Home | Links | ©| Contact Us

Bantry and Dunmanus Bay
Cuan Beanntraí agus Cuan Dun Manus

Overview

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

Back to Top

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).

Back to Top

Bathymetry (Water Depth)

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

Back to Top

Lidar

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.

The oil terminal on Whiddy Island. Lidar shaded relief on left and Lidar aerial photos on right.

 

Dunmanus Bay Coastal areas less than 20 metres deep extending from Foilavaun Point on the north west coast to Dunbeacon Harbour at the head of the bay and west along the south coast to Dooneen Point. Depths to a maximum of 20 metres were achieved, however in places the depths achieved were considerably less due to the high levels of turbidity.


Bantry Bay Coastal areas less than 20 metres deep extending from Bear Island on the north west coast to Bantry at the head of the bay and west along the south coast to Trasloosh Landing, including Glengarriff Harbour and Adrigole Harbour.

All of our Charts for Bantry & Dunmanus can be downloaded in pdf format from this page.

Download Shaded Relief Bathymetry Geotiffs from our Interactive Web Data Delivery System (IWDDS)

Select your area of interest.Offshore Geotiffs - Lidar Geotiffs.

Back to Top

Shaded Relief

The 3D appearance is achieved using software called Fledermaus. By using some vertical exaggeration, artificial sun-shading (usually as if there is a light source in the nw 315°) and colouring the depths using various colour maps, it is possible to highlight the subtle relief of the seabed. This helps us to quickly understand the variation in depths.

A 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).

All of our Charts for Bantry & Dunmanus can be downloaded in pdf format from this page.

Download Shaded Relief Bathymetry Geotiffs from our Interactive Web Data Delivery System (IWDDS)

Select your area of interest.Offshore Geotiffs - Bathymetry Shaded Relief Geotiffs.

Back to Top

Backscatter

Multibeam Systems also collect additional information, including the strength of the acoustic signal (or return) from the seafloor. This is known as Backscatter. Differing seafloor types, such as mud, sand, gravel and rock will have different Backscatter values depending on the amount of energy they return to the sonar head. Rocky areas will typically have high returns while soft sediments like mud are more likely to absorb energy and have low Backscatter returns. These differing values are used to generate a grey-order image (i.e. dark for high returns, bright for low returns) of the seabed which can be used to examine the nature of the seafloor.

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).

Detailed .pdf backscatter charts can be downloaded by clicking here

Download Backscatter Geotiffs from our Interactive Web Data Delivery System (IWDDS)

Select your area of interest.Offshore Geotiffs - Backscatter Geotiffs.

Back to Top

Ground Truthing/Seabed Sampling

To verify the results of remotely sensed sonar data, it is important to collect physical sediment samples from the seabed. These may be from the surface where grabs are used or may penetrate through the seabed and retain the vertical structure of the sediment by using various coring methods. These samples are also critical for the confirming seabed classifications.

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).

Sample 572 (See map above) taken using Box Corer on the Celtic Explorer Leg 1 in 2006

Sample 574 (See map above)taken using a Grab Sampler on the Celtic Explorer Leg 1 in 2006

 

Read more about the sampling on our Blog by clicking on the link below.

CV09_23 Ground Truthing in Bantry and Dunmanus Bays

Back to Top

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).

Sample 572 (see photos above) Sandy gravel composed mostly of bioclast is in Class 2.

Sample 574 (see photos above) Homogenous clay-rich mud is in Class1.

Also, note the variation in colour on the backscatter map which also aids in the seabed classification process.

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.

Back to Top

Shipwrecks

           

To view the shipwrecks in Google and to download Shipwreck Information Sheets please click here

Back to Top

 

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

Back to Top

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.

Back to Top

Return to Survey Details Map

Follow these links to your area of interest on the INFOMAR website:

About | Surveying | Data & Products | News & Updates | Press Releases | Publications | Associated Projects | Image Gallery | Contact Us | Home

Find Us
Geological Survey of Ireland Geological Survey of Ireland
Beggars Bush, Haddington Road
Dublin 4
Marine Institute Marine Institute Headquarters,
Rinville, Oranmore
Co. Galway
The National Development Plan
a modus site