Inverloch Coast Retreats

Storm surges at Inverloch are actively eroding the coast. Roads and lifesaving towers have been threatened and some severely undermined. Friends of the Earth Act on Climate campaigner Lee Ewebank recently visited the area with Victorian Minister for Climate Change Lily D’Ambrosio and saw “an emerging frontline of the crisis—to survey dramatic coastal erosion from intensifying storm surges and rising sea levels.” He wrote of his trip here and the following quotes are from Lee’s article.

The visit followed closely on an ABC News Report with local citizen scientist Aileen Vening. She noted that “It’s a relief that what I’ve been recording and talking about for several years is now finding a wider audience,” and “Unfortunately it has taken the loss of such huge amounts of sand, which means infrastructure is under threat, to make authorities act…This delay has made it so much more difficult and costly to make action effective.” Since 2012 Vening has “documented 36 metres of erosion” – presumably horizontal coastal retreat.

There is a need to elaborate on certain aspects of this. Storm surge as opposed to a gradual but evenly increasing sea level rise is almost certainly the way humans will experience this phenomenon. Further the sand the storm surges remove may be deposited offshore or possibly at other places along the coast leading to an accretion of sand elsewhere.

The natural sea level rise that occurred in Bass Strait from the end of the last ice age till about 6000 years ago saw the sea level rise on average a metre every 100 years for over 12,000 years. Now with human caused warming the sea level rise may be even more rapid than this though at the moment it is still only 3-4 mm per annum. The predictions of sea level rise vary widely and range from about 30cm to approaching 2 metres by 2100.

Another aspect concerning coastal retreat is the not well known and controversial. Bruun’s rule predicts that coastlines will retreat by about 50 times each unit of sea level rise. That would indicate with a sea level rise of about a metre the coast would retreat 50 metres. The current rapid retreat of the coast reinforces this and if it proceeded at the same pace for next 70 – 80 years the coastline would at least be a further 200m inland.

Which leads us to another aspect of this complex situation. The last time greenhouse gases were this high was 3 million years ago. Then the sea level was approximately 25 metres higher than it is now. Unless there is a rapid drawdown of these gases sea levels will rise inexorably until they reach this level perhaps in a thousand years, or with catastrophic change far less. Amongst the large list of urgently needed actions is a long term, planned, orderly retreat from the vulnerable coast.