Numerical Modelling And Video Analysis Of Intermediate Beach State Transitions

Abstract

Numerical modelling of beach morphodynamics is generally recognized as a valuable tool for scientists and coastal managers. However, the utility of numerical models is constrained by our ability to establish that the theoretical dynamics match reality. The integrated modules for simulating wave propagation, hydrodynamics and sediment transport in Delft3D, developed by Delft Hydraulics, were applied to simulate observed beach state transitions in response to wave-induced forcing. Initial model bathymetry was derived from hydrographic surveys conducted at Narrowneck beach during the pre- and post-construction phases of the Narrowneck artificial reef (Boak, McGrath and Jackson 2000, Hutt, Black and Mead 1998). The present study addresses the validity of morphological modelling of an exposed beach by comparing the evolution of a numerical model with data observed using remote imaging. Narrowneck beach on the Gold Coast is a micro-tidal, exposed coast subject to a highly variable wave climate. This beach is monitored by an ARGUS Coastal Imaging system generating high temporal frequency geo-referenced estimates of wave dissipation that may be used to infer sub-tidal bar morphology (Alexander and Holman 2004, Aarninkhof and Ruessink 2004, Turner, Dronkers, Roman, Aarninkhof and McGrath 2001). The numerical model was broadly validated, in that, when driven by similar conditions, the surf zone morphological development is consistent with that observed via optical sensing.