ABSTRACT
Figure 4-1 Pessimistic scenario for effect of calibration: real development, unadjusted model and calibrated model (Virtual reality) (after Roelvink and Reniers, 2011) For the long term forecasts necessary in this study, therefore, a different modelling philosophy ('Realistic analogue’ (Roelvink and Reniers, 2011)) is adopted. The 'Realistic analogue' philosophy essentially commences the simulation with a highly schematised initial bathymetry and allows the model to gradually produce the morphology that is in equilibrium with the main forcing (e.g. tidal forcing) that is to be used in forecast mode. The level of schematisation in the initial bathymetry is extreme in that while the geometry of the coastal system under investigation is very broadly represented, the initial bed is assumed to be more or less flat (i.e. flat bed morphology). Once this initial 'establishment simulation' produces a near-equilibrium morphology that is sufficiently similar to the observed system in terms of channel/shoal patterns and typical morphometric properties, the simulation can be extended into the future with slightly varied forcing (e.g. tidal forcing and slow sea level rise) to qualitatively investigate future system behaviour. It is, however, crucial, that the model generated 'equilibrium morphology' be compared with data to ensure that it is indeed an equilibrium morphology. This requirement, does limit the application of the 'Realistic analogue' philosophy to mature systems that are currently in equilibrium or have previously been in equilibrium prior to human interventions. It is emphasised that the 'Realistic analogue' approach is only suitable for qualitative assessments of long term system response to forcing.
