Dangerous Surf


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Julie Evans

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Dangerous Surf

  1. 1. Dangerous surf   - long period swell Jeff Callaghan, Sean Carson, Julie Evans , Michael Logan, Graham Warren Australian Bureau of Meteorology
  2. 2. Bureau of Meteorology
  3. 3. Acknowledgements <ul><li>Many people have contributed to this project, but we would like to especially thank Ray Rice (Cardno, Lawson & Treloar) for his work on the relative risk, Mark Kulmar (Manly Hydraulics Laboratory), John Diplock (NSW Fisheries), Terry McDermott (The Australian Professional Ocean Lifeguard Assocation), Surf Life Saving NSW, Andrew Short (University of Sydney). </li></ul>
  4. 4. Location Map <ul><li>Length around 2000km </li></ul><ul><li>Continental shelf relatively steep and narrow </li></ul><ul><li>wind and wave energy impacting the coastline is relatively high. </li></ul>Waverider buoys
  5. 5. The Motivation – Rock Fishers <ul><li>Background </li></ul><ul><li>In the nine years between 1992 and 2000 there were 74 rockfishing related fatalities in NSW. </li></ul><ul><li>70% of fatalities occurred during rough or very rough sea conditions </li></ul><ul><li>11% of fatalities occurred during calm conditions </li></ul><ul><li>Rock fishing is recognised as the most dangerous leisure pastime one can undertake in NSW and possibly the world. </li></ul><ul><li>Jones, M (2003) Investigation into the coronial files of rock fishing fatalities that have occurred in NSW between 1992 and 2000 . NS W Water Safety Taskforce </li></ul>
  6. 6. Tide conditions at time of incident <ul><li>Source: Jones (2003) </li></ul>
  7. 7. Sea & Swell <ul><li>Significant Wave Height (Hsig): average height of the waves which comprise the highest one third of waves (crest to trough). </li></ul><ul><ul><li>NSW Average: 1.6m </li></ul></ul><ul><li>Peak Period (TP1): Period of the peak of the energy spectrum (seconds). </li></ul>
  8. 8. June 2007
  9. 9. July 2001 <ul><li>The 11-metre cruiser &quot;Just Cruisin&quot; was found wrecked on Spitfire Bank near the entrance to Moreton Bay and just southwest of Cape Moreton. The boat had been flipped over by the large breakers on 6 July 2001 and the crew of four were never found. </li></ul><ul><li>A yacht was wrecked by large waves on a sandbar near Fraser Island and the lone yachtsman was never found. </li></ul><ul><li>In New South Wales 2 rock fisherman were swept to their deaths, one at Eden and the other off Sydney. </li></ul>
  10. 10. Quikscat: 4 July 2001 0615UTC 4 July 2001
  11. 11. Sydney: 7 July 2001
  12. 12. Sydney: 7 July 2001
  13. 13. January 2005
  14. 14. MSL: 30 Jan 2005
  15. 15. MSL re-anal
  16. 16. Jan 05: CH Buoy data
  17. 17. July 2007
  18. 18. The Data
  19. 19. Percentage deaths at Various Tp1
  20. 20. Relative Risk of Deaths in various Tp1 The relative risk equals the ratio of the percentage of fatalities at TP1 and the percentage frequency of TP1.
  21. 21. Thresholds – Hsig & TP1 <ul><li>Onshore range: angle of incidence is plus or minus 45 degrees from the normal to the coastline. </li></ul>New dangerous wave alert Any > = 14 2 – 2.5 New dangerous wave alert Any > = 12 2.5 - 3 New dangerous wave alert Onshore range > = 10 3 - 4 Dangerous wave alert Onshore range na > 4 Damaging wave warning Onshore range na > 5 Alert Status Angle of incidence TP1 (Seconds) Hsig (m)
  22. 22. Thresholds & data Joint occurrence:~7%
  23. 23. 5 April 1998 – Avoca Beach
  24. 24. 1 April 1998
  25. 25. 2006 – 10 alert events <ul><li>Sunday 8 April 2006 </li></ul>
  26. 26. ‘ Big Sunday’ <ul><li>Hsig=4.5m TP1=17sec Dir=170 </li></ul>
  27. 27. Words ….? <ul><li>Dangerous surf conditions on exposed beaches, rock platforms and ocean bars…. </li></ul><ul><li>Where: Land based and marine forecasts </li></ul><ul><li>Action Statements: </li></ul><ul><li>Surf Life Saving Australia recommends that you stay out of the water and stay well away from surf-exposed areas. </li></ul>
  28. 28. Further Work <ul><li>Ongoing liaison with State Government agencies, emergency services and recreational clubs (eg Recreational Fishing Alliance of NSW ) to raise awareness of the dangers of long period swells within the community. [28 November] </li></ul><ul><li>Onging forecast verification and development of appropriate thresholds for other vulnerable parts of the Australian coastline. </li></ul>