, Thi Thu Hang Le, Thi Thanh Nga Pham, and Martin Kappas. "Modelling surface runoff and soil erosion for Yen Bai Province, Vietnam, using the Soil and Water Assessment Tool (SWAT)." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-227939.
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Applications of the Soil and Water Assessment Tool (SWAT) are common. However, few attempts have focused on the tropics like in the Yen Bai province, Vietnam. Annual water-induced soil erosion (WSE) rates and surface runoff (SR) were estimated. The Nam Kim and Ngoi Hut watersheds were calibrated with accepted agreement between simulated and observed discharge. Correlations between precipitation, land covers, surface runoff and WSE were indicated. Although the estimated average WSE 4.1 t ha−1 year−1 (t ha−1 y−1) was moderate, some steep-bare areas were suffering serious soil loss of 26 t ha−1 y−1 and 15% of the province was calculated at the rate of 8.5 t ha−1 y−1. We found that the changes in WSE significantly correlated with land use changes. As calibrated SR matched closely with the measured data, we recommend SWAT applications for long-term soil erosion assessments in the tropicsNhững ứng dụng của mô hình công cụ đánh giá đất và nước (SWAT) đã được sử dụng phổ biến. Tuy nhiên có rất ít nghiên cứu tập trung vào khu vực nhiệt đới như tỉnh Yên Bái của Việt Nam. Trong nghiên cứu này, giá trị trung bình năm (2001-2012) nước chảy bề mặt (NCM) và xói mòn đất do nước (XM) đã được đánh giá trên cơ sở mô hình SWAT. Các thông số thủy văn của hai lưu vực sông là Nậm Kim và Ngòi Hút được tính toán và kiểm nghiệm với sự trùng hợp tương đối tốt giữa kết quả mô hình và số liệu thực đo. Mối liên hệ giữa lượng mưa, phủ bề mặt, NCM và XM cũng được phân tích và trình bầy chi tiết. Mặc dù giá trị XM năm được ước lượng ở mức trung bình cho toàn Tỉnh (4,1 tấn/ha/năm) nhưng ở một số khu vực nơi có độ dốc lớn và phủ mặt ít lại có lượng XM năm ở mức cao, 26 tấn/ha/năm và 15% tổng diện tích của Tỉnh có giá trị XM là 8,5 tấn/ha/năn. Kết quả nghiên cứu cho thấy sự liên hệ mật thiết giữa sự thay đổi phủ mặt tới giá trị XM. Trên cơ sở kết quả kiểm nghiệm mô hình khả quan, chúng tôi đề xuất sử dụng mô hình SWAT để đánh giá XM trong thời gian dài cho vùng nhiệt đới
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Karambiri, Harouna. "Crues et érosion hydrique au Sahel : étude et modélisation des flux d'eau et de matières sur un petit bassin versant pastoral au nord du Burkina Faso." Paris 6, 2003. http://www.theses.fr/2003PA066169.
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Khadka, Suraj. "A Numerical Study of the Coupled Geomechanical Processes in Sinkholes." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1532970968316002.
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Dutton, Anona L. "Process-based simulations of near-surface hydrologic response for a forested upland catchment: the impact of a road /." May be available electronically:, 2000. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Perkovic, Martin. "Mapping and characterisation of surface damage and wear mechanisms in gun barrels : Gun barrels exposed to cyclic thermo-mechanical loading." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-79026.
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Gun barrels are an important component in advanced defence systems. The gun barrels are used for direct and indirect fire and the material of the gun barrel is exposed to great strains and high temperatures. This sets high demands on the material of the gun barrel. During firing the gun barrel can be damaged. The first damage in gun barrels is the wear of the rifling followed by fatigue. When fatigue occurs cracks can propagate downwards into the bore and could result in catastrophic failure. Therefore investigation regarding the wear, the mechanisms and the underlying factors causing the damage will be performed. How and where the wear in gun barrels occur and also which wear mechanisms causing the wear. Wear in gun barrels involves extreme conditions during firing such as high gas pressure and high temperature from the burning propellant. This thesis work aims to understand how and why wear and damaging mechanisms in gun barrels occurs. Moreover how other ballistic factors influences have on the wear. The wear in gun barrels is caused by erosion from the combustion gases or/and sliding wear caused by the high-speed projectile. The phenomena of wear are complicated and factors like deformation state, types of wear, environment and process are interrelated with each other. These give the rise of wear. In this thesis, samples from three gun barrels were analysed. A new unworn gun barrel, a medium worn gun barrel and a severely worn gun barrel. From the used gun barrels 4 critical positions were identified, then samples from both surface and cross-section were obtained from the gun barrels. The surface and cross-section were analysed using different methods including optical light microscopy and scanning electron microscopy to characterise the surface damage and wear mechanisms. The results from the investigation revealed the dominating wear mechanism to be thermal and chemical erosion at the positions closest to the combustion chamber with heat checks as its signature feature. The heat checks are associated with fatigue cracks developed at the surface and during thermo-mechanical loading, allows it to propagate down into the surface. For both samples at position 2, after the start of the rifling, adhesive wear was obtained too. The adhesive wear was induced by material pick-up from the driving band of the projectile during sliding. In other meaning, the material is transferred from the counter-face to the bore surface. The severely worn gun barrel had been subjected to sliding wear at the muzzle end compared to the medium worn gun barrel which hadn’t experience the same wear rate at the same position. The analysis of the cross-section examination revealed information about the structure and condition of the material. To obtain more information about mechanical properties, a hardness test was performed. The hardness test revealed a hard but brittle surface which can be sheared by the frictional force caused by the sliding projectile. The analysis of the gun barrels revealed information about wear mechanisms and damages in medium and severely worn gun barrels. The detected wear mechanism was thermal erosion, chemical erosion, mechanical erosion and sliding wear.
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Traynor, Janice Mae. "The use of fluorescent dye and site characteristics to evaluate surface erosion on harvested areas in the Vernon Forest District, B.C." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26094.
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Surface erosion on forest lands can cause stream sedimentation and reduce site productivity. In the North Okanagan downstream irrigation and municipal demand require low sediment levels in their water. Higher elevation forest lands have shallow soils developed from nutrient-poor glacial till. To evaluate erosion occurrence on forest lands a research project was initiated in the summer of 1984 on 10 sites in mid-elevation, recently harvested cutblocks in the Vernon Forest Region.
The objective of the study was to evaluate surface erosion and relate erosion intensity to site characteristics. Two separate methods were used to accomplish this. Line transects sampled soil disturbance and examined causal factors for erosion occurrence. Fluorescent dye plots, established on four of the 10 sites, examined rate, distance and patterns of downslope soil particle movement.
Transects were surveyed in a grid pattern across the cutblock and results indicated areal distribution of disturbance. Soil disturbance at the sample point was recorded using 10 classes ranging from bare soil and litter disturbance to deep gouges and deep deposits of soil. Assessment of care-in-logging and identification of existing and potential erosion sites completed the site evaluation. Day-Glo fluorescent pigment was used to tag soil in situ. Dye was applied in August, 1984, in one metre strips across the slope on plots varying in aspect, slope and disturbance. Field measurement of soil movement was completed in the spring of 1985, shortly after snowmelt. Tagged particles were located and illuminated at night by ultraviolet light. A hand held mineral lamp provided sufficient illumination and fluorescence was recorded on color film. Soil-movement ratings, based on visual perception of particle movement, were assigned to each plot. These ratings were compared to plot and site characteristics to identify possible erosion trends.
The results of this study support the consensus of research results reported in the literature. The major sites of erosion are skid trails and the road system. Steep slopes, fine' soil, north aspects and compaction increase potential erosion. Fluorescent dye is an effective soil particle tag allowing distance and pathways of movement to be identified. Day-Glo fluorescent pigment in a solution of acetone was fully satisfactory in adherence to the particle and in persistence under prevailing climatic conditions.Forestry, Faculty of
Graduate
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Russo, Joseph Paul. "INVESTIGATION OF SURFACE FINE GRAINED LAMINAE, STREAMBED, AND STREAMBANK PROCESSES USING A WATERSHED SCALE HYDROLOGIC AND SEDIMENT TRANSPORT MODEL." UKnowledge, 2009. http://uknowledge.uky.edu/gradschool_diss/750.
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Sediment transport at the watershed scale in the Bluegrass Region of Kentucky is dominated by surface fine grained laminae, streambed, and streambank erosion; high instream sediment storage; and surface erosion processes. All these processes can be impacted by agricultural, urban, and suburban land-uses as well as hydrologic forcing. Understanding sediment transport processes at the watershed scale is a need for budgeting and controlling sediment pollution, and watershed modeling enables investigation of the cumulative effect of sediment processes and the parameters controlling these processes upon the entire sediment budget for a watershed. Sediment transport is being modeled by coupling the hydrologic model Hydrologic Simulations Program-FORTRAN (HSPF) with an in-house conceptually based hydraulic and sediment transport model. The total yield at the watershed outlet as well as the source fractions from surface fine grained lamina, streambed, and streambank sources; deposition; and biological generation within the streambed are predicted with the sediment transport model. Urbanization scenarios are then run on the calibrated model so as to predict the sediment budget for the South Elkhorn watershed for present and future conditions.
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Castro, Francisco Leite de. "Erodibility of a dike in case of overflowing." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/13984.
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Mestrado em Engenharia CivilEarthen dikes (or earthen levees) are built all over the world, both in coastal (coastal dikes) and inland areas (riverine dikes), to protect population, infrastructures and resources from high water levels due to storm surges and seasonal floods. Most of these flood defence embankments are not prepared to resist to surface soil erosion of its crest and landside slope induced by overflowing events, and hence, maybe at risk of failure. Mitigation of dike damage by overflow may be accomplished by providing erosion protection on the surface of the crest and dike landside slope. Erosion protection can be conferred by a variety of materials (rip-rap, concrete, geosynthetics, etc.) ranging from hard armouring to light armouring alternatives. The present dissertation focuses on strengthening systems consisting of lightweight, flexible, synthetic mats such as (high performance) turf reinforcement mats and geogrids. The goal of this dissertation was to assess their effectiveness as a slope erosion protection system and to obtain some performance criteria under overflow conditions created through full-scale laboratory testing on a hydraulic model. Waterflow discharge, flow thickness and mean (horizontal) velocity measurements were acquired at one location on the landside slope channel (1V:4H) (near the downward edge of the slope). These measurements allowed to estimate shear stress ranges at the bed channel and Manning’s roughness coefficients. Some tentative empirical equations were presented correlating shear stress and flow thickness estimations with overflowing discharges. The results are strictly limited to the tested coarse-grained soil and rolled erosion control products as well as the range of tested hydraulic parameters possible to be attained on the hydraulic model. The experimental study mainly allowed to obtain some qualitative conclusions, in which it was proven that a reinforced surface soil layer with synthetic mats of a dike slope can withstand higher overflowing discharges than bare soil, without catastrophic sediment motion.
Os diques de terra são construídos um pouco por todo o mundo, quer em zonas costeiras (diques costeiros) quer em zonas fluviais (diques fluviais), com o intuito de proteger a população, as infraestruturas e outros recursos de elevados níveis de água provocados por tempestades e cheias sazonais. A grande maioria destes aterros de proteção de cheias não estão preparados para resistir à erosão superficial provocada na sua crista e talude de jusante pelo galgamento da água e respetivo escoamento sobre os mesmos, e como tal, podem estar em risco de rotura. A mitigação dos danos induzidos num dique pelo galgamento pode ser conseguida por via da proteção da camada superficial de solo sobre a crista e talude de jusante. Existe uma enorme variedade de materiais para proteção contra a erosão (enrocamento, betão, geossintéticos, etc.) que podem variar desde soluções mais pesadas e rígidas a soluções mais leves e flexíveis. A presente dissertação foca-se em sistemas de reforço leves, flexíveis e compostos por redes/tapetes poliméricos tais como as mantas/tapetes de reforço (Turf Reinforcement Mats) e geogrelhas (geogrids). O objetivo principal da dissertação consistiu em avaliar a aplicabilidade destes materiais como sistemas de controlo de erosão, e obter dados relativos ao seu desempenho perante uma situação de galgamento/escoamento criada num modelo hidráulico à escala real. Os valores do caudal escoado, as alturas de água e velocidades médias do escoamento foram medidos numa determinada secção do canal (com inclinação 1V:4H) do modelo hidráulico (secção próxima da zona de transição entre o canal inclinado e o canal horizontal). Estas medições permitiram estimar gamas de valores da tensão de corte aplicada na superfície do canal e do coeficiente de rugosidade de Manning. Algumas equações empíricas (de caráter provisório) foram apresentadas, relacionando a tensão de corte e alturas de água com o caudal escoado. Os resultados obtidos são exclusivamente válidos para o material granular e os produtos em rolo para controlo de erosão (Rolled Erosion Control Products) testados, bem como para a gama de parâmetros hidráulicos proporcionados pelo modelo hidráulico. O estudo experimental permitiu obter principalmente conclusões qualitativas, nas quais ficou comprovado que o reforço de uma camada superficial de solo com Rolled Erosion Control Products permite resistir a caudais superiores, em comparação com uma camada de solo simples, sem que se verifique transporte pronunciado de partículas de solo.
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Kokelj, Steve. "The effect of detachment sliding on surface wash erosion in the continuous permafrost zone, Hot Weather Creek, Fosheim Peninsula, Ellesmere Island, N.W.T." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0003/MQ36709.pdf.
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Safwat, Amr M. "Stochastic Multimedia Modelling of Watershed-Scale Microbial Transport in Surface Water." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406880416.
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Moretto, Renata Lima. "Análise dos efeitos da vegetação na proteção de taludes rodoviários e proposição de alternativas de revegetação na BR-386." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/60725.
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Esta dissertação discute o emprego de técnicas de estabilização de taludes rodoviários de corte e aterros utilizando drenagem superficial e vegetação. Os conceitos de aplicação de vegetação no aumento da resistência do solo, diminuição da poro-pressão e diminuição da erosão superficial do terreno são revisados. O trabalho discute a importância da interação solo-vegetação, sua influência em taludes, a importância da matéria orgânica nos solos, a sucessão vegetal com vegetação nativa. Estes conceitos foram utilizados na análise de um trecho da BR386, entre a entrada para a via de acesso a Progresso até Canoas, atualmente em processo de duplicação. A partir da inspeção de campo foram identificados os principais problemas de instabilidade e erosão da obra. Foram coletadas seis amostras de solos de quatro taludes da obra para caracterização e para melhor descrição dos problemas de ruptura superficial e controle de erosão nos cortes e aterros analisados. Os materiais amostrados envolveram duas amostras com característica de argila de alta plasticidade, uma argila de baixa plasticidade, uma areia siltosa não plástica, uma areia argilosa e uma areia argilosa não plástica. Foram analisados os problemas encontrados em campo, em função do tipo de materiais, tendo sido propostas soluções adaptadas a cada caso, principalmente focando problemas referentes à drenagem e a busca de soluções ambientais eficazes e com preservação do caráter paisagístico.This work discusses the use of stabilization techniques for road cuttings and embankments using drainage and vegetation. The concepts of increase soil strength due to vegetation, decrease of the pore pressure and reduction in erosion of the ground surface are reviewed. The work also discusses the importance of soil-vegetation interactions, their influence on slopes, the importance of organic matter in soils and plant succession with native vegetation. These concepts were used in the analysis of a length of the BR386 highway, between the entrance to the access route to Progress up to Canoas, currently in the process of duplication. From the field inspection the main problems of instability and erosion of the works were identified. Six soil samples were collected from four slopes for soil characterization and better description of the superficial instabilities and erosion control in the cuts and embankments analyzed. The materials involved two samples with characteristic of high plasticity clay, low plasticity clay, non plastic silty sand and sand clay not plastic. The problems encountered in the field were analyzed, considering the type of soils involved and proposals of solutions have been made adapted for each case, mainly focusing on drainage and the search for effective environmental solutions which preserve the landscape character.
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Pankau, Ryan C. "CONCENTRATED FLOW PATHS IN RIPARIAN BUFFER ZONES OF SOUTHERN ILLINOIS." OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/212.
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Riparian buffers in agricultural landscapes are designed to trap pollutants in overland flow by slowing, filtering, and infiltrating surface runoff entering the buffer via sheet flow. However, observational evidence suggests that concentrated flow is prevalent from agricultural fields. Also, over time sediment can accumulate in riparian buffers forming berms that restrict sheet flow from moving into the buffers; these berms ultimately back up surface runoff, resulting in an eventual breakthrough which concentrates runoff. Breakthrough by concentrated flow can lead to gully formation that may reduce the filtering capacities of buffer systems by providing direct conduits to stream channels. This study explores the frequency of concentrated flow paths in riparian buffers at both the field and watershed scale. At the field scale, intensive topographic surveys were conducted at 10 field sites in southern Illinois to characterize concentrated flow paths, accumulated berm sediments, and field area drained by concentrated flow. Detailed digital elevation models (DEMs) were created for each site and riparian buffer and agriculture field characteristics were analyzed to assess the development and occurrence of concentrated flow paths. At each site, soil samples were analyzed to characterize sediment deposition patterns within the buffer. To assess the prevalence of concentrated flow paths at the watershed scale, three watersheds in southern Illinois were selected for walking stream surveys. Five stream segments, approximately 1000 m long, were randomly selected within each watershed and surveyed for the occurrence and size of concentrated flow paths. These data were analyzed with respect to riparian buffer vegetation, buffer width, and surrounding land cover data. Concentrated flow paths were identified in all topographic surveys and all walking stream surveys indicating a common occurrence in agricultural watersheds of southern Illinois. Among field scale sites, concentrated flow accounted for 82.5-100% of the drainage areas contributing to riparian buffers. Results from the watershed scale analysis suggest that concentrated flow paths are significantly more abundant in agricultural land cover, than forested land. Current riparian buffer design principles are based on the assumption that sheet flow is the primary form of surface runoff entering buffers. Furthermore, buffers are installed and not maintained which can lead to berm accumulation and buffer failure. Results from this study indicate that concentrated flow was the prevalent form of runoff at field scale sites. Managers need to consider the occurrence of concentrated flow paths when designing riparian buffers to protect stream water quality.
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Santos, Julio Cesar Neves dos. "MensuraÃÃo da erosÃo do solo no semiÃrido em diferentes usos de terras e escalas espaciais." Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=7299.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoA obtenÃÃo de dados de erosÃo do solo em diferentes escalas espaciais à de fundamental importÃncia, principalmente no semiÃrido do Nordeste brasileiro onde esses dados sÃo escassos. O semiÃrido brasileiro à vulnerÃvel à erosÃo hÃdrica, principalmente devido Ãs suas caracterÃsticas climÃticas, edÃficas e Ãs prÃticas de exploraÃÃes insustentÃveis, resultando no empobrecimento dos solos agrÃcolas e comprometendo a qualidade das Ãguas dos reservatÃrios superficiais (principais reservas hÃdricas da regiÃo). Nesse sentido, o presente estudo objetivou gerar dados bÃsicos de escoamento, produÃÃo de sedimento e analisar os principais processos e fontes de variaÃÃo na perda de solo em diferentes escalas espaciais em regiÃo semiÃrida, bem como os processos naturais atuantes em cada escala, e os efeitos do uso do solo na conservaÃÃo do meio. A Ãrea de estudo està localizada no semiÃrido cearense, na bacia hidrogrÃfica do Alto Jaguaribe no municÃpio de Iguatu, no Centro Sul do Estado do CearÃ. Os estudos de erosÃo e escoamento superficial foram conduzidos em trÃs nÃveis de escala: microbacias com Ãreas em torno de 1 a 3 ha, parcelas de erosÃo de 20 m2 e parcelas de 1 m2, todas sob condiÃÃes de chuvas naturais. Ao todo, foram instaladas quatro microbacias experimentais, seis parcelas de erosÃo de 20 m2 e seis parcelas de 1 m2, sob diferentes usos do solo; Caatinga nativa; Caatinga raleada; desmatamento seguido de enleiramento e cultivo de milho; e desmatamento, queima com cultivo de pastagem. O estudo ocorreu durante os anos de 2009, 2010 e 2011, com chuvas concentradas de janeiro a junho, correspondendo à estaÃÃo chuvosa da regiÃo. As coletas para quantificaÃÃo do volume escoado superficialmente e de amostras para determinaÃÃo da perda de sedimentos foram realizadas a cada evento de chuva erosiva, no acumulado de 24 horas. Ocorreram maiores coeficientes de escoamento e perdas de solo na escala de 20 m que nas escalas de 1 m e de microbacia: em relaÃÃo à escala de 1 mÂ, a parcela de 20 m provoca um aumento da velocidade de escoamento ao longo da vertente, aumentando tambÃm a capacidade de transporte; na escala de microbacia, a presenÃa de Ãreas com baixas declividades atuaram como zonas receptoras de sedimentos. Na Ãrea com cobertura de Caatinga Nativa, a presenÃa de pontos de alta erodibilidade e com solo nu, na escala de microbacia, à responsÃvel pela maior parte das perdas de solo, fato que nÃo pode ser representado na pequena escala de parcela. Jà a Ãrea que recebeu o tratamento de raleamento, apresentou na escala de microbacia menor coeficiente de escoamento superficial e menores perdas de solo em relaÃÃo à Ãrea Caatinga Nativa. O manejo de desmatamento e enleiramento dos restos vegetais e cultivo de milho, proporcionou incremento no coeficiente de escoamento superficial e nas perdas de solo em relaÃÃo ao perÃodo anterior, com cobertura de Caatinga nativa. O tratamento de desmatamento, queimada e cultivo de pastagem (Andropogon gayanus Kunt), resultou nas maiores perdas de solo e Ãgua em relaÃÃo aos demais manejos estudados.
Obtaining data of soil erosion on different spatial scales is of fundamental importance, especially in the semi-arid regions of northeastern Brazil where such data are scarce. The semi-arid region is vulnerable to water erosion, mainly due to its climatic and edaphic characteristics, and the unsustainable land use practices, which result in the impoverishment of agricultural soils, and compromise the water quality of the surface reservoirs (the main water resources of the region). The main goal of this study was generate basic data flow, sediment yield and analyze the main process and sources of variation in soil loss at different scales in semi-arid region. It analyzed the natural process that is operating in each one scale and the land use effects in the conservation of the environment. The study area is located in the semi-arid region of the state of CearÃ, in the watershed of the Upper Jaguaribe in the Iguatu County, in the south central area of the state. Studies of erosion and surface runoff were conducted on three scale levels: watersheds with areas of around 1 to 3 ha, erosion plots of 20 m2, and plots of 1 m2, all under natural-rainfall conditions. In all, four experimental watersheds were installed together with six erosion plots of 20 m2 and six plots of 1m2 with different types of land use; native Caatinga; thinned Caatinga; deforestation followed by bunching and the cultivation of corn, and deforestation, burning and the cultivation of pasture. The study was carried out from 2009 to 2011, with rainfall concentrated in the months of January to June, corresponding to the rainy season in the region. Samples to quantify the volume of surface runoff, and samples to determine sediment loss, were taken for each erosive-rain event in an accumulated period of 24 hours. There were higher runoff coefficients and soil losses on the 20 m2 scale than on the 1 m2 and watershed scales: on the scale of 1 mÂ, the plot of 20 m causes an increase in flow velocity down slopes, also increasing transport capacity; on the scale of the watershed, places with low slopes acted as receiving areas for sediment. In the area with native Caatinga vegetation, the presence of points of high erodibility and of bare soil, on the watershed scale, is responsible for most of the soil loss, a fact that is not present on the small scale of the plots. The area which was thinned out, however, presented a lower runoff coefficient and less soil-loss on the watershed scale, in relation to the area of native Caatinga. After deforestation, bunching of the plant remains, and planting of corn, an increase in the runoff coefficient and soil loss can be seen in relation to the previous period with a coverage of native Caatinga. The treatment of deforestation, burning and the cultivation of pasture (Andropogon gayanus Kunt) resulted in the greatest soil and water losses in relation to the other management strategies studied.
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Lira, Daniely Lidiany Costa. "Assoreamento em densas redes de reservatÃrios: o caso da bacia hidrogrÃfica da barragem Pereira de Miranda, Ce." Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=8835.
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FundaÃÃo de Amparo à Pesquisa do Estado do CearÃO presente estudo tem como objetivo analisar os impactos da densa rede de reservatÃrios da bacia hidrogrÃfica do aÃude Pereira de Miranda (Pentecoste) na produÃÃo de sedimentos e capacidade de armazenamento hÃdrica do sistema. A bacia estudada localiza-se no Nordeste Brasileiro, no Estado do CearÃ, com uma Ãrea de aproximadamente 3.230 km2. Possui uma precipitaÃÃo mÃdia anual de 854 mm e evaporaÃÃo potencial mÃdia observada em tanque do tipo classe A à de 1.464 mm. O solo e a vegetaÃÃo predominante sÃo do tipo luvissolo e caatinga arbustiva aberta. Imagens de satÃlite de anos Ãmidos foram utilizadas para levantamento da aÃudagem na bacia. Foram identificadas unidades de erosÃo derivadas da sobreposiÃÃo de mapas dos parÃmetros da EquaÃÃo Universal de Perdas do Solo (EUPS), o que permitiu a estimativa da erosÃo localizada na bacia e identificaÃÃo de Ãreas potencialmente produtoras de sedimento. Um modelo simplificado foi utilizado para simular a propagaÃÃo de sedimentos pela densa rede de reservatÃrios da bacia. Para estimativa do assoreamento no reservatÃrio Pereira de Miranda, diferentes cenÃrios de estrutura do sistema foram considerados. Foi estimada uma taxa de erosÃo mÃdia na bacia de 59 t.ha-1.ano-1, sendo que 42% da Ãrea da bacia apresenta grau de erosÃo moderado. De acordo com o modelo, o assoreamento do reservatÃrio Pentecoste pode variar de 1,1 a 2,6% por dÃcada, dependendo do cenÃrio considerado. Observa-se ainda que os reservatÃrios de montante podem reter atà 58% do sedimento que chegaria ao aÃude Pereira de Miranda. Os reservatÃrios muito pequenos, com capacidade de atà 100.000 mÂ, embora representem apenas 1,83% da disponibilidade hÃdrica do sistema, sÃo capazes de reter quase 8% do total de sedimento produzido. AnÃlises de sensibilidade mostram que a capacidade de retenÃÃo de sedimentos nos reservatÃrios de montante pode variar de 20 a 58%, dependendo da estrutura do sistema quanto à existÃncia de reservatÃrios de diferentes classes de tamanho. Constata-se ainda que a taxa de reduÃÃo da capacidade de armazenamento hÃdrica do sistema em funÃÃo do assoreamento dos reservatÃrios de montante à relativamente maior do que a observada para o aÃude Pereira de Miranda, devido à retenÃÃo de sedimentos a montante.
The present study aims at analyzing the impacts of the dense reservoir network of the Pereira de Miranda catchment in its sediment yield and water storage capacity of the system. The studied area is located in the Brazilian Semiarid region, in the State of CearÃ, with an area of approximately 3230 km2. It has an average annual rainfall of 854 mm and an annual potential evaporation of 1464 mm. The predominant soil and vegetation type are luvissolo and open shrub caatinga. Satellite imageries from wet years were used to identify the reservoirs of the catchment. Erosion units were identified derived from map overlay of the parameters of the Universal Soil Loss Equation (USLE), which enables the estimation of sediment yield and the identification of areas with high sediment production. A simplified model was used to simulate the sediment routing through the dense reservoir network of the basin. For the estimation of sedimentation at the Pereira de Miranda Reservoir, different scenarios of the system structure were considered. A mean erosion rate of 59 t.ha-1.year-1 was estimated for the basin, in which 42% of the basin area presents a moderate degree of erosion. According to the model, silting of the Pereira de Miranda reservoir may vary from 1.1 to 2.6 %.decade-1, depending on the scenario considered. One may observe that upstream reservoirs are able to retain until 58% of the sediments that would reach the Pereira de Miranda reservoir. The very small reservoirs, with storage capacity below 100,000 mÂ, are able to retain almost 8% of the generated sediments, although they represent just 1.83% of the system water storage capacity. Sensitivity analysis shows that the sediment retention capacity of the upstream reservoirs may vary from 20 to 58%, depending on the system structure concerning the presence of upstream reservoirs from different size classes. One may still conclude that the reduction rate of water storage capacity at the system as a function of reservoir siltation is relatively larger then that observed for the Pereira de Miranda reservoir, due to the upstream sediment retention.
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Amory, Charles. "Érosion éolienne et rugosité de la surface neigeuse en Terre Adélie : observations et approche numérique." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAU007/document.
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Le bilan de masse en surface de l’Antarctique (noté BMS ; résultante de l’équilibre entres les termes d’accumulation et d’ablation) contribue directement aux variations du niveau moyen des mers. Dans le contexte du changement climatique, sa détermination par les modèles atmosphériques est nécessaire pour affiner son estimation présente et future.Les vents violents en périphérie de l’Antarctique de l’Est sont responsables d’un entraînement aérodynamique de la neige en surface qui influence de façon significative le BMS. Le transport de neige par le vent est également à l’origine du développement de formes d’érosion éolienne orientées parallèlement au vent moyen au moment de leur formation et dont la distribution spatiale est un déterminant majeur de la rugosité de surface. Ces éléments de rugosité exercent en retour un effet d’obstacle à l’écoulement qui affecte directement le champ de vent en surface et, par extension, le transport éolien de la neige.Les travaux présentés dans cette thèse portent sur l’observation et la modélisation numérique de l’érosion éolienne de la neige au niveau d’une région côtière de l’Antarctique de l’Est, la Terre Adélie. Dans un premier temps, le modèle atmosphérique régional MAR, qui contient une représentation détaillée des processus de transport éolien, est mis en œuvre à une résolution spatiale de 5 km sur un domaine couvrant la Terre Adélie et comparé sur un mois d’été à des observations météorologiques incluant des mesures continues du vent et du flux éolien massique de neige aérotransportée. Il est montré que les flux éoliens de neige produits par le MAR sont hautement sensibles à la paramétrisation de la rugosité de surface, et qu’une calibration unique de ce paramètre ne permet pas de simuler avec une qualité équivalente le champ de vent en deux points de mesure distants d’à peine 100 km. À partir des observations, les interactions rugosité-érosion sont ensuite étudiées à l’échelle d’évènements individuels d’érosion éolienne. Il est mis en évidence i) que l’effet d’obstacle généré par les formes d’érosion éolienne a un impact inhibiteur sur le flux éolien de neige et ii) que cet effet d’obstacle peut être fortement diminué par l’aptitude des formes d’érosion éolienne à se réorienter parallèlement au vent dominant pendant un événement de transport. L’examen des observations sur une année révèle que ce processus d’ajustement aérodynamique est sujet à des variations temporelles majoritairement reliées à l’historique de la température. Enfin, on montre qu’une reconfiguration du modèle comprenant notamment l’introduction d’une dépendance à la température dans la paramétrisation de la rugosité de surface améliore considérablement la représentation des flux éoliens de neige par le MAR sur l’année considérée. Ces résultats suggèrent qu’une distribution spatiale et temporelle de la rugosité de surface doit être prise en compte dans les modèles atmosphériques pour une simulation réaliste du transport éolien de la neige à l’échelle de l’AntarctiqueThe Antarctic ice sheet surface mass balance (SMB; the result of the balance between accumulation and ablation terms) has a direct influence on variations in the global mean sea level. In the context of climate change, atmospheric models are needed to improve its current and future estimation.Intense surface winds over the coastal slopes of East Antarctica are responsible for aerodynamic entrainment of snow at the surface, which has a significant influence on the BMS. Transport of snow by the wind also produces aeolian erosion features aligned parallel to the prevailing winds at the time of their formation. The spatial distribution of these features is a major determinant of surface roughness. On the other hand, surface roughness is an obstacle to flow and directly affects the surface wind field and, by extension, aeolian snow transport.The work presented here is based on observations and numerical modeling of aeolian snow erosion in a coastal stretch of Adélie Land, East Antarctica. First, the regional atmospheric model MAR, which includes a detailed representation of aeolian transport processes, was run at a spatial resolution of 5 km over a zone including Adélie Land and model results were compared with meteorological observations made over one month in summer, including continuous measurements of the wind and the aeolian snow mass flux. Aeolian snow mass fluxes modeled by MAR were highly sensitive to parameterization of surface roughness, and a single calibration of this parameter was not enough to simulate the surface wind field at two measurement points located only 100 km apart with the same accuracy. Consequently, roughness-erosion interactions were analyzed at the scale of individual aeolian erosion events using observations. The results of this analysis underlined that (i) the barrier effect generated by aeolian erosion features had an inhibiting impact on the aeolian snow mass flux and (ii) that the barrier effect can be strongly reduced by the ability of aeolian erosion features to realign with the dominant wind during a transport event. Examination of observations made over a period of one year revealed that this adjustment process is prone to temporal variations mainly linked to past temperatures. Finally, we showed that reconfiguring the model, including introducing temperature dependence in the parameterization of surface roughness considerably improved the representation of aeolian snow mass fluxes by the MAR model for the year concerned. These results suggest that spatial and temporal distribution of surface roughness should be included in atmospheric models for realistic simulations of aeolian snow transport over Antarctica
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Kokelj, Steven V. "The effect of detachment sliding on surface wash erosion in the continuous permafrost zone, Hot Weather Creek, Fosheim Peninsula, Ellesmere Island, Northwest Territories." Thesis, University of Ottawa (Canada), 1998. http://hdl.handle.net/10393/4070.
Full textAbstract:
An experimental design was developed to evaluate the effect of active-layer detachment sliding on surface wash erosion. Specifically, the aim was to examine to what extent the disturbance of vegetation cover, changes in hydrological conditions due to topographic modification by detachment sliding and the formation of a fresh active layer affect rates of surface wash erosion. Detachment slides generally accumulated more snow than adjacent slopes and yielded greater amounts of surface runoff than vegetated slopes with similar snow covers. Surface drainage was inhibited on well-vegetated hummocky slopes where lags between radiation inputs and discharge responses were greater than at the rilled detachment slide plots. During rainfall events following snowmelt, plot response was affected by antecedent moisture conditions and the vegetation cover: surface flow was generated only in detachment slide scars and at the mixed plots but not on vegetated undisturbed slopes or on the bare undisturbed slope. Suspended sediment concentrations at the fresh detachment slide scars are two orders of magnitude greater than on vegetated slopes. Greater amounts of surface runoff production at fresh scars and the removal of vegetation result in high rates of surface erosion and high sediment yields (1560 g/m$\sp2)$ at fresh detachment slide scars. (Abstract shortened by UMI.)