21 September 2003
Mapping Britain’s drowned landscapes
The drowned plains and valleys of the North Sea and English Channel may soon be revealed by British scientists using a revolutionary scanning technique that can create maps as accurate as those made of dry land. In the process, researchers hope to identify locations – sheltered bays, cliffs that may have contained caves, freshwater lakes, riverside sites - that humans may have chosen for habitation. And these prime sites could then be investigated in detail using divers and robot submersibles, with the aim of finding tools, house timbers preserved in sediments and other evidence of human activity.
Dr. Sanjeev Gupta, leader of a team that has already used the advanced sonar technology off the coast of Sussex, says: “Britain has been occupied by human beings for the past 50,000 years and during that time seas levels have dropped, linking our land to Europe on five occasions. In fact, we were more often connected to the continent than we have been an island. Our current status is really the unusual one. That makes this sort of research all the more important”. In glacial and inter-glacial periods the plains, valleys and huge forests of the land bridge would have been home to herds of reindeers and horses, and men and women would have made their homes by its rivers and lakes.
The new technique, known as bathymetry, uses a special echo sounder to make great sweeps across the sea bed. Previous echo sounders have only been able to plot in two dimensions but computers, satellite positioning devices and associated software can now legislate for ocean swell and ship movement to create a perfect three-dimensional image of the underwater landscape.
Gupta and his team have used bathymetry to map the map the course of the River Arun, which now enters the Channel at Littlehampton, Sussex. Ten thousand years ago, at the end of the last ice age when much of the world’s water was trapped in giant glaciers, the Arun continued for several miles into a valley that had been carved by a south-flowing river that combined the waters of the Thames, Rhine and Seine. Only a vague outline of the extended Arun river bed had been made by previous methods. “What we saw was astonishing,” said Gupta. “The topography was incredibly detailed, rich and complex. We could see the river bed that the Arun had created thousands of years ago and examine the bays and cliffs along the valley. We could see a rocky ledge that might have formed a waterfall, an ideal place for an ancient settlement. We could also see where boats have since sunk and settled on top of this landscape.”
Now English Heritage, which has recently been given responsibility for maritime archaeology in Britain, is approaching government and industry for funding to create a national survey of Britain’s territorial waters and to map regions of the North Sea. Dr. David Miles, chief archaeologist of English Heritage, says: “We have better images of Mars and Venus than of two thirds of our own planet. Now we can put that right. [The new technology] offers us a unique chance to open up our history. There could be dozens of perfectly preserved sites down there. Given that Britain is a maritime nation, for whom the sea has been an immense influence, finding out its secrets around our shores is particularly important. For example, we know there was once a Roman lighthouse near Whitby. We could pinpoint that with this technique.” Bathymetry will also be invaluable in pinpointing lost wrecks. There are some 44,000 recorded shipwrecks off the coast of Britain, but extrapolation of shipping statistics suggests that the actual number may be closer to half a million.
Scientists are keen to map the seabed as soon as possible because of the increase in marine cable laying and channel dredging for container shipping, commercial activities which threaten archaeology and marine life. Key sites could be identified and afforded protected status. “We have a good relation with industry over this,” says Miles. “The money for the bathymetry project was provided by the new ‘aggregates levy’ that companies pay to minimise their environmental impact, and they recognise the importance of this sort of surveying as well.” But companies also gain reciprocal benefits from accurate underwater mapping, including the ability to pinpoint new aggregate sites.
Source: Guardian Unlimited (21 September 2003)