Дисертації з теми "CHANNEL SLOPE"

Tailings (mining waste) disposal is a significant consideration for the mining industry, with the majority of the ore processed in most mining operations ending up as tailings. This creates large volumes of tailings, which must be handled and stored responsibly to avoid potential environmental catastrophes. The most common form of tailings storage facility is the impoundment, where tailings are contained within a basin, with beaches forming around the perimeter of the impoundment and a pond standing in the middle. A relatively new method of tailings storage is to create a 'stack', whereby the tailings solids form a large heap, with the discharge of tailings slurry from the apex of the heap. It is of significant value for mine operators and tailings engineers to be able to predict the shape of the beach that forms in either of these disposal scenarios. The key to being able to do this relies on a method of prediction of the beach slope. The aim of this work is to develop a method of tailings beach slope prediction for tailings slurries that are sub-aerially discharged from a pipe. In this thesis a literature review is undertaken, investigating existing methods for the prediction of tailings beach slopes. These methods are validated against relevant industrial and experimental data. Two separate phases of experimental work have taken place in an effort to investigate tailings deposition behaviour, one at mine sites and the other in a laboratory on a small scale. Three new tailings beach slope prediction models are presented; a simple empirical model enabling quick approximate predictions; an a priori tailings beach slope prediction model based on existing theories of open channel flow, sediment transport and rheology, which is more powerful due to the greater degree of theory in its foundation; and a new semi-empirical model that shares some of the theoretical aspects of the a priori model but offers better predictions due to its empirical calibration to the experimental data. The experimental results, along with 3 other independently collected sets of relevant industrial and experimental data, are used to validate the beach slope prediction models found in the literature, as well as the new beach slope models presented in this thesis. Statistical evaluation of the performance of all of these models is presented to enable comparison. Finally, a new beach shape model is presented for the three dimensional geometric forecasting of the beach surface of a tailings stack. Historic tailings discharge data is run through the beach shape model, and the shapes predicted by the model are compared with aerial survey data of a real tailings stack for validation of the shape model. This work not only presents a new method of tailings stack shape prediction, but also a plausible theory for explaining the concavity of tailings beaches. The stack shape model also has the potential to be developed further for the three dimensional modelling of tailings beaches formed in other types of storage facilities, such as impoundments or valleys.

Submarine channel-levee architecture is a result of interaction between turbiditic flows and the bathymetry that they encounter on the slope and that they themselves construct. However, the spatio-temporal evolution of channellevee systems, i.e., their manner of spatial accretion is not fully understood. In addition, the controls on the patterns of channel distribution and stacking remain relatively poorly understood. The results presented in this thesis are based on the interpretation of a 3D seismic survey located in water depths of about 1000 to 2000 m on the upper slope of the Amazon Fan. The analysis of the data includes two different approaches: on a larger scale, the interpretation of the tectono-stratigraphic analysis of the data; and on a smaller scale, the characterization of the evolution of the channel-levee systems and associated deposits. The methods of analysis used included the mapping of significant horizons and the extraction of sequences horizon slices across the channel-levee systems. The horizon slices allowed visualisation of the vertical distribution of the channel-levee elements and interpretation of their evolution. The seismic data can be divided in two main packages, separated by an unconformity. The pre-unconformity package is characterized by a predominant sub-parallel seismic facies (characterized by continuous, homogeneous and sub-parallel reflections), and is strongly folded and faulted due to gravity tectonics. In this interval, no channel-levee systems were identified, but canyonlike channels with dimensions as large as 2600 m wide and 220 m deep were observed. Conversely, the post-unconformity package comprises a heterogeneous arrangement of seismic facies, and is less strongly deformed. Three upslope-stacked channel-levee systems of Middle Pleistocene age can be distinguished in this interval. Each channel disperses obliquely down the slope, resulting in levee size asymmetry, with the downslope levee being of greatest size. The upslope stacking of channel-levee systems results from a sequence of avulsions on the upslope levees. Bathymetric influence of the older channel levee system is interpreted to dictate the slope-oblique orientation of the new channel. Two main architectural styles were identified, each one associated with different models of spatia-temporal development of channel-levees. A pattern of upstream accretion of the aggradational (channel-levee) component of the channel is associated with the channel narrowing and becoming more sinuous upward. This style is characterized by an onlapping pattern of channel and levee reflections. Downstream accretion of channel-levee is associated with a trend of channel widening and becoming less sinuous upwards. This style is characterized by a downlap pattern of the channel and levee reflections. Each style is related to different evolutionary histories of the turbidite flows and thalweg configuration in relation to the equilibrium profile. Three styles of channel distribution on slope can be distinguished: structurally controlled erosive channels, aggradational channels obliquely oriented to the slope and agradationally confined channels that are vertically stacked. The pre-unconformity erosive channels are diverted and possibly owe their erosive character to active anticlines that kept the paleo-slope above the equilibrium profile. The oblique direction of each channel in the postunconformity interval was inherited from the previous one in a sequence of upslope stacking after systematic avulsion through the left-hand levee. The vertical stacking of channel-levee elements is due to the confinement of the channel between the outsize downslope levee and an upslope anticline which inhibited avulsion in the area. It is probable that each stacked channel-levee element corresponds to a downstream channel avulsion. This study provided important information about the architecture and distribution of channels on the upper-slope of submarine fans subject to gravitational tectonics. Therefore, it can be used as an analogue and help the prediction of sand prone areas in other submarine fans which are not so well imaged.

Chirp-Slope Keying (CSK) is a new and innovative digital modulation scheme for underwater data transmission. The underwater environment brings up several challenges to the manufacturing and operation of communication systems. This thesis shows through analysis and simulations the effectiveness of Chirp-Slope Keying (CSK) in providing a satisfying performance in underwater communication. The experiment consists of modulating a chirp slope by binary numbers (representing our data). '0' is represented by a linear- down chirp and '1' is represented by a linear-up chirp. The received data is first processed by a correlator receiver. Then, the detection of either binary symbol is obtained by the comparison to a threshold. Simulation results for numerous signal-to-noise ratios show that CSK provides satisfying performance for underwater data transmission. The Mississippi gulf coast shallow water Data collected from the National Oceanic and Atmospheric Administration (NOAA), (see appendix), allow us to accurately generate a laboratory model for the channel of interest.

Slope channel systems represent significant but highly variable deep-water stratigraphic features and reservoir targets. Variations in architecture and component facies can take place along strike, depositional dip and stratigraphically. A better understanding of these variations permits improved sedimentological and architectural models. By integrating two outcrops (San Clemente, California and Baja California, Mexico) and one subsurface example (offshore Nile Delta), this study provides an opportunity to investigate cross-channel asymmetry, stratigraphic evolution and variability, vertical facies trends, and controls of slope channel systems. This study demonstrates that cross-channel asymmetry in facies and architecture is a lithology- and scale-independent feature, and preferentially occurs at channel bends and in the upper part of slope channel systems. Facies and architectural asymmetry are generally expressed as amalgamated, coarser-grained deposits displaced to the steeper channel edge (outer bend), and finer-grained deposits dominate towards the gentler channel edge (inner bend). A comparison of the systems exposed in Mexico and buried in the subsurface reveals a similar evolutionary trend, from initial sediment erosion/bypass, through early-stage laterally amalgamated channels, late-stage sinuous channels with levees/terraces, and final abandonment. However, pronounced variations exist in the late stage (e.g., presence or absence of lobes), and abandonment stage (e.g., presence or absence of MTDs plugging and channel avulsion). Additionally, for the first time, this study quantitatively demonstrates that early-stage and late-stage architectural elements are characterized by distinct patterns in preferred vertical facies transitions, based on Markov chain analysis of vertical successions. This study also suggests that both extrabasinal factors (e.g., relative sea-level) induced flow energy cycles and intrabasinal factors (e.g., folding and faulting, MTDs, channel bends) can exert a significant control on the architecture and/or evolution of slope channel systems.

The Isaac Formation in the Neoproterozoic Windermere Supergroup crops out in the Castle Creek South area (southwestern Canadian Cordillera) and consists of a more than 1.2 km-thick, laterally continuous slope deposit formed along the ancestral passive margin of western North America. Within the study area, six channel complex sets have been recognized, of which two, named informally Channels 1 and 3, are the focus of this study. Channel 1 exposes an oblique section of base-of-slope channel deposits, whereas Channel 3, at least in its lower part, is a flow-transverse section. Channels 1 and 3 are 200-300 m thick and laterally extend over 1.1 km, and were initiated following two major falls of relative sea level. Detailed relationships between the intrachannel facies, architecture and geometry within both complex sets indicates that each comprises several vertically-stacked channel complexes that locally are separated by thin-bedded, mudstone-dominated turbidites interpreted to represent channel-abandonment deposits. Each channel complex consists of several channel units, which, in turn, are composed of multiple channel fills. Channel fills are up to 30 m thick and show different infill geometries (amalgamated, semi-amalgamated or layered, non-amalgamated and accretionary), exhibiting systematic lateral changes in fill from channel axis to channel margin. Multistory and multilateral fills in Channels 1 and 3 record a complex repetitive history of channel incision/bypass, aggradation, deactivation, migration and reincision. These erosional and depositional episodes are the result of changes in the equilibrium channel profile, flow parameters, and/or eustatic fluctuations.

Technological development and increased availability of remotely operated vehicles and manned submersibles have significantly increased accessibility to deep environments revealing the presence of rich and diverse macrobenthic assemblages dominated by suspension feeders. These assemblages have been largely exposed to the impacts of fishing activities (especially bottom trawling) in the Mediterranean Sea. Consequently, it is currently urgent to increase knowledge on their distribution, as well as on the ecology and biology of the main species that constitute these macrobenthic assemblages in order to implement effective management and conservation measures. This thesis addressed the characterization of macrobenthic assemblages in the continental shelf and upper slope (40-360 m depth) of the Menorca Channel through a multidisciplinary approach at different ecological levels. Six macrobenthic assemblages mainly segregated by substrate and depth. Hard substrates hosted sponge grounds and coral gardens, whereas crinoid and brachiopod beds occurred on soft sediments. Highest diversity values were found in the shelf edge, probably as a consequence of the bottom heterogeneity and the constant hydrodynamic conditions. Gorgonians were one of the most important and diverse bioengineering organisms in the Menorca Channel, forming dense assemblages that extended over vast areas. Gorgonian assemblages on the continental shelf and upper slope were mostly monospecific, whereas shelf edge assemblages were highly multispecific. Small colonies were dominant throughout the studied bathymetric range, but in deeper environments intermediate and large colonies were more abundant. The good preservation state of most of the observed benthic assemblages and gorgonian populations is probably related to the low pressure of bottom trawling which is mostly concentrated in deeper areas of the continental slope. Paramuricea macrospina is the most abundant gorgonian species in the Menorca Channel. Throughout its distribution, three different chromatic forms were observed. Two forms occurred on the continental shelf, and a third occurred on the shelf edge. Colony shape, sclerite size and shape, and the genetic variability of mitochondrial markers were compared to elucidate if these chromatic forms represented different taxonomic units. Colony morphology barely changed among the three forms resulting as a high conservative character. Conversely, sclerite size and shape significantly differed amongst the three forms, possibly conditioned by genetic and environmental factors. However, no significant differences were observed in the studied mitochondrial markers. The reproductive cycle, energy storage and metabolic requirements of P. macrospina showed significant differences compared to Mediterranean coastal gorgonians. Its reproductive cycle was delayed 2¿3 months respect to shallow species, possibly following the late summer increase in seawater temperature occurring on the Mediterranean continental shelf. Moreover, internal brooding in P. macrospina contrasts with surface brooding in the congeneric Paramuricea clavata. Lipid content was lower and more constant in P.macrospina than in shallow species, and d13C and d15N composition showed almost no seasonal variation, suggesting that food availability in the continental shelf is lower but more constant than in shallower environments. The high oligotrophic conditions of the Balearic Sea apparently contrasts with the high abundance and diversity of active and passive suspension feeders observed in the Menorca Channel. Indeed, the downward particle fluxes quantified during two consecutive years in the Menorca Canyon were comparatively low within the Mediterranean context, reflecting the oligotrophic nature of the study area and the lack of continental inputs of particulate matter. Hydrodynamic settings and resuspenion appear to control TMF.
Les millores tecnològiques i la major disponibilitat de vehicles operats remotament i submains tripulats han incrementat l'accessibilitat a entorns profunds, revelant la presència associacions d'organismes bentòniques riques i diverses, dominades per suspensívors. Aquestes agregacions han estat altament impactades per la pesca al Mediterrani. És urgent incrementar el coneixement, sobre la distribució d'aquestes associacions i aspectes claus de la biologia i ecologia de les principals espècies que les constitueixen per tal d'establir mesures de conservació efectives. En aquesta tesi es caracteritzen les associacions bentòniques de la plataforma i talús continentals del Canal de Menorca a través d'una aproximació multidisciplinària a diferents nivells ecològics. S'han identificat sis associacions bentòniques diferents, que es diferencien principalment pel tipus de substrat i el rang batimètric. En els substrats durs s'hi ha trobat fons d'esponges i coralls, en els fons tous s'hi han trobat camps de crinoïdeus i braquiòpodes. Al marge continental s'hi concentren la diversitat més elevada, probablement resultant de l'heterogeneïtat ambiental i l'hidrodinamisme d'aquest entorn. Al Canal de Menorca les gorgònies són un dels organismes bioenginyers més importants i diversos, formant denses agregacions sobre amplies zones. Les agregacions de gorgònies a la plataforma i part superior del talús eren principalment monoespecífiques, mentre que les del marge continental eren multiespecífiques. Les colònies petites eren les més abundants al llarg de tot el rang batimètric. Tot i així, en entorns profunds les colònies mitjanes i grans incrementaven la seva abundància. El bon estat de les associacions bentòniques i les poblacions de gorgònies probablement resulta de la baixa pressió del ròssec, que es concentra a major fondària. Paramuricea macrospina és la gorgònia més abundant del Canal de Menorca. Al llarg de la seva distribució batimètrica es varen observar tres variants cromàtiques diferents. Dues es varen trobar a la plataforma i una tercera es trobà al marge continental. Per tal d'esbrinar si les diferents variants eren unitats taxonòmiques diferents s'han estudiat la forma colonial, la variabilitat de tamany i formes dels esclerits així com la variabilitat en marcadors mitocondrials. Es va detectar molt poca variabilitat en la morfologia colonial de les tres variants, suggerint que és un caràcter conservatiu. El tamany i la morfologia dels esclerits diferia significativament entre les tres variants, suggerint que estan influenciats per factors ambientals i genètics. No es varen trobar diferències entre els tres marcadors mitocondrials. S'ha avaluat el cicle reproductor, l'acúmul energètic i les necessitats metabòlics de P. macrospina. El cicle reproductiu d'aquesta espècia està retardat respecte les espècies de gorgònia mediterrànies somes. Aquesta situació podria sorgir de l'augment tardà de la temperatura de l'aigua a la plataforma continental mediterrània. El fet que P. macrospina sigui una internal brooder contrasta amb que Paramuricea clavata sigui una surface brooder. El contingut lipídic de P. macrospina és més baix però més constant que el d'espècies somes mediterrànies. D'altra banda la composició de la d13C i la d15N gairebé nos presentaven fluctuacions estacionals. Suggerint que la disponibilitat d'aliment a la plataforma és més baixa però més constant que en entorns somers. Al marge sud del Canal de Menorca hi trobem el Canyó de Menorca. Tot i l'elevada oligotròfia del mar Balear, les associacions d'organismes bentònics a la capçalera del canyó i proximitats són d'una elevada riquesa. S'ha avaluat el flux de partícules durant dos anys consecutius al canyó. Els fluxos recollits eren comparativament inferiors que els registrats en d'altres canyons mediterranis, reflectint la manca d'aportacions continentals. Els processos, de resuspensió i diferents paràmetres hidrodinàmics, semblen controlar el TMF.

Simulation models based on the elliptic mild or steep slope wave equation are frequently used to estimate wave properties needed for the engineering calculations of harbors. To increase the practical applicability of such models, a method is developed to include the effects of rubble mound structures that may be present along the sides of entrance channels into harbors. The results of this method are found to match those of other mathematical models (i.e. parabolic approximation & three-dimensional solution) under appropriate conditions, but they also deviate from results of parabolic approximations in some cases because dissipation can create angular scattering. Comparison with hydraulic model data also shows that this approach is useful for designing pocket wave absorbers that are used to reduce wave heights in entrance channels.

The building blocks of a sedimentary system are essential inputs into studies of reservoir character and comparisons with other sedimentary systems. Yet, our current knowledge of the building blocks of deep water slope channel deposits is still largely speculative. A quantitative approach has been utilised in order to analyse a host of lithological data and objectively identify these sedimentary components. The laterally-extensive and gently-dipping continental slope deposits of the San Fernando Channel System, Baja California, provide the required control on sub-seismic-scale temporal and lateral variations of lithofacies and 3D architecture. High resolution photo-panoramas (with better than 2mm accuracy) of the prominent conglomeratic component of the succession were collected from various key parts of the outcrop. Image analysis of segments extracted from the photo-panoramas generates key parameters for comparison of texture and fabric of conglomerates, such as clast to matrix ratio, major axis length and relative orientation. Statistical analysis of these data enabled the erection of an objective lithofacies scheme for the gravel fraction, the grouping of lithofacies into objectively-defined assemblages, and the establishment of models for the lateral and stratigraphic distributions of these assemblages. 12 lithofacies were objectively identified through hierarchical cluster analysis of 4 quantitative lithological parameters. Statistical analyses indicate significant differences in diversity in the lithofacies assemblages between the early and later parts (termed Stage 1 and Stage 2) of a channel complex set (sensu Sprague, et al., 2002), and to a lesser extent between marginal and axial parts of the system. These can be related to spatial differences and temporal changes in the nature of the turbidity currents flowing through the channel system. Gravelly units become more organised and less diverse with time in one CCS, and each successive CCS more organised at earlier stratigraphic levels than the next, except for the last CCS which is interpreted as influenced by a tectonic paroxysm. These seemingly autocyclic changes in organisation are interpreted as process-responses to changes in equilibrium profile as the nature of confinement changes with the infilling of an initial erosional confinement, to confinement by a master levee and gradual infilling through the evolution of each CCS.

At the Castle Creek study area in east-central British Columbia a well-exposed section about 450 m wide and 30 m thick in the (Neoproterozoic) Isaac Formation was analyzed to document vertical and lateral changes in a succession of distinctively heterolithic strata. Strata are interpreted to have been deposited on a deep-marine levee that was sandwiched between its genetically related channel on one side and an erosional escarpment sculpted by an older (underlying) channel on the other. Flows that overspilled the channel (incident flow) eventually encountered the escarpment, which then set up a return flow oriented more or less opposite to the incident (from the channel) flow. This created an area of complex flow that became manifested in the sedimentary record as a highly tabular succession of intricately interstratified sand and mud overlain by an anomalously thick, plane-parallel interlaminated sand-mud unit capped finally by a claystone.

Continental slope channels, which serve as the primary conduits for sediment transport into the deep marine, occasionally become sites of sediment deposition with excellent reservoir potential. Increasingly reported in the literature are subsurface channel fills exhibiting shingled seismic reflectors that are interpreted to have formed by lateral channel migration. In lower Isaac Formation channels inclined strata are observed but at a lateral scale that is far below industry-seismic detection. Distinctively these flat-based channels are filled with coarse-grained sandstone that transitions abruptly and obliquely upwards into thin, fine grained turbidites. Like rivers, lateral accretion in Isaac channels is interpreted to be the result of the interaction of inertial and pressure forces, but in highly turbulent, highly density-stratified turbidity currents. This resulted in the formation of two superimposed secondary circulation cells that caused enhanced erosion on the outer bank and preferential deposition of coarse-grained sediment along the inner bank.

Deep-water strata of the Neoproterozoic Kaza Group and Isaac Formation (Cariboo Group) in the southern Canadian Cordillera (B.C.) were deposited in a passive-margin basin during the break-up of supercontinent Rodinia. At the Castle Creek and Mount Quanstrom study areas, a remarkably continuous stratigraphic interval throughout these units preserves a record of basin-floor overlain by strata deposited in the lowermost part of the slope. Although similar stratal intervals have been described from ancient and modern deep-marine settings, they still remain poorly understood. Three main stratal units are recognized within the study areas. The lower unit consists of three channel-lobe systems formed in the basin floor to slope transition. Uniquely, siliciclastic-dominated strata here consist of a variety of small- and few large-scale scour elements, indicating transport bypass along the channel-lobe transition zone, in addition to detached or attached depositional lobes composed mostly of distributary channels, fine-grained deposits, and uncommon splays, and a rare slope leveed channel complex. The middle unit is a siliciclastic-dominated succession of stacked, km-scale mass-transport deposits (i.e. debrites and slides), which indicates the more frequent emplacement of increasingly larger mass failures on a prograding slope, and are overlain by fine-grained, splay deposits that are successively overlain by channel, ponded and fine-grained deposits. In contrast, the upper unit is a mixed siliciclastic-carbonate slope succession of the first Isaac carbonate, a regional marker horizon that comprises mostly carbonate-rich and siliciclastic-rich fine-grained strata intercalated with channel and gully complexes that are mostly filled with coarser-grained strata. Abrupt changes in facies trends, stratal stacking patterns and depositional styles throughout these units are largely linked to long-term changes in relative sea level and its control on sediment supply, namely sediment caliber, volume and mineralogy. Notably, in the upper unit, small-scale changes in sediment source and supply are related to shorter sea-level variations superimposed on the long-term eustatic change.

The purpose of this study was to investigate how design changes in Cochlear Nucleus cochlear implants (CIs) (CI24M, CI24R, CI24RE and CI422) affected electrode impedance and ECAP measures, and to determine if these design changes affected post-lingually deafened adults and children with congenital hearing loss in a similar way. Results of this study showed that electrode impedance was inversely related to the area of the electrode contacts in the array: lowest for the full-banded CI24M CI and highest for adults who used the CI422 device which has the smallest electrode contacts of all four devices. The noise floor of the NRT system likely plays a significant role in the finding that CI users with older devices (the CI24M, and CI24R CIs) had higher ECAP thresholds than individuals with the CI24RE electrode array. The position of the electrode array in the cochlea was also found to have a significant effect on ECAP measures. CI users with modiolar hugging (the CI24R and CI24RE CIs) electrode arrays were found to have lower ECAP thresholds than CI users whose electrode arrays were seated more laterally in the cochlear duct (e.g. the CI24M and CI422 implants). The position of the electrode contacts relative to the modiolus of the cochlea was found to be related to slope of the ECAP growth functions. The lowest slopes were found in CI24RE users. It also had a significant impact on the width of the channel interaction function. Electrode arrays seated further from the modiolus have significantly more channel interaction than electrode arrays that hug the modiolus of the cochlea. Differences between results recorded from post-lingually deafened adults and children with congenital hearing loss were minimal. The difference only reflected on the ECAP slopes. Slopes in children with congenital hearing loss were significantly steeper than those recorded from adults. This may indicate that children with congenital hearing loss may have better neural survival than adults with acquired hearing loss. In conclusion, the results of the current study show evidence of the effects of variations in design and function of the implanted components of the Nucleus CI. Perhaps the most significant finding from the current data set is that electrode arrays located closer to the modiolus of the cochlea have lower thresholds and exhibit less channel interaction than electrode arrays that are positioned more laterally. An argument could be made that lower stimulation levels and less channel interaction may result in better outcomes and/or longer battery life. For CI candidates who do not have significant residual acoustic hearing, the CI24RE implant might be a better choice than the more recently introduced CI422 electrode array.

Restoration of stream channels have become a common way of trying to restore both the channels and the ecosystems that earlier have been channelized mainly to facilitate the movement of timber. According to previous studies a lot of the restoration has been performed without a sufficiently detailed plan and with too little focus on how the landscape interplay with the restoration, which makes the potential to learn from possible mistakes minimal. In this study, a hydrological analysis of Hjuken river was done to examine if remote data through an analysis using GIS could be used for identifying three different process domains (lake, slow-flowing reaches and rapids), and if it is possible to determine which process domain it is by examining three different variables: channel slope, surficial geology and the geomorphologic characteristics in the landscape. Based on the statistical treatment and the analysis of the data, the result shows a significant difference between every process domain and variable except for the channel slope when it comes to slow-flowing reaches and rapids. This tells us that all the variables that has been analysed could be a crucial factor in most of the cases. However, the result does not seem reliable compared to previous studies. The conclusion of the study is that the error from the identification of the process domains is from the orthophotos. Remote data is too weak to use as the only source for this kind of analysis. However, the definition of process domains is probably more diffuse than today’s description. There needs to be more studies on each process domain, it is probably not enough with three different types, either there should be subclasses for each process domain or even more process domains.

Process domains categorizes sections of streams according to its local dominant processes. These processes often reflect on the local ecology and the streams appearance. But the underlying reason why these different process domains are formed are still not completely certain. In this study the distribution of the process domains: lakes, rapids and slow-flowing reaches in the Bjur River catchment were compared to the geological factors of slope, surficial geology and landforms to see if any connections could be found. The possibility of using GIS (geographic information systems) and remote data to distinguish these stream types and to connect them to the different studied geological factors were also examined. The hypothesis for this study is that the geological factors of slope, surficial geology and landforms all should have an influence over the distribution of the process domains in Bjur River. The analysis was executed through map-studies in ArcGIS and statistical analysis in Excel. All process domains showed statistical significance towards the studied geological factors. The slope was generally steeper in the rapids than in slow-flowing reaches and lakes. The surficial geology displayed more fine-grained sediment (peat) in proximity to lakes and slow-flowing reaches whilst till was more abundant close to rapids. Hilly moraine landscapes were most common around lakes, while rapids displayed a high percentage of glacio-fluvially eroded area. Slow-flowing reaches also showed to have around 44% of its studied points around glacio-fluvially eroded area, and 43% at areas without any major landforms. Even if the statistical analysis and figures display a difference between the different process domains, it is still difficult to say which of these geological factors that plays the most crucial role for their development. However, by using remote data and through studies over slope, adjacent surficial geology and landforms the different process domains can be differentiated from one another.

This dissertation reports on the methods and results of a three-phased investigation to estimate the annual volume of ephemeral-channel-focused groundwater recharge attributable to urbanization (urban-enhanced groundwater recharge) in the Sierra Vista subwatershed of southeastern Arizona, USA. Results were used to assess a prior estimate.

The first research phase focused on establishment of a study area, installation of a distributed network of runoff gages, gaging for stage, and transforming 2008 stage data into time series of volumetric discharge, using the continuous slope-area method. Stage data were collected for water years 2008 - 2011.

The second research phase used 2008 distributed runoff data with NWS DOPPLER RADAR data to optimize a rainfall-runoff computational model, with the aim of identifying optimal site-specific distributed hydraulic conductivity values and model-predicted infiltration.

The third research phase used the period-of-record runoff stage data to identify study-area ephemeral flow characteristics and to estimate channel-bed infiltration of flow events. Design-storm modeling was used to identify study-area predevelopment ephemeral flow characteristics, given the same storm event. The difference between infiltration volumes calculated for the two cases was attributed to urbanization. Estimated evapotranspiration was abstracted and the final result was equated with study-area-scale urban-enhanced groundwater recharge. These results were scaled up to the Sierra Vista subwatershed: the urban-enhanced contribution to groundwater recharge is estimated to range between 3270 and 3635 cubic decameters (between 2650 and 2945 acre-feet) per year for the period of study. Evapotranspirational losses were developed from estimates made elsewhere in the subwatershed. This, and other sources of uncertainty in the estimates, are discussed and quantified if possible.

Thesis (MSc)--Stellenbosch University, 2013.
This study presents a facies outcrop characterization and petrographical analysis of Unit B of the Permian Laingsburg Formation. Unit B is interpreted as a base-ofslope system, which represents a strikingly sand-rich succession. The base-of-slope system is defined by a channel-levee complex. The study provides systematically a clear understanding and description on reservoir heterogeneities, in terms of facies distribution, physical processes and architectural elements. The dataset included detailed sedimentary logs, photomosaic interpretations, supplemented by a petrographical study to determine the textural and compositional attributes of the studied sandstones. Seven lithofacies was recognised within Unit B, based on detail observation and description on grain size and sedimentary structures. They mainly consist of 1) thick to massive bedded ‘structureless’ sandstone, 2) horizontal and ripple cross-laminated thin-medium bedded sandstone, 3) silty sandstone, 4) structureless siltstone, 5) hemipelagic mudstone, 6) muddy slump, and 7) sandy slump. Palaeocurrent analysis indicates that the mean sediment transport direction of Unit B was to the E and NE. Lithofacies 1 comprises thickly to massive bedded, frequently amalgamated, mostly very-fined grained sand, mixed grading, irregular to sharp upper contacts, structured upper bedding planes, large floating mudstone clasts and granules, rare groove and flute casts. Also, scour and fill features have been documented. Lithofacies 1 has been interpreted to result from channelized sandy debris flow currents. Lithofacies 2 composes of thin-medium bedded, very fine-grained sand, ungraded, sharp upper contacts, discrete units with traction bed forms, horizontal and cross-lamination, mud-draped ripples, internal erosional surfaces and preserved crests. Lithofacies 2 shows diagnostic sedimentary features for a deep-water bottom reworking current. Lithofacies 5 composes of very fine–grained mud, ‘structureless’ to finely horizontally laminated, fissile mudstone. Deposition resulted from suspension settling of mud fractions out of a low-energy buoyant plume. Lithofacies 6 composes of contorted and convoluted bedding, steeply dipping layers and irregular upper contacts. Deposition occurred via slumping on an unstable slope. Lithofacies 7 composes of fine–grained ‘structureless’ sandstone, amalgamated units, with dark floating mudstone granules. Lithofacies 7 has been interpreted to form from channelized flows evolving into slump deposition on an unstable slope. The petrographic data reveals that the reservoir quality of the sandstones is strongly controlled by depositional processes and diagenetic products. The sediments of the Karoo Basin appear to be diagenetically controlled as a function of burial depth. The major diagenetic products controlling the reservoir quality of the sandstones, includes compaction (mechanical and chemical), and authigenic porefilling constituents (quartz cement, feldspar dissolution and partial to complete replacement, calcite cement, chlorite and illite). Compaction played a major role in the evolution of the sediment, as compared to the effect of quartz cementation, and is considered here to have caused irreversible destruction of depositional porosity and permeability. The sediment has undergone intense mechanical compaction during early-stage diagenesis, low temperature and shallow depth of burial (probably the first 2 km). The high burial palaeotemperature (250 ± 500C) or more specifically the high geothermal gradient of the Karoo Basin consequently increased the number of diagenetic reactions. The high burial temperatures may have increased pressure dissolution and quartz cementation. With compaction been limited, quartz cementation and the authigenesis of chlorite and illite at deeper depths may have had a profound effect on the permeability distribution of the studied sandstones. After the completion of diagenesis, the pore systems of these sandstones were completely destroyed by low-grade regional burial metamorphism.

Navigation and location technologies have been reaching in a major interest where Global Navigation Satellite System (GNSS) is mostly adopted. The limitation of this technology is that direct sky view is needed for reliable positioning. In indoor environments, however, it is difficult for GNSS technology to provide a reliable performance in positioning due to the signal attenuation and blocking caused by buildings and construction materials. For this reason, the growth in indoor applications has focused the research in new techniques for attempting mitigate the poor GNSS performance on this type of environments In the context of indoor positioning, multitude of emerging technologies for localization based on ultrasound, infrared, Ultra Wide Band (UWB), Zigbee, inertial navigation and other non-GNSS technologies have been proposed but special equipment is required and a large number of signal sources are needed. However, Wireless Local Area Network (WLAN) technology is widely used in indoor positioning. While the same requirements are also needed as the other technologies in order to improve the positioning accuracy, in terms of cost and ability, Wireless-based indoor location is widely used due to the already deployment of Anchor Points (AP) in urban and indoor areas. There are several methods for indoor positioning purposes e.g ToA (Time of Arrival), Received Signal Strength (RSS) measurements, AoA (Angle of Arrival), fingerprinting and so on. Most of the network-based location estimations use RSS measurements because almost all mobile devices are afforded to use this type of measurements. So, this thesis is centered in WLAN RSS-based positioning systems. The first step for indoor positioning is the distance estimation between the user and the AP. Theoretical and empirical propagation channel models are used to translate the difference between the transmitted and Received Signal Strength into an estimated range. A Propagation channel model built the radio map and also report changes in the environment. There are several models in the literature to characterize this channel. Indoor RSS-based localization has become a popular solution, but standard techniques still consider a time invariant simple single slope path loss channel model with a priori known constant channel parameters. While some contributions considered the RSS-based localization problem using a single path loss model with unknown parameters, the general solution that considersa generalized distance dependent measurement model is an important missing point. This thesis considers the two-slope channel model and proposes a robust indoor positioning solution based on a parallel architecture using a set of Interacting Multiple Models (IMM), each one involving two Extended Kalman filters (EKF) and dealing with the estimation of the distance to a given AP. Within each IMM, the two-slope path loss model parameters are sequentially estimated with Maximum Likelihood Estimate (MLE) to provide a robust solution. Finally, the set of distance estimates are fused into a standard EKF-based solution to mobile target tracking. In addition, the benchmarks derived in this thesis to evaluate the performance of our IMM-EKF algorithm are the Cramér Rao Lower Bound (CRLB) and the Posterior Cramér Rao Lower Bound (PCRLB) providing a guidance in the improvement of the experimental design. The CRLB is used to assess the estimation of model parameters and the PCRLB for tracking solution. This, combined with a path-loss exponent estimation, the channel calibration algorithm is validated with an online range estimation. The central theme throughout this thesis is to develop a completely online two-slope channel calibration and, simultaneously, a mobile target tracking algorithm. The performance of the method is assessed through realistic computer simulations and validated with real RSS measurements obtained from experimental tests in a typical office environment.
Las tecnologías en navegación y localización han estado obteniendo un gran interés en los últimos años donde el Sistema Global de Navegación por Satélite (GNSS) aparece como el más utilizado para estos fines. No obstante, una de las limitaciones del GNSS es la necesidad de tener una visión directa al cielo para así garantizar un posicionamiento bastante fiable. También, al utilizar solamente tecnología GNSS en espacios interiores (más conocidos en el mundo científico por entornos indoor), se es complicado conseguir un buen desempeño en términos de posicionamiento debido a la atenuación e interferencia de la señal causada por los edificios y materiales de construcción. Por esta razón, y debido al crecimiento en aplicaciones dentro de entornos indoor, la investigación de nuevas tecnologías para posicionamiento en interiores se ha centrado en intentar mitigar el mal desempeño de la tecnología GNSS en este tipo de ambientes. En el contexto de posicionamiento en interiores (indoor positioning), se han propuesto multitud de tecnologías emergentes para localización basadas en ultrasonido, infrarrojo, Banda Ultra Ancha (UWB), Zigbee,navegación inercial y otras tecnologías que no sean GNSS. Sin embargo, se requiere de equipo especial y un gran número de fuentes de señal. A pesar de ello, la tecnología en Redes de Área Local Inalámbricas (WLAN) es ampliamente utilizada en el posicionamiento en interiores. Aunque la tecnología WLAN tenga los mismos requerimentos que el resto de tecnologías, en términos de coste y practicidad, los sistemas de posicionamiento basados en redes inalámbricas se utilizan con mayor frecuencia debido al ya existente despliegue de estaciones base (AP) en áreas urbanas e interiores. Existen varias técnicas que sirven para fines de posicionamiento en interiores. Por ejemplo, utilizando el tiempo de llegada de la señal (TOA), las mediciones de la potencia de la señal recibida ( RSS), el ángulo de llegada (AoA), la técnica fingerprinting entre otras. Esta tesis está centrada en sistemas de posicionamiento basados en mediciones WLAN-RSS. Un modelo de canal de atenuación de interiores contruye un mapa de cobertura y también es capaz de reportar los cambios en el entorno indoor. El posicionamiento indoor basado en mediciones RSS se ha convertido en una solución bastante popular, pero las técnicas comunes consideran un modelo de pérdidas por trayectoria de una pendiente, invariante en el tiempo y con un conocimiento previo de los parámetros del canal que se consideran constantes. Esta tesis considera el modelo de pérdidas por trayectoria de pendiente dual y propone una solución robusta para posicionamiento en interiores basado en una arquitectura paralela conformada por un conjunto de algoritmos de Interacción de Múltiples Modelos (IMM) donde cada IMM involucra dos Filtros de Kalman Extendidos (EKF) para el proceso de estimación de la distancia entre el AP y el usuario. Dentro de cada IMM, los parametros del modelo de pérdidas por trayectoria de pendiente dual se estiman secuencialmente utilizando la estimación por máxima verosimilitud (MLE) y así proveer una solución robusta. Finalmente, el conjunto de distancias estimadas se fusionan en un EKF para tener una solución final de la posición del usuario. Además, las cotas de referencias que son derivadas en esta tesis y que sirven para evaluar el rendimiento del algoritmo IMM-EKF son la Cota Inferior de Cramér Rao (CRLB) y la Cota Inferior de Cramér Rao Posterior (PCRLB) que servirán de guía para el perfeccionamiento del diseño experimental. El tema central de esta tesis es desarrollar un algoritmo online para posicionamiento indoor que simultáneamente sea capaz de hacer la calibración del canal de propagación. El desempeño del método se evalúa mediante simulaciones por computadora que se validan con mediciones RSS reales obtenidas a partir de pruebas experimentales.

The main subject of the present thesis is the triggering of debris flows, which has been studied from a geomorphological and from a hydrological point of view. The thesis is a compilation of three papers, each one focused on a specific part of the triggering mechanism. In fact, debris flows are dangerous events, typical of mountain territories all over the world and they necessitate the concurrence of many variables to be triggered. In the last decades, different studies stated that the main variables involved in the initiation of a debris flow are: terrain slope, water input and sediment availability. If these factors exceed some specific critical thresholds, the probability of a debris flow triggering can be very high. However, the fact that so many variables are involved makes these events difficult to forecast. In the present study, we analysed different aspects related to the triggering probability. For this reason, the thesis is composed of three different papers: (1) Chapter 2, titled “On the criteria to create a susceptibility map to debris flow at a regional scale”; (2) Chapter 3, titled “Correlation between the rainfall, sediment recharge and triggering of torrential flows in the Rebaixader catchment (Pyrenees, Spain); (3) Chapter 4, titled “Rainfall durations and corresponding dominant mechanism for the initiation of debris flows in three basins characterized by different geomorphological settings”. In Chapter 2, we analysed the geomorphological variables of the catchments that have the most important role in the triggering of debris flows. We used a model named Flow-R that works at a regional scale (allowing to analyse an entire valley) to study the potential triggering areas, neglecting the hydrological part of the mechanism. In fact, starting from a real case study (event of 4th August 2012), we used the collected data regarding the triggering and deposition areas to model the debris flow event. We analysed the morphological parameters that had better discriminate the potential triggering areas from the zones in which the erosion and slope failure are highly improbable. In Chapter 3, we studied the two triggering variables related to water input and sediment recharge. In this case, we focused on: (1) rainfall, investigating its influence on the triggering of debris flows and on the accumulation and mobilization of sediments; (2) sediment availability, considering the registered debris flow volumes as the previously available sediment quantity inside the triggering area, in the period before the triggering of the event. The analysed catchment is in the Spanish Pyrenees and it is a good case study because since summer 2009 it has been equipped with a monitoring station (rain gauges, piezometers, video cameras, geo-phones). Therefore, the rainfall datasets registered with a time interval of 5 minutes inside the catchment are relatively long and allows to study potential correlations between the water input and the sediment mobilization. We searched if there are any correlations between the volume of the triggered event and the total precipitation of the recharge period (the period between the considered debris flow and the previous one). We then analysed the correlations between the maximum rainfall intensities of the triggering rainfall events and the volume of the debris flows. Finally, we used a parameter called “rainfall erosivity” that, calculated for each rainfall event, considers at the same time the total precipitation, the maximum intensity and the kinetic energy of the rain. This parameter has been calculated using two different time scales: (1) for the single triggering rainfall event; (2) as the sum of all the rainfall events happened during every recharge period. The results are interesting because it is clear that rainfall scarcely influences the quantity of the mobilized sediment, evidencing that there are other important variables involved in this mechanism. Whereas, the triggering or non-triggering of a debris flow is strongly dependent on the rainfall erosivity of the triggering rainfall event. After these two analyses, made at the regional scale and at the basin scale, in Chapter 4 we went more in the detail, focusing on the headwater basins (the upper parts of debris flow catchments). We analysed three study areas: (1) the headwater basin of Rio Rudan, located in the south side of Mount Antelao (Italian Dolomites); (2) the headwater basin of Rio Chiesa, located in the south side of Col di Lana (that is also located inside the dolomitic region, but it is characterized by a different geology, mainly composed of volcanic and sedimentary rocks); (3) the headwater basin of Rio Rebaixader, located in the Spanish Pyrenees (mainly composed of metamorphic rocks). In each headwater basin, we extracted three control cross sections along the channel network. For every cross section we calculated the critical triggering discharge for the debris flow initiation using the formulas of Gregoretti and Dalla Fontana (2008) and of Whittaker and Jaggi (1986). Then, we made some hydrological simulations using the software FLO-2D, using as water input different hyetographs created using the Intensity-Duration equations of Gregoretti and Dalla Fontana (2007) and of Cannon and Ellen (1985). These simulations allowed us to verify which is the minimum rainfall duration (related to the corresponding rainfall intensity) needed to reach the critical discharge in the control cross sections. To test also the possible shallow slope failure triggering mechanism, we also made a slope stability analysis in the three initiation areas, using the geotechnical parameters derived from the analysis of terrain samples collected inside the headwater basins. These two different analysis gave an overall view on the mechanism of mobilization of sediments in the analysed areas. The results show that the critical discharges in the three basins are comparable, whereas the slope stability analysis evidences some differences between the basins. In fact, Rio Rudan resulted generally more stable than the two other basins, even with high saturation conditions of the terrain. This can mean that in this basin the principal triggering mechanism is the “channel-bed failure”, whereas in the two other basins mechanisms of “shallow slope failure” are also probable.
La seguente tesi è stata sviluppata in forma compilativa, come raccolta di articoli. Il filo conduttore di tutto il manoscritto è l’analisi del fenomeno di innesco di colate detritiche. Questo tipo di eventi, tipico di zone montane di tutto il mondo, necessita della concomitanza di particolari fattori per poter accadere. Negli ultimi decenni, differenti studi a riguardo, hanno dimostrato che tra le principali variabili in gioco nel determinare l’innesco di una colata, ci sono: la pendenza del terreno, una sufficiente quantità d’acqua e una certa disponibilità di sedimento nell’area sorgente che possa venire mobilizzata. Questi fattori, quando concomitanti sopra ad una certa soglia limite, determinano una elevata probabilità di innesco di un fenomeno di colata detritica. Il fatto però che ci siano in gioco molte differenti variabili, rende questi meccanismi molto difficili da comprendere e predire con estrema esattezza. In questo studio, si è cercato di analizzare tutti gli aspetti legati alla probabilità di innesco per dare un quadro complessivo del fenomeno, prendendo in considerazione differenti variabili in differenti aree di studio. Per questo motivo la tesi è strutturata in tre parti distinte: ad un primo capitolo introduttivo in cui viene presentato il fenomeno di colata detritica nella sua interezza, segue il Capitolo 2, intitolato “On the criteria to create a susceptibility map to debris flow at a regional scale”. In questa parte della tesi, vengono analizzate le variabili geomorfologiche del terreno che incidono maggiormente nel possibile innesco di una colata detritica. Utilizzando un modello chiamato Flow-R che lavora a scala regionale (permettendo di analizzare un’intera vallata e non solamente singoli bacini), si è trascurata la parte idrologica del fenomeno concentrandosi sulla morfologia del terreno. Partendo infatti dai dati reali (dati di pioggia, volumi di colate, mappatura delle aree di innesco e delle aree di deposito) misurati durante e successivamente l’evento del 4 agosto 2012 che ha interessato l’intera Val di Vizze (Provincia di Bolzano) si è cercato di ricostruire nel modo più verosimile l’innesco e la propagazione di colate nel territorio analizzato, cercando di trovare i parametri morfologici che permettessero di discriminare accuratamente le possibili aree sorgenti dalle zone in cui invece l’erosione e l’innesco sono altamente improbabili. Proseguendo con il Capitolo 3 della tesi, denominato “Correlation between the rainfall, sediment recharge and triggering of torrential flows in the Rebaixader catchment (Pyrenees, Spain)” si è invece passati ad analizzare le due variabili pioggia e quantità di sedimento, legate all’innesco di colata detritica. In questo caso, a differenza della precedente analisi, ci si è concentrati: (1) sulla pioggia, analizzando se questa influisca non solo nel determinare lo switch innesco si/innesco no, ma provochi degli effetti anche sull’accumulo e/o mobilizzazione dei sedimenti nelle aree di innesco; (2) sulla quantità di sedimento disponibile per un eventuale innesco di colata, considerando i volumi detritici registrati come il sedimento disponibile, nell’area di innesco, durante il periodo pre-colata. Il bacino analizzato in questa seconda parte della tesi, si trova nei Pirenei spagnoli ed è un ottimo caso studio in quanto fin dall’estate 2009 è stato equipaggiato con una stazione di monitoraggio che comprende pluviometri, geofoni, piezometri e videocamere. La serie storica dei dati di pioggia, che viene registrata con un intervallo temporale di 5 minuti, è quindi relativamente ampia. Inoltre, essendo questo un bacino caratterizzato da un’elevata frequenza di fenomeni di colata detritica e di correnti iperconcentrate, si è avuta a disposizione una serie di una ventina di eventi (con relativo volume di detriti) registrati sempre a partire dall’estate 2009. Una serie di dati di questo tipo, permette quindi di effettuare analisi molto più approfondite rispetto a quelle che si possono fare in singoli bacini non costantemente monitorati in cui ci si limita a prendere in considerazione le giornate caratterizzate da eventi di colata. Si è quindi studiato se ci fosse correlazione tra il volume dell’evento innescato e la quantità di pioggia caduta nel periodo trascorso tra l’evento di colata stesso e il precedente (questo viene denominato in letteratura “periodo di ricarica”). Si sono successivamente verificate le eventuali correlazioni tra l’intensità massima degli eventi di pioggia del periodo di ricarica e il volume del successivo evento innescato. Per fare uno studio più complesso si è deciso di utilizzare una variabile denominata “rainfall erosivity”, questo parametro calcolato per ogni evento di pioggia registrato, mette insieme la quantità totale di precipitazione misurata con l’energia cinetica della pioggia stessa, calcolata utilizzando la massima intensità media nella mezz’ora. Con questo parametro si è differenziato tra la pioggia totale caduta durante il periodo di ricarica e la pioggia del singolo evento innescante. I risultati ottenuti sono molto interessanti, infatti risulta chiaro come la pioggia abbia un’influenza relativamente scarsa sull’accumulo di sedimenti e sulle quantità mobilizzate, dimostrando come queste quantità siano influenzate da altre variabili in gioco, mentre l’innesco o il non innesco di una colata è fortemente dipendente dall’energia dell’evento di pioggia che si verifica sul bacino. Dopo aver svolto una prima analisi a scala regionale e una seconda a scala di singolo bacino, nel Capitolo 4 si è entrati ancora più nel dettaglio, prendendo in considerazione solamente il sottobacino di testata. In questo capitolo, intitolato “Rainfall durations and corresponding dominant mechanism for the initiation of debris flows in three basins characterized by different geomorphological settings”, sono state analizzate tre differenti aree studio: (1) il sottobacino del Rio Rudan, che si trova nel versante meridionale del Monte Antelao, in pieno territorio dolomitico; (2) il sottobacino del Rio Chiesa, posto sul versante meridionale del Col di Lana, caratterizzato da una geologia differente rispetto al primo, composta da una mescolanza di rocce vulcaniche e sedimentarie; (3) il sottobacino del Rio Rebaixader, che si trova nei Pirenei spagnoli ed è composto principalmente da rocce metamorfiche. In ognuno dei tre sottobacini, sono state estratte tre sezioni di controllo, lungo la rete idrografica, e per ognuna di esse sono state calcolate le relative portate critiche di innesco di colata detritica utilizzando le due formule di Gregoretti e Dalla Fontana (2008) e Whittaker e Jaggi (1986). Successivamente in ciascuno dei sottobacini, utilizzando il software di modellazione FLO-2D, sono state effettuate diverse modellazioni idrologiche utilizzando come input di pioggia, differenti pluviogrammi creati utilizzando le equazioni di Intensità-Durata sviluppate da Gregoretti e Dalla Fontana (2007) e da Cannon e Ellen (1985). Queste indagini hanno permesso di verificare quale sia la durata minima di pioggia (legata alla corrispondente Intensità soglia) necessaria per raggiungere la portata critica di innesco nelle sezioni di controllo analizzate. Per completare lo studio sul meccanismo d’innesco nei tre sottobacini analizzati, è stata fatta anche un’analisi di stabilità di versante, utilizzando i parametri geotecnici derivanti da campioni di suolo prelevati nelle aree di innesco. Queste due analisi danno insieme una visione complessiva del modo in cui le colate detritiche si sviluppino nelle aree analizzate. I risultati mostrano infatti come, in tutti e tre i sottobacini, le portate critiche di innesco siano comparabili come grandezza, mentre le analisi si stabilità di versante evidenziano come il bacino del Rio Rudan sia mediamente più stabile rispetto alle altre due aree, anche in condizioni di elevata saturazione del suolo. Questo fa pensare che in questo bacino il meccanismo di innesco più probabile sia il cosiddetto “channel bed failure”, mentre negli altri due bacini ci sono sicuramente anche fenomeni di “shallow slope failure” che avvengono nelle aree dissestate di versante portando grandi quantità di detriti all’interno del reticolo idrologico.

Failure of slopes adjacent to the UK transport infrastructure causes delays and these are expensive assets to repair and maintain. Understanding the processes that lead to failure will assist asset managers both now and in the future in the context of a changing climate. The EPSRC-funded multidisciplinary FUTURENET project investigated the effect of climate change on the resilience of the UK transport network and this thesis is a part of that project considering the weather patterns leading to slope failures along transport infrastructure slopes within the UK. To that end a series of slope failure case studies were investigated to understand the processes leading to failure. These were compiled using nationally held datasets as well as news reports. This research used data from the FUTURENET partners that hold national data sets and asset management information. This shows the wide reaching remit of a multidisciplinary collaborative project such as FUTURENET, but also highlights the limitations of datasets collected and used for very specific purposes and not necessarily suited to wider research. From these case studies a suite of slope failure weather thresholds were developed. These thresholds consider the antecedent period, water content within the slope through the soil moisture deficit and triggering rainfall through comparison to the long term average rainfall. Consideration was given to possible future weather using weather event sequences (WESQs), possible weather patterns for 2050 derived from the UKCP09 climate projection data. By considering these possible weather patterns with the slope failure thresholds a picture of a possible future was evaluated.

Long linear earthwork assets constructed in high-plasticity overconsolidated clay are known to be deteriorating due to long-term effects of wetting and drying stress cycles as a result of seasonal weather patterns. These stress cycles can lead to shallow first-time failures due to the mobilisation of post-peak strength and progressive failure. Design requirements of new earthworks and management of existing assets requires improved understanding of this critical mechanism; seasonal ratcheting. Incremental model development and validation to allow investigation of multiple inter-related strength deterioration mechanisms of cut slope behaviour in high-plasticity overconsolidated clay slopes has been presented. Initially, the mechanism of seasonal ratcheting has been considered independently and a numerical modelling approach considering unsaturated behaviour has been validated against physical modelling data. Using the validated model, the effects of slope geometry, design parameter selection and design life have been considered. Following this, an approach to allow undrained unloading of soil, stress relief, excess pore water pressure dissipation, seasonal ratcheting and progressive failure with wetting and drying boundary conditions has been considered. Hydrogeological property deterioration and the potential implications of climate change have been explored using the model. In both cases the serviceable life of cut slopes is shown to reduce significantly in the numerical analyses. Finally, a model capable of capturing hydrogeological behaviour of a real cut slope in London Clay has been developed and validated against long-term field monitored data. Using the validated model, a climate change impact assessment for the case study slope has been performed. The numerical analyses performed have indicated that seasonal ratcheting can explain shallow first-time failures in high-plasticity overconsolidated clay slopes and that the rate of deterioration of such assets will accelerate if current climate change projections are representative of future weather.

x, 108 p. : ill. (some col.) A print copy of this title is available through the UO Libraries. Search the library catalog for the location and call number.
This paper examines the capability of LiDAR data to accurately map river water surface slopes in three reaches of the Sandy River, Oregon, USA. LiDAR data were compared with field measurements to evaluate accuracies and determine how water surface roughness and point density affect LiDAR measurements. Results show that LiDAR derived water surface slopes were accurate to within 0.0047,0.0025, and 0.0014 slope, with adjusted R2 values of 0.35, 0.47, and 0.76 for horizontal intervals of 5, 10, and 20m, respectively. Additionally, results show LiDAR provides greater data density where water surfaces are broken. This study provides conclusive evidence supporting use of LiDAR to measure water surface slopes of channels with accuracies similar to field based approaches.
Committee in Charge: W. Andrew Marcus, Chair; Patricia F. McDowell

The aim of this research was to study the relationship between rock slope stability and glacial processes. An in-depth analysis of our current understanding of how glaciated rock slopes develop instability and movement during deglaciation is presented; this shows that understanding is incomplete without an appreciation of the variable mechanical behaviour of glacier ice. In this thesis, I argue that: (1) The ductile behaviour of ice at low strain rates allows movement of rock slopes buttressed by ice. Field evidence and simple force models are used to explore rate of movement of ice-contact slopes and the conditions under which they evolve. The results indicate that large rockslides can move and deform glacial ice at rates of 10-2 to 102 m-yr. This implies that ice-contact slope movement may be important for slope evolution and the erosion and entrainment processes of glaciers; and (2) the elastic strength of glacier ice at the high strain rates associated with seismic shaking enables ice to modify the response of the surrounding rock to seismic shaking. To explore this, numerical analyses of the interaction between glacial erosion, glacier mass, topography, and earthquake shaking intensity are undertaken. Shaking of mountains of variable shape and with different levels of ice inundation is simulated using FLAC 6.0. The results suggest that complete inundation by ice can significantly reduce shaking intensity. This, in combination with glacial steepening of slopes, may make recently deglaciated slopes more prone to coseismic failure. In the final chapter of the thesis, I present a conceptual model of the evolution of slope stability during stages of glaciation and deglaciation. The model incorporates the ideas presented in the thesis. I then offer recommendations for how our understanding of these processes can be further advanced.

The shift towards collegiality is a new setting for many teachers. Most teachers work alone, in isolation from their colleagues and collegial collaboration requires organisational structures. The aim of the study is to describe and analyse upper secondary mathematics teachers’ collective practice,developed in a professional development initiative. This study is a case study and the empirical data is generated through observations and an interview of a group of four teachers at a school who met on a weekly basis throughout a term. Their discussions focused on the mathematical concept of slope in a setting of learning study. This thesis is the case of when mathematics teachers focus discussions on slope and draws on Wenger’s Communities of Practice Perspective, as a unitof analysis, and addresses the question: What are the characteristics of practice when upper secondary mathematics teachers focus discussions on slope in the setting of a learning study? The analysis accounts for characteristics of the aspects of practice, through the coherence of mutual engagement, joint enterprise and shared repertoire in the community of practice. The teachers are engaged around finding small changes in their teaching that could give major effect in students learning. They negotiate what the students need to know in order to understand the relation between Δy and Δx. The characteristic of practice is a conceptual mapping of the concept of slope. It reveals students’ partial understanding of related concepts due to how they were given meaning through previous teaching. The conceptual mapping of slope goes back as far as to the student’s partial understanding of the meaning of subtraction. However, what emerges is in relation to the teachers’ experience of avoiding students’ difficulties with negative difference when teaching slope. It turns out to be a negotiation and a renegotiation of teaching slope for instrumental understanding or conceptual understanding. An overall characteristic of practice is that it develops in a present teaching culture.

The development of two Arctic Trough Mouth Fans (TMFs), the Storfjorden and Kveithola TMFs, is investigated by means of sub-bottom and seismic reflection profiles, multibeam bathymetry and sediment samples allowing their detailed stratigraphic architecture to be defined. We find that the TMFs mainly consist of an alternation of rapidly deposited glacigenic debris flows during glacial maxima and a sequence of well-layered plumites and hemipelagic sediments, which were mainly deposited during the deglaciation phase of the adjacent glacial trough. We have identified eight units above regional reflector R1, which indicate that the ice sheet reached the shelf edge within the Storfjorden Trough on at least three occasions during the last ~200 ka. A shallow subsurface unit of glacigenic debris flows suggests that the ice sheet had a short re-advance over the northern and central part of Storfjorden after the Last Glacial Maximum. From stratigraphy, core and literature data, we estimate that ice sheets reached the shelf edge between 19.5 to 22.5 ka, 61 to 65 ka and 135 to 167 ka. Detailed seismic imaging allows us to refine the sedimentary model of Arctic TMFs. The main differences to previous models involve gully formation during not only the deglaciation phase, but also during interglacials by dense shelf water cascading, and a specific timing for the occurrence of slope failures (i.e., shortly after the deglaciation phase). High mean sedimentation rates during glacial maxima of up to 18 kg m-2 yr-1 likely allow excess pore pressure to develop in the water rich plumites and hemipelagic sediments deposited in the previous deglacial period, particularly where such plumites attain a significant thickness. Climate variations control sediment supply to the continental slope as well as glacial advances and retreats. This hypothesis has been investigated by using a combination of geophysical and geotechnical data. The results of compressibility and permeability testing are used together with margin stratigraphic models obtained from seismic reflection data, as input for numerical finite elements models to understand focusing of interstitial fluids in glaciated continental margins. BASIN software has been used to model the evolution of the Storfjorden TMF from 2.7 to 0.2 Ma. The model results show that onset of glacial sedimentation (~1.5 Ma) has a significant role in developing permeability barriers (tills) on the shelf decreasing the vertical fluid flow towards the sea floor and switching it towards the slope. Prior to 220 ka, the higher values (up to 0.6) are located below the shelf edge and in the distal area. In turn, Plaxis software has been used to perform a detailed high resolution hydrogeological model of the four glacial/inter-glacial cycles. Ice loading during Glacial Maxima caused a rapid consolidation of the shelf sediments with high fluid expulsion rates towards the shallower plumite sediments on the slope. This caused an overpressure increase inside these layers up to 0.6. The higher overpressures occurred during the Last Glacial Maximum and few thousand years after. Present day overpressures reach maximum values of 0.7 on the shelf. A detailed slope stability analysis through the Last Glacial Maximum, last deglaciation and Holocene has been carried out. Safety factor (SF) of the margin was reduced to one half due to overpressures development during the Last Glacial Maximum with minimum values of ~1.2 which were preserved through the last deglaciation. These low values occurrence match with the time when most of the landslides identified in the study are occurred. Although the safety factor values are close to the instability, mechanisms as glacio- eustatic rebound induced earthquakes can be considered as a final trigger.
L’evolució de dos ventalls glacials, Storfjorden i Kveithola, s’ha investigat fent servir dades geofísiques i mostres de sediment. D’aquesta manera s’ha pogut establir de forma detallada la seva estratigrafia. A partir de l’anàlisi estratigràfic i dades de literatura s’ha pogut establir que el gel va ocupar la plataforma continental com a mínim en tres ocasions durant els últims ~200 ka: 19.5 a 22.5 ka, 61 a 65 ka i 135 to 167 ka. A més la bona cobertura i resolució de les dades geofísiques ha permès de refinar el model d’evolució dels ventalls glacials. Les diferències més important respecte a treballs previs corresponen a que la formació de xaragalls no dóna només en els deglacials, sinó també en els interglacial degut a les aigües denses de plataforma, i també l’ocurrència de esllavissades durant la deglaciació del marge. En aquest estudi queda palès el control climàtic en la tassa de sedimentació, els sediments dipositats i els avanços i retrocessos de gel. Aquestes variacions influeixen en el patrons de fluid del subsòl i el desenvolupament de sobrepressions en els sediments. Aquesta hipòtesi ha estat investigada utilitzant models d’elements finits (BASIN i Plaxis) a partir de les dades geofísiques i assajos geotècnics. La modelització dels darrers 2.7 Ma mostra que l’inici dels períodes glacials, fa aproximadament 1.5 Ma, va promoure la formació bandes de baixa permeabilitat (tills) a la plataforma. La càrrega de gel a la plataforma durant els màxims glacials, va provocar una ràpida consolidació dels sediments subjacents i l’expulsió de l’aigua intersticial, incrementant així el flux de fluids cap al talús superior. Alhora, aquest flux focalitzat cap als sediments més permeables del talús (plumites) va incrementar dràsticament les sobrepressions. Les sobrepressions màximes van tenir lloc durant l’últim màxim glacial i els següents mil·lennis. Degut a aquestes sobrepressions, el factor de seguretat del talús es va reduir a la meitat, arribant a valors de 1.2 al final de l’últim màxim glacial. Tot i els que aquest valors són baixos, els terratrèmols provocats pel rebot glacio-eustàtic han de ser considerats com a desencadenants finals de les esllavissades identificades a la zona.

This thesis comprises three original papers about learning rate of change in school mathematics. The overall aim of the thesis is to contribute with knowledge in this particular area of research. Within this aim, each of the original papers contribute with its own perspective. The theoretical framework used in the thesis is variation theory of learning (Marton & Booth, 1997; Marton, 2015), by which learning is seen as experiencing a phenomenon in a new way. This theoretical point of departure is reflected in the research question of the thesis: What is critical to discern to use and express rate as a measure of the relation of changes in two quantities? The empirical study was conducted as a learning study (Pang & Marton, 2003). A learning study is an iterative, interventional research arrangement in which teachers and researchers collaboratively explore a specific ability, the object of learning, worthwhile for the students to learn. The object of learning related to this thesis, ‘to express the quantitative rate of change of a linear relation’, was explored in a series of three research lessons at a secondary school. Data consists of students’ responses to written pre- and post-tests, and lesson videos. Some data have been analysed during the on-going empirical study and some data have been analysed after it was concluded. Principles from variation theory have been used as tools for analysis throughout the study. Main results of Paper I demonstrate how two critical aspects are identified and revised through the process of learning study. In Paper II the results indicate that qualitatively different questions in a task may affect students’ ways to relate changes in two quantities. The results of Paper III suggest how different perspectives of slope may promote homogeneity as an aspect of rate. Results also comprise six critical aspects of the object of learning, four of which was identified by revisiting the results of Paper II. In summary, the critical aspects also specify the meaning of a covariational perspective of rate. Results are discussed in relation to previous educational research about rate of change, covariation of quantities and students’ conceptions of rate and slope. Further research directions are suggested.
Den här sammanläggningsuppsatsen omfattar tre artiklar om förändringstakt i matematik. Uppsatsens övergripande syfte är att bidra med kunskap till detta specifika forskningsfält. Inom ramen för detta syfte bidrar var och en av de tre artiklarna med sitt eget perspektiv. Det teoretiska ramverket i uppsatsen är variationsteori (Marton & Booth, 1997; Marton, 2015). Ur detta teoretiska perspektiv ses lärande som ett erfarande av ett fenomen på ett nytt sätt. Denna teoretiska utgångspunkt har färgat uppsatsens övergripande forskningsfråga: Vad är kritiskt att urskilja för att använda och uttrycka förändringstakt somett mått på relationen mellan förändringar i två storheter? Den empiriska studien genomfördes som en learning study (Pang et al., 2003). Learning study är en iterativ, intervenerande forskningsansats där lärare och forskare i samarbete utforskar en specifik förmåga, lärandeobjektet, något som är värdefullt för elever att lära sig. Lärandeobjektet som behandlas i denna uppsats, ’att uttrycka förändringstakten i en linjär relation kvantitativt’, utforskades i en serie av tre lektioner på en högstadieskola. Data består av elevers svar till skriftliga uppgifter i för- och eftertest, samt videoinspelade lektioner. Data har analyserats både under den pågående empiriska studien, och efter att den avslutades. Principer från variationsteori har använts som analysverktyg genom studiens gång. Huvudresultaten av Artikel I visar hur två kritiska aspekter identifieras, revideras och förfinas genom learning study som process. I Artikel II tyder resultaten på att kvalitativt olika frågor i en uppgift påverkade elevernas sätt att relatera förändringar i två storheter. Resultaten i Artikel III visar hur olika perspektiv på lutningen hos en graf kan föra fram homogenitet som en aspekt av förändringstakt. Uppsatsens resultat omfattar framför allt sex aspekter som är kritiska att urskilja för att utveckla förmågan att använda och uttrycka förändringstakt som ett mått på relationen mellan förändringar i två storheter. Fyra av dem identifierades då resultaten av Artikel II tolkades utifrån ett variationsteoretiskt perspektiv. Som helhet specificerar också de kritiska aspekterna innebörden av ett samvarierande perspektiv på förändringstakt. Resultaten diskuteras i förhållande till tidigare forskning om lärande om förändringstakt, samvariation mellan storheter och elevers uppfattningar av lutning. Några vidare forskningsriktningar pekas ut.

Pregnant polar bears (Ursus maritimus) construct maternal dens out of snow in the autumn where they give birth to and raise altricial young. In recent years, there has been a decrease in polar sea ice extent and thickness, which has led to changes in denning behavior. One such change in the southern Beaufort Sea (SBS) is that polar bears are selecting maternal den sites on land, rather than on unstable sea ice. This change, coupled with expanding petroleum exploration along Alaska's North Slope, heightens the likelihood of bear-human interactions at maternal den sites. The purpose of this research was to 1) describe polar bears' post-den emergence behavior, establishing a benchmark for comparison to identify behavioral changes associated with climate change and disturbance, and 2) explore factors influencing the efficacy of a currently used den detection method, forward-looking infrared (FLIR). Maternal den sites were observed along Alaska's North Slope from March to April of 2009 and 2010. The mean length of stay at den sites post-emergence was 11.3 ± 7.5 d. The mean date of den emergence was 14 March; abandonment 26 March. Adult females were generally inactive (58.4% out-of-den time) with standing being the most prevalent activity (49.9%). Cubs were generally active (76.7%), playing more than any other activity (45.3%). Bears spent the majority of their time in the den (97.3% for adult females and 99% for cubs) with short bouts of intermittent activity (× = 7 min 42 s). We documented the death of one member of a triplet polar bear litter at its den site. All three cubs showed low activity levels relative to other cubs observed, and one died within one week of den emergence. Necropsy confirmed that the dead cub had a low body weight and was malnourished. Capture later confirmed that the two surviving cubs were also undersized. Triplet litters are often smaller and suffer higher mortality rates than singletons and twins. This cub was not only a triplet but also born following 2 y of record minimum sea ice extent, both of which may have played a role in this cub's death. Concurrent with the den emergence portion of this work, we conducted a separate study to identify limitations and optimal conditions for locating dens using FLIR. We took handheld FLIR images of three artificial dens under varied conditions. We tested variables hypothesized to influence detectability with linear models using a zero-inflated negative binomial distribution. Solar radiation, wind speed, and den wall thickness reduced the likelihood of detecting dens. The negative effect of wind speed on detectability increased with increasing distance. To maximize the efficacy of hand-held FLIR, den surveys should be conducted when solar radiation is <16 w/m2 (night) and when wind speed is <10 km/h (6 mph). Adherence to these guidelines will maximize the protection FLIR can afford to denning bears.

Purpose: The purpose of this study is to examine how changes in long and short interest rates as well as in the slope of the yield curve affect the stock returns of the four major Swedish banks; Svenska Handelsbanken, Nordea Bank, Swedbank, and Skandinaviska Enskilda Banken. Further, the aim of the research is to compare these findings to how the banks perceive that such changes affect their stock returns. The objective is thereof to detect differences and similarities between regressions and interviews, in order to contribute with insights to how the banks can handle their exposure to interest rate risk. Theoretical Framework: Previous research show that banks’ stock returns are affected by many factors, including cash flow news, interest rates, size of the business, and the macroeconomy as a whole. However, banks’ interest rate margins are set to market rates so these are more exposed to and affected by changes in interest rates, especially short ones, than are non-financial institutions. Furthermore, the low interest rate levels and forecasting errors that have been seen lately have contributed to greater uncertainty and higher risk exposures, making banks’ sensitivity increase. Methodology: A mixture of a qualitative and a quantitative methodology is used, where the former consists of interviewing the banks and the latter of regressions through secondary data from Thomson Reuters Eikon and the Riksbank. Conclusion: The major Swedish banks’ stock returns are generally affected by changes in short interest rates but not by changes in long interest rates, with the exception of Handelsbanken being impervious to all such changes. Swedbank’s stock returns are most sensitive than the other banks’ stock returns and it is the only bank affected by changes in the yield curve slope. However, the banks seem to perceive no crucial difference in how their stock returns are affected by changes in short interest rates and long interest rates, concluding that their perceptions of long interest rates are not as in line with our results as are their perceptions of short interest rates. However, it tends to be a more diffuse relationship between changes in long interest rates and stock returns than between changes in short interest rates and stock returns.

La variabilité climatique et les événements extrêmes associés comme le phénomène El Niño (ENSO) représentent les épisodes les plus difficiles à gérer dans le Versant Pacifique Péruvien. En outre, une préoccupation croissante sur la disponibilité en eau a lieu depuis les années 1970s. Une documentation approfondie des régimes de précipitations et des débits est un élément clé de tout plan de gestion de l'eau et notre recherche est la première étude sur la variabilité hydroclimatique à l'échelle mensuelle et annuelle dans la zone d'étude au cours des quatre dernières décennies (période 1970-2010). Tout d'abord, un traitement de base de données exhaustif a été effectué pour surmonter certaines limitations et notamment celles liées aux conditions géographiques des Andes. Deuxièmement, le régime des précipitations a été étudié avec une approche de régionalisation liée aux conditions de séries temporelles non stationnaires. Une méthode mixte associant la méthode des clusters k-means et la méthode du vecteur régional a été proposée. Neuf régions ont été identifiées avec des régimes homogènes de précipitation tenant compte d'un gradient latitudinal et altitudinal. Un bilan hydroclimatique a ensuite été fait à l'échelle de bassin versant, abordant la problématique du climat et de l'anthropisation et leurs influences potentielles sur les séries chronologiques hydroclimatiques. Le cadre théorique de Budyko-Zhang a été utilisé et a permis d'identifier 11 des 26 bassins versants à faible influence climatique et anthropique (i.e. des conditions quasi-naturelles). Le régime des débits a ensuite été étudié pour ces conditions et une extension pour l'ensemble des 49 bassins versants de la zone d'étude a été effectuée. Un modèle hydrologique régional est proposé via deux modèles conceptuels agrégés à l'échelle de temps annuelle et mensuelle (GR1A et GR2M respectivement). Un test d'échantillonnage différentiel (DSST) a été utilisé pour améliorer la robustesse de la modélisation par rapport aux conditions climatiques contrastées entre années sèches et humides dans les conditions semi-arides. Enfin, la portée de la thèse couvre (1) une revisite de la relation ENSO/précipitation en prenant en compte les neuf régions identifiées et de plusieurs indices ENSO afin de discriminer l'influence des deux types d'El Niño (El Niño du Pacifique Est EP et du Pacifique Central CP) ainsi que l'influence de la variabilité atmosphérique (i.e. l'oscillation Madden et Julian) et aux conditions océaniques régionales. La méthodologie proposée consiste en l'analyse des composantes principales, ondelettes et de cohérence, les corrélations glissantes et l'analyse de la covariance spatiale afin de mettre en évidence la modulation décennale significative du phénomène ENSO ainsi que sa croissance à partir des années 2000s où la relation ENSO/précipitations s'inverse par rapport à la décennie précédente. Les deux modes de co-variabilité dominants entre la température superficielle de la mer dans le Pacifique tropical et les neuf régions montrent des caractéristiques dominantes de l'influence de l'ENSO: une augmentation des précipitations sur les régions aval dans le nord pendant El Niño EP et une diminution des précipitations sur les régions amont le long des Andes lors des événements El Niño CP. (2) La sensibilité au changement hydroclimatique est explorée via l'analyse des tendances hydroclimatiques comme indicateurs de changement de l'hydroclimatologie régionale. Les résultats montrent un réchauffement important dans la zone d'étude avec une moyenne de 0,2°C par décennie. En outre, les changements dans les trajectoires dans l'espace de Budyko (i.e. direction et amplitude) ont révélé que six bassins versants étaient sensibles à la variabilité du climat (i.e. probablement avec une grande sensibilité au climat futur) et aux changements d'utilisation du sol et où les précipitations et la température sont les facteurs prépondérants du changement de ces environnements
Climate variability and associated extreme events as El Niño phenomenon (ENSO) represent the most difficult episodes to deal with along the Peruvian Pacific slope and coast. In addition, a growing water concern takes place since seventies. In-depth documentation of precipitation and runoff regimes becomes a key part in any water management plan and this research offers the first hydroclimatic variability study at monthly and annual time step in the study area over the last four decades (1970?2010 period). First, an exhaustive database treatment was carried out overcoming some limitations due to Andean geographical conditions. Second, precipitation regime was studied with a regionalization approach under non-stationary time-series conditions. A combined process consisting in k-means clustering and regional vector methodology was proposed. Nine regions were identified with a homogeneous precipitation regime following a latitudinal and altitudinal gradient. Third, a hydroclimatic balance is done at catchment-scale addressing the issue of climate and anthropogenization and their potential influences over hydroclimatic time series. The theoretical Budyko-Zhang framework was used and allowed identifying 11 out of 26 catchments with both low climate and anthropogenization influence (i.e. unimpaired conditions). This hypothesis was verified with the use of land use and land cover remote sensing products as MODIS and LBA imagery. Then, runoff regime was studied under unimpaired conditions and an extension over 49 catchments of the Peruvian Pacific drainage was done. A regional runoff model is proposed via two conceptual lumped models at annual and monthly time scale (GR1A and GR2M respectively). A Differential Split-Sample Test (DSST) was used to cope with modelling robustness over contrasted climate conditions as dry and wet years according to the semi-arid conditions. These results also showed an increasing regional discharge from arid Peruvian Pacific coast towards the Pacific Ocean. Finally, the scope of the thesis covers (1) a revisitation of ENSO/precipitation relationship considering the regionalized precipitation and several ENSO indices in order to discriminate the influence of the two types of El Niño (the eastern Pacific (EP) El Niño and the central Pacific (CP) El Niño) as well as the influence of large-scale atmospheric variability associated with the Madden and Julian Oscillation, and of regional oceanic conditions. The proposed methodology consisting in principal component analysis, wavelets and coherence, running correlations and spatial covariance analysis, highlights the significant decadal modulation with the larger ENSO impact in particular in the 2000s, ENSO/precipitation relationship reverses compared to the previous decade. The two dominant co-variability modes between sea surface temperature in the tropical Atlantic and Pacific oceans and the nine regions show salient features of the ENSO influence: increased precipitation over downstream regions in northern Peru during EP El Niño and decreased precipitation over upstream regions along the Pacific slope during CP El Niño events. (2) The sensitivity to hydroclimatic change is explored by hydroclimatic trend analysis as changes indicators of regional hydroclimatology. According to significant upward trends in annual temperature found in all catchments, results showed a significant warming in the study area with a mean of 0.2°C per decade. Also, changes in trajectories in the Budyko space (i.e. direction and magnitude) over the 11 selected catchments revealed that six catchments were shown to be sensitive to climate variability (i.e. likely with high sensitivity to future climate) and land use changes, where precipitation and temperature are the main drivers of these environments changes

Since 1880 air temperature at global scale rapidly increased of c. 0.85 °C likely due to the increasing amount of anthropogenic greenhouse gas, and is forecast to increase over the 21st century as well. Cold-adapted species of the high latitude/altitude are the first to be threatened by such climate change, due to the progressive reduction of their suitable areas. Microclimatic heterogeneity at landscape level is supposed to play a key role in this scenario providing warm-stage refugia, sites able to preserve suitable climate conditions for cold-adapted species in spite of the ongoing climate warming. Active rock glaciers and debris-covered glaciers (periglacial and glacial landforms characterized by debris with underlying ice) were proposed as potential warm-stage refugia in mountain regions, due to the microclimate effect of underlying ice and the thermal inertia provided by the debris fraction. Besides microclimate heterogeneity at landscape level, macroclimate heterogeneity at regional scale (e.g. the contrast between continental and oceanic climates of inner and peripheral mountain ranges, respectively) can be important, since drive the distribution of periglacial and glacial landforms as potential warm-stage refugia and the effects of climate change themselves on high mountain landscapes (e.g. temporal pattern of glaciers retreat) and ecosystems (e.g. temporal pattern of primary successions on ice-free glacial landforms). Aim of this study was to analyze the ecological features of periglacial and glacial landforms (active rock glaciers and debris-covered glaciers on inner mountain ranges, glacier forelands and recent moraines on peripheral mountain ranges) to test whether they have the main key-requirements to act as potential warm-stage refugia for cold-adapted species. Concerning active rock glaciers and debris-covered glaciers, we considered as key-requirements a cold microclimate able to support cold-adapted species and the ability to cross the altitudinal zonation of mountain ecosystems, thus supporting cold-adapted species in adverse climate contexts. Concerning glacial landforms on peripheral mountain ranges, we considered as key-requirement a relatively slow colonization pattern able to long-lasting support pioneer cold-adapted species in spite of the primary succession development. The study was carried out in different areas of the Italian Alps (Adamello-Presanella, Ortles-Cevedale, Monte Rosa, Orobian Alps) in which different landforms were analyzed and compared. A multidisciplinary approach was followed, considering both the abiotic (ground surface temperature and humidity, soil physical and chemical parameters) and biotic variables (plant and arthropod communities). Our results show as active rock glaciers and debris-covered glaciers does not differ from the surrounding debris-featured iceless landforms for soil parameters, but for a cold microclimate likely due to the underlying ice. The microclimate can explain why these landforms differ from the surrounding ones for the occurrence of cold-adapted plant and arthropod species. On the Alps, active rock glaciers are unable to cross the altitudinal zonation of mountain ecosystems, thus can only enhance the occurrence of cold-adapted species within their normal altitudinal distribution. By contrast, debris-covered glaciers can cross the climatic treeline, allowing cold-adapted species to live even below their normal altitudinal distribution. However, the relative altitudinal distribution of active rock glaciers and debris-covered glaciers can be inverted on mountain systems drier than Alps, suggesting a similar ecological role of such landforms in opposite macroclimate conditions. Moreover, our results suggest that mountain systems characterized by oceanic macroclimate could prevent the extinction risk for pioneer cold-adapted species along a chronosequence of glacier retreat, due to the long-lasting persistence of glaciers at relatively low altitudes (as a consequence of high winter precipitations) and the slow colonization of ice-free glacial landforms (as a consequence of long-lasting snow cover and temperatures around zero). Peripheral mountain ranges in particular outlines as oceanic areas of crucial biogeographical importance during both the opposite climate extremes: in cold-climatic stages they can provide refugia for a lot of species, as a consequence of the relatively low ice-sheet expansion; in warm-climatic stages they may provide refugia for cold-adapted species in particular, as a consequence of their climatic, thus glaciological and ecological features.

In eastern Australia, the New England Fold Belt (NEFB) comprises an ancient convergent margin that was active from the Paleozoic until the late Mesozoic. Considerable effort has been expended in understanding the development of this margin over the past twenty years. However, proposed tectonic models for the orogen have either been too broad, ignoring contradictory local evidence, or too locally specific without paying attention to the 'big picture'. The research presented in this work addresses the issue of appropriate scale and depth of geological detail by studying the NEFB at the terrane-scale. Using one succession, the Silverwood Group of southeast Queensland, this work demonstrates that detailed sedimentological studies and basin analysis at the terrane-scale can help to refine hypotheses regarding the tectonic evolution of the NEFB. The Silverwood Group (Keinjan terrane), located approximately 140 km southwest of Brisbane, Australia, is a succession of arc-related basins that developed within an ancient intraoceanic island-arc during the mid-Cambrian to Late Devonian. From the base of the succession, the group consists of five formations totalling -9700 m. These include the Risdon Stud Formation (2500 m), Connolly Volcanics (2400 m), Bald Hill Formation (2450 m), Ormoral Volcanics (600 m) and the Bromley Hills Formation (1700 m). The Long Mountain Breccia Member (300m) is a separate unit which forms the lower part of the Bromley Hills Formation. The entire succession has been thrust west over the Late Devonian to Early Carboniferous Texas beds. Elsewhere, the Silverwood Group is unconformably overlain by and faulted against Early to Late Permian units including the Rokeby beds, Wallaby beds, Tunnel beds, Fitz Creek beds, Eight Mile Creek beds, Rhyolite Range beds and Condamine beds. Of these Permian units, all but the Condamine beds form part of the Wildash Succession. To the west, southwest and south, the Silverwood Group is intruded by the Late Triassic Herries and Stanthorpe Adamellites. All of these sequences and the two plutonic intrusives are unconformably overlain by the Jurassic sediments of the Marburg Sandstone. The Silverwood Group and Texas beds consist of various lithologies including grey, purple- grey, green and green-grey volcaniclastic conglomerates, sandstones, siltstones or mudstones, massive and laminated chert, polymict or monomict breccias, muddy breccias, muddy sandstones, and volcanic rocks. Volcanic rocks include various tholeiitic metabasites, dolerite, meta-andesites and infrequent metadacite. In the Silverwood Group, these volcanic rocks are often accompanied by mafic pyroclastic rocks (e.g. peperite and hyaloclastite). Facies analyses of these lithologies has led to the recognition of 19 deep-marine turbiditic and volcanic/volcaniclastic facies that were deposited by three main processes: i) gravity-flow processes (e.g. low- and high-density volcaniclastic turbidites and mass-flows), ii) chemical/biological processes (siliceous oozes- chert) and iii) direct initiation by volcanic processes (e.g. flows, hypabyssal intrusions and associated pyroclastic facies). For the Silverwood Group, the defined facies occur in distinct vertical associations that form recognisable 3rd and 4th-order architectural elements such as channel, levee, suprafan lobe, outer-fan, basin plain, mass transport complex, volcanic flows, syn-sedimentary sills and syn-sedimentary emergent cryptodomes. These architectural elements are represented in a series of deep-marine depositional environments including slope, shelf-edge failure, submarine-fan and subaqueous basaltic volcanoes. The Risdon Stud Formation and parts of the Connolly Volcanics were deposited along a 'normal' clastic or mud, mud/sand-rich and/or sand/mud-rich slope. Both upper and lower slope environments are represented and in both formations, the slope is speculated to have faced eastwards and prograded away from an active arc located west. Sediments from both successions accumulated at palaeodepths of 1200 to 2000 m. Although sediments from the upper part of the Bald Hill Formation were also deposited on a slope, these sequences have subsequently collapsed into the depocentre to form extensive slump deposits accompanied by olistoliths of older arc crust. The lower part of the Bald Hill Formation formed by similar processes, although the failure was far more extensive (>20 km along strike). This latter part of the formation is interpreted to be a major shelf-edge failure succession. Upper parts of the Bald Hill Formation also accumulated at palaeodepths of 1200 to 2000 m, but the deposition of these sediments occurred farthest from the shelf and at the greatest depth compared to the Risdon Stud Formation and Connolly Volcanics. Lower parts of the Bald Hill Formation were deposited at palaeodepths of approximately 1700 m. Subaqueous basaltic volcanoes are prominent in the Connolly Volcanics, Bald Hill Formation and Ormoral Volcanics. In the Bald Hill Formation, igneous rocks were emplaced into the shelf-edge failure succession as a series of syn-sedimentary sills and cryptodomes. These high-level hypabyssal rocks occasionally became emergent above the sediment-water interface, whereupon they were partially resedimented. In some parts of the Bald Hill Formation, the hypabyssal intrusions were blanketed by basin plain deposits that are contemporaneous with the slumps and olistoliths in the upper part of the formation. The intrusive rocks were emplaced at 1700 m palaeodepth. Unlike the Bald Hill Formation, the Ormoral Volcanics and lower parts of the Connolly Volcanics form thick accumulations of extrusive volcanic and pyroclastic rocks that built a significant volcanic pile. Volcanic and pyroclastic facies within these successions were deposited proximal to their source (0-10 km of vent). Extrusive rocks within the Ormoral Volcanics are thought to be derived from intrabasinal fissure-vents located at palaeodepths of 1700 to 3100 m. Igneous rocks from the Connolly Volcanics, Bald Hill Formation and Ormoral Volcanics have the petrological and geochemical characteristics of back-arc basin basalts (BAB) that were sourced from undepleted to slightly enriched Fertile MORB Mantle-wedge (FMM). The FMM material was variably enriched in trace elements by fluids derived from the subducting slab prior to emplacement of the igneous rocks. Immediately following emplacement, these rocks were hydrothermally metamorphosed under conditions of low-pressure and transitional low to high-temperature (200-300 °C). By contrast, igneous rocks within the Texas beds lack enrichment in subduction components and are characteristic of N-MORB. The Bromley Hills Formation is a sand-rich point-source submarine fan deposited at palaeodepths of 500 to 2000 m. The fan was initiated by a mass transport complex resulting from subaerial collapse of a basaltic-andesitic stratovolcano. The submarine fan is characterised by two repetitive stages of retrogressive sedimentation during which channel-levee elements (inner-fan channels) are overlain by suprafan lobe elements (mid-fan) and then by outer-fan deposits as sea-level rises within the depocentre. Both inner-fan channels and suprafan lobes show centralised stacking patterns with limited lateral migration that indicate the depocentre was laterally restricted during sedimentation (e.g. submarine ridges). The Bromley Hills Formation exhibits all the characteristics typical of an active margin fan that formed by a combination of tectonic stage initiation followed by eustatically controlled regressive deposition. Volcaniclastic sediments of the Silverwood Group range in composition from lithic to lithic- feldspathic wackes and arenites, although they are mainly lithic or feldspathic-lithic wackes and arenites. Many samples are tuffaceous (25-75% pyroclasts), particularly those from the Connolly Volcanics, Ormoral Volcanics and Bromley Hills Formation. Samples in the Bald Hills Formation and Texas beds can be classified as quartz-rich. The majority of the Silverwood Group was sourced from an undissected intraoceanic island-arc, although sediments within the Bald Hill Formation exhibit a provenance that is characteristic of uplift within the arc (recorded as a 'strike-slip continental arc' model). Epiclastic sediments from the Texas beds were sourced from a transitional to dissected continental arc. Formations of the Silverwood Group were mostly deposited in a series of intra-arc basins within an ancient intra-oceanic island arc, although the lowermost formation developed in a marginal basin (Risdon Stud Formation). All of the basins were located east of the active arc (behind the arc), keeping in mind the present location of the Group relative to the Texas-Coffs Harbour megafold. The entire succession formed during four-phases of arc-related basin development that coincide with major changes in the strain regime of the arc. From the base of the succession, these changes are: I) mid Cambrian to late Silurian marginal basin sedimentation- relative compression within the arc (Risdon Stud Formation), II) late Silurian to Early Devonian intra-arc rifting- relative extension within the arc (Connolly Volcanics), Ill) Early to early Middle Devonian basin collapse followed by intra-arc rifting- relative extension to compression (Bald Hill Formation and Ormoral Volcanics) and IV) early Middle to Late Devonian intra-arc submarine fan sedimentation- relative compression (Bromley Hills Formation). Comparing the Silverwood Group against equivalent terranes of Cambrian to Devonian age within the New England Fold Belt (NEFB) suggests that the Gamilaroi terrane, Calliope Volcanic Assemblage, Willowie Creek beds and Silverwood Group all formed as one intraoceanic island-arc during the Early to Late Devonian. Prior to this, significant differences in the sedimentological evolution of these terranes suggests that they occupied different positions relative to each other within the one arc. It is proposed that the NEFB formed as a result of dual west-directed subduction zones during the Cambrian to Middle Devonian period. During this time, a single intraoceanic island-arc located seaward of the Australian craton developed above a west-directed subduction zone. This arc was separated from the craton by a marginal sea. A second west-directed subduction zone was located beneath a continental arc developed on the Australian craton. Cambrian to Early Devonian terranes within and along the Peel Fault are proposed to form a part of the ancient subduction zone present beneath the intraoceanic island-arc (Weraerai and Djungati terranes). Collision of the intraoceanic island-arc occurred during the Late Devonian, at which point west-directed subduction occurred beneath the Australian craton and the accreted intraoceanic island-arc. Following collision, a new continental volcanic arc was established that was active during the Late Devonian to Early Carboniferous.

Volume overload is a common feature in patients on haemodialysis (HD). This contributes significantly to the cardiovascular disease burden seen in these patients. Clinical assessments of the volume state are often inaccurate. Techniques such as interdialytic blood pressure, relative blood volume monitoring, bioimpedance are available to improve clinical effectives. However all these techniques exhibit significant shortcomings in their accuracy, reliability and applicability at the bed side. We evaluated the usefulness of a dual compartment monitoring technique using Continuous Segmental Bioimpedance Spectroscopy (CSBIS) and Relative Blood Volume (RBV) as a tool to assess hydration status and determine dry weight. We also sought to evaluate the role of Atrial Natriuretic Peptide (ANP) and B-type Natriuretic Peptide (BNP) as a volume marker in dialysis patients. The Retrospective analysis of a historical cohort (n = 376, 55 Diabetic) showed a significant reduction in post-dialysis weights in the first three months of dialysis (72.5 to 70kg, p<0.027) with a non-significant increase in weight between months 6-12. The use of anti-hypertensive agents reduced insignificantly in the first 3 months, increased marginally between months 3-6 and significantly increased over the subsequent 6 months. The residual urea clearance (KRU) fell and dialysis times increased. The cohort was very different to that dialysing at Tassin and showed a dissociation between weight reduction and BP control. This may relate to occult volume overload. CSBIS-RBV monitoring in 9 patients with pulse ultrafiltration (pulse UF) showed distinct reproducible patterns relating to extra cellular fluid (ECF) and RBV rebound. An empirical Refill Ratio was then used to define the patterns of change and this was related to the state of their hydration. A value closer to unity was consistent with the attainment of best achievable target weight. The refill ratio fell significantly between the first (earlier) and third (last) rebound phase (1.97 ± 0.92 vs 1.32 ± 0.2). CSBIS monitoring was then carried out in 31 subjects, whilst varying dialysate composition, temperature and patient posture to analyse the effects of these changes on the ECF trace and to ascertain whether any of these interventions can trigger a change in the slope of the ECF trace distinct to that caused by UF. Only, isovolemic HD caused a change in both RBV and ECF in some patients that was explained by volume re-distribution due to gravitational shifts, poor vascular reactivity, sodium gradient between plasma and dialysate and the use of vasodilating antihypertensive agents. This has not been described previously. These will need to be explored further. The study did demonstrate a significant lack of comparability of absolute values of RECF between dialysis sessions even in the same patient. This too has not been described previously. This is likely to be due to subtle changes in fluid distribution between compartments. Therefore a relative changes must be studied. This sensitivity to subtle changes may increase the usefulness of the technique for ECF tracking through dialysis. The potential of dual compartment monitoring to track volume changes in real time was further explored in 29 patients of whom 21 achieved weight reductions and were able to be restudied. The Refill Ratio decreased significantly in the 21 patients who had their dry weights reduced by 0.95 ± 1.13 kg (1.41 ± 0.25 vs 1.25 ± 0.31). Blood pressure changes did not reach statistical significance. The technique was then used to examine differences in vascular refill between a 36oC and isothermic dialysis session in 20 stable prevalent patients. Pulse UF was carried out in both these sessions. There were no significant differences in Refill Ratios, energy removed and blood pressure response between the two sessions. The core temperature (CT) of these patients was close to 36oC and administering isothermic HD did not confer any additional benefit. Mean BNP levels in 12 patients during isovolemic HD and HD with UF did not relate to volume changes. ANP concentrations fell during a dialysis session in 11 patients from a mean 249 ± 143 pg/ml (mean ± SD) at the start of dialysis to 77 ± 65 pg/ml at the end of the session (p<0.001). During isolated UF levels did not change but fell in the ensuing sham phase indicating a time lag between volume loss and decreased generation. (136±99 pg/ml to 101±77.2 pg/ml; p<0.02) In a subsequent study ANP concentrations were measured throughout dialysis and in the post-HD period for 2 hours. A rebound in ANP concentration was observed occurring at around 90 min post-HD. The degree of this rebound may reflect the prevailing fluid state and merit further study. We have shown the utility of dual compartment monitoring with CSBIS-RBV technique and its potential in assessing volume changes in real time in haemodialysis patients. We have also shown the potential of ANP as an independent marker of volume status in the same setting. Both these techniques merit further study.

碩士
逢甲大學
水利工程與資源保育研究所
96
A numerical model is set up to simulate the density current on slope channel by solving the Navier-Stokes equations and advection-diffusion equation. This thesis presents a finite difference method with MAC staggered grid system. We apply the turbulent model, Large Eddy Simulation (LES), to calculate the influence of turbulence. By coordinate transformation, unregular physical region can be transformed to rectangular computational region. It is easy to handle the numerical process. The concept of Schmidt number, the ratio of momentum and mass mixings, is used in advection-diffusion equation. QUICK scheme is used for convection terms in advection-diffusion equation. The numerical model can capture the KH instability and convection instability of the density current. The simulation results are in good agreement with the experimental data, such as the concentration profile and the reach time of the head of the density current. Sensitive analysis showed that the range of turbulent Schmidt number of saline water between 100 and 1000 is suggested.

碩士
國立交通大學
土木工程學系
84
This study intends to develop a procedure to generate synthetic data for typical rivers in Taiwan. Four approaches were involved in development including data collection and analysis, file conversion to computer format, slope classification, and regression analysis for slope and the fundamental river parameters. In fact, the characteristics of a non-dimensional channel profile can be captured by Johnson SB distribution curve. Under the least square fitting, the complex channel profiles were represented by 3-parameter Johnson SB distribution parameters (γ,δ,α). It is rather straightforward to have these representative curves classified into categories with clustering analysis. Therefore, if the slope type is determined, the synthetic data about the river parameters can be generated through the above derived regression equations.

碩士
中原大學
資訊工程研究所
82
In the field of channel routing problem, Mixed Slope Model (MSM) is a young routing model.Mixed Slope Model has two wiring directions(+45°,-45°) than the directions (0°,90°) that Manhattan Model has.In this thesis, we propose a new multi- terminal channel router for Mixed-Slope Model.The proposed method is essentially a combination of the methods of greedy router and maze router. The algorithm in this thesis has following benefits: 1.Mixed Slope Model has less constraints than the Manhattan Model. And we have more chance to obtain better solution in channel routing. 2.We initially use greedy routing method to rapidly interconnect most of nets, and then employ minimum cost oriented maze router in order to interconnect the remaining nets. As a result, high connection ratio can be achieved. 3.The router algorithm in this thesis provides that net on one layer can be overlapped by other net on different layer. 4.We use objected-oriented technology to develop this algorithm. And it is convenient for modifying and extending. Extensive experiments have been made to test the performance of our router. As we expected, in most of the channels under tested, fewer tracks are needed in Mixed-Slope model than that in the MM. to route the channel completely. In some classical examples such as Shift by N Channel and Reverse by N channel, we can get solutions as well as other routers or better. In particular for Perfect Shuffle Permutation Channel we can get better solution which use tracks of the optimal solution. And we can also get better solution of Burstein Difficult Channel than the result of other router.

The Scotian margin of the east coast of Canada has a large theoretical gas hydrate stability zone (GHSZ) yet review of extensive industry seismic data reveals a prominent BSR at only one location. 3D seismic reflection and long offset (9 km) pre-stack 2D multichannel seismic data were used to study the velocity structure and geophysical characteristics of the hydrate zone and surrounding regions. The Mohican Channel study area shows a unique double BSR at 300 to 450 m below the seafloor in the western section of the study area immediately adjacent to the Mohican Channel in a water depth range of 1500- 1930m. The topmost BSR (BSR 1) is the more extensive of the two covering an area of 150 km2 in the 3D volume and a calculated area of 280 km2 using 2D industry and single-channel seismic profiles outside of the study area. BSR 2 covers an area of ~50 km2 and occurs approximately 80m below BSR 1. A system of polygonal faults is prominent in the area and some faults appear as conduits for gas leakage into the GHSZ. Fluid escape features are common on the surface of BSR 1 but rare on the seafloor suggesting that fluid flux is at lower levels than in the past.