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Bantry and Dunmanus Bay
Cuan Beanntraí agus Cuan Dun Manus


Bantry Bay is the largest of the long marine inlets in south-west Ireland. It is approximately 35 km long, running in a south-west to north-easterly direction. The entrance to the bay is approximately 10 km wide, narrowing to 3-4 km at its head. Bere Island, situated on the north shore adjacent to Castletown Berehaven, and Whiddy Island lying near the head of the bay on the southern shore are the two largest islands in the bay. Rivers enter the bay at Melagh River near Bantry, Owvane River at Ballylicky, Coomhola River at Dromkeal, Glengarriff River at Glengarriff, Adrigole River at Adrigole.

Dunmanus Bay to the south of Bantry Bay is divided by the Sheep’s Head and Mizen peninsulas. The bay is nearly 7 km wide from Sheep’s Head to Three Castle Head and 25 km long from mouth to its head at Four Mile Water. The largest islands within the bay are Carbery, Furze, Horse and Cold Islands. The Durrus River drains into the bay at Durrus.

Location of Bantry and Dunmanus Bays, Cork in the southwest of Ireland.

Ordnance Survey of Ireland (OSI)/Government of Ireland OSI License No EN 0047207

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INFOMAR Survey History

INFOMAR surveys of Bantry and Dunmanus Bays began in 2004 when the Celtic Explorer mapped a small area of seabed around Dursey Head as part of a larger survey of the southwest priority area. In 2006, the Celtic Explorer was used to map the outer reaches of both bays. Later in the year, IMAR survey were contracted to continue the survey, covering the middle and inner bay up to Whiddy Island and the channel between the Beara peninsula and Bear Island in Bantry Bay.

Also in 2006, a Tenix LADS lidar survey mapped the nearshore and shallow waters in both bays. This was particularly effective at Whiddy Island, the channel between the Beara peninsula and Bear Island and at Glengarriff. September 2007 saw the remaining seabed of both bays surveyed using the Celtic Voyager to achieve complete coverage of both bays.

Coverage from all surveys involved in mapping Bantry and Dunmanus Bays for the INFOMAR project (Click image for more detailed map).

Details of surveys undertaken in Bantry and Dunmanus Bays (Click image for more detail).

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Bathymetry of Bantry and Dunmanus Bay (Click image for more detailed map).

In general terms, the bathymetry of the area is as expected with relatively shallow areas within the bays which deepen moving offshore. Water depths range from 0 metres to 76 metres to the southwest of the bays. It is interesting to note that due to the structural control (outlined above) on the bays, the rocks are often steeply dipping into the ocean resulting in sea cliffs. Where this occurs, particularly on the outer Sheep’s Head, the water depth increases rapidly to depths of 40 to 50 metres.

In contrast, the channel to the north of Bere Island is relatively shallow with water depths closer to 20 metres. However, this depth is sufficient for the large numbers of fishing and recreational vessels that use Castletown Bere harbour to shelter from rough sea conditions from the southwest and south.

For a more detailed chart of the bathymetry of Bantry and Dunmanus Bays click here

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Shaded Relief

MBES shaded relief image of the pipeline and pilings for the jetty at the former Conoco Phillips oil storage facility at Whiddy Island where the Betelgeuse oil tanker exploded while docked at the deep water jetty used for transferring oil to the terminal on shore in 1979 (Click image for more detailed map).

Shaded Relief North East Chart Overview Chart & Shaded Relief North West Chart Overview Chart

Full shaded relief chart for Bantry and Dunmanus Bays are available for download here

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MBES backscatter image of the outer reaches of Bantry Bay and approaches to Castletownbere. Rock outcrops appear dark with surrounding sediments various shades of grey depending on grain size and texture. The NNE to WSW ‘grain’ of the regional geology is especially apparent (Click image for more detailed map).

Full backscatter chart for Bantry and Dunmanus Bays is available for download here

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Ground Truthing/Seabed Sampling

A range of seabed sampling has been undertaken in Bantry and Dunmanus Bays, both historically and under the INFOMAR project. These include grab samples, vibrocores and video footage. The locations of the grab samples have been mainly determined by the seabed classification made from the multibeam data.

Seabed sampling locations from Bantry and Dunmanus Bays where Van Veen grab, Day grab and Box core instruments were used to ground truth INFOMAR datasets (Click image for more detailed map).

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Seabed Classification

The classification of the multibeam dataset from Bantry and Dunmanus Bays resulted in the creation of a 5 class classification divided into two types of rock, reflecting the different textures observed from rock outcrops in the bay. Three more classes divided the sediments into Gravels and Coarse Sand, Coarse to Medium Sand and Fine Sand to Mud.

Seabed Classification Chart for Bantry and Dunmanus Bays (Click image for more detailed map).

Download a more detailed chart of the seabed classification of Bantry and Dunmanus Bays here

Further information about the classification process can be found in the Data Processing section.

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INFOMAR in Google Earth

To view and navigate around the Bantry and Dunmanus Bays datasets in Google Earth, click on the links below.

Merged Datasets

Bantry MBES

Dunmanus MBES

LiDAR Bantry

LiDAR Dunmanus

To view additional datasets in Google Earth please click here

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Data Access

Full details outlining the process to gain access to datasets for the bay above or all INFOMAR data can be found in the INFOMAR | Data page of this website.

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Return to Survey Details Map

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