Reef Breakwaters for Coastal Protection Safety Aspects and Tolerances

Submerged artificial reef breakwaters in the nearshore coastal zone can create the potential for a range of recreational activities as well as beach protection. As such, safety is an important issue when considering the design and construction of these types of structures. Investigations have been carried out for the proposed Palm Beach reefs and this paper provides an overview of the potential safety hazards and litigation threats presented by an artificial submerged structure to all potential users. Investigations into the safety aspects of these structures has incorporated: - extensive monitoring of the Narrowneck artificial reef [Gold Coast, Australia] - observations of natural reefs and beach breaks - physical model testing of a 1:10 sale submerged reef constructed of sand-filled geotextile containers at the Deagon Hydraulics Laboratory. The studies assessed the effect of a number of design parameters, including water depth above crest, roughness of the slope and truncation of the toe, on these safety aspects. The paper also covers the impact of achievable tolerances on the design, performance and safety of these structures and provides a number of guidelines for the design, management and maintenance of these structures in order to provide an acceptable level of risk.