Browsing by Author "Skibbe, Yasmin"

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    Coastal erosion and accretion of beaches - the effect of storm duration, water levels and long waves on selected numerical models
    (Stellenbosch : Stellenbosch University, 2016-12) Skibbe, Yasmin; Theron, Andre Karl; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: Varying water levels, storm duration and long waves all have a significant impact on cross-shore beach profile development. Although it is generally known that these parameters have an impact on beach profile development, little research have been done to identify the specific effects of these parameters on cross-shore beach profile development. Furthermore, it is not clear whether numerical models can be used to predict the individual effects of these parameters on cross-shore beach profiles. Data specific to varying water levels, storm durations and long waves were obtained and analysed to gain an understanding of the effect of these parameters on cross-shore beach profile responses. Three cross-shore sediment transport and morphology models (SBEACH, XBEACH and DUNERULE) were selected and their sensitivity to varying water levels, storm durations and long waves were analysed. The physical scenarios were then modelled in SBEACH, XBEACH and DUNERULE to assess whether any or all of the models could be used to predict accurate beach profile responses under the impact of the studied parameters. Although DUNERULE is sensitive to different water levels, it does not have the ability to model scenarios where water level varies throughout the impact period. Neither SBEACH nor XBEACH predicted consistent beach profile responses under varying water levels, but SBEACH did perform marginally better than XBEACH. It was found that the impact of storms with different durations was well predicted by SBEACH, XBEACH and DUNERULE. Free long waves were only modelled in SBEACH and XBEACH and the results indicated inaccurate predictions from both models. XBEACH was the only model that could predict cross-shore beach profile response under bichromatic wave conditions, but these predictions proved to be inaccurate. It was noted that none of the models predicted accretive conditions when the physical data indicated that sediment accretion occurred. It is recommended to assess the model accuracies based on field data (instead of just flume data) for further studies. More prototype flume experiments should be done on the effect of long waves on cross-shore beach profile responses during storm conditions. In order to obtain better XBEACH model results, extensive model calibration should be done.