This thesis presents a study of three similar, yet contrasting, arroyos: the Rio Puerco, New Mexico and the Santa Cruz and San Simon Rivers in Arizona. Arroyo systems have been subject to several periods of cut and fill within recent geologic time. The most recent incision phase occurred during the mid- to late-19th Century, enabling subsequent morphological changes to be observed. Observations indicate that these systems have developed distinct geomorphological reaches, which evolve at different rates within the constraints of the specific controlling variables, most importantly discharge, sediment load and artificial alteration. Thus, location-for-time substitution cannot be assumed. Within the continuum of morphological change, six stages were identified, enabling a general model of arroyo evolution to be developed. Precipitation has increased in the south-western USA. However, within the arroyos studied, some gauges have seen a concurrent increase in discharge, whereas others have experienced a decline. It was discovered that the different responses were explained by the interaction between discharge and morphology at different stages of evolution. The first four stages of arroyo evolution differ little from those proposed previously. However, this study has emphasised the necessity of recognising the event-driven nature of morphological change within the system during these stages. Since some change occurs during each flood, the arroyo morphology is controlled by a combination of the flow variability and channel-deforming events. As aggradation predominates, the arroyo develops a quasi-stable form, creating a feedback between discharge and morphology. High-magnitude flows are suppressed and aggradation is promoted, permitting continued stabilisation until a quasi-equilibrium form is attained, typified by a trapezoidal active channel and densely vegetated inner floodplain. These morphological changes alter the discharge regime sufficiently that lower-magnitude flows assume greater relative effectiveness. It is not until a quasi-equilibrium morphology becomes adjusted to the effective discharge, at which point the effective discharge becomes a truly channel-forming and maintaining flow.

Hydrological, hydrochemical and sedimentological observations were undertaken in the catchments of Feevispa (Feegletscher), Findelenbach(Findelengletscher) and Gornera (Gornergletscher), Swiss Alps, in an attempt to use meltwater characteristics as indicators of the nature and functioning of glacial hydrological systems. Annual and seasonal hydrographs of the Feevispa allowed calculation of catchment water balance. Considerable annual variation resulted from excess icemelt over snow accumulation giving greater outputs than inputs. Diurnal hydrograph analysis showed that large quantities of water are stored in Feegletscher and Gornergletscher. Rapid erratic fluctuations of subglacial sediment supply caused involutions in daily clockwise suspended sediment concentration-discharge hysteresis loops in the Gornera. During draining of the Gornera, exceptionally high discharges evacuated large quantities of sediment from beneath Gornergletscher, but bequeathed no lasting impact on conduit capacity. Close interval sampling and continuous monitoring of sediment concentration permit interpretation of the nature of ice-meltwater-sediment interactions on Alpine glacier beds. Chemical composition of meltwaters emerging from the glacier portals was monitored during several ablation seasons. Electrical conductivity, a surrogate measure of ionic content, was continuously recorded and Na+, K+, Ca2+ and Mg2+ determined by atomic absorption spectrophotometry. Meltwaters from glacier surfaces have low solute contents, of atmospheric origins, whereas after passage through internal conduits; meltwaters become chemically enriched from lithospheric contact. Marked diurnal variations (clockwise hysteresis) of solute concentration in portal meltstreams reflect the mixing in varying proportions through time of waters of different compositions, delimiting trapezoidal solute concentration discharge relationships. Two components of discharge through Findelengletscher and Gornergletscher were separated on the basis of chemical composition using a simple mass-balance mixing model. A large proportion of total flow passes rapidly through major moulin-arterial canal networks. For basal flow, two contrasting regimes were discriminated, both independent of (Findelengletscher) and interlinked with (Gornergletscher) cavity storage at the ice-bedrock interface.

The application of many existing numerical models of river channel morphology is limited by their inability to account for bank erosion and changing channel width through time. In this research, a physically-based numerical model which simulates the evolution of channel morphology, including channel width, through time has been developed and tested. Predictions of channel evolution are obtained by solving deterministically the governing equations of flow resistance, flow, sediment transport, bank stability and conservation of sediment mass. The model is applicable to relatively straight, sand-bed streams with cohesive bank materials. In the channel evolution model, a method is used to solve the shallow water flow equations, and to account for lateral shear stresses which significantly influence the flow in the near bank zone. The predicted distribution of flow is then used to predict the sediment transport over the full width of straight river channels. Deformation of the bed is calculated from solution of the sediment continuity equation. Predictions obtained in the near bank zone allow the variation in bank geometry to be simulated through time. Since bank stability is determined by the constraints of the geometry of the bank and the geotechnical properties of the bank material, channel widening can, therefore, be simulated by combining a suitable bank stability algorithm with flow and sediment transport algorithms. In combining bank stability algorithms with flow and sediment transport algorithms, there are two paramount considerations. First, the longitudinal extent of mass failures within modelled reaches must be accounted for. Second, it is necessary to maintain the continuity of both the bed and the bank material mixture in the time steps following mass failure, when the bed material consists of mixtures of bed and bank materials with widely varying physical properties. In this model, a probabilistic approach to prediction of factor of safety is used to estimate the fraction of the banks in the modelled reaches that fail in any time step. Mixed layer theory is then used to model the transport of the resulting bed and bank material mixture away from the near bank zone. Comparisons of model predictions with observations of channel geometry over a 24 year period indicate that the new model is capable of simulating temporal trends of channel morphology with a high degree of accuracy. The model has been used successfully to replicate the form of empirically-derived hydraulic geometry equations, indicating that the model is also able to predict stable channel geometries accurately. The numerical model has also been used to investigate the influence of varying the independent variables and boundary conditions on channel adjustment dynamics.

The sheltered bays of the Orkney Islands are backed by extensive dune systems that commonly contain archaeological sites, many of which now protrude from cliffed sections due to coastal erosion. In an area where other dating techniques are often precluded due to a lack of organic dating material, this research establishes that optically stimulated luminescence (OSL) dating can provide a viable and robust alternative by dating wind blown sands within the sites to constrain the archaeological age. Since this is the case, the OSL chronology can also be applied to natural sites where no archaeological chronology exists and so be used in palaeoenvironmental reconstruction. Six periods of increased sand movement are recorded in the Orkney Islands at the sites sampled; the Neolithic, the Bronze Age, two periods in the Iron Age, the Viking/Medieval period and the Little Ice Age. The phases of sand movement identified using OSL in the Orkney Islands are also identified at other sites in Scotland and north-east Europe and support the chronologies derived from other environmental indicators such as tree rings and peat bogs. It is suggested that at least two events may be related to the deterioration in climate subsequent to the eruption of Hekla 4 in the late Neolithic and Hekla 3 in the late Bronze Age. However, OSL dating requires that the latent luminescence signal within quartz and feldspar is rapidly reduced to near zero by exposure to light, yet the rate and extent of bleaching depends on the length of time that the grains are exposed and the light intensity at the time of exposure. Bleaching experiments used here confirmed that not only is there a difference in the rate of bleaching between quartz and feldspar depending on the light intensity, but that there is also a difference in the rate of bleaching between samples from different geological areas and this needs to be taken into account in future research. The residual levels from the Orcadian modern beach sands (<0.5 Gy) suggest that some samples collected for OSL dating may be partially bleached and a new technique, the psi (?) ratio, is proposed here to identify partially bleached sediments.

This thesis describes research into remotely sensed weather radar information systems and specifically addresses three problems; 1) Weather radar data processing; 2) Real-time flood forecasting models and 3) Computer system design for the realisation of the real-time flood forecasting system using radar data. Quantitative rainfall measurements utilising weather radar is of high temporal and spatial resolution when compared with traditional rainfall measurements. Analysis was carried out to assessth e type of radar datap roductsr equired for operational use in flood forecastings ystem. This includes issues of data processing such as quantisation, temporal sampling and spatial sampling. The influence of the data process on hydrological applications is also addressed. Theoretical analysis was carried out to probe the characteristics of Transfer Function Models and robust flood forecasting modelling procedure is proposed. The proposed model is always stable and physical realisable and is described as PRTF (Physical Realisable Transfer Function model). Algorithms and software for the identification of PRTF are presented. It was found that such a model is easy to identify and more importantly it can be updated robustly in real time. By changing the impulse response of the PRTF, it has been found that significant improvements can be observed in river flow simulation. A RST (Rainfall S eparation Tank) model was developed and incorporated into the PRTF model. The adaptivity of the PRTF also has the potential to make use of high spatial resolution radar rainfall data and could be further incorporated into an Expert System suitable for real-time application. Finally, the thesis includes the development of the WRIP system (Weather Radar Information Processor). Such a system can process weather radar information and use it for the real-time flood forecasting. The system design consists of database design, user interface design and program design. An object-oriented computing concept is used in the program design. The final system is currently in test operation within the N. R. A Wessex Region, including the man machine interface (MMI) incorporating a portable computer based data acquisition and display system known by the acronym `STORM' (System To Obtain Radar Rainfall Measurements).

Currently, the system that developing countries use to map coffee crops is expensive, tedious and inaccurate; therefore coffee maps cannot be updated frequently and production cannot be accurately estimated. If such countries could map coffee crops in a cost-effective way, they would have an advantage in terms of setting the prices and getting a higher return for their product. Here I hypothesize that coffee systems can be properly characterized and mapped using the spectral and spatial information derived from satellite images and topographic data. I also believe that during the spatial analysis of the data, the additional information provided by an object-based approach (comprehensive information about the shape and context of a particular area) provides more information than a pixel-based one, traditionally used in the integration of Remote Sensing and Geographic Information Systems (GIS). I statistically analyzed spatial and spectral characteristics of different coffee systems (monoculture, polyculture and agroforestry systems) in three study areas in Colombia of 70km2 each. I integrated satellite images and topographic grids using both pixel-based and object-based approaches in a hierarchical approach and the results were compared. Following this hierarchical approach, a preliminary classification was performed to reduce the number of classes spectrally similar to coffee systems. Then in a second step, the classification was refined using decision rules from the statistical analysis of objects (composed of at least 3 pixels). Finally, using the same objects, the classification was refined further, through linear spectral unmixing. The results show that the rule-based classification combined with an object-based approach can improve the overall accuracy of the classification by 3% and by 17.47% for the coffee class when compared to the pixel-based analysis. The linear spectral unmixing, however, does not contribute to improve the classification a / Actuellement, le système que les pays en voie de développement emploient pour cartographier les récoltes de café est cher, pénible et imprécis. Ainsi, les cartes de café ne peuvent être mises à jour fréquemment et la production ne peut pas être estimée avec exactitude. Si ces pays pouvaient cartographier les récoltes de café d'une manière plus économique, ils auraient un avantage pour fixer les prix et obtenir des revenus plus élevés pour leur produit. Je pose ici l'hypothèse que les zones de café peuvent être correctement caractérisés et cartographiés en utilisant l'information spectrale et spatiale dérivée des images satellites et des données topographiques. Je suppose également que pendant l'analyse spatiale des données, l'information additionnelle fournie par une approche 'object-basée' (informations complètes sur la forme et le contexte d'une zone particulière) fournit plus d'informations que qu'une approche 'pixel-basée', traditionnellement utilisée dans l'intégration de la télédétection et des systèmes d'information géographiques (GIS). J'ai analysé (statistiquement) les caractéristiques spatiales et spectrales des systèmes de café dans trois secteurs d'étude en Colombie de 70km2 chacun. J'ai intégré des images satellites et des grilles topographiques en utilisant les 2 approches 'pixel-basée' et 'object-basée' dans une approche hiérarchique et les résultats ont été comparés. Des objets ont été formés sur la base de la similitude spectrale des bandes 2.3.4 5 et 7. Après l'approche hiérarchique, une classification préliminaire a été effectuée pour réduire le nombre de classes spectralement semblables aux systèmes de café. Alors, dans une deuxième étape, la classification est affinée en utilisant des règles de décision sur l'analyse statistique de plus petits objets (composés de 5 pixel ou moins). Finalement, en utilisant les mêmes objets, la classification a été de nouveau affin

Climate change is expected to have a significant impact on arctic regions, most notably in ice-rich permafrost regions. Retrogressive thaw slumps, backwasting resulting from the exposure of ice-rich permafrost, are a prominent thermokarst feature throughout the arctic and are projected to increase in frequency and extent under warming climate scenarios. However, there is limited information on retrogressive thaw slump activity and field observations are complicated by dynamic interactions between morphology and climate. This work attempts to further define these controls to increase understanding of retrogressive thaw slump processes. Spatial variations in headwall retreat indicate energy input and morphological influence on the landform. Morphologic factors such as ice face angles and the nature of ground ice are observed and analyzed for a relation to ice ablation and headwall retreat. Additionally, spatial microclimates are investigated to define the specific energy conditions at the ablating ice face. Analysis indicates that air temperatures in the vicinity of the ice face vary from exterior temperatures in response to solar radiation and wind speed and direction. Periods of high solar radiation and winds originating from upslope of the headwall potentially create a feedback process for headwall retreat. / Les changements climatiques auront des impacts significatifs sur les regions arctiques, particulièrement les régions de pergélisol. Les glissements régressif dû au dégel (retrogressive thaw slumps), sont le résultat de l'exposition du pergélisol riche en glace. Ces glissements sont des formes de terrain (thermokarst) communes aux régions arctiques, et leur fréquence et distribution risquent d'augmenter due aux scénarios de changements climatiques. Toutefois, nous avons des connaissances limitées sur l'activité des glissements régressif dû au dégel et les observations de terrain sont compliquées dues aux interactions dynamiques entre la morphologie et le climat. La présente étude tente de définir les facteurs de contrôle afin d'améliorer notre compréhension du processus des glissement régressif dû au dégel. Les variations spatiales du retrait du mur frontal (headwall) indiquent un intrant d'énergie et une influence morphologique de la forme de terrain. Les facteurs morphologiques, tels l'angle du front de glace et la nature de la glace souterraine ont été observées et analysées en relation avec le taux d'ablation de la glace et le retrait du front (headwall). De plus, les patrons spatiaux de micro-climat ont été étudiés afin de définir les conditions spécifiques d'énergie au front d'ablation de la glace. Les analyses ont indiqué que la température de l'air à proximité de la paroi de glace varie comparativement à la température extérieure, en réponse à la radiation solaire et la vitesse et direction du vent. Les périodes de haute radiation solaire et les vents qui proviennent du haut du mur frontal ont le potentiel de créer un processus de retrait du mur frontal.

Soil carbon storage is an important ecosystem service of tidal salt marshes, but is this service maintained under an agricultural use? Sheep grazing on Quebec's Île Verte, in the upper estuary of the St. Lawrence River, provided an opportunity to examine whether seven summers of grazing negatively affected soil carbon storage in high latitude tidal salt marshes. I compared plant biomass and soil properties in grazed and ungrazed sections. Above- and below-ground production was assessed through plant litter, end-of-season standing crop, and roots and rhizomes in ingrowth core measurements. Edaphic properties were measured from 10 cm soil cores. The grazed marsh had higher soil carbon density and belowground biomass, yet lower aboveground biomass. Greater soil carbon density was attributable to grazing, as at this latitude, marsh soil remained frozen through April. Greater solar exposure of grazed soils during spring and summer allowed for warmer soils and thus a longer growing season for belowground growth. / Le stockage de carbone dans les sols est un service important dans l'écosystème des marais salants, mais ce service est-il maintenu lors de l'utilisation agricole? Des moutons broutant sur l'Île Verte, dans l'estuaire supérieur du fleuve du Saint Laurent, nous donnent l'occasion de mesurer si sept étés de broutage ont négativement affecté le stockage de carbone de sol des marais salants de latitude élevée. J'ai comparé des biomasses et des propriétés de sol dans les sections broutés et intactes. La production à la surface et souterraine de la litière végétale sont évaluées par la récolte à la fin de la saison, et les racines et rhizomes dans des mesures d'échantillons de sols. Des propriétés édaphiques ont été mesurées à partir d'échantillons de sol de 10 cm. Le marais brouté avait une densité plus élevée de carbone de sol et de biomasse souterraine, mais une baisse de biomasse en surface. Une plus grande densité de carbone de sol était attribuable au pâturage, comme à cette latitude, le sol de marais reste gelé jusqu'en avril. Pendant le printemps et l'été, une plus grande exposition solaire des sols réchauffe les sols et apporte une plus longue période de croissance végétale.

Land use and land cover change are complex phenomena that operate across multiple scales, necessitating a multiple methods research approach. This thesis demonstrates how multiple methods can be used to investigate land use and land cover in the Malaprabha watershed, Karnataka, southern India at multiple scales. First, supervised classification through analysis of satellite images is carried out across the entire watershed in order to map specific crops, irrigation use, and multiple cropping rotations. Second, four qualitative field methods, namely semi-structured interviews, focus groups, participant observation and transect walks, are employed to gather data on the mechanisms and meanings of two particular land uses, irrigation and crop choice, in three villages within the Malaprabha watershed. By combining both remote sensing and qualitative field-based approaches, this research shows the utility of a multiple methods approach in uncovering the multi-scalar dimensions of land use and land cover in a complex agricultural landscape. / L'occupation du sol et les changements de couverture végétale sont des phénomènes complexes qui s'opèrent à différentes échelles, exigeant d'une approche de recherche qu'elle envisage des méthodes multiples pour les appréhender. Cette mémoire présente comment une combinaison de méthodologies peuvent être utilisées pour une investigation à différentes échelles de l'emploi des terres et de la couverture végétale dans le bassin versant du fleuve Malaprabha, situé dans l'état de Karnataka, dans le sud de l'Inde. Premièrement, une classification supervisée de la couverture végétale de la totalité du bassin versant a été menée à partir de l'analyse d'images satellites. Ceci a permi de cartographier certaines cultures, l'utilisation d'irrigation, et les séquences de rotation des cultures. Deuxièmement, afin de collecter de l'information sur le fonctionnement et le sens accordés à deux pratiques agricoles, l'irrigation et le choix de cultures, quatre méthodologies qualitatives ont été utilisées dans trois villages, à savoir, des entrevues semi-structurées, des groupes de discussions, de l'observation participante, et des parcours de transects. En combinant l'analyse d'images satellites et les méthodologies qualitatives, cette recherche démontre l'utilité d'une approche multi-méthodologique pour lire les différents jeux d'échelles dans l'emploi des terres et les changements de couverture végétale au sein d'un paysage agricole complexe et hétérogène.

The rapid change in climate currently being recorded in the Western Canadian Arctic is projected to have a major influence on the permafrost ground that underlies more than half of Canada's landmass. The isolation of this vast landscape has inhibited scientific research consequently limiting the body of knowledge on sub-surface permafrost features. Specifically, there is limited information about massive ground ice units, large tabular bodies of ice with a gravimetric moisture content greater than 250% (percent dry weight). Massive ground ice bodies originate from the burial of surface ice, such as glaciers or snowbanks or from the in-situ freezing of groundwater, termed intrasedimental ice. The environmental history held within the ice provides valuable information on the progression of past climates and the high water content frozen within this ice can cause widespread changes on the topography, infrastructure and ultimately the people of this region who use the land. Located in the headwalls of retrogressive thaw slumps on Herschel Island, Yukon, natural exposures of massive ground ice provided an ideal setting for studying ice units with uncertain origins. Within this study, seventeen distinct massive ice units, observed in four different exposures, were sampled for laboratory analysis. The aim of this research is to resolve the origin of these less understood massive ice bodies with a recently developed tool that analyzes the molar ratios of atmospheric gases occluded within the ice units. This is supported with the recognized method of cryostratigraphy, O-H stable isotopes analysis and geochemical measurements. The results of these tests, presented in two manuscripts, reveal a complicated cryotic history that identifies massive ice units with atmospheric and intrasedimental characteristics. An isolated unit of white ice observed in the upper portion of a retrogressive thaw slump exhibits a strong atmospheric signature with low atmospheric gas ratios of N2/Ar and δD vs. δ18O regression line that closely parallels the local meteoric water line (LMWL). An atmospheric origin for this unit of ice is further supported by low conductivity values measured within the ice unit. These chemical investigations combined with an equally conclusive cryostratigraphic examination suggest that this massive ice unit is a recently buried snowbank. A proposed model of snowbank burial is also presented to clarify and support this conclusion. A distinctive unit of blue coloured ice exposed at an ocean bluff contained occluded gasses with molar ratios of N2/Ar and O2/Ar gas that were strongly correlated to the same gas ratios measured in the current atmosphere. A vertical transect within a large retrogressive thaw slump on the south shore of the island distinguished seven separate massive ice units in addition to an ice wedge. Two of the units measured revealed intrasedimental ice origins due to low N2/Ar atmospheric gas ratios and high conductivity values. A third isolated unit of white ice, confined by unconformities, reflected a molar gas ratio of N2/Ar that strongly correlated with the N2/Ar ratio of the current atmosphere measured during the study. An atmospheric source for this ice was further supported by a δD vs. δ18O regression line similar to that of the LMWL. These findings provide a new layer of interpretation adding to the previously established body of knowledge and produce a more decisive explanation to the origin of massive ice units on Herschel Island. This work is relevant for understanding the origin and nature of the massive ice units, the geomorphic response to past climates and providing important information for the responsible development and management of this landscape in the future both on Herschel Island Territorial Park and throughout the Western Canadian Arctic. / Le changement rapide du climat actuellement observé dans l'Arctique de l'Ouest Canadien devrait avoir une influence majeure sur le pergélisol représentant plus de la moitié de la masse continentale du Canada. L'isolement de ces vastes étendues a limité les efforts de recherche scientifique à leur sujet et par conséquent le niveau de connaissances des caractéristiques du pergélisol. Plus particulièrement, peu d'information existe au sujet des unités massives de glace de sol, c'est-à-dire de grands corps tabulaire de glace avec une teneur en humidité gravimétrique supérieure à 250% (pour cent en poids sec), que l'on retrouve dans ces régions. Ces glaces de sol peuvent provenir de l'enterrement d'étendue de glace en surface, tels que des glaciers, des bancs de neige, ou encore de la congélation in situ d'eaux souterraines, autrement nommées glaces intrasedimental. La glace de sol peut fournir de précieuse information sur l'historique et l'évolution des climats passés. La haute teneur en eau congelé dans la glace peut causer d'importants changements dans la topographie, pour les infrastructures et ultimement pour les habitants de cette région qui font usage du sol.Situé dans le mur de tête de glissements de dégel rétrogressif de l'île Herschel au Yukon, des affleurements de glace souterraine fournissent un cadre idéal pour étudier des unités de glace ayant des origines incertaines. Pour la présente étude, dix-sept unités de glace massive distinctes, observée dans quatre expositions différentes, ont été échantillonnés pour l'analyse en laboratoire. Le but de cette recherche est de comprendre l'origine de ces unités de glace massive moins bien connues en faisant usage d'un outil récemment développé permettant d'analyser les rapports molaires entre differents gaz atmosphériques occlus à l'intérieur des unités de glace. Cette approche repose sur la méthode reconnue de cryostratigraphy, sur l'analyse d'isotopes stables O-H ainsi que sur des mesures géochimiques. Les résultats de ces tests, présentés en deux manuscrits, révèlent une histoire cryotique complexe identifiant des unités de glace massive avec des caractéristiques atmosphériques et intrasedimental.Une unité isolée de glace blanche ayant été observée dans la partie supérieure d'un glissements de dégel rétrogressif présente une signature atmosphérique forte avec de faibles ratios de gaz atmosphériques N2/Ar ainsi qu'une droite de régression δD vs. δ18O qui se rapproche étroitement de la ligne d'eau locales météorique. L'hypothèse d'une origine atmosphérique pour cette unité de la glace est soutenu par de faibles valeurs de conductivité mesurées à meme l'unité de la glace. Ces études chimiques combinées à un examen cryostratigraphique tout aussi concluant suggèrent que cette unité massive de glace est en fait un banc de neige récemment enterré. Un modèle d'enterrement de banc de neige est également présenté à clarifier pour appuyer cette conclusion.Une unité distincte de glace de couleur bleue exposée par un bluff océanique contient des gaz occlus avec des ratios molaires de N2/Ar et de O2/Ar fortement corrélées aux mêmes ratios mesurées dans l'atmosphère actuel. Deux des unités mesurées révélé une origines de glace intrasedimental en raison du faible taux de N2/Ar gaz atmosphériques et d'une conductivité élevée. Une troisième unité de glace blanche isolée et confinée reflète un ratio molaire des gaz N2/Ar fortement corrélée avec le ratio N2/Ar de l'atmosphère actuel. Une origine atmosphérique pour cette unité de glace est aussi soutenue par une ligne de régression δD vs. δ18O similaire à celle de l'LMWL.Ces résultats fournissent une nouvelle couche d'interprétation qui s'ajoute aux connaissances précédemment établies et fournissent une explication plus robuste quant à l'origine des unités de glace massive sur l'île Herschel.