Tidal surge

Thursday 7th July 2011

A report by Tim Bulmer

On Monday 27th June at approximately 13.15, I was preparing the support boat ready to accompany the day’s Encounter Cornwall canoe expedition.

The neap tide was still about two hours before high water. I had brought the boat from its mooring to the slipway and tied it up and returned to the store for more equipment. I was in the store for about five minutes and when I returned to the boat, I saw, to my horror, that the incoming tide was going out fast.

Already the boat was high and dry on the slipway and the water level had receded by well over a metre in just a few minutes. I watched as the tide continued to rush out, leaving craft moored on the river aground once again.

In the distance, I saw a breaking wave the full width of the river rushing in towards Lerryn. The wave, with its white, breaking crest must have been about a foot in height, but the water behind the wave was the height of the breaking crest.

It passed through Lerryn, leaving the moored boats yawing and plunging over the wave and turbulent water that followed it. Within another five minutes the water returned to its original height and our support boat was afloat once again.

It was a most extraordinary phenomenon – one I have never witnessed before – similar to small tsunami or Severn Bore.

Although not witnessed by me, I am reliably informed that a second surge of a similar size occurred on the outgoing tide at about 6pm that evening.

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