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The morphodynamics of a gravel barrier beach in Devon, (Slaptou Sands: tau/S 0.15 - 0.25, D50 2 - 8min), was studied with reference to its sedimentology. Three time scales were sampled for nearshore hydrodynamics, intertidal morphologies and sedimentologies. A series of surveys were carried out over individual tidal cycles (sampling every 5-10 mins for between 6 and 9 hrs); on consecutive low tides over half-lunar tidal cycles (1-2 cross-shore profiles-sampled every 0.5-1 min, on 2 spring-spring tidal cycles comprising 26 and 24 tides, respectively); and finally every 2 weeks at spring low tide, over 1 calendar year (13-17 profile lines surveyed and sampled for sediment over 3.25-4.25 1an). In order to further our understanding of gravel beaches, sediment data needs to be collected at a resolution similar to that of the hydrodynamics. Innovative automatic sediment sizing techniques based on digital images of sediments were therefore developed, and software written, to allow the collection and analysis of high-resolution sediment data. The gravel beach step and berm are accretionaiy features, tidally modulated, and evolve under different time scales. A new technique to determine bed mobility from the nearshore, using underwater ^adeo cameras, was devised. Nearshore sediment transport was suggested as being related to sub-incident wave frequencies. No aspect of morphological change could be found to have a statistically significant association with sedimentological change, but dimensional-reduction techniques did satisfactorily detect association. The lack of co-variance and obvious patterns is stochastic noise, not parameterisation. The barrier underwent asymmetrical rotation over one year, highlighting the importance of alongshore sediment transport processes on this supposedly 'swash aligned' beach. A statistical model based on the log-hyperbolic distribution of sinface particle sizes was found to be a reasonable predictor of mean net sedimentation over individual tides. Its complicated parameter space could possibly map onto a simpler plane based on traditional moments. Sediment trend vector models based on sorting alone out-performed a traditional approach. Moments of a surface grain-size distribution appear to be inappropriate to characterise sedimentological change at time-scales greater than a semi-diurnal tidal cycle. Sub-surface sampling on the intertidal zone on diurnal and semi-lunar time-scales is useful in assessing the dynamics of the step, itself an important mechanism for onshore and offshore net volumetric transport.

Cross-shore sediment transport is the dominant process causing beach profile evolution. The ability to model cross-shore sediment transport allows prediction of the future beach state be made. Due to a balance between opposing mechanisms, cross-shore sediment transport is difficult to predict. One route to make these predictions is with the development of measurement based parameterisation. This study builds on previousp arameterisationtsh at have relatedc ross-shorev elocity moment (predictorso f suspendeds edimentt ransporta ccordingt o the energeticsa pproacht o sediment transport)t o normalisedd epth( a proxy of cross-shorep osition),t o presenta new shapef unction parameterisationT. he presentp arameterisatiohna s beend evelopedf rom field measurementosf depth-integratedcr oss-shores uspendeds edimentt ransportm easuredd uring a month long field campaigna t SennenC ove, Cornwall, UK. This parameterisationis an improvemento f the previouss hapef unction parameterisationin three key areas;i ) removest he dependencyo n the energetics approach, and so includes all transport mechanisms, ii) incident energy (parameteriseda s breakpointd epth- hb) is considereda, nd so allows this shapef unction to be usedu nder a wide rangeo f energyc onditions,i ii) the swashz one processesa re consideredin detail. The new shapef unction parameterisationis the sum of four components hapef unctions that represenmt eana nd oscillatoryt ransporti n the surf- and shoalingz onea nd on- and offshore transporti n the swash-zoneA. s eachc omponents hapef unction respondsin dividually to energy level, the net-transport shape function responds to varying conditions. Under high-energy conditions the shape function predicts onshore transport in the shoaling zone, offshore transport in the surf zone and onshore transport in the inner swash zone, while under low energy the shape function predicts all onshore transport with a peak outside the breakpoint and in the inner surf-zone. The shapef unction is implementedin a simple heuristicp rofile evolutionm odel that allows the examination of beach behaviour of under varying conditions to be examined over long (decadal) time-scalesP. reliminaryr esultss how that the shapef unction model is able to replicateo nshore and offshoreb ar migration,b ar developmenat nd bar degenerationo ver timescalen ot previously modelled.F uture work will use this model to investigatet he responseto subtletiesi n driving conditions,s ucha s the varying effect of seasonalityc omparedto randoms torms.

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Fine sediment acts as a critical transport vector for nutrients, trace metals and organic contaminants, and can have a severe detrimental effect on aquatic ecology and the viability of riverine habitats. An understanding of the II!.oyement of fme sediment within river catchments is therefore important. Modelling is an important tool for understanding and managing the catchmetn sediment delivery system. Existing modelling tools fall broadly into two categories: simple empirical models based on statistical relationships in observed data; and highly complex process-based models based on physical modelling of the mechanical processes involved in sediment delivery. De Roo (1998) expressd the need for a new type of model that makes a compromise between the catchment and process representation of complex models and the simplicity and wide-ranging applicability of empirical models. The aim of this thesis is to develop a new model that fulfils this need. The development of the model is guided by three criteria: • the model must require only readily available and significant data; • the model can use only a limited number of key variables and parameters; • the model should only include the dominant key processes controlling sediment delivery. In order to meet these criteria, new process-informed equations representing the key processes of sediment delivery are derived based on a review of existing modelling approaches. These equations simulate catchment hydrology and the processes of sediment erosion, transport and deposition within a semi-distributed model structure. The model is applied to three lowland catchments in Berkshire, England: the Upper Kennet, the Lambourn and the Enborne. Model output is shown to successfully reproduce observed river flows and suspended sediment concentrations, although there is a consistent underprediction ofthe highest flows and concentrations in all three catchments. The model successfully simulates the contrast between the hYdrology and sediment delivery of the Upper Kennet and Lambourn Chalk catchments and the clalbtchment of the Enborne. The model is subjected to a Monte Carlo based General Sensitivity Analysis. This analysis confirms the efficacy ofthe hydrological model and identifies the transport capacity of direct surface runoff as the critical process in the determination of in-stream suspended sediment concentrations. The results of the model applications and the sensitivity analysis are used to assess the success of the model in meeting the stated criteria. This assessment shows the model to be efficiently modelling the key elements of the catchment sediment delivery system.

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No description available.

No description available.

The research in this thesis should prove useful for any future study investigating the diagenesis of biosiliceous sediments.

The progress of modern hydrocarbon exploration into increasingly deepwater settings has led to a renewed interest in deepwater fold and thrust belts. Deepwater fold and thrust belts often form as a result thin-skinned compression above a ductile substrate, such as overpressured shale or salt. The compression driving deformation in these settings accommodates up-dip extension due to gravitational collapse of passive margin deltaic systems. Deformation in these settings is accompanied by a range of coeval sedimentary processes which interact with the deforming seafloor topography both at large scales to form kilometre-thick growth sequences, and at smaller scales involving individual flow events. Thus, in order to fully understand how these systems evolve, it is necessary to link structural and sedimentary processes when developing conceptual models which may then be applied to predicting facies distributions in these settings. Imaging of deepwater fold and thrust belts using three-dimensional (3D) seismic data permits detailed investigations to be carried out into the development of, and interactions between, features such as folds, growth sequences and submarine channel levee systems. Although such data has already been used to advance our understanding of many deepwater depositional systems, it has not been fully utilised to study the interactions between deformation and sedimentation in these settings. The aim of this study is to utilise 3D seismic data volumes from the Eastern Nile Foldbelt and the deepwater western Niger Delta to study the interactions between sedimentation and deformation, and to extract some general principles which can be applied to other deepwater fold and thrust belts. The scale of investigation ranges from growth sequences - which are up to two kilometres thick, to more detailed interactions between smaller scale (c. 500m in width) submarine channel levee systems and fold growth. For the first time, a coherent set of end-member interactions between submarine channel systems and evolving seafloor structures is presented. These interactions form a descriptive framework and serve as a basis for comparing submarine channel responses to deformation from various deepwater fold and thrust belt settings. Transitions between these interactions is controlled by factors such as relative timing and rates of deformation compared to sedimentation, and recognition of these interactions allows more accurate inferences to be made regarding the evolution of seafloor relief during folding. The interactions between submarine channel development and folding also depends on the fold structural style which is critical in controlling the nature of localised accommodation space adjacent to the fold. Changes in accommodation space associated with folding can result in dramatic spatial variations in channel morphology over less than a hundred metres. This study also documents the strong control on growth sequence development and internal architecture as a result of variations in structural style along strike. Relationships such as overlap and onlap can be used to predict submarine channel responses to folding, given a knowledge of the fold structural style. The internal architecture of growth sequences is also dependant on compensational stacking relationships, and the case study from the Niger Delta shows an important example of how mass transport deposits play a key role in filling local accommodation space and influencing subsequent sedimentation pathways. The results presented in this thesis demonstrate that 3D seismic data can be a powerful tool in our understanding of deepwater fold and thrust belt systems, and that linking structural and stratigraphic investigations can provide new insights into the interactions between deformation and sedimentation.