Friday, August 2, 2024

Shining a spotlight on Irish Sea shipwrecks

Point cloud representation of the SS Tiberia, highlighting the detailed structural features discernible through MBES.
(Image courtesy: Ulster University)

From Hydro by Fabio Sacchetti, Alexander Callaway

Maritime history comes alive in two evocative World War I shipwreck bathymetric images

The data for the images of the sunken vessels SS Tiberia and RMS Leinster, submitted as entries to the Kongsberg Discovery Multibeam Image Contest 2023, was captured during seabed mapping carried out by the Agri-Food and Biosciences Institute (AFBI) in Belfast and by the Irish Marine Institute in collaboration with Ulster University, respectively.
These and a multitude of other wrecks speak to the need for ongoing monitoring, both for heritage preservation and to manage potential environmental risk.

The Kongsberg Discovery Image Contest was established in 2014 and is open to all professional users of the company’s family of single and multibeam echosounders (MBES).
Images are not required to date to the current competition year.
Of the 70-plus entries in the 2023 contest, the images of SS Tiberia and RMS Leinster were among the top three winners – providing an excellent platform to highlight the cultural relevance of wrecks and the need for appropriate management.
We would also like to highlight the enduring collaboration between our institutions and Kongsberg Discovery, of which these images are a result.
 
 
Shipwrecks abound

According to UNESCO, beyond the known shipwrecks worldwide there are an estimated three million undiscovered wrecks dotting our ocean floors.
These man-made artefacts are now recognized as an integral part of our submarine landscape, ocean ecosystem and cultural heritage.
Shipwrecks have multiple values, providing a unique snapshot of the past and hotspots of biodiversity in seabed locations that can often be comparatively featureless.

Shipwreck protection

In the Republic of Ireland, legislation such as the National Monuments Act (1987) gives blanket protection to all wrecks more than 100 years old.
There is no such protection for shipwrecks in Northern Ireland (NI); however, as part of the UK it has adopted the rules set out in the Annex to the 2001 UNESCO Convention on the Protection of the Underwater Cultural Heritage as best practice and continues to pursue ratification.
In addition, under the Historic Monuments and Archaeological Objects NI Order (1995), Protection of Wrecks Act (1973) and Protection of Military Remains Act (1986), wrecks in NI waters may be scheduled for protection.
The Marine and Coastal Access Act NI (2009) also offers some protection to shipwrecks through control of disturbance and salvage.
This is particularly important because many wrecks still contain large quantities of dangerous materials such as explosives and fuel, which under certain circumstances can pose a serious threat to the marine and coastal environment.

INFOMAR’s dedicated shipwreck map viewer (left) and 3D modelling function.

Mapping, preserving and monitoring required

Pivotal action is required to manage such challenges.
Firstly, national efforts must be in place to survey as many wrecks as possible, with adequate spatial resolution to establish comprehensive databases for future monitoring initiatives.
The Irish Marine Institute has been pursuing this goal for the last 25 years through the former Irish National Seabed Survey and the ongoing INFOMAR National Seabed Mapping Programme, whose ultimate aim is to complete mapping of the Republic’s entire offshore territory by 2026.
During this time, more than 500 shipwrecks – over half of them previously unidentified or uncharted – have been successfully and meticulously mapped.
There are over 20,000 recorded wrecks in UK waters, rendering targeted monitoring of each of them unfeasible.
Although wreck monitoring is not one of AFBI’s direct responsibilities, data is often acquired from wreck sites during surveys with other priorities.
The Fisheries and Aquatic Ecosystems Branch (FAEB) of AFBI has a long history of seabed mapping and is a member of the UK Centre for Seabed Mapping (UKCSM), which has a dedicated Wreck Mapping Working Group tasked with improving coordination and investigations of UK wrecks.

‘Collect once, use many times’

SS Tiberia and other nearby wrecks have been used for many years as part of the calibration process of the AFBI’s MBES due to their proximity to Belfast, and have been covered during multidisciplinary surveys undertaken for the FAEB’s Seabed Mapping project.
With the passage of time, many older wrecks are beginning to decay and break up, which has consequences for historical and marine archaeological perspectives as well as for pollution management.
Although not originally intended for this purpose, the ‘collect once, use many times’ approach means that this survey data provides an important resource for informing multiple disciplines.
Disseminating this extensive resource among the broader community, supporting research and public engagement, requires dedicated tools and sharing infrastructure.
To meet this need, INFOMAR has pioneered a shipwreck Web Map Viewer and Sketchfab channel, enabling the visualization of over 200 models in 3D (Figure 1).
Much of the data acquired in UK waters is available to download through the Admiralty’s Bathymetry Data Service.
The second action point is to develop long-term management strategies for wrecks that have either historical relevance or those that contain potentially dangerous materials.

Fitting a Kongsberg Discovery EM 2040 Mk II single RX MBES system to RV Corystes.

Wreck preservation

The UNESCO Convention strongly advocates the in situ preservation of shipwrecks where possible.
This includes assessments of local environmental characteristics that can be used to determine long-term stability, enabling an appropriate management and risk mitigation strategy to be devised accordingly.
Understanding the historical context of wreck sites and surrounding seabed processes is crucial in determining such strategies.
Seabed mapping using high-resolution MBES is often the fastest and most reliable method of providing data for characterizing these sites in a non-intrusive manner.
However, this data only offers a snapshot of seafloor and wreck morphology at the time of collection.
Wreck preservation is a long-term process, often involving repeated time-lapse surveys, photogrammetry and laser and video investigations to assess change over time.

 
SS Tiberia, top winner of the KD image competition.
(Image courtesy: Agri-Food and Biosciences Institute)
 


The role of CFD

To fully understand the stability and lifespan of shipwrecks, it is fundamental to analyse the complex hydrodynamic processes acting upon them.
Recent studies conducted at Ulster University (Northern Ireland) have shown how computational fluid dynamics (CFD) modelling has the potential to reconcile vortex shedding and quantify shear stress that generate scouring and erosion in the vicinity of complex obstacles.
The results of these forces can cause stress on wreck superstructures, potentially causing instability and disintegration (e.g. Quinn & Smyth, 2017; Majcher et al., 2022).
In addition, CFD can be used to track pollution dispersion in complicated environments and is a critical tool for emergency- response exercises that AFBI supports NI government departments in enacting.
Maximizing survey equipment

A key element of the Marine Institute-Ulster University survey in 2015 (which generated the data for the RMS Leinster image, Figure 3) was the selection of equipment settings and survey plan strategies chosen specifically to optimize data quality (Wesley, 2019) and to ‘squeeze’ everything out of the available survey equipment.
Survey strategies included using the shortest available pulse lengths, employing highly sensitive bottom tracking algorithms, maximizing data density settings while minimizing swath width, and strategically planning survey lines in every possible direction to thoroughly map even the most challenging parts of the superstructure of sunken vessels.
This was complemented by meticulous compensation of oceanographic conditions, achieved through regular sound velocity profiling and use of top-of-the-line inertial measurement unit (IMU) and differential GNSS (DGNSS) solutions, ensuring precise positioning of all soundings and effectively compensating for vessel motion and tidal changes.
Millions of soundings were collected per wreck, providing unparalleled data density and quality, enabling the creation of accurate 3D models then used for archaeological research and public dissemination.

 
RMS Leinster image from Ulster University survey in 2015 (EM 2040 dual RX).
(Image courtesy: INFOMAR)

Exceptional MBES data quality

SS Tiberia and RMS Leinster, in 65 and 30 metres of water, respectively, are part of a larger selection of World War I shipwrecks regularly monitored by various organizations.
These include the Irish Marine Institute, which originally mapped them with MBES over two decades ago; Ulster University, which conducted two dedicated survey campaigns in 2015–2016 (Westley, 2019) using a Kongsberg Discovery EM 2040-07 dual RX mounted on the research vessel Celtic Voyager; and AFBI, which generated data for the SS Tiberia image in 2022 during patch testing as part of the sea acceptance test following installation of a Kongsberg Discovery EM 2040 MKII single RX MBES system 0.4 TX / 0.7 RX mounted on the AFBI research vessel Corystes.

Unique marine monuments

The two wrecks are historically important for both countries but provide different perspectives on the sinking of vessels.
One resulted in catastrophic loss of life, while the other occurred with no casualties.
As a well-preserved wreck, SS Tiberia is a popular site for scuba divers who can visit without the risk of disturbing a maritime grave.

SS Tiberia was torpedoed by German submarine U-19 1.5 miles east of Blackhead at the mouth of Belfast Lough on 26 February 1918 while on voyage from Glasgow to New York carrying general cargo.
All hands survived the attack through a combination of the ship’s lifeboats and rapid assistance from shore (Irish Wrecks Online, 2020) as there were many witnesses on land.
The data used in the winning image shows how the shipwreck is still well preserved, sitting upright on the seabed with some of the masts and smaller structures still visible.
This data is the latest in a time series that will allow continued monitoring and inform management of the wreck into the future.

The opposite can be said for the RMS Leinster, a Royal Mail Ship torpedoed by German U-boat UB-123 in the Irish Sea on 10 October 1918.
The ship, carrying civilians, military personnel and mail, sank within 12 minutes.
Of the 771 people onboard, 501 perished during the attack, making it the largest single loss of life in the Irish Sea.
Among the casualties was the ship’s captain, William Birch.
The ship sank just outside Dublin Bay, roughly four nautical miles (7.4 kilometres) east of the Kish Bank Lighthouse.
The U-boat crew also perished shortly afterwards when their submarine struck a mine.

Conclusion

With the most significant shipwrecks on the Irish continental shelf already catalogued and mapped with some level of detail, questions now arise regarding the next logical steps to assess how to preserve and monitor these resources.
One thing is certain: although undergoing gradual disintegration, some shipwrecks pose an increasing risk to the environment due to corrosion that can breach sealed compartments, potentially releasing large quantities of oil and other pollutants.
Various projects, such as the North Sea Wrecks, Remarco and the Endure underwater heritage programme, have already begun to pave the way, examining shipwreck degradation, pollution spillage risks and methods for preserving these sites for future generations using advanced techniques such as photogrammetry surveys and virtual museums.
Meanwhile, in terms of calibration targets, there is a wealth of data not collected for any specific survey purpose that could be used for archaeological and monitoring assessment.
The repeated nature of calibration across years makes this data a good source for monitoring the condition of – and identifying any change at – targeted wrecks.
Efforts by the likes of the UKCSM’s Wreck.

Mapping Working Group to co-ordinate survey effort, data sharing and knowledge exchange between disparate organizations will enhance the value of this data and increase available resources for sites of national interest and importance.
Further surveys, research and studies to ensure the responsible management of this vast underwater legacy by the respective national authorities would be most welcome.

Links :
at

No comments:

Post a Comment