Using satellite data, researchers have found that shipwrecks near the coast can leave sediment plumes at the sea's surface that help reveal their location.
Using data from the NASA/USGS Landsat 8 satellite, researchers detected plumes extending as far as four kms downstream from shallow shipwreck sites.
The discovery demonstrates for the first time how Landsat and Landsat-like satellites may be used to locate the watery graves of coastal shipwrecks.
An estimated three million shipwrecks are scattered across the planet's oceans.
Most maritime mishaps take place close to shore where hazards to navigation -- such as rocks, reefs, other submerged objects and vessel congestion -- are abundant.
A quarter of all shipwrecks may rest in the North Atlantic. In the narrow southern end of the North Sea, World War II-era shipwrecks are plentiful.
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Now, Matthias Baeye and Michael Fettweis from the Royal Belgian Institute of Natural Sciences, Rory Quinn from Ulster University in Northern Ireland and Samuel Deleu from Flemish Hydrography, Agency for Maritime and Coastal Services, have found a way to use freely available Landsat satellite data to detect shipwrecks in sediment-laden coastal waters.
Their study, conducted in a coastal area off the Belgium port of Zeebrugge, relied on a detailed multibeam echosounder survey of wreck sites, previously conducted by the Flemish government.
This part of the Belgian coast is strewn with shipwrecks, in often sediment-laden waters.
Using 21 Landsat 8 images and tidal models, the researchers mapped sediment plumes extending from the wreck locations.
They found that the two ships with substantial portions of their structure unburied created sediment plumes that could be traced downstream during ebb and flood tides.
The study, published in the Journal of Archaeological Science, looked at shipwrecks in waters as deep as 50 feet.
Given that coastal waters are typically shallow, often sediment-laden and where most shipwrecks occur, this new shipwreck detection method could prove useful for marine archaeologists.