Supermoon king tide sees Karuah River rise 2.5m

Monday night’s supermoon is believed to have played a part in the king tides which saw the Karuah River reach exceptional heights this week. 

Water pushed past the embankments and spilled into Longworth Park, covered infrastructure owned by oyster farmers who operate along the river and at one stage covered the wharf near Karuah Bridge.

According to the Bureau of Meteorology, the tide rose to 2.3m about 9.30am on Monday and peaked at 2.5m about 10am on Tuesday. 

The high tide was still 2.3m on Wednesday, but was expected to drop to 1.97m on Thursday.

The king tides came after a supermoon event on Monday night.

Stephen Cole from Cole Bros Oysters said in the seven years he and brother Dean have owned and operated a shop next to Longworth Park they had not seen the river so high.

“When there’s a full moon the high tide is always higher but after the supermoon on Monday, we had three king tides in a row,” Mr Cole said.

“We’ve been here seven years and haven’t seen it [river] that high before.

“We had 20cm of water throughout the shed. We were working in gumboots.”

With the water now receding, the river’s banks are covered with stick, debris and rubbish.

What is a supermoon?

Supermoon is a popular term for the lunar event which coincides with a new full moon and the moon making a closer-than-usual approach to Earth.

Because the moon orbits Earth in more of an oval rotation than a circle it means that sometimes it is much closer to Earth than normal.

Combine that with a full moon and you have yourself a supermoon.

What is a king tide?

A king tide is a popular term for an especially high tide. King tides only occur a few times per year.

What causes a king tide?

In a lunar month the highest tides occur at the time of the new moon and full moon, when the gravitational forces of the sun and moon are in line. These are called spring tides and they occur about every 14 days.

In any one year there will be two spring tides that are the highest, one during summer the other during winter. These are often referred to as king tides.

Are all king tides the same?

During normal weather conditions the height of the king tides will be similar from year-to-year. However, in abnormal weather conditions (severe storms, for example) the low air pressures and strong winds at these times can elevate the sea level above the expected height.