Certain parts of Ireland have always been susceptible to floods. They are mentioned frequently in The Annals of the Four Masters and similar chronicles of antiquity. But we will never know if, for example, the incident referred as "the eruption of the nine lakes" of 1629 BC can be compared to the current flooding in our southern counties. Be that as it may, this most recent spate is among the worst, if not the worst, in living memory. The depression which appeared so suddenly and unexpectedly on our southern doorstep last weekend has moved little in the intervening days.
As a consequence, its associated thundery fronts have remained almost stationary over Munster and south Leinster and the easterly flow of wind around the depression's northern flank has acted like a conveyor belt to sweep in thundery rain from the Celtic and the Irish Seas.
Records are being broken hour by the hour. When the figures finally come to be analysed it seems likely that large areas of the southern half of the State will be seen to have had more than 200 mm of rain, or more than 8 in over the space of a few days. This is much more than twice the normal monthly rainfall for the whole of August.
This most recent episode marks the third successive year in which serious floods have been experienced in Ireland, following as it does hot on the heels of the Co Galway inundation in March 1995, and the repeat performance in Clonmel in 1996.
Cumulative rainfall amounts on this occasion, however are much higher. To find records of rain having fallen in comparable quantities it is necessary to go back to 1986, and the infamous "Hurricane Charley".
Not entirely by coincidence, one suspects, that memorable rainstorm also occurred in August; on the 25th of that month the rain poured down in unprecedented quantities, breaking long-established records and leaving widespread flooding in its wake.
The heaviest of Charley's rain fell in the Dublin and Wicklow mountains, with 280 mm, or 11 in, being recorded on Kippure. Nearer sea level, the 200 mm recorded at Kilcoole, Co Wicklow, set a new Irish record for the greatest amount of rainfall in a day. Over the catchments of the Dodder and Dargle Rivers, falls in excess of 150 mm were the norm, and both rivers overflowed their banks, flooding more than 400 houses and businesses to a depth of several feet.
Throughout Ballsbridge and Sandymount in Dublin, and further south in Bray, dozens of families were hurriedly evacuated as their homes succumbed to the most severe conditions to hit the area for more than two generations.
The worst flooding before that had occurred 81 years previously, almost to the day, and it affected almost the same neighbourhood. On August 25th, 1905, the focus of attention was Bray, Co Wicklow, where the flooding necessitated the evacuation of more than 1,000 people from their homes. The gauge at Bray Garda station recorded 113 mm of rain that day, and in the centre of Dublin, 85 mm were measured. Recent events in our southern counties are comparable to both these episodes, and will be remembered just as long, confirming the reputation of August, well known in meteorological circles, as a particularly dangerous month for torrential falls of rain.
Further evidence of the potential wickedness of the current month is available from the Fastnet storm of August 13th, 1979 - the one that sank a fleet of yachts and caused the death by the drowning of 15 participants in the Fastnet Yacht Race. This storm was remarkable for the ferocity of its winds rather than for the amount of rain it carried, but closely resembled our current visitor in the unexpectedness of its arrival, and in its explosive development in the same location, just a little south of Ireland.
Yet it seems like only yesterday since we were suffering from lack of rain. In April this year in Munster and Leinster, there was hardly a single April shower worthy of the name, confirming a six-week absolute drought which had followed a winter during which the total rainfall over much of the country was less than 75 per cent of average. Ironically, at that time, a mere three months ago, the spectre of severe water shortage stalked the land.
The contrast emphasises a pattern that has been a very striking feature of our weather in recent years - relatively short, very wet spells, often with interludes of severe flooding, interspersed with long periods when there is very little rain.