Monitoring of a multifunctional submerged geotextile reef breakwater

Abstract

A large reef has been constructed offshore from Narrowneck on the Gold Coast, Queensland, Australia. The reef provides a submerged, low visual impact, coastal control point to stabilize the nourished northern Gold Coast beaches. As the reef is in a popular tourist and surfing area, it has also been designed and constructed to enhance recreational amenity. For safety and cost efficiency, the reef has been constructed of very large sand filled geotextile units. Experience with the design and construction of such structures is limited and the inclusion of improved surfing as secondary design criteria increases the complexity. To facilitate evaluation and modifications to the reef there is a comprehensive monitoring program, which includes the use of ARGUS video imagery to assess the changes in the shoreline related to wave conditions at the wave rider buoy nearby. Divers are studying the physical performance of the sand filled geotextile containers, as well as the extent and diversity of the marine ecosystem which has exceeded expectations. There have been a number of storm wave events during the monitoring period. The data obtained from the monitoring is being used to modify the long term Narrowneck reef shape, and to design other proposed reefs in the area.