John McGrath

Marine Ecosystem Enhancement on a Geotextile Coastal Protection Reef - Narrowneck Reef Case Study -

The Narrowneck Artificial Reef [Gold Coast, Australia] was constructed in 1999/2000 out of large sand-filled geotextile containers. It quickly became evident that the containers provided an excellent substrate for marine flora and the development of a diverse ecosystem. As a result, the reef has become popular with locals for fishing, diving, snorkeling and spearfishing. In the years since it was constructed, monitoring of the ecological aspects of the reef has been undertaken. While macroalgae and pelagic fish dominate the reef, it is also home to a wide variety of benthos, fish and other marine fauna. Influenced by the East Australia Current and wave action from the Pacific Ocean, driven by the South East Trade Winds, the reef exhibits a different community structure in comparison to other natural reefs of the Gold Coast. The popularity of the Narrowneck Reef has clearly shown that enhancing the ecological environment and improving recreational amenity have potential benefits on eco-tourism as well as local biodiversity.

Monitoring of a multifunctional submerged geotextile reef breakwater

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.