December 2014, high tide and calm conditions at Brookes Jetty, St Kilda. (pic: Baykeeper)
Hard to believe that the highest tide recorded in Port Phillip Bay (in 1936) was just 150 mm below the deck of Brookes Jetty. But tides are tricky! While there are two high tides each day, the time interval between them is never the same. Due to the gravitational effects of the moon and the sun they pay no mind to our western time clock and calendar. While the moon takes 27.5 days to complete a cycle, due to its orbit it returns to the same place in relation to earth only once every 18.6 years. Also, tide heights vary greatly due to wind and air pressure. So to observe gradual sea level rise we need consistent observations over several years. The Victorian Government is anticipating sea level rise of no less than 0.8 m by 2100.
Green Cross Australia’s Witness King Tides project is encouraging communities across Victoria to photograph and upload images of king tides to highlight coasts and infrastructure that are vulnerable to king tide flooding. Happy snappers can upload their pics to the Witness King Tides web portal to create a visual database to assist future planning and climate adaptation. The witnesskingtides.org website tells people about upcoming king tide events, outlines best spots along the coast to see the impact, and gives great advice for taking photos to upload and share.
