Although it is by no means unknown, even today, for a bridge to be carried away in a heavy flood, such catastrophes are much less frequent than they used to be. This is a deliverance due more to skilful engineering than to any lack of water or any improvement in our Irish weather.
Bridges across rivers in olden times tended to be built insecurely of wood. Even when stone was used, the arches were low and narrow and incapable of allowing flood waters to flow through them unimpeded. In circumstances of severe flooding, the waters, and any flotsam they might carry with them, would pile up behind the arches to obstruct further the swollen river's flow. Successive consignments of debris acted like so many battering rams in continual attack, until eventually the fragile structure could sustain no more. Modern bridges, with wider arches and more slender piers than the older ones they have replaced, have much less strain to bear.
Over the centuries, therefore, one of the great difficulties faced by the city fathers of our capital was that of keeping the city's many bridges intact. The annals of Dublin abound with tales of "most disastrous chances/Of moving accidents by flood and field,/Of hair-breadth 'scapes in the imminent and deadly breach". One J. Ferrer esq, for example, writing in 1787, described how the bridge across the Dodder at Ringsend was demolished by a flood. Ringsend, he wrote, "resembled a town which had experienced all the calamities of war, and that had been sacked by an enemy. The unfortunate inhabitants were in a manner excluded from all intercourse with Dublin. They were attacked by the overbearing floods which issued from the mountains in irresistible torrents and completely demolished the bridge".
A few years later, in December 1802, the rebuilt bridge succumbed to floods again when more than 3 ins of rain fell in the Dublin area in 24 hours. On this occasion, Ringsend bridge was not the only one to suffer; Ormonde bridge was washed away also.
And 260 years ago today, on September 11th, 1739, the bridge at Donnybrook was one of several to succumb. A contemporary diarist has left us his impressions: "Donnybrook bridge was thrown down, as also was Enniskerry bridge near Power's Court. Several ricks of corn and hay, with many chairs, stools and tables, were seen floating in Donnybrook River, and it is imagined that many cabins have been carried away."