Friday, September 19, 2014
Sunday, September 14, 2014
I have been looking for the effects of sea level rise, and in particular related erosion along the coast, for some time now. What I have observed was this erosion is not as simple as many sea level rise models might suggest. In particular I had not noticed so much erosion at the pathways leading down to the beach. This suggested the ocean was not advancing a fast as many fear, There was erosion, but it would be just one of the 5 “official” paths at a time that would show erosion at the base of the path. This along with other observations suggested to me that the erosion was mainly localised at any given time. This year has seen more significant events but they still seem somewhat localised.
At the moment there is a very big “step” at the bottom of the beach one ramp (about 1.2m), where recent high tides have washed deep back into the dunes and also the revegetation fencing and drainage pit. Again there is ample evidence to suggest that the amount of erosion is more localised, rather than generally along the beach. Although this years king tides (around the time of full moons) and strong swells have lead to more erosion scarps along much of the coast than over the past couple of years.
The super moon term has caught the public’s imagination, but I strongly doubt it alone is responsible for a super tide. The moon was however a full moon and it occurred as the moon is closest to the earth, so there will be a contribution. The real culprits are combination of three additional things. Strong swells associated with a significant storm front last Tuesday (often this is referred to as a storm surge) The low air pressure associated with the storm which crossed the coast at Venus Bay just on sunset. Finally the presence of deep gutter (rip area) just south of beach one ramp (see photo below) which focused the wave action at a small semi-circular area in front of the ramp.