Beach response to sea level rise is investigated experimentally with monochromatic and random waves in medium scale laboratory wave flumes. Beach profile development from initially planar profiles, and a 2/3 power law profile, exposed to wave conditions that formed barred or bermed profiles and subsequent profile development following rises in water level and the same wave conditions are presented. Experiments assess profile response to a step-change in water level as well as the influence of sediment deposition above the still water level (e.g. overwash). A continuity based profile translation model (PTM) is applied to both idealised and measured shoreface profiles, and is used to predict overwash and deposition volumes above the shoreline. Quantitative agreement with the Bruun Rule (and variants of it) is found for measured shoreline recession for both barred and bermed beach profiles. There is some variability between the profiles at equilibrium at the two different water levels. Under these idealised conditions, deviations between the original Bruun Rule, the modification by Rosati et al. (2013) and the PTM model predictions are of the order of 15% and all these model predictions are within ±30% of the observed shoreline recession. Measurements of the recession of individual contour responses, such as the shoreline, may be subject to local profile variability; therefore, a measure of the 2 mean recession of the profile is also obtained by averaging the recession of discrete contours throughout the active profile. The mean recession only requires conservation of volume, not conservation of profile shape, to be consistent with the Bruun Rule concept, and is found to be in better agreement with all three model predictions than the recession measured at the shoreline.

Disequilibrium-type models for two beach profile parameters, P, the shoreline position and net bulk sediment transport, are developed for laboratory experiments that demonstrate morphological hysteresis in the evolution to equilibrium of beach profiles under sequences of different wave climates. The model principle follows the classical disequilibrium approach but with non-monotonic relationships between the forcing and the chosen beach profile parameter at equilibrium, Peq, previously verified and presented in part 1 of this work (Baldock et al., 2017). Two such relationships are required to model beach profile evolution that exhibits morphological hysteresis. The model coefficients are derived for monochromatic and random wave experiments and subsequently used to model data obtained from cyclic erosive and accretive wave conditions of shorter durations, alternating through multiple cycles. In these conditions equilibrium conditions were not reached and hysteresis does not occur. The model is used to investigate the morphological feedback between the outer and inner bars and the resulting behaviour of the bulk transport, and the relative depth over the bar crest is shown to be an attractor in this case. The model coefficients and morphological timescales derived from the cyclic experiments are very similar to those derived from the equilibrium experiments for the bulk transport. Normalised mean square model errors range from 1%-20% when applied to independent data. The data from the cyclic wave conditions can be inverted to derive the conditions expected at equilibrium, which match those observed, indicating a robust model relationship between the forcing and Peq. The relationship between the forcing and Peq can also be determined directly from the cyclic experiments. This approach may be more robust than 2 determining the relationship from periods where P is stationary since, in a time-series of P versus the forcing, stationary points can occur due to changes in wave conditions, in addition to the instances when P=Peq.

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Erosion has been a focal point in sediment transport research while sediment accretion has been neglected until recent times. This thesis addresses some components of accretive sediment transport through modelling and new experimental measurements.The existing Grab and Dump model (Nielsen, 1988), a simple sediment transport model over rippled beds, is generalised to reflect a wider range of flow conditions, including acceleration skewed flows, boundary layer streaming, sheet flows, and cases with superimposed current. The revised model is compared to another semi-empirical sediment transport model and is found to have similar predictive abilities for small scale laboratory data. The results show that there are limitations to the model and more work is required to accommodate flows with no acceleration skewness and under the sheet flow regime.The local approximation method for non-linear irregular waves (Nielsen, 1989) is updated for converting surface elevation data into velocity, as many sediment transport models require velocity time series as input while surface elevation data are more readily measured and available. Data from three experiments are used to investigate this method, which was previously used to convert pressure measurements to surface elevation. The results are compared to the spectral transfer method, and found to perform similarly in most locations apart from near the breakpoint, where it performs better due to an additional multiplier which accounts for the increasingly negative timemean velocities closer to shore.New beach profile experiments were undertaken with an emphasis on the beach profile at equilibrium under random waves. The beach profiles were subjected to waves of various heights, with each case run until the profile appeared to be at equilibrium, for both accretive and erosive conditions. It was observed that the profile under accretive conditions behaves in a cyclic manner, where the outer bar is destroyed and recreated from the inner bar moving offshore, a process which also has a much longer time scale compared to the profile evolution under erosive conditions. The experimental profile measurements are used to evaluate an equilibrium type total sediment transport model utilising the relationship between the dimensionless fall velocity parameter and cross-shore bulk sediment transport proposed by Baldock et al. (2011). The model is applied to both laboratory and field measurements, and compared to an existing equilibrium shoreline model. The model is found to perform well under laboratory conditions where the profiles reach equilibrium but faces limitations with field measurements, which is an area for future work.ii Declaration by author Contributions by others to the thesisNo contribution by others. Statement of parts of the thesis submitted to qualify for the award of another degreeNone.iv

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