Lee Catchment Flood Risk Assessment and Management Study

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Inishcarra and Carrigadrohid hydro-electric dams

The River Lee hydro-electric scheme was built during the period 1952 to 1957. Inishcarra Dam is located approximately 13km west of Cork City with Carrigadrohid Dam a further 14km upstream. The dam at Inishcarra is 250 meters long and 45 meters high while Carrigadrohid Dam is 22 meters in height and 130 meters long. Between them, the dams  generate almost 80 million units of electricity a year. The construction of the dams created two lakes which stretch from Inishcarra upstream to the Gearagh. The lakes cover an area of approximately 14 square kilometres and have a storage capacity of 45 million cubic meters.

Over the last 50 years, the River Lee hydro-electric scheme has had a number of important benefits for the people of Cork including the generation of green electricity, the management of flood waters, storage of water for the Cork Harbour water supply and the creation of a significant leisure amenity.

The construction of the dams and storage reservoirs also resulted in a number of negative impacts including the loss of the private lands and homes, the destruction of the Gearagh forests and the collapse of the wild salmon fisheries. The ESB have made a significant contribution to reverse the impacts on the environment with the introduction of the fish hatchery at Carrigadrohid and the re-establishment of significant salmon and coarse angling on the River Lee. The Gearagh is now a wild life sanctuary and designated as an area of special conservation. This was established through the co operation of the ESB, NPWS and other bodies.

The dams on the River Lee play an important role in the management of flood risk in the Lee valley through the provision of storage and controlled discharge of flood waters. Inflow from the upper Lee catchment is controlled at Carrigadrohid through storage in the reservoir and controlled discharge via Carrigadrohid’s generating station and spillway gates. Inishcarra reservoir provides additional flood storage potential and controlled discharge via Inishcarra generating station and three overflow spillway gates.

During a storm event, rainfall data from the upper Lee catchment together with information on water levels in the reservoirs is transmitted to a central control room. Operations at both reservoirs are co-ordinated to optimise flood water management and are co-ordinated with forecast high tide levels in Cork City. Flood warnings are issued by the ESB to those known to be at risk of flooding downstream of Inishcarra dam.

Flooding downstream of Inishcarra Dam is affected by a number of factors including the additional flows to the River Lee from the Bride, Shournagh and Curragheen catchments which comprise over 30% of the overall River Lee catchment area. Additionally, high tide levels and storm surges affect water levels in the River Lee in the vicinity of Cork City.

Photos

Blarney Castle

Lough Allua

Reservoir upstream of Carrigadrohid dam

Inishcarra Dam (image courtesy of the ESB)

Key Activities

The key activities to the project are

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Non-Technical Summary for SEA Environmental Report published(more)

Consultation on the draft Flood Risk Management Plan (more)

Consultation on Lee Predictive Floodmaps (more)