Nerang River and Sealevel Rise
Yesterday was the highest tide of the year and the highest for the last 12 months and the photo of the sea level against this old sea-wall, I took this morning at the top of the tide at slack water.
We built this wall 48 years ago and the SL is around 300 mm [12 ins] below the step. Last January”s KT was around 200 mm [8 ins] below this step.
During the ’60s and ’70s the king tides always came to the top of this step except when there was flooding and/or sea surge from cyclonic conditions, in which case those king tides came above the step. In recent years the SL has not reached this step…
During the mid ’80s the Southport Seaway was installed which widened and deepened the entrance of the Nerang River to the Pacific Ocean allowing much more water to pass in and out with each tide and as a result the low tides became lower and the high tides became higher but the king tides remained much the same but possibly [if anything] slightly higher. This all reflected the higher tide range in the ocean than in the river.
Even with all this extra flow enabling better equilibrium between river and sea levels, the sea levels not only have not increased over the life of this wall [48 years], but have actually gone down.
Coinciding with the king tide today was a fresh easterly wind [50 - 59 km/h], a slightly lower than normal barometric pressure [1012 hpa], rain and squalls and therefore some stormwater runoff. All factors that would increase SLs not reduce them.
Official tide gauges for Southport are of very short duration.
I realise that my benchmark is only a rough guide but if SLs were rising as claimed then they would at least be where they were 48 years ago, not a foot lower.