Abstract
A morphological modelling concept for long term nearshore morphology is proposed and examples of its application are presented and discussed. The model concept combines parameterised representations of the cross-shore morphology, with a 2DH area model for waves, currents and sediment transport in the surf zone. Two parameterization schemes are tested for two different morphological phenomena: 1) Shoreline changes due to the presence of coastal structures and 2) alongshore migration of a nearshore nourishment and a bar by-passing a harbour. In the case of the shoreline evolution calculations, a concept often used in one-line modelling of cross-shore shifting of an otherwise constant shape cross-shore profile is applied for the case of a groyne and a detached breakwater. In the case of alongshore bar/nourishment migration an alternative parameterization is adopted. All examples are presented, analysed and discussed with respect to the question of realistic representation, time scale and general applicability of the model concept.
Highlights
Shoreline morphology is the result of nearshore waves and currents acting on the coastline
Erosion corresponds to increasing longshore transport, whereas accretion corresponds to decreasing longshore transport, i.e. the shoreline evolution is connected to gradients in the longshore transport rates
OF THE MODEL CONCEPT In the present paper a model concept is formulated as a hybrid of the detailed 2DH area model and a geometric simplification and parameterization of the morphology
Summary
OF THE MODEL CONCEPT In the present paper a model concept is formulated as a hybrid of the detailed 2DH area model (for waves, currents and sediment transport) and a geometric simplification and parameterization of the morphology (the one-line model is an example of this). The morphological model forces the head of the bar to migrate rapidly onshore during the first couple of days, after which the distance from the shoreline to the head of the bar remains almost constant as shown in Figure 15 where the bar position is schematised at different time steps. A simulation of the morphological development of a bar that bypasses the harbour Hvide Sande at the Danish Noth Sea coast is performed in order to determine whether the streamline approach described previously gives reasonable results This particular problem has been examined by Grunnet et al (2009) in a study to investigate a revised harbour layout with improved conditions for bypass of sediment. It is not possible to prescribe an equilibrium location for the bypass bar and only the streamlines have been used to determine the evolution of the planform of the bar
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