The last days have seen some swell arriving at the eastern beaches of Sydney. They were big but not as big as the swells that battered our coast in early June during the East Coast Low that became known as the #sydneystorm. Significant wave heights (the average of the largest 1/3 of the waves) reached 4 m according to MHL’s measurements on the Sydney Wave Buoy; during the #sydneystorm, significant wave heights reached 6.5 m at the peak of the storm.
Figure from Manly Hydraulics showing wave characteristics during the sculptures storm http://new.mhl.nsw.gov.au/data/realtime/wave/Buoy-syddow
The beach at Tamarama showed some impressive erosion which caused damage to some of the sculptures in the Scultures by the Sea exhibition. In fact, the data from our beach monitoring programme (collected by Tommy Fellowes) show that, as a consequence of the swell, the beach eroded almost as much as during the #sydneystorm. The figure below shows in blue the before (continuous) and after (dashed) beach profiles in the middle of the beach for the #sydneystorm. The same figure shows in red the before (continuous) and after (dashed) for the same profile for the sculptures storm.
So, if the storm was much smaller, why did it erode so much? Because the beach had not had enough time to recover since the #sydney storm.
The following graph shows a time series of the beach width and volume since March 2016. It can be appreciated that the beach volume was at its maximum value (since our monitoring started) just before the #sydneystorm. There had been recovery since then, with some of the lost sand returning to the beach under fair weather conditions.
Just before the sculptures storm, the beach had a lot less sand than before the #sydneystorm. The result was that a much smaller storm left the beach in a similar state as the much larger storm that occurred a few months ago.
Long-term beach monitoring gives us tools to understand beach behavior so we can prevent hazards and minimize risks.Essential tools to adapt to Climate Change.
Our current research involves monthly beach surveying in the eastern beaches (Bondi, Tamarama, Bronte, Coogee and Maroubra) as well as estuarine beaches in Botany Bay and the Pittwater (estuarine beach work is in collaboration with Shari Gallop from Macquarie University). We are currently self-funding this research because we think it is important. We are also looking for partners to sponsor us. Please get in touch if you have any ideas!