Gold Coast Seawall: Status Investigations and Design Review

Abstract

Tomlinson, R.B.; Jackson, L.A., and Bowra, K., 2016. Gold Coast seawall: Status investigations and design review. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 715–719. Coconut Creek (Florida), ISSN 0749-0208.As part of the development of a whole-of-coast strategy for coastal protection on the Gold Coast, Queensland, Australia, the structural integrity of the so-called A-Line Seawall has been investigated and a review of the design of the wall has been undertaken. The seawall is located along the 1967–74 erosion scarps and extends for much of the length of the developed shoreline of the Gold Coast. In combination with beach nourishment these terminal seawalls are an integral part of the long-term management of Gold Coast beaches. The standard seawall design and alignment were adopted by the City in the early 1970s with the only structural design change in over 40 years being an option in the 1980's replacing the clay / shale tertiary layer with geotextile. The status investigations were aimed at evaluating the present condition and damage modes of the existing seawalls after long term service. Methods included potholing, Ground Penetrating Radar and excavation / peel back of the armour layers. The review found that the standard seawall designs conformed to present standards but upgrading in the future would be required. Future exposure levels and design conditions were developed along the coastline. It has been concluded that upgrading and completion of a continuous seawall will be required for the future security of Gold Coast beachfront assets. With the uncertainty regarding the rate and extent of changes to sea levels and design wave heights, a staged approach is practical.