The effect of climate on the fluvial system has long been investigated due the significant impact it can have on a river’s hydrological regime and fluvial processes. In recent years this interest has increased as global changes in climate are expected to bring more frequent high magnitude flood events globally and to North West Europe in particular. Despite the knowledge that the frequency and magnitude of floods is to increase, less is known about the geomorphological implications of this for river channels and where channel instability is likely to occur at both the river network and national scale. This is certainly the case in Scotland where increased flooding is expected and large floods have been abundant over the last two decades. To manage Scottish river catchments effectively in the future, in terms of hazard mitigation and nature conservation, river managers need to be able to predict not only how climate will impact flood magnitude and frequency in Scotland but the effect these changes will have on the internal dynamics of river channels in terms of erosion, sediment transport and deposition, and morphological dynamics. Such knowledge will ensure adequate measures are implemented to reduce fluvial risks to humans and to maintain and preserve valuable river habitats and linked species. In this thesis, several novel methods incorporating field, laboratory and GIS-based analysis, have been investigated as a means of predicting how climate change will affect channel stability in Scottish rivers and the implications of this for river management and river ecology. This includes (i) analysing the potential change in the frequency of geomorphologically-active flood flows with climate change; (ii) the use of stream power thresholds to predict changes in channel stability on a national scale with climate change; and (iii) using a Digital River Network developed using geospatial data to predict changes in the rate of bedload transfer and channel stability with climate change. Studies were undertaken on 13 different rivers across Scotland from north to south and east to west. vii As a case study of ecological implications, the thesis also examines how changes in habitat and stability of freshwater pearl mussels (Margaritifera margaritifera) may be altered by increased flooding. Predictions of the frequency of geomorphic activity, channel stability, rate of bedload transfer, and the stability of freshwater pearl mussel habitat with climate change are discussed along with the methods used to obtain these outcomes. The results all suggest an increase in the frequency and rate at which bedload is transferred through the river system and an increased frequency of flood flows resulting in greater channel instability. Morphological responses vary spatially with some river reaches experiencing greater increased erosion and transport potential than others. Climate change effects on the freshwater pearl mussel are: increased occasions of disturbance and transport downstream and the importance of specific populations in more stable environments for ensuring population recovery post flooding is highlighted. It is hoped that the methodologies developed for predicting changes in channel stability with climate change will provide useful screening tools to regulatory agencies which can be developed further to assist management decisions in the future which aim to reduce fluvial hazards and maintain good quality river environments for the species that inhabit it. The approaches used in this study allow for the identification of areas at high risk of morphological and ecological change, and the pro-active planning and management of sediment-related river management issues and nature conservation.

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Free-flowing water currents such as tides and unregulated water courses could contribute to world electricity production given the emergence of robust technical solutions for extracting the energy. At Uppsala University, a concept for converting the energy in water currents to electricity using a vertical axis turbine with fixed blade-pitch and a direct-drive permanent magnet generator is studied. Technological equipment for extracting energy from water currents can be studied at desktop to some extent, but physical realizations, first in a laboratory setting, and later in a natural aquatic setting, are necessary. For this reason, a laboratory generator has been constructed and evaluated, and an experimental setup comprising turbine, generator and control system has been constructed. The turbine and generator are to be deployed in the Dalälven River in Söderfors, and operated from an on-land control station. The author has worked with constructing and evaluating the low-speed laboratory generator, participated in the design and construction of the Söderfors generator, and designed and constructed the control system for Söderfors. The generator design incorporates a low rotational speed, permanent magnets, and many poles, in order to adapt the generator to the nature of water currents. Simulations and experimental data for the laboratory prototype have been compared and show that the simulation tool used is adequate for design studies of this type of generator. The generator has also been shown to be able to operate with the intended turbine design and range of water velocities. The control system to be used in Söderfors has been tested in a laboratory environment. Simulations of the control system show that it should be able to operate the turbine and generator at the desired rotational speeds in water velocities up to about 1.8 m/s. Simulations of the system have also shown that maximizing system power output may not correspond with maximizing turbine power.

Recent advances in remote-sensing technologies and analysis methods, specifically airborne-LiDAR elevation data and corresponding geographical information system (GIS) tools, present new opportunities for automated and rapid fluvial geomorphic (FGM) assessments that can cover entire watersheds. In this thesis, semi-automated GIS tools are used to extract channel centerlines and bankfull width values from digital elevation models (DEM) for five New England watersheds. For each study site, four centerlines are mapped. LiDAR and NED lines are delineated using ArcGIS spatial analyst tools with high-resolution (1-m to 2-m) LiDAR DEMs or USGS National Elevation Dataset (NED) DEMs, respectively. Resampled LiDAR decreases LiDAR DEM resolution and then runs spatial analyst tools. National Hydrography Dataset (NHD) lines are mapped by the USGS. All mapped lines are compared to centerlines delineated from photography and LiDAR DEMs. Bankfull widths at each site are determined through three methods. Regional regression equations are applied using variables derived from LiDAR and NED DEMs separately, producing two sets of width results. Additionally, the Hydrogeomorphological Geoprocessing Toolset (HGM) is used to extract widths from LiDAR data. Widths are also estimated visually from aerial photos and LiDAR DEMs. Widths measured directly in the field or derived from field-data are used as a baseline for comparison. I find that with a minimal amount of preprocessing, specifically through DEM resampling, LiDAR data can be used to model a channel that is highly correlated with the shape and location of the mapped channel. NED-derived channels model the mapped channel shape with even greater accuracy, and model the channel location only minimally less accurately. No tool used in this study accurately extracted bankfull width values, but analysis of LiDAR data by the HGM toolset did capture details that could not be resolved using regression equations. Overall, I conclude that automated, computerized LiDAR interpretation needs to improve significantly for the expense of data collection to be cost-effective at a watershed scale.

Rising energy demand, fossil fuel costs, and greenhouse gas emissions have led to a growing interest in renewable energy integration. Remote communities, often accompanied by high energy costs and abundant renewable energy resources, are ideal cases for renewable energy integration. The Queen Charlotte Islands, also known as Haida Gwaii, are a remote archipelago off the northwest coast of British Columbia, Canada that relies heavily on diesel fuel for energy generation. An investigation is done into the potential for electricity generation using both tidal stream and wave energy in Haida Gwaii. A mixed integer optimization network model is developed in a Matlab and GAMS software environment, subject to set of system constraints including minimum operational levels and transmission capacities. The unit commitment and economic dispatch decisions are dynamically solved for four periods of 336 hours, representing the four annual seasons. Optimization results are used to develop an operational strategy simulation model, indicative of realistic operator behaviour. Results from both models find that the tidal stream energy resource in Haida Gwaii has a larger potential to reduce energy costs than wave energy; however, tidal steam energy is more difficult to integrate from a system operation point of view and, in the absence of storage, would only be practical at power penetration levels less than 20%.

Common behavioral trends and characteristics of alluvial channels including rivers are extensively discussed in the literature. However, little is known about the hydrodynamic effects of seepage on alluvial channels. Factors like sand bed resistance, stream power of the channel, incipient motion of bed particles, and geometry of the channel cross section are significantly affected by seepage. This thesis presents the experimental investigations that are aimed to find out the quantitative effect of seepage, through a sand bed in downward (suction) direction, on the above mentioned factors. The problem in the sediment transport analysis is that the knowledge of complex interaction of several parameters with seepage cannot be fully obtained. In order to generalize the results, experiments are conducted in four rectangular smooth walled sand bed flumes under steady and fairly uniform flow conditions. Among the four, one is the Large Tilting Flume (LTF), which is 25 m long, 1.80 m wide and 1.00 m deep and with a seepage length of up to 20 m. This LTF is specially built at hydraulic laboratory, Indian Institute of Science exclusively for the present research work especially on alluvial channel regime. The experimental channels are designed to apply controlled amounts of uniform seepage flow in either direction in one flume (Flume-2), and only in downward direction to other three flumes (Flumes 1, 3 and 4). The application of seepage is perpendicular to the sand bed thickness over a sufficient length of the main channel. Appropriate instruments are used to accurately measure the basic experimental variables such as discharge in the main channel, seepage discharge, flow depth, water surface and bed slope, seepage gradients and cross sectional profiles. Experiments are carried out at different conditions (plane beds and curved shape channels) as explained below: Plane sediment beds Series – 1: Experiments to determine incipient motion of bed particles under no-seepage condition. Series – 2: Experiments on the non-transporting condition of the bed particles under both no-seepage and seepage condition. Series – 3: Experiments on the transporting condition of the bed particles under both no-seepage and seepage condition. Curved shape channels Series – A: Experiments to verify Lane’s (1953) geometric profile against higher discharge than prescribed by Lane (1953). Series – B: Experiments to verify the Lane’s (1953) geometric profile by allowing the discharge prescribed by Lane (1953). Series – C: Experiments to predict the final geometric profile by applying suction to Series – B experiments. A wide range of sediment particles are tested. Five different sized uniform sands (d50 = 1 mm, 0.56 mm, 0.65 mm, 1.00 mm and 1.77 mm) and gravel of size d50 = 8.00 mm are used for experimentation. Among the six sizes, three sizes (d50 = 0.56 mm, 0.65 mm, 2 mm) are used for seepage experimentation. The experimental data from the present experiments along with the available data from other sources on more sizes of sand are analyzed, thus covering a wide range of sand sizes. The following important results are obtained from the analysis. A new resistance equation has been developed for plane sediment beds (with little or no-transport) such that the average velocity in the channel depends on the shear velocity Reynolds number. A careful study has been done on incipient motion and concluded that incipient motion is better explained by critical stream power criterion for plane sediment beds. With the help of critical stream power criterion, a straightforward design procedure using design tables/design curves and analytical methods are presented to solve six possible design problems. For plane and non-transporting beds, in general, the stream power in the channel increases with suction and decreases with injection. The increase and decrease depend on the seepage power intensity parameter (NP), initial value of stream power (Ωbo), and critical stream power of the particles under no-seepage condition (Ωco). An expression relating all the influencing parameters is established to quantitatively estimate the stream power (Ωbs) variation with both the types of seepages, i.e., with suction and injection. It is found that the seepage has a significant influence in changing critical stream power for incipient motion of the bed material and the value is significantly different from the no-seepage critical value. An expression is established to quantitatively estimate the critical stream power with seepage (upward and downward) for a given critical stream power (Ωco) of the bed material under no-seepage conditions and initial stream power (Ωbo). It has been established that critical stream power curve used to define incipient motion is valid only for no-seepage condition of the bed and it cannot be used for sand beds under seepage condition, as seepage effects significantly alters the stream power. From the wide range of experimental data (including the observations from LTF) it is found that suction (downward seepage through the sand bed) enhances the transport or aids the incipient motion of bed particles which are initially at rest. Thus, suction reduces the stability and increases the erosion of bed particles when compared to no-seepage conditions. However, it is found that injection (upward seepage) affects in an opposite way, i.e., it can reduce the transport rate or even inhibit the incipient motion. Thus, injection increases the stability and reduces the erosion of bed particles when compared to no-seepage conditions. Therefore, it is concluded that suction increases the mobility of sand particles where as injection decreases their mobility. An expression to find the incipient motion with seepage (both suction and injection) is established in terms of stream power’s (Ωco, Ωbo and Ωbs) based on the present experimental data along with others' data. With the help of these expressions design procedure is developed for ten types of possible problems. A numerical model for spatially varied flow has been developed with the help of the seepage governing equations, developed in this thesis, to compute flow profiles along the channel length. A methodology of predicting the location of incipient motion section in sand bed channels affected by seepage is also presented. Channel geometry affected by seepage (suction) is established in the form of regression relationships for perimeter, flow depth and slope of the channel. Different combinations (bi-variate and tri-variate) of dimensional and non-dimensional regression relationships are developed. An approach to channel design has been developed based on the application of functional analysis of the salient variables that control the channel behavior. And also, it has been established that, Lane’s (1953) profile almost matches with experimental profile for no-seepage condition. The present investigation clearly shows the significance of seepage in altering the hydraulic and sediment transport behavior of sand bed channels. From the practicing engineer’s point of view it is hoped that present design procedures will be helpful in safe guarding the seepage affected channels.

La migration latérale est reconnue comme un processus majeur à préserver pour le bon fonctionnement des écosystèmes aquatiques. Ce travail explore sa variabilité spatiale dans le Sud-Est de la France en appui à la mise en œuvre de la Directive Cadre sur l’Eau.Une première partie développe un cadre méthodologique et des outils géomatiques pour la caractérisation géomorphologique et l’analyse multi-scalaire des systèmes fluviaux à partir de données disponibles à large échelle. Un premier article présente la démarche générale basée sur l’agrégation et la désagrégation spatiale d’objets vectoriels. Un second article aborde spécifiquement le problème de l’agrégation spatiale et vise à comparer des techniques statistiques pour la sectorisation d’un continuum en tronçons homogènes. Des exemples illustrent l’intérêt et les limites des outils développés.Une seconde partie porte sur la régionalisation de la dynamique latérale des lits fluviaux. Un troisième article caractérise et modélise son intensité à partir de variables simples à extraire à l'échelle régionale. Il montre qu’elle est structurée spatialement et positivement corrélée à la puissance fluviale. Néanmoins, des limites inhérentes à la modélisation empirique et la nécessaire prise en compte de variables complémentaires à l’échelle régionale émergent (apport sédimentaire notamment). Un quatrième article porte spécifiquement sur les lits à tresses et montre que près de la moitié des 1200 kilomètres recensés avant la construction des grandes infrastructures ont disparu du fait de pressions anthropiques directes et indirectes. Il révèle par ailleurs la grande diversité géomorphologique de ce style fluvial dans le bassin rhodanien. / The channel migration is a key process for preserving the aquatic ecosystem functioning. This work explores its spatial variability throughout the South-East French hydrographic network for the implementation of the European Water Framework Directive.A first part develops a methodological framework and geomatic tools for the characterization and analysis of the fluvial systems for a range of scales from spatially continuous data available at the large scale. A first paper introduces the methodological framework based on the spatial disaggregation and aggregation of geographical objects. A second paper focuses specifically on the aggregating problem and aims to compare statistical techniques for delineating homogeneous reaches along a continuum. Examples illustrate the potentialities and limits of the tools we developed. A second part focuses on the regionalization of the channel migration. A third paper characterizes and models the migration rates from simple variables that can be extracted at the large scale. We show that the migration rate is spatially organized and positively controlled by the gross stream power. Nevertheless, limits of the regional-scale empirical modeling emerge, as well as additional variables that should be integrated (particularly the sediment supply). A fourth paper focuses specifically on braided rivers and shows that near the half of the 1200 kilometers censed prior to the major infrastructure construction disappeared due to direct and indirect human impacts. It also reveals the high geomorphic diversity of the contemporary braided rivers in the Rhône basin.