Dr Alexander Atkinson1, Nick Naderi1, Jessica Ryan-Slinger1
1Department of Environment and Science, Deagon, Queensland
Abstract:
Annual maintenance dredging is undertaken at the Tweed River Entrance located on the border between New South Wales and Queensland. Dredge material removed during these operations is deposited offshore from Gold Coast beaches to assist in mitigating erosion. Research was undertaken by the Queensland Government Hydraulics Laboratory (QGHL) to investigate the potential of targeting these dredge depositions to also improve surf amenity. This presentation showcases results of physical and numerical modelling undertaken as part of these investigations.
The physical model features a representative Gold Coast beach profile in a laboratory wave basin. Data collected from this model is used to validate a time-domain numerical wave model (SWASH) against a variety of deposited sand mound shapes, wave conditions and water levels. The validated numerical model may be used to assist in the design of future mound shapes to improve surf amenity temporarily (i.e. before the deposited sand becomes integrated with the surrounding bathymetry through natural processes).
In 2020, a dredging campaign provided an opportunity to place 33,000 m3 of sand offshore from Bilinga beach. The placement remained for three months until the mound was incorporated into a storm bar. Anecdotal reports indicate an improvement in the wave quality at the site following the placement, with some surfers enjoying more consistent waves. The geometry of this mound formed the first physical model test. The results show larger waves breaking over the mound, and smaller waves reacting to the mound, changing direction and focussing, which improved wave breaking characteristics towards the beach.
Biography:
Alex runs the coastal physical modelling facility at the Queensland Government Hydraulics Laboratory in the Department of Environment and Science. In addition to various projects associated with more traditional coastal protection structures, physical modelling of the Albany Artificial Surf Reef, Palm Beach Shoreline Project, and Narrowneck Artificial Reef Renewal also considered surf amenity.
Dr Atkinson’s PhD was attained at the University of Queensland in the field of beach dynamics. His Master’s in Environmental Science was completed through the University of Sydney, where he completed a research project on wave runup.