THE Giant's Causeway, Newgrange and Skellig Michael's stairway to heaven are this country's best known (and only) international heritage sites. However, under a new UNESCO convention which is due to become legally binding later this year, Ireland may have a fair percentage of some three million additional "monuments" requiring protection worldwide.
The fact that these "new" monuments have been forgotten till now suggests in itself that they aren't at risk. Not so, say marine archaeologists and those sports divers who are committed to ensuring that the many wrecks around this coastline are not exposed to depredation.
It is not just the odd treasure hunter they are referring to. Construction of new harbours, marinas, the laying of fuel pipelines and sub-sea cables can have a profound impact on the archaeological potential of the marine environment.
Now a group of scientists on the western seaboard is making its own contribution. New techniques developed by the team at NUI Galway will facilitate mapping and cataloguing artefacts and data beneath the water. Dr Colin Brown and Mr Kevin Barton, of the university's Applied Geophysics Unit, have built on their department's expertise in terrestrial archaeological geophysics to produce high-resolution underwater geophysical imaging.
The development is the result of informal contacts between archaeologists, divers and scientists, at a time of rapid advances in technology. "About five or six years ago, Kevin Barton applied geophysical techniques to a terrestrial archaeological survey at Rathcroghan mountain in Roscommon. He came up with some great images," Dr Brown says. At the time, the Marine Institute had purchased high-resolution equipment for offshore geotechnical survey work. "We took advantage of this and booked the institute's research vessel, the Celtic Voyager," Dr Brown says.
In the spring of 1997 Mr Barton did some work at Clonmacnois, one of the country's most important archaeological sites at the junction of the Eiscir Riada and the Shannon. Initial results were described as encouraging. Bridge timbers lying in sediments beneath the Shannon bed were "imaged" by ground-penetrating radar.
The beauty of high resolution archaeological geophysics is that it is "non-invasive" and involves using equipment like the aforementioned radar, which beams radio waves into the soil and picks up reflections from buried features, along with side-scan sonar and differential global positioning systems (DGPS).
High-frequency side-scan sonar systems can yield "real-time" images of material type and relative topography to port and starboard of a boat's track. The width of the image is normally about two to three times the depth of water. The "sonograph" is described by experts as a "tonal map" of the river bed, where dark areas can indicate strong acoustic returns, perhaps from wood, metal, stone and coarse sedimentary material.
Then there is seismic reflection, which can give a profile of objects actually buried in the river bed. High-resolution magnetometers can pick up anomalies which may lead to the discovery of small iron objects on or within river-bed sediments. The one challenge facing users of the bewildering array of equipment is interpretation. As with land-based archaeology, an infinity of objects can emit a similar signal.
The techniques were put to good effect to map the site of La Surveillante, a French frigate of the 1796 expedition which was scuttled in Bantry Bay after being severely damaged in storms. Last May a site survey involving divers, remote sensing, sediment coring and underwater photography was conducted on the wreck, lying partially buried in 34 metres of water opposite the Whiddy Island oil terminal. It was the Celtic Voyager's first archaeological cruise, and it was co-ordinated by NUI Galway's Applied Geophysics Unit.
Although conditions were difficult, side-scan images allowed the scientists to map the wreck site and the surrounding field of debris, while sub-bottom profiling or seismic reflection gave valuable information on the depth and stability. Preliminary results were prepared for Duchas, the Heritage Service. The interim report of that survey, published recently by the team leader, Mr Colin Breen, at the University of Ulster, notes that a lot more work is required to build up an accurate picture.
Last year Duchas also commissioned the Galway team to survey an area near Bere Island in the north-west of Bantry Bay, using the university's own vessel, RV Conamara. The results indicated that there could be a shipwreck or wrecks and debris, and the information has been referred to the Heritage Service's archaeological diving unit for further investigation.
The NUI Galway team will be returning to La Surveillante as its main marine test bed, and hopes to earmark a lake project. The current focus is on its riverine site at Clonmacnois, for which it has received funding from the university's millennium research fund. Ms Deirdre O'Hara has been appointed project researcher for a three-year programme in association with Duchas, the University of Ulster, Coleraine, and Management for Archaeology Underwater.
Initially, the work will mean development of a geophysical platform which will be used to deploy instrumentation capable of carrying out a systematic survey. The digital data will then be processed and interpreted to produce maps which will guide divers to investigate potential archaeological targets like submerged bridge structures, dug-out boats, walls and flagstones associated with piers. The team believes that the information will add to the current fund of knowledge about the Clonmacnois site and its environs.
Naturally, the university is very proud to have the only academic group in the Republic with the expertise in this area. As a direct result, an Irish underwater archaeological network has been formed to exchange ideas and information. One of its main aims is to host an international conference in underwater archaeology, which will be held some time next year.
