Under-fire agencies promise interim flood measures

THE two state agencies in the firing line since Cork’s devastating winter flood have again defended their actions but have vowed to implement interim changes.

However, the ESB is dependent on the Office of Public Works (OPW) to deliver the structural defences along the river Lee that will allow it implement major changes to its dam management procedures, thereby allowing it discharge greater volumes of water without causing a flood downstream.

But work on those structural defences will not begin until well into 2012.

In the meantime, the ESB has introduced a pilot project for the winter and reduced by 50cm the winter spill levels — the levels at which it must discharge water — at both the Inniscarra and Carrigadrohid dams.

In the meantime, the OPW says it is committed to minimising flood risk in Cork city.

An OPW spokesman said before long-term flood defences can be designed or built along the lower reaches of the Lee, a lot of computer modelling work and technical reports must first be completed.

Prior to commissioning consultants to undertake the design of the structural flood-defence components of a flood-risk management scheme for the city, a number of priority actions are being undertaken, the spokesman said. These include topographical and structural surveys of the existing defences within, and upstream of, Cork city to understand exactly what additional defences may be required, and updates to the Lee CFRAMS hydrodynamic river model, including all of the new flood levels collected during the November 2009 flood.

This will allow engineers to determine the most accurate design flood-profile for a range of extreme tidal conditions, as well as discharge scenarios from the Inniscarra reservoir, the spokesman said.

“The Lower Lee and Cork City Flood Risk Management Works are at procurement stage for consultants who will take the works through to construction,” he said.

The OPW is also conducting a detailed in-house study on flood forecasting for the River Lee, he said.

Work is also under way on the Strategic Review of Flood-forecasting and Warning in Ireland, with the first round of consultation complete, and the final report due for delivery in early 2011, he added.

The ESB has also defended its actions on the days leading up to the flood disaster, and its handling of the situation on November 19.

A company spokesman said its reservoirs at Carrigadrohid and Inniscarra operate within a band of levels which are required for hydro-electric generation purposes, and also because of the need to ensure adequate water extraction facilities for Cork city, and adequate minimum river flows in a drought situation.

He said the entire Lee catchment was hit by a number of large rainfall events during November 2009, and that flood warnings were issued on November 16, and for three days prior to the flood the ESB discharged the maximum possible amount of water from Inniscarra without breaching the river banks.

“The three-day inflow to the reservoirs during the flood was approximately two-and-a-half times their combined normal storage capacity,” he said.

“ESB had no option but to release the water on November 19, in order to protect the integrity of the dam, in the interest of public safety.

“The presence of the dams reduced the peak flow at Inniscarra by approximately one third.”

He pointed out that under the current statutory framework governing the company’s operation, it cannot cause a flood downstream prior to a natural flood arriving in the reservoirs.

“The issue of the increased likelihood of downstream flooding, caused by discharges on foot of an adverse weather forecast when such forecasted heavy rainfall does not materialise, must also be addressed as part of the CFRAMS process,” he said.

But he warned the ESB reservoirs on the Lee have limited storage capacity.

“They are small relative to the overall catchment inflows and therefore have a limited capacity to alleviate floods, even if levels are low,” he said.

In a preliminary report on the 2009 flood, ESB International has estimated the flood return period to be in the order of 50-100 years.

This report has been provided to the OPW.

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