Although parts of Clonmel, Co Tipperary, remained covered by floodwater yesterday, residents and borough officials watched with relief as the abnormally high level of the River Suir fell slowly throughout the day. Attention turned to the origins of the problem which has brought serious flooding to the town three times in the past three years.
Along with periodic heavy rainfall, the cause of the flooding of Clonmel and villages such as Ardfinnan and Newcastle, as well as large tracts of surrounding farmland, lies in the scale of the Suir catchment.
Appropriately described as a majestic river, the main channel of the Suir extends for a length of 174 kilometres, with its multiple tributary rivers adding a further 530 kms. Its total water catchment area is estimated at some 3,500 kilometres, much of which is mountainous land in counties Tipperary, Kilkenny and Waterford.
This vast natural basin collects enough precipitation to create a water flow, at the Clonmel constriction, which amounts to an average of 200,000 cubic metres an hour throughout the year. In the past few days, that figure could be multiplied several times.
Ironically, it is thought that the site of the ancient town was probably chosen by the Normans as a place to settle because it was low on the river, and as the town developed, its buildings were designed to cope with and to harness the strength and volume of the water flow.
The quays were built in their present form around the year 1790. The borough engineer, Mr Jim Keating, says the builders of substantial houses alongside the river 200 years ago had designed their levels to protect them against floodwater. Extensions added over the subsequent two centuries did not adhere to the same levels and became vulnerable to flooding.
Records in the town hall show that flooding incidents leading to property damage were relatively frequent in the 1920s, 1930s and 1940s. The frequency declined later but has increased again in the 1990s.
The return of the problem in recent years may be due in part to the way the town has developed, but there may be wider reasons arising from modern practices of intensive land use and inappropriate land management.
An experienced local mountain walker said yesterday that vast mountain areas in the catchment have been overstocked and overgrazed by sheep, denuding the hills of vegetation and leading to rapid water runoff when there is heavy rain.
Lower down, the use of heavy farm machinery has compacted the land and reduced its capacity to absorb sudden deluges of water. Peat bogs, which can hold vast quantities of water like a sponge and release it slowly, have been stripped or drained.
The Blackwater river, which overflowed its banks and flooded the village of Blackwater, Co Wexford, on Monday is not one of the five major rivers of the south-east, as could have been inferred from yesterday's report. It is a minor relative of the more substantial River Blackwater which flows into Youghal Bay.