Decoding dangers of the deep

UNSW engineers are analysing treacherous waves off Sydney's coast to help make the dangerous sport of rock fishing safer.

Rock fishing inside

UNSW researchers are working to improve safety in one of the State's most dangerous sports, rock fishing, through gaining a better understanding of hazardous wave conditions.

By analysing wave movements off the most dangerous rock platforms along the Sydney coast, coastal engineers at UNSW's Water Research Laboratory have been able to determine what type of sea conditions lead to the treacherous waves that can sweep fishermen into the water.

The research has found that fishermen are in danger of being swept from rocks even in relatively calm coastal swells of around 1.6m and that the second or third wave in a set, not the first, is more likely to be a freak wave capable of knocking a fisherman off his feet. The project aims to provide supplementary information to improve ocean condition forecasts and wave information from offshore buoys. When complete, it could lead to the development of a warning system to predict which sea characteristics produce dangerous waves and a guide showing hazard zones on rock platforms.

Project leader Dr Bill Peirson said rock fishermen were almost always exposed to some risk. Using data from earlier research, on the force and volumes of water capable of washing people off flooded causeways, he and his team came up with worrying findings.

"Rock fishing is one of the most dangerous sports in Australia and we show why: rock fishermen are working completely outside the hazard guidelines we would have for people working in floods," he said.

Dr Peirson and research associate Tom Shand used survey data from nine of the most dangerous rock fishing platforms between Warriewood and Little Bay to create an average model. The model was used in a wave tank to determine how different wave formations behaved on impact and when they would "overtop" or wash over a platform.

"What we are showing is that within the wave groups the hazard changes remarkably. It's normally the second or third wave that's dangerous," Dr Peirson said.

"The thing that came out of this research is that wave groups change their form as they propagate across the surface of the ocean and where they are in that cycle is important.

"When you couple the hazards with rising tides and the sporadic nature of wave groups, it's easy for people to be caught unawares. Once someone is knocked over, their exposure to the drag of the waves increases enormously."

Media Contact: Peter Trute, UNSW Media Office | 02 9385 1933 | 0410 271 826 | p.trute@unsw.edu.au