Bank erosion processes are identified on the basis of current geomorphological and engineering literature and some preliminary field observations. Equations are developed to describe the stability of a bank in relation to the failure mechanisms associated with these processes. The terms in the equations are fundamental parameters of hydraulics and soil mechanics. The equations describe the static equilibrium of a potential failure surface in terms of a factor of safety. The lowest factor of safety for the potential failure surfaces associated with the various erosion processes, defines the case of limiting stability and the critical mode of failure. Comparison of the various factors of safety indicates the relative effectiveness of the process and allows identification of the dominant process (or processes) for a specific bank. Some of the stability analyses are standard civil engineering techniques, others are presented here for the first time. Special emphasis is placed upon consideration of low composite banks, which are ubiquitous to flood plain rivers with coarse beds. These banks are characterised by cantilever overhangs in the upper bank. Three modes of failure are identified and analysed. Beam and tensional failures dominate banks with highly cohesive top strata, shear failures are more likely in sandy soils with a low degree of cohesion. The accuracy and reliability of the new equations is tested by applying them to specific sections of bank at several experimental sites. Flow parameters are measured using an electromagnetic flowmeter and the patterns of secondary flow close to eroding banks in meander bends are closely investigated. Engineering parameters for bank materials are examined using standard civil engineering techniques. Predictions based on these data and the theoretical equations are tested against observations of bank erosion processes made using standard techniques for geomorphological process studies. The study shows that the stability of natural river banks can be described successfully using equations which are based on the basic principles of hydraulics and soil mechanics. It is apparent from the study that all river banks are fluvially controlled. This is the case because the nature of erosion processes operating on the bank is determined by the degree of fluvial activity at the base. The new equations presented here are not yet fully developed and further work is required before any of them could be adopted as standard techniques. They do however have a sound theoretical basis and their functional form is thought to be correct. In this case the equations should merit further consideration and development.

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This thesis investigates the long-term changes and shorter-term variability in monthly, seasonal, and arL'1ual discharge between 1882 and 2004 of two rivers, the Severnaya Dvina (SD) and the Sukhona (SU), draining north-western Russia, and links these changes to climatic variability. The Severnaya Dvina is one of the largest rivers of the lUetic Ocean basin and changes in its discharge can potentially affect the Thermohaline Circulation. The SU is a tributary to SD and results have been used to corroborate findings obtained for SD. It has been suggested by previous studies that discharge of the rivers draining the Eurasian sector of the Arctic basin has significantly increased. However, these studies started during one afthe warmest and driest periods on record in the 930s. Analysis of the discharge records of the SD and the SU has shown that that there has been no long-term, linear change in discharge. Strong interdecadal variability characterises both records and a number of significant shifts from lower to higher discharge occurs. The early part of the records (1882 - the early 1930s) is characterised by high annual discharge with many strong positive anomalies. A period of low discharge started in the dry 1930s and continued until the early 1970s. The last decades were characterised by average annual discharge. The main implication from this study is that freshwater inflow trom European Russia into the Arctic Ocean has not changed since 1882. Oscillations in regional climate and large-scale atmospheric circulation (telecop..nection patterns) drive discharge variability. There are close causal links between variability in regional precipitation, air temperature, snow cover, evaporation, and discharge. Variability in teleconnection indices (most importantly North Atlantic Oscillation, Scandinavian and East Atlantic Jet pattern) explains between 13% (summer) and 48% (winter) variance in seasonal discharge. Construction of regression models simulating hydrological variability using climatic variables shows close agreement between modelled and observed values of summer, autumn, and winter discharge of the SD

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Scarp and Vale' topography is typified by the Cotswolds region with the present-day landscape being the aggregate of earlier tectonic movement and surface processes. The primary aim of this thesis is to disentangle these landscape components, the .feedbacks between them and their driving mechanisms. Modelling suggests that flexure, in response to denudational unloading, may account for ~35% of local Pleistocene relief. Shape-fitting, between the model and landscape observations, shows the local lithosphere to be relatively weak and the uplift to be spatially varying. River longitudinal profiles adjust to extrinsic variables, such as tectonic movement, base level change and climate fluctuation. Parametrisation of 66 Cotswold draining rivers revealed trends, in their concavity and steepness index, consistent with those of the modelled uplift. Similar trends were sought from geomorphic analysis of the fluvial sinuosity and basin hypsometry. There is a morphological control to channel sinuosity as it is found to be dependent upon flow orientation. A positive relationship is observed. between hypsometric integral and proposed uplift, for the dip-slope basins. The accumulated geomorphic evidence does not prove the flexure modelling results, however, they are consistent with it. Viscoelastic modelling calculates the rate of lithospheric relaxation. It predicts high ' initial uplift rates which decrease rapidly and the attainment of topographic equilibrium within ~2o-50 ka of unloading. This is significantly lower than the climate cycle duration of 100 ka. Linking this result with a terrace aggradation and incision model, a schematic model of landscape evolution is produced. This incorporates the regional background uplift, a fluctuating climate, and episodic incision to which there is a flexural feedback. It is concluded that the Pleistocene has experienced a number of 'incision - flexural uplift aggradation' cycles controlled temporally by the fluctuating climate.

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The landscape around us has been formed over periods of million, s of years by the erosion of the land by water, wind and ice. In this thesis, we focus on the interaction between the overland flow of water and the surface of a hillslope and the consequent formation of river channels. vVe derive a model to describe the evolution of the hillslope and investigate the linear stability of the system and the process of channelisation. In Chapter 4, we derive an equation to describe the evolution of the cross-section of a river channel. Modelling the full evolution of a hillslope depends on us being able to integrate the river channel into the hillslope. In Chapter 5, we recognise the existence of the river bank which allows us to formulate equations to compute the longitudinal profiles of the channels. Finally, we attempt to evolve a topography numerically in the hope of producing river networks.