Science Interviews


Sun, 4th Dec 2011

Studying Shipwrecks

Dave Parham, University of Bournemouth

Part of the show Underwater Archaeology and Underwater Welding

Diana - Shipwrecks are often described as underwater time capsules.  They can give us a snapshot in time from the bygone years, glimpses into military life, trading relations between countries, social life, and construction techniques.  And to discuss the archaeology of shipwrecks, we have with us an archaeologist with mask, fins, and spare snorkel: Dr. Dave Parham from Bournemouth University.  Hello! So, I know you've been working on the Swash Channel Wreck.  So tell us a bit about that.  What's the history behind it?

Dave -   Itís an early 17th century Ė probably a Dutch-owned - merchantman that was wrecked outside Pearl Harbour and found about 10 years ago now.

Diana -   What sorts of problems are facing it when itís in its current state?

Dave -   Well itís been buried since it was wrecked sometime in the 1630s but gradually over the last 10 or 20 years, it started to become exposed.  So the wreck itself and its contents have been preserved by being buried, but are now exposed to the elements and being rapidly degraded.

Diana -   So how has it become exposed?  What processes have caused that to happen?

Dave -   Itís natural erosion.  I think the seabed in the area was affected by Victorian coastal engineering which means that the sediment flow into the bay is less than it used to be and what was a large sand bank is gradually becoming smaller.

Diana -   I see.  So, when you've got timbers and things that will decay naturally, then this becomes a very big problem.  So what kind of methods can you use to conserve a wreck like that?

Dave -   Itís difficult when they're on the seabed because nature is taking the seabed away and itís quite a hard thing to stop that.  You can cover them.  Weíve covered parts of the wreck in a sort of plastic matting and sandbags and covered it back up again and we also put more sand on it.  But ultimately, if the whole seabed around it is reducing, you're on to a bit of a losing battle.

Diana -   And are sandbags the only methods you can use to shore ships like that up, or are there other things, other sorts of structural ways of solving the problem?

Dave -   You can use other methods to trap sediment on top of the wreck.  You can buy sort of plastic sea grass that traps sand from the water column and allow it to fall onto the wreck is another way of doing it.  But the simplest ways is sandbags and this sort of plastic matting which seems to work well.

Diana -   Okay, so that's the structural bit of the ship, but what about the stuff that's inside it?  How do you conserve the bits and pieces that were wrecked with it?

Annelise divingDave -   Again, itís the same thing. As long as you can keep the sediment on top of the wreck, then the material that's contained within the sediment will be alright as long as itís not exposed.  So itís all about trying to keep the seabed as it was, trying to maintain it in one place.

Diana -   I see.  And then how do you decide what you're going to leave down there and what you're going to raise to the surface?

Dave -   We made a decision - along with English Heritage who manage the site - that we would leave everything on the seabed that we thought we could maintain there, which is about 80% of the site, and then remove what is in fact the bow of the wreck, which actually juts out into a shipping channel.  We're removing that because we didnít think that we could have a chance of saving that.  So it was a pragmatic decision really and that we would save and leave everything on the seabed that we could and only remove the stuff that we didnít think stood any chance of surviving.

Diana -   I see, and what kind of bits have you removed so far?

Dave -   We excavated the bow of the wreck.  Itís the bow that's the most endangered so we uncovered that and we excavated the contents of that so weíve uncovered the structure and weíve been gradually taking that structure apart so that allow us to raise it as individual timbers rather than a big object.

Diana -   Okay and then how did you go about actually raising it and how deep is this buried underwater?  With kind of problems did you face?

Dave -   Itís not very deep.  Itís only in about 7 meters of water; but itís on the exposed location; itís exposed to prevailing winds and itís also within a shipping channel that has significant tidal movements.  Our biggest problems are natural.  A combination of wind and tide mean that we can only dive on the site a few weeks each month which makes it difficult to plan anything too far ahead and so there is a natural problem for us.

Diana -   And what are the bits of machinery that you used to lift this stuff up from the sea?  Do you use airbags?  Do you lift it all by hand?

Dave -   No, itís all been quite simple.  The majority of material is being lifted by hand.  The large shipís timbers, weíve placed those on a steel frame that is raised onto a crane barge.

Diana - And once you've got it all out of the water then what happens?  Does it all get taken apart and taken to the museum and then reconstructed?

Dave -   All the material that have come up is going to be analysed and studied.  The structure itself is going to be recorded completely and weíre hoping to raise the money to conserve the structure and then place that on display in Poole museum.

Diana -   I see and what's going to come up next?

Dave -   Next will be the bow of the wreck.  We took that apart in the summer and weíve been planning to raise it now for almost 6 weeks but weíve been hampered by the weather conditions Ė all these gales and rain that we have mean that we can't dive.  So weíre currently waiting on the weather.

Diana -   The windsurfers will like it though! Moving on to a slightly different subject, I mean, what is the most striking thing that you've seen on a wreck apart from this one?

Dave -   The most striking thing I've seen on the wreck are actually some of the materials from this site because weíve got carvings on the wreck, weíve got the early shipís carvings in the United Kingdom and quite a striking sight. Weíve got two carvings of mermen, fish's tail and a manís head.  One very large carving of a male head, which is on the head of the rudder, and weíve got a couple of much smaller carvings of sort of gargoyles, which are from around the gun ports on the wreck.  So this is all decoration that was on there originally but it is very striking to look at and very unusual for it to survive.

Diana -   Well, fantastic! But why would they have carvings like that on a merchant ship?

Dave -   Itís a status indicator I think. This is owned by an organisation; itís trying to make a point, somebody that is demonstrating that they are something above and beyond the rest of their competitors.  Itís a very large merchant ship for its time and this is all about demonstrating to your competitors, and people around you, that you're somebody worth trading with.

Diana -   And can anyone see these carvings yet?

Dave -   They're currently being conserved but weíre hoping to have some of them available for public display in Poole museum next year.

Diana -   Fantastic!  Well thank you very much.  That was Dave Parnham from University of Bournemouth.


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