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Tuesday, September 02, 2008

Newcastle West flooding report to be published tonight

(new details, report published)

The findings of a Severity and Impact report into the devestating flooding of Newcastle West and surrounding areas on August 1st will be revealed a public meeting this evening.

At the event a joint meeting of the County Council and the local Business Association will hear the results of a Severity and Impact Report, which is being prepared by JBA Consulting.

The publication of the report follows on from a public meeting that took place in the aftermath of the flash floods that occurred in the town.

A month's worth of rain fell in just five hours causing the River Arra to burst its banks for the first time in living memory. Millions of euro worth of damage was believed to have been caused.

The meeting, being held the Ballintemple Inn at Newcastle West will begin at 8.45pm.

NEW DETAILS (8.48pm)
The report has been published and recommends that analysis should be undertaken, in conjunction with the Office of Public Works, to assess the capacities of the River Arra and its tributaries along with individual structures along the channel to identify flooding risks in the future.

Particular areas of concern include in the report include Cullenagh Bridge, the Bridge Street crossing, the culvert below the Bedding Store, Mill Falls Apartments, Courtenay Bridge and the Bridge of Tears.

The report stated that "Water flowed through the town, both via the channel and the roads, inundating many properties and moving debris and vehicles in its path. Water depths of up to 1.8m above road level were recorded in the town".

The report also concluded that the flooding event was was a one in a 650 year occurrence.

Some key conclusions of the report into the flooding found the following,

The Arra catchments are very steep with a dense river network upstream of the town. Newcastle West sits at the confluence of three main rivers; the Dooally, the Arra and the Mash;

- July was an exceptionally wet month which resulted in fully saturated ground conditions prior to the storm;

- During the storm, 10% of the expected annual rainfall fell in 5-6 hours giving a rainfall return period of up to 1 in 650 years;

- Water sheeted off the upper slopes, over-whelming field drains and ditches and forming overland flow routes upstream of Newcastle West town Some properties were flooded as a result of water returning to the channel;

- In the town itself, the river channel and structures were also overwhelmed. In response to public concern, it is noted that Mill Falls Apartment and the new Bridge of Tears have greater capacity to pass flow than other structures on the channel.

The reports also outlined the following recommendations,

- Available data on the channel and structures should be supplemented with additional channel topographic survey and structure survey as required;

- Further detailed hydraulic analysis should be undertaken, in conjunction with the OPW, to assess the capacities of the channel and individual structures in order to identify actual risk associated with each of them. This includes in particular Cullenagh Bridge, the Bridge Street crossing, the culvert below the Bedding Store, Mill Falls Apartments, Courtenay Bridge and the Bridge of Tears (both structures);

- JBA Consulting visually recorded wrack marks throughout the whole town. It is recommended that these marks be surveyed at a later date to give a more detailed analysis of flood levels;

- Flood outlines for planning should be produced for the 1% AEP and 0.1% AEP events to align with forthcoming Government Flood Planning Policy;

- Development of a detailed Digital Elevation Model (DEM), ideally using LiDAR, to produce a detailed flood event outline;

- Compilation and analysis of questionnaires, including further interviews should they be deemed necessary.
The report has been published this evening at the public meeting and is available from from tomorrow morning.

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