CAUSE AND EFFECT
Sir, - The recent floods in the south east, in Carrick on Suir and Clonmel in particular, has caused an outburst of indignation and cry of blame without any mention of one of the most important causes of flooding in this as in other areas.
Simply put, the spread of agricultural drainage schemes and land reclamation has caused a huge acceleration in the manner in which rain water drains from the fields and hills. This in turn means that after heavy rain the rivers rise much more rapidly, that the flood is of much shorter duration, and that the peak of the flood is far higher than previously occurred.
These tendencies have been exacerbated by the removal of ponds, and the straightening and canalisation of rivers (i.e., the building of embankments which narrow the river and prevent floods from spreading out over fields and marshlands).
Mature woodlands could be expected to slow the run off from mountains, but most of our forests are not mature and cannot hold back the rainfall. Indeed the first task undertaken by An Bord Coilte on acquiring a hill site is to send in the drainage ploughs. These machines dig deep trenches, at right angles to the contour lines hurrying the water from their property.
The great midlands bogs, many with 20 or 30 feet of turf acted as sponges, taking up vast amounts of water in wet weather and releasing it slowly in dry conditions. These too have been effectively eliminated by major drainage needed for their commercial exploitation, for fuel and peat.
If that were not bad enough all of these factors contribute to the acute water shortages which so many cities and towns have experienced in recent years.