Re: Expert pours water over flood plan, Sentinel Times, July 22.
Whilst agreeing with Mark Harrigan’s criticisms of the Bass Coast Shire Council’s Land Subject to Inundation Overlay, the CSIRO report he quotes and his own statements contain some errors.
The effects of wind direction on storm surge in different parts of Western Port are different to the CSIRO report and to Mark Harrigan’s assumptions.
I have information on Cowes, Rhyll and Tooradin and this is presented below.
My father worked as a professional fisherman from Rhyll from 1926 and he always said that we got the highest tides at Rhyll when a spring tide was combined with a north-west gale.
Conversely, an easterly or south-easterly wind has the reverse effect and produces lower tides.
My own observations have backed this up and I have photos going back 90 years which show this.
The highest tide at Rhyll that we know the exact height of was back in the 1980s when it just covered the decking on the Rhyll Jetty.
These tide heights should be similar for the Silverleaves area which is only a short distance away.
The most recent storm surge at Tooradin was on June 4, 2010 with a westerly wind which blew for three days with the tide level increasing each day until the water was almost up to the bridge beams and house blocks were flooded.
It was the worst flooding that locals had seen in 50 years.
Possibly the worst storm recorded at Cowes since settlement was from the north-west and occurred in June 1923.
The Argus of June 20 reported:
“During the recent terrific gales off the coast, the jetty at Cowes, Phillip Island was swept from end to end by such heavy seas as had never been known in Westernport. At times the jetty was under water owing to the abnormally high tides. Some idea of the storm is gained from this picture which shows a succession of rollers breaking over the little pier which at its seaward end was considerably damaged.”
The photo shown above is similar to the one in the newspaper and was taken at the same time.
I have seen Cowes jetty in storm force winds and have never seen seas like this. One could expect major erosion along the north shore of Phillip Island with a storm similar to this.
The storm surge in different areas of the bay is far more complex than the CSIRO assumes and far more research to define the effects of different wind directions is needed before adoption of C82.
If maximum storm surges occur with a north-westerly along the Silverleaves shore as I suspect, additional damage will be done by the waves generated by the winds and should be taken into account in the analysis.
John Jansson, Civil Engineer, Rhyll.