THE DOWNPOUR which led to the worst flooding in living memory in the Co Limerick town of Newcastle West was a once-in-650-years event, according to the findings of a new report.
Millions of euro worth of damage was caused to homes and businesses in the west Limerick town on August 1st when the river Arra burst its banks. Details of an impact report into the flooding were revealed at a public meeting in Newcastle West last night.
According to the report, which was compiled by JBA Consulting on behalf of Limerick County Council, 10 per cent of the expected annual rainfall fell over a six-hour period on one night.
The report says that the average amount of rain which fell on Newcastle West and its environs on the night in question was 85.9mm. “Assuming a storm duration of five to six hours, this rain equates to up to a 0.15 per cent annual exceedence probability (AEP) or a return period of up to 1 in 650 years.”
The report estimates that more than 200 properties suffered flood damage. However, a precise figure will not be available until further analysis has been carried out.
Water depths of up to 1.8m above road level were recorded in the town. Witness statements and a site visit helped to establish the pathway of the flood.
“Although a number of people were rescued from property or vehicles, no one was seriously injured during the event. Power and water supplies were also affected for a time. . . Road closures, both as a direct result of the flooding and due to subsequent landslides, remain in place in some areas,” the report says.
Newcastle West lies on the downstream reach of the Arra, which is a tributary of the river Deel. There are no recording gauges on the Arra, but there are two level-recording gauges on the Deel near the Arra at Deel bridge and Grange bridge. According to the report, these gauges showed water levels in excess of any previously-recorded event: by 600mm at the Deel bridge and by 400mm a Grange bridge.
Among the recommendations contained in the report is the need for further hydraulic analysis in conjunction with the Office of Public Works (OPW) to assess the capacities of the channels and individual structures and thus identify actual risk associated with each of them.
These structures include Cullenagh bridge, the Bridge Street crossing, the culvert below the bedding store, Mill Falls apartments, Courteny bridge and the Bridge of Tears.
Other recommendations include the surveying of water marks recorded by JBA Consulting throughout the town to give a more detailed analysis of flood levels.
According to Gerry Behan, deputy county manager of Limerick County Council, the local authority, in conjunction with the OPW, “now looks forward to following through on the key recommendations outlined in the report”.
The report will be made available in full on the Limerick County Council website at www.lcc.ie from today.