High tides may bring huge floods to capital


MAJOR flooding fears have been raised as Dublin braces itself for "unusual" high tides in a fortnight.

The Metropolitan Emergency Planning group was put on full alert yesterday because of the potential risk.

The move followed a warning from the State's Marine Institute of a period of "unusually high tides", which could pose high flooding risks for the city.

These will reach a peak in Dublin around September 10 and in Galway at the same time.

Ringsend and other parts of Dublin were devastated by floods in 2002.

The Marine Institute says that tide levels in Dublin of 4.5 metres are predicted at 12.30am on September 10. On the same day in Galway, tide levels of 5.52 metres at 7.45 pm are expected.

Tom Leahy, Dublin's deputy city engineer, revealed yesterday that the Metropolitan Planning Emergency Group was put on standby to monitor the risk of flooding in the run-up to September 10.

The group is made up of the four Dublin local authorities, the gardai, the Heath Services Executive and the Coastguard.

"This group is on alert as there may be an issue. We will be looking at the situation very closely over the coming week," Mr Leahy said. "Between three to five days before the period we will be in a better position to determine if there is a significant issue or not."

The emergency group is due to meet later this week to assess the situation.

The high tides occur at the autumn and spring equinoxes. They are linked to the tilt of the moon and its orbit around the earth. Storm surges occur when high tides coincide with onshore winds and low-pressure conditions.

The Meteorological Office said yesterday it was too early to predict if there were going to be conditions conducive to floodingon September 10.

29/08/2006 Irish Independent


Flood alert as high tide set to hit


THE highest tides in Ireland for 20 years are on their way - with the potential to bring devastating floods to low lying coastal areas including Dublin, Cork, Galway and the south east.

But homeowners in vulnerable areas will have only three days' notice that their homes are under threat from the record Spring tides and a once every two decade occurence that will bring the highest tides since the late Eighties.

It is all down to the phenomenon known as the nodal cycle, which relates to the tilt of the moon and the elliptic nature of the moon's orbit around the earth. The nodal cycle causes an extremely big spring tide to occur once during this 18.6-year cycle.

When the nodal cycle high coincides with the twice yearly Spring and Autumn equinoxes, it can spell trouble for those areas that are prone to flooding.

That's going to happen in the coming weeks with the tides reaching their high point in Dublin on September 10 and Galway on October 8.

The differences in date between the west and east coasts are due to mitigating local factors concerning the effectsof the Irish Sea and the open Atlantic.

Record high tides don't necessarily mean homes will be flooded. The weather is a key component in creating the conditions for flood.

Storm surges occur when high tides coincide with weather patterns causing onshore winds and low pressure (storm) conditions.

Onshore winds create waves that drive water ashore and low atmospheric pressure allows the tides to rise even higher against the reduced downward pressure of the air.

"The high tides we are going to experience in September and October are only actually 0.1 metre above the highest normal Spring tide which equates to about 10 centimetres. Any problems that may occur will be due to bad weather - in other words, a storm surge combining with this high tide," according to Dr John Joyce of the Marine Institute.

"Trying to predict that is difficult. The UK have a comprehensive set of computer based models so coming up to the very high tide they can feed all the information into a computer looking at weather, tide levels, wind speed and direction and barometric pressure so they can predict two or three days in advance what the affect is likely to be.

"In Ireland we are somewhat behind in this area but we are working to catch up and we now have five meteorological weather buoys around the coast and we have number of tide gauges which are reporting information in real time. We are working to get those two elements combined in a computer model.

"These high tides could be a problem but we will be monitoring the situation closely. We will issue warnings if necessary but with the best will in the world we will only be able to give three days notice of an impending threat of flood," Mr Joyce added.

In 2002 Ringsend and Irishtown in Dublin were badly hit by floods when high tides combined with a storm surge. Work has since been completed to improve flood defences.

JEROME REILLY Irish Independent 28/08/20