Cables Artificial Surfing Reef

Cables Artificial Surfing Reef photo courtesy lifeonperth.com

Latitude: 32°S

Aspect: west

Foundation: limestone bedrock

Wave climate: estimate, 80% of days greater than knee height, 11 days per year overhead (WA M&H)

Swell direction: Cables is more open to northwest, though westsouthwest swell is predominant

Wind patterns: morning land breeze easterly offshore, predominant sou'wester side/onshore

The worlds first Artificial Surfing Reef was built at Cable Station, Perth, Western Australia in January 1999. Locals call it Arto's.

Site selection was assisted by M Crawfords 1988 master planning approach that included a critique of every Perth surf spot. Initial concept sketches were provided by Andrew Pitt and published in Tracks Magazine in November 1991 'Underwater Surgery' (3pg pdf 7.8mb). Andrew’s plan and cross section sketches were used in a promotional video that assisted with the funding applications.

download the article, 3pg pdf, 7.8mb

The goal of the project was to create a more consistent surf spot within the Perth metropolitan area. The Perth Artificial Surfing Reef Committee specified design criteria that ‘surf should work with swell sizes ranging from 0.5m high to 3.5m....’. The reef was constructed with more than 10,303 tonnes of quarried granite at a cost of several million dollars. Funding was provided by the Western Australia Department of Sport and Recreation. The reef was installed over uneven Tamala limestone bedrock. The solid reef armour has proven resistant to wave attack, all credit and respect to the engineers who built it.

The quality of the wave breaking pattern at Cables is not in dispute. See the following You Tube link for surfing at Cables and Perth. Most surfers agree Cables is one of the better surf spots in the region - when and if, its on. Lack of consistency is the issue. Unfortunately, the reef delivers few surfable days per month. After construction, reef performance was monitored by Stacey Bancroft in 1999. The key performance indicator was ‘surfable days’, simply defined as ‘the presence of people out surfing’. Yes or no. The monitoring indicated less than 14% of days through the Autumn/Fall season, less in Summer, though more days in Winter. The ongoing validity of the figures is now questionable because the reef enjoyed 'novelty status' popularity in the first years of existence. Though Bancrofts methodology is pure brilliance because of its simplicity.

Cables locals claim the reef is not surfable with wave height under chest height. That's a problem when you consider Perths small wave climate: ranging from usually less than waste high in summer, to under chest high in winter. Outer reefs and Rottnest Island restrict much of the available wave energy. Cables most open swell window is to winter north west swells, though westsouthwest swells are predominant on the coast of Western Australia. Short period (wind) waves under 6 seconds occur approximately 20% of days per year, dominate summer and are typical of waves under waste high. Strong side-onshore sou'west winds dominate year round.

Wave height should not be an issue; just a design constraint. Clearly the reef, in its current form, has failed to meet the design brief ‘surf should work ..from 0.5metres..’ Essentially, the reef is too deep for the available wave height climate.

Andrew Pitt undertook a dive survey at Cables and estimated the shallowest section of the reef to be 1.5m deep at the lowest low tide. Other sections of the reef are deeper, the tide mostly higher.

Cables reef needs some fine tuning. To increase the number of surfable days per year, maintenance works should include: capping the reef to make it shallower (more small days) and extending the nose of the reef ridge further seaward to draw in more swell and increase wave height (more of the 'swell magnet' effect).

Conclusion: clearly define design objectives and be sure the final design will meet the objectives.

Illustration: Cables Surfing Reef - Plan and elevation sketches, as published in Tracks magazine November 1991 "Underwater Surgery for Better Waves"

Andrew Pitt (B.Larch UNSW) is the principal Surfing Reef Architect

at Surfing Ramps and provided initial concept sketches for Cables Reef

Cables Reef lineup, the reef is 300m offshore. Photo courtesy lifeonperth.com

Cables Reef: granite boulders (now) covered in algae. Photo Andrew Pitt