Science Spin July 2008

Mapping Ireland's offshore

By Sean Duke

The first serious modern effort to comprehensively map Ireland's seabed began in 1999 with the establishment of the Irish National Seabed Survey. This ran for seven years up to 2005, and it mapped many of our deeper waters. Somewhat counter-intuitively the deeper waters are easier to map, as the technology used, multi-beam sonar covers a greater area when applied to deep waters than it does close to shore.

Following on from the Seabed Survey, was the INFOMAR project - Integrated Marine Mapping for the Sustainable Development of Ireland's Marine Resource. This began in 2006, and the goal is to map those areas that were not mapped by the Seabed Survey. These include 26 bays and three areas. The areas are off the Dingle Peninsula, off the south coast from Cork over to Hook Head, and along the east coast, from the Arklow Banks almost up to Drogheda. This effort was expected to take 20 years, but the Marine Institute, who are joint partners in INFOMAR with the Geological Survey of Ireland, the GSI, are putting a proposal to government that it be 'telescoped' into 10 years. The funding for INFOMAR is expected to run at about €4 million per annum.

Benefits

John Evans, Marine Institute, is the joint programme manager of INFOMAR, along with Koen Verbruggen at the GSI. There are a number of areas where the mapping of Irish offshore provides immediate and direct benefits for society. The first is safety, said John. "They're discovering a lot of shoals [areas where the water levels become quickly and unexpectedly shallow] that are just not marked on the charts, because the mechanism that was used in those 18th and 19th century chartings was basically that they dropped a lead line, they just did a point every here and there, and from that they deduced what the contours were." With this approach the surveyors could miss large areas. "What we are discovering is there are lots of areas where there are shoals. They are quite a significant hazard to navigation."

The information from INFOMAR is passed on to the UK Hydrographic Office, the body that is responsible for providing charts of British and Irish waters, and they update their charts. This provides benefits to the leisure or commercial user of the seas, and it also provides vital information on the seabed topography for shipping that is entering important ports around Ireland, such as Limerick, Foynes and Dublin.

Ireland has legal obligations, explained John, under a UN sponsored agreement called SOLAS, the Safety of Lives at Sea. What this essentially means is that the government is responsible for ensuring that adequate maps of the seabed are available. At the moment, if there was a major oil spillage in an area of the Irish offshore that wasn't mapped, the shipping company could claim that the accident was due to inaccurate seabed charts. The legal responsibility, and the cost, of the clean-up would then shift from the company to the government, and the taxpayer, and the costs could be huge.

There is also a requirement on the Irish government to meet the EU Habitats Directive. This Directive requires Ireland to define areas that are deemed to be biologically sensitive, and this applies to the offshore as well as to land areas. INFOMAR enables researchers to draw up a physical habitat map for the seabed, which means that activities in that area must be monitored to ensure that no damage is being done. The new information provides the means to make decisions on how commercial activities, such as fishing, oil and gas exploration and aquaculture, should, if at all, take place, inside the biologically sensitive areas in our offshore.
Another benefit arises in the case of a request from an individual or company that wishes to place an ocean energy device in the offshore. In the past, when marine maps were old and sometimes inaccurate, an individual wishing to place such a device in the sea, would have to use old maps to make decisions about where to place it. Today, with INFOMAR, advice can be given about where best to locate the energy device.
Elsewhere, in Galway the data produced from INFOMAR is facilitating the work of a project called Smart Bay, run by the Higher Education Authority and the Marine Institute. This project involves the wiring of Galway Bay with wireless and fibre optic cable - right around the entire Bay - to provide real-time water pollution monitoring.
Technology
A technique called multi-beam sonar was the prime technology used during the Seabed Survey. The sonar sends a swath of founds down to the seabed, and an arc of information bounces back up from the seabed. However, when the sonar technique is used closer to shore, the job of surveying gets progressively harder using multi-beam. The swath of sound being sent down to the seabed becomes smaller, and the lines that a ship has to sail during the survey, thus, become closer and closer, and, therefore, the surveying takes longer the closer to shore the ship is positioned.
For this reason, a new technology was adopted for INFOMAR, which, unlike the Seabed Survey, was mainly a project about surveying the near-shore areas. This technology is called LIDAR (light detection and ranging) and it is an area where Ireland is right up there with the best in the world. The technology involves the use of lasers, and it is highly successful in Irish waters down to about 15 metres depth. In clear waters the technology is useful down to 40 metres. Normally, LIDAR is used to determine features on land, but in Ireland it has been used to map shallow waters.
The way it works is that a laser is attached underneath a plane, the plane flies over the area to be surveyed, and two beams are shot downwards. One beam of light hits the sea surface and its reflected back, and the other hits the sea floor and is bounced back. The difference in relative time it takes for each beam to return back to the detector helps determine the depth of water, and the shape of the seabed. It is important to know exactly what the tides are doing when using this technique, and this is one of the reasons why tidal gauges have been installed in locations all around the Irish coast.
LIDAR was used in the surveying off the Dingle Peninsula and Galway Bay out to the Aran Islands, for instance. One issue with LIDAR is that the data that comes back is not as good as multi-beam sonar data. There is no 'backscatter data' which is data that is used to determine the precise nature of the seabed sediments. This means that quite a lot of point sampling of seabed sediments must be done with LIDAR. The plane, owned by an Australian company, did about 10 days flying around the Irish coastline, and generated a huge amount of data.
Deficit
Up until recently, said John Evans, Ireland had a huge knowledge deficit in terms of what was known about our offshore waters. A key starting point in building up a marine research infrastructure was the arrival of the research vessel, the Celtic Explorer, which was commissioned in 2003. This vessel gives Ireland, for the first time, a substantial research capability. In addition, Ireland has been aggressively targeting international research vessels present in our waters. International law sates that Ireland, in such circumstances must be permitted to place a person onboard. In addition, the Irish demand that the data generated from such research be shared.
"Ireland is really coming from a deficit position, we have been catching up over the last 10 years, and we are now in a position where we are doing things that other countries aren't doing," said John Evans. "We make the data freely available. It feeds into electronic charting systems that are being used by commercial fishermen, it's being used by researchers, and we don't know what [else] the data will be used for. The data will be there long after we are gone and it will be a national asset. There are probably 30 to 40 research projects running around the country that are either directly or indirectly using our data," he concluded.