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Mulroy Bay
Cuan Mhaoil Ruaidh

Overview

Mulroy Bay is located in Co. Donegal in the northwest of Ireland, around 15 km north of Letterkenny. The bay is situated between the Fanad Head peninsula to the east and the Rosguill peninsula to the west.

Location of Mulroy Bay, Co. Donegal in northwest Ireland.

The sinuous and convoluted Mulroy Bay is approximately 22 km long along a central axis from the mouth of the bay to Milford at the southern most reaches of the bay. However, the width of the bay changes regularly along its length with the mouth of the bay close to 2 km wide from Melmore Head and Ballyhoorisky Head. South of Donaghmore Beach the channel narrows to just over 200 metres and continues relatively narrow for around 10 km in a general NW to SE trend before passing through an area known as The Narrows between Mark’s Point and the Hassans Islands and the peninsula across the channel which is roughly 150 metres distant. The bay then extends to an open water area known as Broad Water where the channel is approximately 1.6 km wide. Moving south the bay gradually narrows before its termination at Milford.

Photo of the coastline along Mulroy Bay taken from the RV Geo during a sampling leg in July 2007.

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INFOMAR Survey History

INFOMAR surveys of Mulroy Bay consists of a lidar survey that was undertaken in 2005 in the upper reaches of the bay from the mouth to The Narrows (see above). The relatively shallow water and notable water clarity due to good weather that was experienced in August and September of 2005 meant that a large portion of the bay was surveyed in the safest, fastest and so most cost effective manner.

Another Lidar survey was completed in 2010 by Pelydryn.

Coverage from survey legs undertaken to survey Mulroy Bay. (Click image for more detail)

Survey Coverage polygons can be downloaded as a shapefile from our Interactive Web Data Delivery System (IWDDS).

Select your area of interest. Vector datasets - Offshore - Offshore Shapefiles

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

2010 LiDAR Surveying

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Bathymetry (Water Depth)

Bathymetry of the upper reaches of Mulroy Bay

The bathymetry of Mulroy Bay shows deeper water at the mouth of the bay, close to 30 metres deep just seaward of the two headlands at Melmore and Ballyhoorisky. Inside the bay, there is a distinctive channel of deeper water with depths on average of approximately 5 to 8 metres with relatively shallow areas around the channel around 2 or 3 metres deep.

Along the channel, several depressions in the seabed increase water depth up to 13 metres. Also at Fanny’s Bay where the orientation changes from N/S to NW/SE, a shallow bank is located in the inside bend of the bay where water was measured to be just below 1 metre deep. As expected there is an overall trend of water shallowing from around 20 metres at the mouth of the bay to about 5 metres or less around The Narrows area.

Bathymetry of Mulroy Bay & Lough Swilly. (Click image for more detail)

All of our Charts for Mulroy Bay can be downloaded in pdf format from this page.

You can download Bathymetry xyz data from IWDDS

(Data Type: Vector Datasets, Region: Offshore, Theme: Bathymetry (Survey Leg) entire survey leg or Bathymetry (Survey Line) for individual tracklines. Take note of the survey names in INFOMAR Survey History.

You can also download the bathymetry data in ArcGIS GRID format

You can download Lidar xyz data from IWDDS

(Data Type: Vector Datasets, Region: Offshore, Theme: Lidar.

You can also download the Lidar data in ArcGIS GRID format

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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.

Shaded relief image of data collected in 2005 lidar survey. (Click image for more detail)

Shaded relief image of Mulroy Bay & Lough Swilly. (Click image for more detail)

All of our Charts for Mulroy Bay 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.

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

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Ground Truthing/Seabed Sampling

A range of seabed sampling has been undertaken in Mulroy Bay. In July 2007, the RV Geo was mobilised to ground truth the Lidar data collected in 2005. This sampling leg successfully recovered grab samples and video footage from the upper reaches of Mulroy Bay.

In 2010, Aquafact conducted a sampling campaign in Mulroy Bay. Full Particle Size Analysis (PSA) was carried out on the samples.

Locations of grab samples for Mulroy Bay.

Sample locations can be downloaded as a shapefile from our Interactive Web Data Delivery System (IWDDS).

On the IWDDS Select your area of interest. Vector datasets - Offshore - Offshore Shapefiles

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Geology

Mulroy Bay Geology


Mulroy Bay is a narrow, winding body of water that works its way inland through the ancient, deformed metamorphic rocks known as the Dalradian.

Its seaward entrance is actually flanked on either side by a younger, igneous rock called granite. The rocks on the seafloor just offshore from the granite coastline may be an extension of the same and exhibit faulting and fracturing – these structures can be seen in the INFOMAR seabed data as linear features in the otherwise craggy, rocky seabed and may give further insight into the tectonic history of the area.

Onshore Bedrock Geology shapefiles can be downloaded from our Interactive Web Data Delivery System (IWDDS).

On the IWDDS Select your area of interest. Vector datasets - Onshore - Bedrock

Offshore Geology shapefiles can be downloaded from our Interactive Web Data Delivery System (IWDDS).

On the IWDDS Select your area of interest. Vector datasets - Offshore - Offshore Shapefiles

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3D Movie Flythrough

Click play below to view a 3D movie flythrough of the seabed of Mulroy Bay. The changing colours represent changes in water depth with red and orange for shallow water, yellow and green for intermediate depths and light and dark blue for deeper water. The flythrough begins with an overview, moves towards the northern end of the bay before plunging beneath the surface and travelling along the relatively deep water channel as it winds and turns through the bay. The flythrough passes over banks and troughs in the seabed before finally emerging at the Narrows before zooming out for a final overview from a SE aspect.

 

The INFOMAR project acknowledges and thanks the United Kingdom Hydrographic Office (UKHO) for allowing the Admiralty Chart for Mulroy Bay to be used as a reference map for the area.

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INFOMAR in Google Earth

To view and navigate around the Mulroy Bay dataset in Google Earth, click on the links below.

LiDAR Mulroy Bay

To view additional datasets in Google Earth please click here

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

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

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