Morphological modelling of strongly curved islands

Abstract

Land reclamations and island coasts often involve strongly curved shorelines, which are challenging to be properly modeled by numerical morphological models. Evaluation of the long term development of these types of coasts as well as their response to storm conditions requires proper representation of the governing physical processes. Not all types of numerical models are equipped to represent an entire island and allow waves from any direction. In this paper we demonstrate XBeach’s capabilities of plying a curvilinear grid around a small-scale circular island and exchanging model variables between the lateral boundaries by the recently implemented cyclic boundaries. The small-scale physical model tests by Kamphuis and Nairn (1984) were modeled with XBeach using both the stationary and the nonhydrostatic wave model on a rectangular as well as a curvilinear grid. The wing-bars that typically develop in Kamphuis’ tests are represented in the model, albeit that the angle of the bars is different. In a different XBeach model series, we investigate the behaviour of a larger scale curved coastline model under extreme storm conditions, for varying coastal radius. The results show that maximum erosion occurs at the locations where the incident wave direction is under an angle of 45 degrees with the coastline, and the coastal radius is of secondary importance.Hydraulic EngineeringCivil Engineering and Geoscience